The Final Report Vineeth

GOVT. POLYTECHNIC COLLEGE

KOTTAYAM

DEPARTMENTOF

MECHANICAL ENGINEERING2011-2012

A SEMINAR REPORTON

SELECTIVE LASER SINTERING

SUBMITTED BY:

VINEETH .K.VREGISTER NUMBER:

89020412

Seminar Report ‘11 MOCT

Dept.of mechanical GPTC, Kottayam

GOVT. POLYTECHNIC COLLEGEKOTTAYAM

DEPARTMENT OF MECHANICAL ENGINEERING2011-2012

CERTIFICATE

This is to certify that this Seminar titled “SELECTIVE LASER SINTERING” presented By “VINEETH KV” Reg. no.89020412 student of final year "MECHANICAL ENGINEERING in partial fulfillment of the requirements for the award of Diploma in Mechanical Engineering under The department of technical Education, Kerala, during the academic year 2011-2012.

Internal Examiner: ………….. External Examiner: ……………

Seminar co-ordinator: …………. Head of section: ……………….

Place: ……………..

Seminar Report 2011-12 SELECTIVE LASER SINTERING

Date: …………..

ACKNOWLEDGEMENT

First of all I thank the ALMIGHTY for the successful

completion of this seminar of mine.

I am extremely thankful to our Principal Mrs. C.G.

Anitha owed me to conduct this seminar at the college

campus which had taught many lessons in the field of

public speaking.

My special thanks goes to Mr. REJIKUMAR P M

who is the Head of the Dept. of MECHANICAL ENGINEERING

my seminar guide for helping me to take the seminar on

this topic also for the kind help he has extended to me for

the preparation on the seminar.

I would be failing in my duty if I don’t express my

gratitude to our seminar guide Mr. P.P RAVEENDRAN

NAIR, Mr. SAJIKUMAR, Mr. RAJMOHANPILLAI, Mr. N

BABU, Lectures in the department, who have given their

presence throughout the conduct of the seminar and given

me a lot of guidelines so that I could improve a lot in my

seminar.

I also thank to my Friends who have given me

constant supports all throughout the preparation and the

conduct of the seminar.



Above all I wish to thank GOD almightily for the

competition of this seminar work successfully.

VINEETH .K.V



ABSTRACT

Selective laser sintering (SLS) is technique by which parts are

building layer by layer. The SLS is a free form fabrