Linear Motion Technology from Bosch Rexroth

www.boschrexroth.com

Linear Motion Technology from Bosch Rexroth for use under special ambient conditions

Use in special operating conditions

Bosch Rexroth AG, R999001439/2021-01

2

Table of contents | Use in special operating conditions

R999001439/2021-01, Bosch Rexroth AG

3

General 4Normal conditions of use 4Materials used 5Explanations regarding the plastics used 5RoHS directive 7REACh regulation 8Potentially explosive atmospheres – ATEX 8Electrostatic discharges – ESD 9Paint-wetting impairment substances – PWIS 9

Temperature 10Basic principles 10Temperature limits 10

Clean room 11General information 11Basic principles 11

Standards and directives 11Terms 12Clean room classes 13Comparison between the different standards and guidelines 14General and product-specific recommendations 15Preferred product versions for clean room use 15Factors influencing clean room classification 16Product-specific recommendations 20Other notes 20

Tested products from DC-LT 21Profiled rail systems and integrated measuring systems 21Linear motion systems and electromechanical cylinders 22

Food zone 23Directives and standards 23

International standards 23European Union directives and standards 23Organizations 24

Hazard analysis 25Definitions 25Special hazards 25Structure of the HACCP plan 26

Product requirements for specific areas 26Production areas 27

Working zones 27Cleaning 28

Material selection 28Detergents 28

Hygienic design 30Lubricants for food industry applications 31

Basic principles 31Suitable lubricants for Rexroth Linear Motion Technology products 31Miscibility and preservation 31

Plastics in food industry applications 32Other notes 32Bosch Rexroth products for use in Food & Packaging 33

NRFG ball rail system in production zones as per EN 1672-2 33Electromechanical cylinder EMC-xxx-xx-2 34

Vacuum 35Basic principles 35Materials 35

Plastics and lubricants 36Metal materials 37

Linear Motion Technology products under vacuum 37Design measures 37

Dry room 38Basic principles 38Linear motion technology products in dry rooms 38

Corrosive environments 39Basic principles 39Galvanic coatings 40Use of corrosion-resistant steel 41Coating systems 41Product overview 42

General 43

4 Use in special operating conditions | General


Rexroth offers Linear Motion Technology from guideway to drive elements for a wide variety of applications. Rexroth products can in principle be used under many different environmental conditions, as long as the appropriate specifications are complied with. This brochure provides background knowledge for the use of Rexroth products in special environmental conditions and helps users to find solutions for a broad spectrum of applications.If in doubt, users should contact Rexroth for advice. The last chapter contains a checklist developed specifically for this purpose, which can be submitted along with inquiries.

Normal conditions of useRexroth recommends that all guideway and drive units should be used under normal environmental conditions.The following can be regarded as normal conditions of use which will not have any influence on life expectancy or result in undesirable interactions.

▶ No contamination ▶ No exposure to metalworking fluids ▶ Use in a dry environment ▶ Not in a dry room ▶ Use at room temperature ▶ Not in clean room environments ▶ Not under vacuum ▶ Not in food industry applications ▶ No exposure to chemicals ▶ No electrical current flowing through the components ▶ No radioactive radiation

If the environmental conditions differ from those stated above, Rexroth, with its many years of experience, is available for consultation.

General

5 General | Use in special operating conditions


Materials usedThe table below shows an overview of the materials used in each product. This table covers only the main components of the products. The individual components are sometimes produced in different versions, and the table does not include information on these or on any applied coatings or auxiliaries used (e.g., adhesives, paint additives).

Product Steel Wrought aluminum alloy

PA66 PBT POM TPE Preservative Dynalub

Ball screw assembly x x1) x2) x x x x

Planetary screw assembly x x x x

Ball rail system 3) x x4) x x x x x

Roller rail system x x5) x x x x

Linear bushing and shaft 6)

Compact (C) x x x x

eLINE x x x x x

Super A+B x x x x

Standard x x7) x x

Segment x x8) x

Super H+SH x x x x

Radial x x x

Torque x x x

Integrated measuring system x x x x x x x x

Linear motion systems x x x x x x x x

1) PA66 is used for size BASA 32x5Lx3.5 and 40x10Lx6.2) PBT is currently used for the front lube unit of ball screw assemblies.3) Some with NBR seals.4) Type FNS and SNS runner blocks are available with a block basic body made of wrought aluminum alloy.5) In roller rail system gen. 1, PA66 is still used, but not in the RSHP.6) Different plastics are used in the linear bushing and shaft depending on type.7) PA66 is used with standard LB < Ø 12 mm.8) PA66 and PA11 are used in the segmental linear bushing and shaft.

Explanations regarding the plastics used



▶ Polyamides (abbreviation: PA) are thermoplastic polymers. In chemical terms, PA66 (also known as nylon) is a condensation polymer consisting of identical building blocks bonded together via amide groups (polyamide). PA66 was the first synthetic fiber to be manufactured exclusively from inorganic substances (carbon, water, air). PA66 is tough, impact-resistant, abrasion-resistant and has high thermal shape retention. This plastic can therefore be used for many different kinds of mechanical functional elements. In segmental linear bushings, PA11 is also used. Compared with PA66, PA11 is softer but absorbs much less water.

▶ PBT is a thermoplastic polyester based on polybutylene terephthalate. The special characteristics of PBT include good mechanical and physical properties such as rigidity, toughness, temperature stability, friction and wear resistance, excellent surface quality of parts molded from this material, and good dye absorption. It can be joined using all standard methods such as welding, mechanical fastening and adhesive bonding, and permits printing, painting, hot embossing and laser marking.

▶ Polyoxymethylene (abbreviation: POM), also known as polyacetal or polyformaldehyde, is a semi-crystalline, thermoplastic polymer. Because of its high rigidity, low friction values and excellent dimensional stability, POM is used as an engineering plastic especially for precision parts.

▶ Thermoplastic elastomers (linear elastomers; abbreviation: TPE) are plastics that behave similarly to classic elastomers at room temperature but can undergo plastic deformation when subjected to heat, and therefore exhibit thermoplastic behavior. Among this class of thermoplastic elastomers, Rexroth frequently uses the materials TEEE and TPU. TEEE is a thermoplastic elastomer based on polyester. The international abbreviation TEEE stands for "Thermoplastic Elastomer Ether Ester". TEEE combines many of the main properties of highly resistant elastomers and flexible plastics: exceptional toughness and flexibility, high creep resistance, impact resistance and long-term bending strength, flexibility at low temperatures and good retention of properties profile at elevated operating temperatures. TEEE is also resistant to a large variety of chemicals, oils and solvents. Thermoplastic polyurethane (TPU) is an elastomer characterized by high resistance to abrasion, good resistance to oils, greases and solvents, and excellent resistance to weathering, combined with high elasticity.



RoHS directiveBosch Rexroth is conversant in the EU Directive 2011/65/EC on "Restriction of the use of certain hazardous substances" in electrical and electronic equipment (RoHS). Bosch Rexroth Linear Motion Technology products usually do not fall within the scope of the EU directive 2011/65/EU. However, it is well known that our customers' products are mostly within the scope of application of the RoHS directive. For this reason, all materials are selected in such a way that the products of Bosch Rexroth Linear Motion Technology comply with the requirements of the RoHS directive.

The substances listed in Directive 2011/65/EU ▶ lead ▶ mercury ▶ cadmium ▶ hexavalent chrome ▶ polybromated biphenyle ▶ polybromated diphenyl ether

and the materials supplemented by the Delegated Directive 2015/863/EU ▶ bis(2-ethylhexyl) phthalate ▶ benylbutylphthalate ▶ dibutylphthalate ▶ diisobutylphthalate

are not used deliberately to manufacture the products, nor added to them, or, if present, do not exceed the limits prescribed in the directive.

A general confirmation in this document is not possible. However, it is possible to view the available manufacturer's declarations in the media directory of Bosch Rexroth Linear Motion Technology at any time.



REACh regulationThe acronym "REACh" comes from "Registration, Evaluation, Authorization and Restriction of Chemicals". It refers to Regulation (EC) No. 1907/2006, the EU's regulation on chemicals, which took effect on 06/01/2007. Being an EU regulation, it is equally and immediately valid in all Member States.

At Bosch Rexroth, we work closely and extensively with our vendors to implement REACh requirements. Our customers can rest assured that we are meet our legal obligations.

In order to comply with the information requirements set out in Art. 33 of the REACh regulation on SVHC substances in products, we are always working on this to check the plant material and materials used in order to publish any necessary customer information promptly. The currently available customer information can be found at any time at www.boschrexroth.com/REACH

Potentially explosive atmospheres – ATEXThe acronym "ATEX" comes from the French abbreviation for "ATmosphères EXplosibles".Since 04/20/2016, Directive 2014/34/EC has had binding effect throughout the European Union for all electrical and non-electrical equipment. This directive establishes the rules for marking products that may be used in potentially explosive environments.

Linear Motion Technology components/systems by Bosch Rexroth AG are not designed for use in potentially explosive environments. For this reason, these products do not fall under Directive 2014/34/EU and are not declared in conformity with the ATEX directive.



Electrostatic discharges – ESDThe abbreviation "ESD" stands for "ElectroStatic Discharge".

Electrostatic discharges are disruptive voltage discharges caused by large differences of potential. These discharges generate a brief, high electrical current and can ignite flammable materials. In certain circumstances, this creates a risk of fire or explosion, as well as a risk of injury from electric shock. Electrical components are often affected or even destroyed by such discharges.

Requirements for protecting against ESD are primarily defined in electronics manufacturers' factory standards. Since they do not pertain to personal safety, unlike, e.g., ATEX, they are not subject to any legal provisions and there are only a few public standards.

Linear Motion Technology products are not susceptible to the effects of electrostatic discharges. However, it cannot be ruled out that Linear Motion Technology products may produce electric charges that can result in electrostatic discharge.

Paint-wetting impairment substances – PWISIn the automotive industry in particular, PWIS-free components are required, especially on paint lines. PWIS's are substances that create craters, i.e., punctiform, funnel-shaped indentations in paint.

These substances are mostly: ▶ Silicones and silicone oils ▶ Perfluorinated hydrocarbons ▶ Surfactants, especially silicone-based surfactants/fluorosurfactants ▶ Greases ▶ Other non-polar, highly volatile organic compounds

In Linear Motion Technology components and systems Bosch Rexroth AG does not use raw or operating materials containing PWIS's in the manufacturing of Linear Motion Technology replacement parts and assemblies.However, since auxiliary materials, such as release agents for molding tools or paint additives, may contain silicone, a total absence of silicone is not certain. This means Bosch Rexroth cannot guarantee a completely silicone-free product.

10 Use in special operating conditions | Temperature


Temperature limitsProduct Lower operating

temperature Upper operating temperatureLower storage temperature

Upper storage temperature

Ball screw assembly -10 °C +80 °C -15 °C +80 °C

Planetary screw assembly -10 °C +60 °C -15 °C +80 °C

Ball rail system

without ball chain -10 °C +80 °C -15 °C +80 °C

with ball chain 0 °C +80 °C -10 °C +80 °C

Roller rail system -10 °C +80 °C -15 °C +80 °C

Linear bushing and shaft 1) -10 °C +80 °C -15 °C +80 °C

Integrated measuring system 0 °C +50 °C -10 °C +70 °C

Linear motion systemsMechanical system -10 °C +60 °C -10 °C +60 °Cw/ Rexroth servo motor 2) 0 °C +40 °C 0 °C +40 °C

1) Permissible operating temperature of the standard LB in all-steel version without seals: -10 °C to 200 °C. Segmental LB Niro version: upper operating temperature = upper storage temperature = 65 °C.

2) Loss of performance at 40 °C or higher

The "storage temperature" is the temperature when the equipment is not in operation.

The upper temperature limits depend primarily on the plastic parts integrated in the products and the lubricants used. These values are based on the retention of mechanical material characteristics and the avoidance of thermal aging. The lower temperature limits are based on the retention of mechanical material characteristics and functional reliability of the products.

+80 °

-10 °

The information on temperature limits for the products is based on the limits for the individual parts, especially plastic parts (no change in physical and chemical material properties), as well as experience gained from practical applications and function tests in the laboratory and in testing bays.

When used in environments with freezing temperatures, humidity levels (condensation) must be taken into account.No assurance can be given that the products will function properly if ice forms on them. This can lead to considerable disruptions. Impact and vibratory load must be avoided in order to protect the plastic parts. The choice of lubricant must also be carefully considered.Travel performance may deteriorate sharply at temperatures below -10 °C.

The table below shows the temperature limits for products of Linear Motion Technology from Bosch Rexroth.For environments with temperatures outside these limits, suitability for use must be checked for each specific application.

TemperatureBasic principles

11 Clean room | Use in special operating conditions


Clean roomGeneral informationMany of today’s industries make high demands on their production facilities. Examples include microelectronics, precision engineering, the food industry, pharmaceuticals and medical technology.

In these industries, cleanliness is paramount. This applies to the air, the equipment used, the workplaces (e.g. surfaces, machinery, tools), the media employed (e.g. gases, liquids, chemicals) and the clothing of operating personnel. The overall cleanliness of the rooms depends on all of these points. Production and processes are carried out in what are referred to as clean rooms. The cleaner the air in these rooms is, the better the clean room classification with regard to the ISO class. This classification is based on the measured particle count and particle size in a defined volume of air (see chapter "clean room classes"). These particles are released by persons and processes or are carried into the clean room through air conditioning supply and exhaust lines.

For Bosch Rexroth, it is of crucial importance that our products release only as many particles as permissible during operation so that a clean room retains its classification and is not downgraded. To obtain such data, our products can be tested for clean room compliance and then certified (see chapter "Classification results to date").

Basic principlesThis chapter covers important basic information that is required for clean room applications.

Standards and directives

There are a number of standards and guidelines relating to clean room classification. Brief descriptions of these are given below. The applicability and range of clean room classifications covered by these documents can be found in chapter "clean room classes".

DIN EN ISO 14644-1 ▶ This standard relates to "Clean rooms and associated controlled environments". The DIN EN ISO 14644 standard

comprises eight parts. Part 1 deals with the classification of air cleanliness.

US Federal Standard 209E (withdrawn in Nov. 2001) ▶ Although this standard was withdrawn in November 2001, it is still frequently mentioned when defining clean room

classes. It deals with "Airborne Particulate Cleanliness Classes in Clean Rooms and Clean Zones".

Guideline VDI 2083 Sheet 1 ▶ Guideline VDI 2083 (the German association of engineers) Sheet 1 of this guideline relates to clean room technology

and "particulate air cleanliness classes".

EU GMP guidelines ▶ These guidelines form part of the EU legislation on medicinal products and are therefore used mainly by the

pharmaceuticals industry. GMP stands for "Good Manufacturing Practices". The legislation consists of several volumes. Volume 4, "Good manufacturing practice (GMP) guidelines", deals with the classification of clean rooms.

12 Use in special operating conditions | Clean room


Terms

Important terms used in clean room technology are explained below using the definitions given in VDI 2083 Sheet 1.

Classification ▶ Distinction of classes of air cleanliness by defining limits. The limit of a class is the maximum permissible particle

concentration for a specified particle size.

Particle ▶ Solid or liquid object with defined physical borders and a particle size of at least 0.1 µm, but no more than 5 µm.

Particle size ▶ Diameter of any particle, determined by comparison with defined reference particles.

Particle concentration ▶ Number of individual particles per unit volume of air.

Clean area ▶ Area within a room, an installation, or a machine, where the conditions are specified as for a clean room, and which

may be enclosed by a further area.

Clean room ▶ Room with a defined concentration of airborne particles, so designed and used as to minimize the number of particles

carried into, or generated in, the room, and deposited in the room, and where other parameters relevant to cleanliness, such as temperature, humidity, and pressure are controlled as required.



Clean room classes

This chapter provides an overview of the different classification systems for clean rooms according to the defined specifications.

As per DIN EN ISO 14644-1:Selected airborne particulate cleanliness classes for clean rooms and clean zones

Classification of air cleanliness based on the particle concentration

ISO classification number (N)

Maximum permissible concentration limits (particle/m3) equal to and larger than the considered sizes shown below

0.1 µm 0.2 µm 0.3 µm 0.5 µm 1.0 µm 5.0 µm

ISO Class 1 10 d) d) d) d) e)

ISO Class 2 100 24 10 d) d) e)

ISO Class 3 1,000 237 102 35 d) e)

ISO Class 4 10,000 2,370 1,020 352 83 e)

ISO Class 5 100,000 23,700 10,200 3,520 832 d),e)

ISO Class 6 1,000,000 237,000 102,000 35,200 8,320 293

ISO Class 7 c) c) c) 352,000 83,200 2,930

ISO Class 8 c) c) c) 3,520,000 832,000 29,300

ISO Class 9 c) c) c) 35,200,000 8,320,000 293,000c) Due to the very high particle concentration, information on concentration limits is not available in this table section.

d) Sampling and statistical limits for particles at low concentrations are not suitable for classification.e) Sample collection limits for particles at low concentrations as well as for particles larger than 1 µm are not suitable for classification due to possible particle losses in the

sampling procedure.

As per US Federal Standard 209E: ▶ Here, particle measurement is in cft (1 cubic foot = 28.3 liters). Correspondences between the classification systems

are shown further below.

EU GMP guidelines:Classification according to EU-GMP Directive

Particulate air cleanliness class

Maximum particle concentration value(particles equal to or larger than the particle size per cubic meter of air)

Idle (at rest) Operation

0.5 µm 5.0 µm 0.5 µm 5.0 µm

A 3,500 1 a) 3,500 1 a)

B 3,500 1 a) 35,000 2,000

C 35,000 2,000 3,500,000 20,000

D 350,000 20,000 not specified b) not specified b)

a) The cleanliness classification (room classification) in accordance with the EU GMP is fundamentally different from that in DIN EN ISO 14644 and VDI 2083 as concerns the reference particle size 5 µm (classes A and B, at rest) and the sample volume 1 m³. Strict proof of the EU GMP room classes by applying the methodology and statistics of these technical rules can therefore only be given for classes C and D.

b) The requirements and limits for this area depend on the type of processes to be performed.



Comparison between the different standards and guidelines

Designation Maximum permissible number of particles per cubic meter as per DIN EN ISO 14644-1

DIN EN ISO 14644-1 1)

EU GMP guidelines 1)

US Fed. Std. 209E SI 1) ≥ 0.1 µm ≥ 0.2 µm ≥ 0.3 µm ≥ 0.5 µm ≥ 1.0 µm ≥ 5.0 µm

1 10

2 100 24 10

3

M1.5 (1) 2)

1,000 237 102 35

1,240 265 106 35

4 10,000 2,370 1,020 352 83

M2.5 (10) 2) 12,400 2,650 1,060 353

5

A / B

M3.5 (100) 2)

100,000 23,700 10,200 3,520 832

3,500

26,500 10,600 3,530

6

M4.5 (1,000) 2) 1,000,000 237,000 102,00035,20035,300 8,320

293247

7

C M5.5 (10,000) 2)

352,000 83,200 2,930

350,000 2,000

353,000 2,470

8

D M6.5 (100,000) 2)

3,520,000 832,000 29,300

3,500,000 20,000

3,530,000 24,700

9 35,200,000 8,320,000 293,000

1) Consider different occupancy states (example is "at rest").2) Classification based on cubic foot.



General and product-specific recommendations

There are general recommendations for use of Rexroth products in a clean room which can contribute to the reduction of the particle emission, regardless of product. This chapter includes tips that are only valid for special products and individual sizes.

It is important to know that the topic of clean rooms cannot be viewed "linearly". Due to very complex processes, the clean room class will basically not deteriorate if, for example, the travel speed is increased. This happens in most but not all cases. Depending on the linear motion components or systems, the particles can be distributed more evenly at higher travel speeds. By this, a better clean room class may be achieved.

Furthermore, a clean room class must not be derived from the installed individual components for a linear motion system as the particles are distributed differently. Linear motion systems are frequently assessed slightly better than the installed components.

Preferred product versions for clean room use

Preference should be given to certain product versions for use in clean room applications. The following points are especially advantageous to achieve improved clean room capability with our standard products.

Corrosion-resistant steelThe use of corrosion-resistant steel prevents the release of particles which would otherwise occur with incipient or progressive corrosion.

Surface coatingsIf corrosion resistant steel cannot be used, surface coating may be a suitable alternative.

LubricantJust as with standard applications, lubricated (preferably grease-lubricated) linear guides should be used for clean rooms. Clean room compliance tests were conducted with the standard lubricants normally used by Bosch Rexroth. The results are shown in the "Classification results to date" chapter.In principle, all lubricants from Bosch Rexroth are suitable for use in clean rooms. At the molecular and atomic level, however, there is always an emission that may have to be considered for the application.



Factors influencing clean room classification

There are several different factors influencing clean room classification for Linear Motion Technology products.The most important of these are:

Travel speedIn most measurements, the travel speed has the greatest influence on the result. With higher travel speeds, more turbulences occur and the frequency of contacts between friction partners increases. With higher travel speeds, the temperatures are increased as well. In this way, there is a decrease in viscosity of the grease and more lubricating particles will be released.

AccelerationThis parameter has no impact on the clean room class in so far as more strokes can be moved at higher accelerations and consistent duty cycle. With every stroke, a certain number of particles is released. When increasing the number of strokes, the number of particles is increased as well.

LoadThe number of particles increases as the load increases. A higher load results in higher friction between the moving parts and therefore abrasion. With higher loads, lower clean room classes are to be expected. The weight of conveying means and conveyed material for clean room applications must be kept as low as possible.

Duty cycleThe duty cycle has a significant impact on the particle emission. No (or significantly reduced) additional particles are generated in pause times. Tests have shown that the particle emission is reduced by a factor of 10 when reducing the duty cycle from 100 to 10 %. This leads to an improvement by one clean room class.

Lead (with screw drives or linear motion systems with screw drives)The centrifugal force releases the lubricant particles which must be reapplied when the spindle passes through the nut. The centrifugal force is directly proportional to the square of the travel speed and therefore to the square of the rotary speed. This means that the centrifugal force is quadrupled due to the doubling of the rotary speed. More and larger particles are released. Therefore, a screw drive with a high lead should ideally be chosen for clean room applications.

Installation position (relative to the air flow)Clean rooms often have laminar air flow. These currents flow around the individual components. Depending on the installation position, the air flow can cause less or more particles to be released. This can be explained in graphic terms when one considers a drilled hole. If the air flows sideways across the hole, fewer particles will be detached from the inside of the hole than if it flows directly into the hole.

GeometryEach part and component in the clean room hinder the air flow. A fast and controlled discharge of generated airborne particles is required in order to support the laminar air flow in the clean room. A flow-optimized construction is beneficial to prevent impound, eddy and wake spaces. However, it is not easy to put this into practice.



HeatHeating leads to increased particle emission. This has an impact on the emission of lubricating particles and the motor attachment area in linear motion systems. The internal molecular motion of the particles increases at higher temperatures. Due to the reduced viscosity of the grease lubricant, individual particles are released from the grease mixture more easily. If the temperature increases due to a longer and constant load, there will be a buoyancy above the motor. If there are any particles, they will not be removed downwards with the laminar air flow but whirled up. Tests have shown that more particles are generated above the electric drive unit than below it. If, for example, a linear motion system is installed horizontally, this aspect is less interesting as the particle emission of the motor attachment has little impact on the work point. However, the position of the motor must be observed if the linear motion system is installed vertically. So far, Rexroth did not carry out any tests on the better positioning of the motor above or below the system.

LubricationTests at Fraunhofer IPA have shown that the particles in a linear motion system with ball screw drive consist of a metal/grease mixture. The particles are released by the rotary motion of the ball screw drive. Overlubrication leads to increased particle emission. If there is too little lubrication, the particles cannot be bound and the clean room is increasingly contaminated.

ExtractionIdeally, exhaust (suction) systems can remove any particles from the clean room directly at the point where they are generated. Furthermore, the exhaust system in linear motion systems ensures that there is a vacuum in both chambers in front of and behind the carriage. In this way, hardly any contaminated air escapes and the clean room classes usually improve. For this, however, an extraction on both sides of the carriage (ideally at the end of the frame) is required.



The air flow may affect the required ISO class at the work point. At this point, the best possible classification is usually required whereas lower ISO classes may be sufficient at other positions.

Air flow in clean room environments

In clean rooms with higher clean room classes (ISO 6 to 9), there often is a turbulent mixed air flow; in clean rooms with lower ISO classes, there is a laminar air flow for a directed discharge of the particles. Following air flows are possible in clean room environments:



Not product-specific possibilities for improvement

There are potentials for optimization applicable to all available types and sizes for linear components, linear motion systems and electromechanical cylinders.

Vacuum extractionPerformed tests have shown that the particle emission is reduced by extraction of the interior. An extraction is very helpful at low travel speeds. This partially led to an improvement of up to two clean room classes. At higher travel speeds, greater accumulation pressure in the system interior is generated which must be countered by the vacuum extraction. Therefore, ports for extraction on both ends of the linear motion system are recommended.

A vacuum or the suction volume flow are key parameters for air extraction. The higher the vacuum or the suction volume flow, the more effective the vacuum extraction. However, the generation of a high vacuum or suction volume flow is associated with high energy costs.So far, Bosch Rexroth does not offer linear motion systems with air extraction. If they are still to be equipped with an air extraction, it is recommended to install it in the places where the particles are released. In belt-driven systems, for example, this would be as close to the end enclosures as possible.

Particles are generated by recirculating the toothed belt. By drilling the end enclosures, it is ensured that the overpressure is reduced or that the vacuum is generated throughout the entire stroke.

EnclosuresEnclosures do not reduce the number of generated particles but prevent them from being emitted into the clean room environment. The particles are therefore not detected. A bellows around the ball screw assembly, for example, protects the clean room environment. The bellows depends on the particles; they stick to the bellows. The prerequisite for this is that the bellows itself does not emit any particles.

Some competitors enclose their motor. Due to the heat dissipation of the electric drive unit, there are local temperature differences in the clean room. There is a buoyancy above the motor. The competitors build a flow-optimized enclosure for the drive unit. It must be ensured that the motor is sufficiently cooled with an enclosure.

Closing of openingsOn the motor attachment, there are holes and slots on the various variants of linear motion systems for mounting the coupling or the belt side drive. Forces and torques are transmitted in these areas of the system which leads to abrasion and increased particle generation on the dynamic elements. The emission of particles is prevented by covering the holes (e.g. with a plastic mounting hole plug or adhesive tape).

If the holes are located on the bottom side, they are in a dead zone and the particles are not carried out of the clean room. Depending on the installation position of the linear motion systems, it must be ensured that the holes are not positioned in the dead wake of the clean room during clean room applications.



If possible, it should be ensured that the applications are optimized regarding the clean room suitability. Machines, incl. the used linear units with additional components, are suitable for clean rooms if they have little impact on the laminar air flow.

If possible, wires should not be able to move and not rub against each other or other components. There are special energy chains for use in the clean room. Standard products are not suitable. Ideally, energy chains are not used at all or arranged below the work point.

The motor attachment is often significant for the classification. An encapsulated construction contributes to the improvement.

Product-specific recommendations

Lead of screw drivesThe highest lead possible should be used, as the rotary speed is reduced at the same travel speed. Therefore, fewer particles are emitted into the environment radial to the screw axis.

Drive with linear motion systemsBelt-driven linear motion systems should be preferred for the application in a clean room. Due to the rotary motion of the screw, screw drives lead to a higher particle emission. When using linear motion systems with a screw drive in a clean room, a high lead should be chosen to reduce the rotary speed.

Motor attachment for linear motion systemsThe motor attachment in linear motion system often has a high particle emission. This is due to the openings on the flange. The clean room suitability can be optimized by covering the openings and holes. The belt side drive which is generally better encapsulated should be preferred over the motor attachment variant with flange and coupling. The material pairing aluminum/plastic (coupling) is not suitable for applications in a clean room, especially if forces and torques are to be transmitted. This leads to abrasion and particle emission.

Other notes

For clean room applications, the following points should be considered. ▶ For applications with clean room requirements, it is very difficult to make any general statement about whether

products from Rexroth will comply with a particular clean room class. Detailed information about the application should be obtained in order to be able to make as accurate an estimation as possible based on past experience. This information includes travel speed, duty cycle, loads, installation position and the type of exhaust systems.

▶ If certification, including documentation, is requested, the reason for making this request should be investigated in all cases. For a complete machine installed in a clean room, certification of the entire system should be considered. In this case, the behavior of the individual components is normally of secondary importance.

▶ If a clean room application also includes specifications for operation under vacuum, the notes given in chapter "Vacuum" should be considered as well as the above.

Further constructive measures



Tested products from DC-LT

Currently, Rexroth does not offer any products specially developed for clean rooms. However, many serial products are suitable for applications in clean rooms without special preparation.Rexroth had the suitability of a selection of linear components, linear motion systems and actuators tested at Fraunhofer IPA or Assembly Technology (DC-AT). IPA or DC-AT certificates which may be provided to customers are available for all test pieces listed in chapter 4.5.

According to the standard, derivations to products of similar series and sizes are not permissible. However, it has been shown in practice that comparisons can be made in such cases.

All tests were conducted at a duty cycle of 100 %. Shorter duty cycles may lead to better results (see chapter "Factors influencing clean room classification"). Other installation positions or travel speeds require retesting in order to be able to draw accurate conclusions.If in doubt, users should contact Rexroth for advice. The last chapter contains a checklist developed specifically for this purpose, which can be submitted along with inquiries.The certificates specified in this chapter are valid for all listed products from Rexroth which did not undergo a design modification after September 2020 that could influence the clean room behavior.

Profiled rail systems and integrated measuring systems

* based on BSHP



Screw drives

Linear motion systems and electromechanical cylinders

23 Food zone | Use in special operating conditions


Food zoneDirectives and standardsIt is important to understand the legislation affecting the food processing and packaging industry in order to ensure compliance with the special requirements and demands applying to this industry, thus avoiding unnecessary risks.

International standards

ISO 14159 ▶ This is a standard on hygiene requirements for the design of machinery. It covers

several areas, including food processing. It complies with the 3-A standards and is similar to European Standard EN 1672-2.

ISO 8086 ▶ A general guide to inspection and hygiene regulations for dairy plants.

European Union directives and standards

European machinery directive 2006/42/EU ▶ This directive contains the requirements for machine safety from the design perspective and deals with the safety of machine operators. Safety means, primarily, the avoidance of risks and, secondly, protection against risks. Machinery manufacturers label their machines with the CE mark themselves and bear full responsibility. There are also hygiene requirements applying to the food processing industry, such as ease of cleaning and smooth surfaces.

EN 1672-2 – Standards for machinery used in the food industry ▶ Food processing machinery – Safety and hygiene requirements – Basic concepts – Part 2: Hygiene requirements.

While the European machinery directive concerns only the safety of the operator, this standard contains measures for avoiding risk both to the operator (1672-1) and the consumer (1672-2). The standard applies to all machinery used in food production. In addition to continuous production, it covers batch processing, whether in open or closed processes.

Regulation (EC) No. 852/2004 on food hygiene ▶ This regulation includes rules on the maintenance and control of hygiene in the food processing industry (see HACCP).

Regulation (EC) No. 10/2011 on plastics ▶ Indicates which plastics are permitted in the food processing industry.

24 Use in special operating conditions | Food zone


EN 415 – Safety of packaging machines ▶ This standard, still partly in preparation, will cover the safety requirements for the design, construction, installation,

commissioning, operation, adjustment, maintenance, decommissioning and scrapping of various types of packaging machines and equipment.

Other standards and guidelines ▶ DIN 10516: This draft standard offers guidance for selecting and implementing suitable measures for cleaning and

disinfecting machinery and equipment used in the food processing industry. ▶ ISO 20653: Standard for electrical equipment in road vehicles, defining the protection ratings provided by enclosures

against external influences (IP codes).

Organizations

There are several organizations worldwide that can be contacted for detailed information.

FDA ▶ The mission of the United States Food and Drug Administration (FDA) is to promote and protect public health in the US

by helping safe and effective products to reach the market in a timely way and by monitoring products for continued safety after they are in use. The Code of Federal Regulations published by the FDA is an important reference for approved engineering materials.

3-A ▶ The Sanitary Standards Symbol Administrative Council, known in the industry as the 3-A, grants authorizations to use

thie 3-A symbol on dairy and food equipment that meets 3-A Sanitary Standards for design and fabrication. ▶ Based in the US, this organization has considerable experience in setting up voluntary standards for the food

processing industry, particularly the dairy industry.

EHEDG ▶ The European Hygienic Engineering & Design Group is an independent group that works on establishing important

guidelines and methods of testing for preserving safety in the food production process. The group consists of representatives of machine manufacturers and representatives of the relevant authorities.



Hazard analysisThe Hazard Analysis Critical Control Point (HACCP) system is considered an effective and rational procedure for guaranteeing the safety of food products. According to Regulation (EC) No. 852/2004, this hazard assessment must be applied to food production. The aim is not, however, to establish one specific HACCP plan for specific products. Instead, HACCP systems have to be set up by each individual manufacturer and adapted to the specific processing conditions.

Definitions

Control Point (CP) ▶ This term signifies each point or each process in a specific food processing system that, if not controlled, will not lead

to an unacceptable health hazard.

Critical Control Point (CCP) ▶ This term signifies each point or each process in a specific food processing system that, if not controlled, will lead to an

unacceptable health hazard.

Special hazards

HACCP should uncover special hazards (biological, chemical and physical).

Biological hazards ▶ The first of the three hazard classes covers biological and microbiological hazards and can be subdivided into three

more classes: bacteria, viruses and parasites (protozoa and worms).

Chemical hazards ▶ A chemical is a substance which is either used in a chemical process or results from such a process. All food products

are made up of chemicals, and all chemicals can, depending on the quantity, be toxic.

Physical hazards ▶ Physical hazards are often described as external substances or foreign bodies. This includes any physical material

that does not occur naturally in food and can lead to illness (including psychological trauma) or personal injury (Corlett, 1991).



Structure of the HACCP plan

As an example, an HACCP plan can consist of seven parts. Other alternatives are possible.

Hazard analysis ▶ All possible hazards must be identified and classified according to type. It is also necessary to show how these hazards

can be avoided.

Determination of Critical Control Points ▶ The Critical Control Points (CCPs) for each production process have to be determined.

Establishment of limits ▶ The limits or limiting criteria of each CCP must be established.

Removing or monitoring CCPs ▶ The first solution is to remove the CCP. If this is not possible, a system needs to be set up for monitoring the CCPs

(e.g., who monitors which CCP and how often).

Stipulating corrective measures ▶ Corrective measures need to be determined in case the limits/limiting criteria are not observed.

Establishing routines ▶ Routines must be determined to ensure that the stipulated processes and measures are observed. (monitoring of

CCPs: establishing limits; removing or monitoring CCPs; stipulating corrective measures).

Drawing up of documentation ▶ The HACCP system must be documented.

Product requirements for specific areasDifferent requirements apply to different processing areas. For Linear Motion Technology components, this means a variety of specific requirements that products must meet.Components used in the food production process must be easy to maintain in order for precautions to be taken against microbiological contamination. This means the components must be easy to clean and must be protected against contamination.In general, it is unusual for Linear Motion Technology components to come into contact with food. If they do, however, the surfaces must be resistant to the foodstuff. In addition, these surfaces must be easily accessible to allow both visual inspection and manual cleaning.



Production areas

The EN 1672-2 standard defines three different zones which pose different requirements for selecting Linear Motion Technology components.

Food zone ▶ This zone includes all surfaces that come or could come into contact with food where there is a risk of food

splash returning into the food process. In addition to the general requirements, the materials used must be corrosion-resistant and non-absorbent. The design must permit thorough and complete cleaning, with a surface

finish which will prevent particles from remaining in small cavities. The use of bolts, screws, etc. should be avoided. The surfaces should be self-draining and without dead spaces. Food grade lubricants should be used. These requirements also apply to other areas if there is a risk of cross-contamination.

Splash zone ▶ This includes surfaces where the food may splash or flow along, but where there is no risk of it remaining in

the food process. The requirements on materials and design are similar to those for the food zone but somewhat less stringent.

Non-edible lubricants may be used, provided that this has no adverse effect on the food product.

Non-food zone ▶ All zones that are not food zones or splash zones. General requirements apply here. Any exposed surfaces

should be made of corrosion-resistant or corrosion-protected materials. The surfaces should be easy to clean and self-draining wherever possible.

Working zones

Regardless of the type of production zone, components should be selected as appropriate for dry or wet zones. These zones can be defined as follows.

Wet working zones ▶ Zones in which liquid, moist or sticky food flows around the machine parts, or areas which are wet-cleaned or

disinfected. Linear Motion Technology components must be selected having regard to their exposure under known conditions of pressure and time.

Dry working zones ▶ Zones in which no water or wet media can come into contact with machine parts and where the relative

humidity is equal to that of the normal area (up to 70%).



CleaningWhether dry or wet cleaning is used, the cleaning process is a basic requirement for hygiene in the food industry.

Material selection

The choice of materials for machinery and equipment in the food processing and packaging industry depends on the detergents and cleaning methods used. Looking at the matter another way, good hygienic design enables cleaning to be done in a shorter time, at lower temperatures and with less aggressive detergents, thus saving time and expense.To select the right components for a specific application so that they will withstand the cleaning process, the components should be judged by their corrosion resistance, hygienic suitability and their electrical protection rating.

Detergents

Cleaning of food machinery and equipment must take place in accordance with the manufacturer’s instructions. Detergents, too, must be used as directed by the manufacturer. It is important that materials, detergents and cleaning methods are compatible with each other.

The rankings given on the following page are based partly on information from leading detergent suppliers and partly on our own practical experience. The most important exceptions to the above in our experience over the years are as follows:

If POM plastic (polyoxymethylene) is not properly dried after cleaning with acid, there is a risk of formaldehyde being formed. In general, the characteristics of plastics differ from case to case and from grade to grade. The risk of absorption must therefore be considered. Our own experience with plastics in the food industry is better than the tables normally indicate.

Carbon steel is resistant to alkaline cleaning. The difference between corrosion-resistant steel and carbon steels becomes very noticeable in strongly acidic environments. However, phosphoric acid is commonly used in detergents, and low-grade steels such as AISI 420 can withstand this for short periods. It must be remembered that detergents usually contain inhibitors which protect the material.One of the biggest risks is galvanic corrosion, which occurs when, for example, stainless steel comes into contact with aluminum in a wet environment. This occurs, for example, when corrosion-resistant steel is placed in contact with aluminum in a wet environment. Aluminum cannot withstand either strongly alkaline or strongly acidic conditions. Its resistance can be improved by anodizing or coating, but improvement will depend on the quality of the surface treatment.Generally, surface treatment is good, as long as the coating remains intact. If it is damaged, this can increase the rate of corrosion.



Corrosion resistance classes Hygiene classes Protection classes

Class Materials Class Design Class Protection against touch, foreign bodies and water

1 - acid-resistant, stainless steel- plastics, e.g. PVC, polyethylene, PTFE, silicone rubber

1 Hygienic design- smooth surfaces (no cracks or pores)- rounded corners and edges- no dead spaces- self-draining

1 High IP67 (4) rating. Protection against dust, water and detergents. Water must not enter when the operating equipment is immersed in water under specified conditions of pressure.

2 - hard chrome plated steel- Steels like e.g. AISI 420.430F- nickel-plated steel and brass- chemically nickel-plated and anodized aluminum- plastics, such as polyamide 6.6, POM, rubber, PU, nitrile rubber, NBR, Perbunan

2 Clean construction- there are some dead spaces- self-draining

2 Medium IP65 (4) rating.Protection against dust and splash water. A jet of water spraying from all directions onto the operating material must have nodetrimental effects.

3 - galvanized steel- bronze, brass, zinc- plastics such as polycarbonate- untreated aluminum

3 Standard design- no complete avoidance of dead spaces- very easy-to-clean cleaning

1 = Excellent, 2 = Good, 3 = Normal Possible areas of application for linear motion technology components.



Hygienic designThe following are essential factors to ensure appropriate hygienic design in terms of the hazard zones defined in, e.g., the HACCP system.

Bearings ▶ Unless absolutely unavoidable, bearings should not be installed in food contact zones. Bearings used in food zones

must be lubricated with food grade lubricants and installed so as to permit free-flow cleaning and disinfection.

Gaps and crevices ▶ These have a detrimental effect on cleaning due to surface defects, such as scratches and cracks. Smooth surfaces in

compliance with operational and hygiene requirements are preferable in this respect.

Dead spaces ▶ Spaces in which a product, ingredient, cleaning or disinfecting agents or soil can be retained or incompletely removed

during cleaning must be avoided or designed so that they are drainable and easy to clean and disinfect where required.

Outlet ▶ Self-draining design and finish that prevent any liquids from remaining. If not otherwise possible, easy methods for

removing residual liquid should be ensured.

Threaded fastening elements ▶ Fastening elements, such as screws, bolts, rivets, etc. are hygienically risky and should be avoided. If unavoidable,

they should be placed so they are easy to clean and disinfect.

Inside angles and corners ▶ To ensure optimum flow rates of cleaning and disinfecting agents as well as to avoid hazards, corners should have

a suitable radius and narrow angles should be avoided.

Connections ▶ A direct metal-to-metal joint should be avoided, or if the joint is permanent, it should be continuously welded and free

of imperfections. Removable joints must be truly hygienic.

Seals ▶ Sealing off or filling in an area to prevent unwanted penetration or emergence of materials.



Lubricants for food industry applicationsBasic principles

The NSF (National Sanitation Foundation) follows the same practice as previously applied by the FDA (Food & Drug Administration), and classifies lubricants for the food industry into two categories, in accordance with the specifications of the USDA (United States Department of Agriculture):

H1 H2

Permissible for incidental contact with foods. Permissible in food industry applications, but not for direct contact with foods.

Products approved according to Category H1 can be used as lubricants, release agents or anti-corrosive preservative films for devices and machine parts which may come into incidental contact with foods. Only as much lubricant as is necessary to achieve the desired technical effect may be used. Anti-corrosive preservative films must be completely removable without residues.Products approved according to Category H2 can be used as lubricants, release agents or anti-corrosive preservative films for devices and machines in applications where there is no possibility of their coming into contact with foods.The NSF approval certificate for Category H1 or H2 products contains an NSF registration number alongside the product designation.FDA approvals do not contain the H1 or H2 code, but a descriptive text.Approvals remain valid and are internationally recognized as long as the products correspond to those approved and have identical designations.

Suitable lubricants for Rexroth Linear Motion Technology products

Before selecting a lubricant, an analysis is made using the HACCP system to establish whether there is any risk of food contamination.If a risk cannot be excluded, NSF H1 lubricants must be used. NSF H1 lubricants are food grade lubricants and are legally acceptable, are not damaging to health, have a neutral taste and are internationally recognized.This means food grade lubricants simultaneously satisfy technical, chemical and microbiological requirements, while their performance is comparable to that of normal industrial lubricants.

At Bosch Rexroth, various lubricants have been tested for their tribological suitability for use in our products and compatibility with the plastic parts used (in particular, the material of the ball chain), and classified as suitable.Information on the tested lubricants can be supplied by Bosch Rexroth upon request. If these lubricants are employed, users should be aware that the relubrication intervals will be up to 50% shorter than those stated in the catalog data.

Miscibility and preservation

H1 lubricants or release agents (preservatives) only have H1 approval in neat, i.e., unmixed condition (including at the point of lubrication). A mixture of two H1 approved lubricants does not have H1 approval.



Plastics in food industry applicationsAlmost all of the plastics used in Rexroth products do not have BGA, FDA or NSF approvals for use in food industry applications (exception see "Bosch Rexroth products for use in Food & Packaging").

Other notes▶ Rexroth products cannot be used for direct contact with foods.▶ In "indirect" zones (i.e., where there is no possibility of direct contact with foods), Rexroth products can be used,

provided this has been agreed in close consultation with the customer (see also chapter "Bosch Rexroth products foruse in Food & Packaging").

▶ Peripherals and bought-in parts, such as bearings, gears, etc., must be checked for suitability for food industryapplications (lubricant, plastics compatibility) → to be determined in consultation with manufacturers, vendors.

▶ In the food industry, the products are often exposed to attack by acids (milk, apple juice).For this reason, corrosion resistant steel is used. Coatings generally do not suffice. Aluminum materials should also beavoided.

▶ Some manufacturing systems are cleaned with high-pressure equipment and special cleaning agents. The cleaningagents in particular can have a very detrimental effect on the plastic parts (degradation, swelling) and on the steel(corrosion) used. The majority of our products have not been designed to withstand these. It is therefore essential tocheck on a case-by-case basis.

▶ Deposits or accumulations (e.g., on ball guide rails) must be monitored. Linear Motion Technology products shouldtherefore be appropriately protected.

▶ Minor contamination of the lubricant due to abraded plastic particles (seal wear) must always be expected(see illustration). Dripping or spinning off of the lubricant can result in contamination of foods or components that arein direct contact with foods.

▶ Remedy: Precautions must be taken to prevent contaminated lubricants from coming into contact with foods orcomponents that are in direct contact with foods through dripping, spinning off or by any other means.

Lubricant contamination due to plastic abrasion on the guide rail

33Food zone | Use in special operating conditions


Bosch Rexroth products for use in Food & PackagingFor use in the packaging industry and in food industry zones, Bosch Rexroth has developed the NRFG ball rail system and the EMC-xxx-xx-2 electromechanical cylinder.

NRFG ball rail system in production zones as per EN 1672-2

This ball rail system is made exclusively of corrosion-resistant steel in accordance with DIN EN 10088 and AISI/NSF51, and the plastics TPE and POM. The plastic parts are made of material certified under Regulation (EC) No. 10/2011 on plastics and FDA 21 CFR.

Food zone▶ The use of NRFG ball rail systems is not permissible, because:

– Gaps/crevices and dead spaces are present by design.– It is not possible to completely clean the NRFG ball runner block.– The surfaces of the NRFG ball rail systems are not self-draining.– There is a hazard of food splash returning to the food process.

Splash zoneThe use of NRFG ball rail systems permissible with restrictions, if:– The adjacent assembly as a separating guard or covering for the NRFG ball rail system to protect it against food splash.– Viscid and acidic liquids do not come into contact with the NRFG ball rail system.

Non-food zoneThe use of NRFG ball rail systems in the non-food zone is permissible, when:– The zones are not food or splash zones.– General requirements apply.– Exposed surfaces are made of corrosion-resistant materials.– The surfaces are easy to clean and self-draining wherever possible.

Regardless of the type of production zone, NRFG ball rail systems should be selected as appropriate for dry or wet working zones.

Wet working zones▶ NRFG ball rail systems in these zones should have an adjacent assembly with a separating guard or cover.

Dry working zones▶ The use of NRFG ball rail systems is permissible.



Electromechanical cylinder EMC-xxx-xx-2

The hygienic design of the EMC with smooth surfaces prevents the formation of dirt and allows for easy cleaning of the cylinder. Initial lubrication with NSF H1 grease is available as an option.If the IP65 housing option is selected, the cylinder complies with IEC 60529, meaning it is sealed against dirt and water jets.The IP65+R (resistant) option offers additional chemical-resistant seals between the cap/barrel and the aluminum profile. The material for the piston rod seal is compatible with all water-based and alkaline cleaning agents and complies with FDA 21 CFR 177.1520. The lube connection, the port for pressure compensation and the hexagon nut are made of stainless steel.

35 Vacuum | Use in special operating conditions


VacuumBasic principlesA vacuum is the state of a gas when the pressure of the gas is less than 300 mbar, i.e., lower than the lowest atmospheric pressure occurring at the Earth’s surface (1 mbar = 100 Pa = 1 hPa; 1 Pa = 1 Nm-2).

Vacuum range Pressure [mbar]

Low vacuum (LV) 1000…1

Medium vacuum (MV) 1…10-3

High vacuum (HV) 10-3…10-7

Ultra high vacuum (UHV) < 10-7

Source: DIN 28400 Part 1

This is associated with the undesirable effect of outgassing. This effect occurs under vacuum when the kinetic energy of the particles is greater than their bonding energy. Outgassing is the term generally used to describe the release of gases from liquid or solid substances. It involves the following phenomena:

▶ Desorption: This is a process in which foreign atoms/molecules (mostly H2O) detach themselves from the surface of a solid body (the reverse of adsorption). The desorbed particles possess enough energy to overcome the energy of the bonds holding them to the solid body. Desorption primarily occurs on the surface of solid bodies.

▶ Evaporation: This is the transition between the liquid and the gaseous state of a pure substance at boiling point or the transition between the liquid and the gaseous state of a mixture of substances (e.g., oils, plastics) around the boiling point. The difference between boiling and evaporation is that evaporation describes the transition to the gaseous state without reaching the boiling point.

▶ Sublimation: This describes the instantaneous transition of a substance from the solid to the gaseous state. Water freezes during evacuation (the freezing point falls as the pressure drops). The ice that is formed in this way sublimates slowly. This contaminates the vacuum for a long period, which retards the evacuation process.

MaterialsThe following points should be noted:

▶ If the outgassing level is too high, it may not be possible to reach the target vacuum pressure. ▶ Porous surfaces and materials have a greater tendency to outgas. Cast materials in particular have pockets

(internal cavities). Because of this porosity, air can "leak" out and thus disturb or prevent the generation of a vacuum. ▶ Undesirable interactions between the materials introduced into the vacuum and the process taking place in the vacuum

should be avoided. ▶ The ratio of the outgassing of plastics to that of steel ranges between 100 and 1,000. This means replacing plastic

components with steel ones is helpful. ▶ The ratio of the surface area or volume of plastics to the steel surface (incl. tank wall), as well as the ratio between the

lubricant surface or volume to the steel surface can be useful in assessing whether these materials/media could hinder vacuum formation due to their outgassing rate.

▶ Cleanliness is essential, since contaminants themselves as well as any media trapped inside them can outgas.

36 Use in special operating conditions | Vacuum


Plastics and lubricants

The saturation vapor pressure of water at 20 °C is 23 mbar. The starting point for desorption can therefore be considered to be around this level.In plastics and lubricants specifically, outgassing and boiling are variables that depend on pressure and temperature. At room temperature, plastics generally do not pose a problem in a vacuum down to approx. 10-4. For the low vacuum and part of the medium vacuum range, i.e., at pressures down to approx. 10-2 mbar, experience has shown that the standard grease used by Bosch Rexroth is suitable at temperatures up to 40 °C.Under higher vacuum, at certain temperatures and depending on the length of exposure, this standard grease will lose its lubricity due to splitting of the base oil. Greases for vacuum applications therefore frequently use fluorine-based oils with low vapor pressure (polyfluoropolyether, or PFPE).This means such vacuum lubricants should be used in vacuums from 10-2 mbar to 10-6 mbar, or at pressures down to 10-2 mbar and temperatures above 40 °C, but their compatibility with our products must be checked first. These lubricants must meet the following specifications or have the following properties:

▶ Suitability for lubricating ball bearings ▶ Ideally also function as corrosion protection ▶ Heat resistance ▶ Lowest vapor pressures over a broad temperature range ▶ Chemical resistance to the media present in the vacuum ▶ Low water absorption rate ▶ No interactions between the lubricant and the plastic parts coming into contact with it

Before using these lubricants, the point being lubricated must be cleaned with a cleaning agent that is compatible with the lubricant being used. Switching from one type of lubricant to another is not possible during operation, since the there must be no mixing of lubricants. Rexroth products being used in vacuum applications should not be provided with conventional preservatives in order to prevent interactions with the vacuum lubricant and contamination of the vacuum.The lubrication intervals stated in the product catalogs do not apply when used under vacuum.Outgassing can cause lubricants to lose their lubricity (thus becoming useless) and may cause plastics to change dimensions or become brittle, as well as disturbing the formation of the vacuum. In addition, the air quality may be negatively affected or contaminated (see chapter "Clean room").The process taking place in the vacuum should tolerate hydrocarbons to ensure that any outgassing lubricant does not disturb the process.In principle, all lubricants are suitable for use under vacuum. The desired vacuum range defines the type of lubricant. The following chart shows the vacuum ranges where standard lubricants can be used and those where low-boiling lubricants must be used.

UHV HV MV LV

Vacuum range 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 10 102 103 mbar

10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 10 102 103 104 105 Pa

Low-evaporation lubricants Standard lubricants

No mixing of lubricants.Parts must be cleaned before lubrication.

Closed-pore lubricant insert required (hardening).

Standard productsLV … low vacuum

MV … medium vacuumHV … high vacuum

UHV … ultra high vacuum

37 Vacuum | Use in special operating conditions


Metal materials

For vacuum applications, corrosion-resistant materials are preferred in order to avoid the risk of corrosion. The reason for this is that a rust layer is very porous, which leads to a greater rate of outgassing.Aluminum should preferably not be anodized because the anodizing layer also has a very porous structure.

Linear Motion Technology products under vacuumDue to the interactions between all factors (material, lubricant composition, pressure, temperature, media involved in the process, etc.), it is not possible to make any generalized statement regarding the suitability of all products for use in a vacuum. Products should be checked for suitability on a case-by-case basis (cf. chapter "Plastics and lubricants").

The critical factor is the outgassing rate of the individual components, which can vary considerably according to the material, pressure and temperature involved. This may make it impossible to reach the required vacuum level and/or to keep the atmosphere in the evacuated container free from contaminants. Generally, the suitability of Rexroth products for use under vacuum is limited by the suitability of the plastics and lubricants (cf. chapter "Plastics and lubricants").

Ball chains may not be used under vacuum since they are subjected to high mechanical stress, and embrittlement could lead to premature failure of the runner block.Regarding the effect of temperature (upper limit or temperature-dependent vapor pressure), metal materials should be preferred over plastic materials. Considering the effect that corrosion of these parts can have, versions made of corrosion-resistant materials are ideal. Products which meet both conditions include Rexroth ball screw assemblies (with steel recirculation elements) and standard linear bushings, in both cases made of corrosion-resistant steel and without seals.

For profiled rail systems and linear motion systems, there are currently no versions without plastic parts available, but their use under vacuum is conceivable, provided all boundary conditions are properly assessed. The metal components of profiled rail systems and linear motion systems are usually available in corrosion-resistant versions. In all cases, particular attention should be paid to the lubricants.

The IMS Integrated Measuring System should not be used in a vacuum. Pressure differences of up to only 200 mbar can be tolerated, otherwise the sensor plate will deform. The sensor housing is made of anodized aluminum and the effects of a vacuum on the printed circuit board (PCB) have not been studied.

Design measuresParts, threaded fasteners and other types of connections can contain pockets of air, which may make evacuation difficult or impossible ("virtual" leakage). This can be avoided by sealing or drilling into such cavities (e.g., by cross holes in blind threaded holes to ensure pressure equalization).Wherever possible, plastic parts should be protected against process-related heat radiation and/or heat conductance (e.g., by shielding them from heat radiation) to prevent outgassing.In addition, linear bearings should be protected from process-related contamination in vacuum atmospheres (e.g., very fine, aggressive dusts).

38 Use in special operating conditions | Dry room


Dry roomBasic principlesBattery cell manufacturing places extreme requirements on the production environment. Lithium-ion batteries, for example, are manufactured in environments containing less than 1% humidity, since lithium combined with water vapor and lithium hydroxide produce hydrogen and heat. Humidity over 1% has a negative impact on the quality, performance and endurance of the batteries.

The level of moisture in the air is often expressed by the dew point. The air is first cooled down to the dew point, where condensible air moisture precipitates. The air is then reheated to room temperature and passed into the dry room. This means, for example, that a humidity level of 1% at room temperature can be achieved by first cooling the air to -37 °C. In practice, though, battery cell manufacturing strives for significantly even lower dew points if extreme humidity requirements far below 1% must be met.

Linear motion technology products in dry roomsTo the current level of knowledge, established Linear Motion Technology products are suitable for dry room use. While metallic materials are generally usable in dry rooms, both the lubricant and the plastics used must be tested for suitability. Linear motion system accessories must be tested separately.

Lubricant ▶ There are no issues with using lubricant in a "dry room environment". Just the opposite: Moisture is detrimental to

lubricant, which is why production focuses on low water content.Plastics

▶ Established linear guides and screw drives only contain plastic that is risky for dry rooms (POM and TPE). However, some types (ball screw assemblies, the size 55 ball rail system, certain types of linear bushing) contain plastic parts made of PA.

PA has a relatively high water absorption rate in humid environments. If it "dries out", its dimensions can change and its brittleness increases drastically. This can cause problems in products with PA.

See chapter "Materials used" for an overview of the plastics used in each product.

Linear motion system accessories ▶ Motor and even controller components are sensitive to dry room environments (e.g., coil encapsulation, power

electronics). Information must be obtained from the manufacturer. Switches and wiring must also be checked for dry room suitability.

39 Corrosive environments | Use in special operating conditions


Corrosive environmentsBasic principlesIn order to achieve comparative pretensioning of over 2,000 N/mm² typically required in ball bearings, it is essential to use hardenable materials (e.g., 60 HRC or 700 HV). Normally, these materials will be carbon steels which have been hardened to achieve martensitic structures. However, because of their microstructure, these steels are susceptible to corrosion.If Linear Motion Technology products are to be used in corrosive environments, a check should first be made to see whether the products can be shielded from the corrosive substances. This can be done, e.g., with a bellows.If shielding is not possible, or if the specifications call for higher corrosion resistance, the following two options have proved acceptable when weighing up cost and technical performance factors:

▶ Galvanic coatings ▶ Use of corrosion-resistant steel

Corroded runner block in an extreme test in metalworking fluid

40 Use in special operating conditions | Corrosive environments


Galvanic coatingsYellow chromating (zinc-iron), which was frequently used in the past, is now no longer offered as it contains Chrome VI ions (hexavalent chromium). In the automotive industry, hexavalent chromium is now no longer permitted because of the "End of Life Vehicles" directive. The RoHS directive also prohibits the use of Chrome VI (see chapter "RoHS directive").

Today, the standard coating used at Bosch Rexroth is thin, dense hard chrome plating.

While yellow chromating was an active cathodic corrosion protection, the hard chrome plating relies purely on the barrier provided by the chrome coating to achieve its anti-corrosive effect on steel. As a pure metal, chromium has a low electrochemical potential and corrodes very easily. However, the very thin chromium oxide layer which forms at the surface is thermodynamically very stable and thus prevents any further oxidation of the chromium. This also protects the base metal under the coating from corrosion. Hard chrome layers are resistant to many chemicals. Although chromium coatings do exhibit good resistance to organic acids as well as phosphorus and nitric acid compounds, in view of the thinness of hard chrome coatings, their resistance to acids and alkalis tends to decrease at a faster rate.

The specific difference between classic chrome coatings and a thin-layer hard chrome coating lies in the structure of the coating. A classic chrome coating has microscopic cracks in its structure, whereas the thin-layer hard chrome coating has no such cracks. The special structure is one of the factors which makes the hard chrome layer so hard. The hardest chrome coatings are almost as hard as corundum. They are therefore harder than (case) hardened steels and can achieve the same hardness as the intermetallic bonding layer in nitrided steels. This explains the exceptional abrasion resistance of the hard chrome coatings. Depending on the paired materials, the friction coefficient can be lower than that of other metals and their alloys.

Microcracked hard chrome on heat-treated steel Microcrack-free thin-layer hard chrome coating

During hard chrome coating (Tmax approx. 60 °C) there is no measurable distortion of the workpieces. Chromium is non-toxic and food safe.

The hard chrome-plated versions of our products achieve the same load capacities as the standard versions.

In addition to the described single thin-layer hard chrome coating, it is also possible to modify this coating. Here, a two-layer system is used. The base metal is first protected with a thin, dense hard chrome coating, and a second coating is applied on top of this. The second coating is even thinner than the thin-layer hard chrome coating (down to the nanometer range). Possible choices for the second layer are chromium oxide (thin-layer hard chrome coating Duralloy-LC "black") and silver.



Use of corrosion-resistant steelProducts made of corrosion-resistant steel (for ball bearings based on DIN EN ISO 683-17 and DIN EN 10088) are specifically intended for use in applications involving aqueous media, very dilute acids, alkalis or salt solutions. These products are especially suitable for environments with a relative humidity of over 70% and temperatures above 30 °C.Such conditions are found mainly in cleaning plants, electroplating and pickling lines, vapor degreasing plants and refrigeration systems.Since they have built-in corrosion protection, the products are also ideal for use in clean rooms and for general PCB assembly. Other possible areas of application include the pharmaceutical and food industries. This corrosion protection option offers the highest corrosion resistance, but a reduction in load capacities has to be taken into account.

Coating systemsCoating Composition Thick-ness Color Hardness Process

temperatureCorrosion protection

Suitability for rolling contact

Friction reduced

Raydent Type LSL (BL)

Thin-layer hard chrome with fluoropolymer

1 … 2 µm Black Approx. 800HV

Approx. 90 °C

Metal passivity and fluoropolymer; approx. 24 h salt spray test

Not suitable 1) By fluoropolymer

Black finishing Chemical surface oxidation

1 µm Dark brown to black

Substrate surface hardness

Approx. 140 °C

oxidic passivity + oil preservation;approx. 1h salt spray test

Suitable, practically rolls onto the substrate

no

Zinc phosphating (bondering)

Zinc or manganese phosphate

3 … 5 µm gray to dark gray

Ductile layer

Approx. 110 °C

By preservative; up to 24 h salt spray test

Not suitable no

Thin-layer hard chrome (current series)

Chrome plating (microcrack-free); molecular bondingto base material

1 … 5 µm Matte grey Approx. 1,000 HV

Approx. 60 °C

Metal passivity and molecular bonding to substrate;400 h salt spray test

Suitable 1) no

Thin-layer hard chrome with chrome oxide layer(Duralloy LC)

Chrome plating (microcrack-free); molecular bondingto base material

2 ... 6 µm Black Approx. 1,000 HV

Approx. 60 °C

Metal passivity and molecular bonding to substrate;400 h salt spray test

Suitable 1) by mixed chrome oxide

Thin-layer hard chrome with silver coating

Chromium layer (microcrack-free); molecular bonding to base material

2 ... 6 µm Silvery, matte

Approx. 1,000 HV

Approx. 60 °C

Metal passivity and molecular bonding to substrate; 400 h salt spray test

Suitable by silver coating

Zinc-iron Cathodic metal deposition

3 ... 10 µm Yellow, black/olive iridescent

Approx. 140up to 200 HV

Approx. 80 °C

Cathodic corrosion protection; approx. 120 h salt spray test

Ductile; pushed to side, with cathodic effect

no

1) Determined through travel tests.



Product overviewOverview of products available at Bosch Rexroth for corrosive environments:

Product or format Standard chrome plated made from corrosion-resistantsteel

Ball screw assembly x x 1) x 2)

Planetary screw assembly x

Ball rail system

Guide rail x x x 3)

FNS/FLS/FKS SNS/SLS/SKS x x 4) x 5)

FNN/FKN/SNH/ SLH/SNN/SKN x x 4)

BNS/CNS x x

Mini ball rail system x

Roller rail system x x

Linear bushing and shaft

Shafts x x x

Compact/eLine/ standard/segmental x x

Super A+B/Super H+SH/ Radial/torque x

Integrated measuring system x

Linear motion systems x x 6) x 7)

1) On request2) on request (only for d0 = 20 mm)3) Version available for SNS rails size 15 to 35.4) Version available for runner blocks for various sizes.5) Version available for runner block size 15 to 35.6) MKK/MKR available with chrome-plated ball rail system and ball screw assembly screw.7) Version available for EMC piston rod.



Checklist for environmental conditions

GeneralDesignation

Product, material number

Installation position

(horizontal, vertical, overhead, etc.)

Type of lubrication

Exposure to contaminants

(media, shavings, dust) Standard: no exposure

Maximum Load

Fmax [N]

Required service life

L [km or h]

Maximum travel speed

vmax [m/s]

Maximum acceleration rate

amax [m/s2]

TemperatureOperating temperature

tmin/tmax [°C] Standard: -10 °C to 80 °C

Clean roomRequired clean room class

(as per DIN EN ISO 14644-1) Standard: no special requirements

Air flow in clean room environments turbulent laminar vertical laminar horizontal

Attached motor, if present

(incl. attachment)

Exhaust method Standard: no additional exhaust system

VacuumVacuum range Low vacuum Medium vacuum High vacuum Ultra high vacuum

Standard: no special requirements

Application pressure p [mbar]

Standard: > 300 mbar (ambient pressure 1,013 mbar)

Food industry, dry room, corrosive environment, radioactive radiationSpecial requirements, application area

Standard: no special environment involved

Other information

Detailed information can be found in the relevant chapters.Please include the checklist for environmental conditions with your inquiry/order.



This guide was prepared with the utmost care.All information has been checked for correctness.If, nevertheless, faulty or incomplete information occurs, no liability can be accepted.In case of doubt, the information from the relevant catalogs apply.

Since our products are subject to continuous development, changes must be reserved.

R999001439/2021-01replaces R999001439 (2017-10)© Bosch Rexroth AG 2021Subject to modifications!

The data specified above only serves to describe the product.No statements concerning a certain condition or suitability for a certain application can be derived from our information. The information given does not release the user from the obligation of their own judgment and verification. It should be noted that our products are subject to a natural process of aging and wear.

Bosch Rexroth AGErnst-Sachs-Straße 10097424 Schweinfurt, GermanyTel. +49 9721 937-0 Fax +49 9721 937-275www.boschrexroth.com

Find your local contact person here:www.boschrexroth.com/contact

Linear Motion Technology from Bosch Rexroth

Documents

Transcript of Linear Motion Technology from Bosch Rexroth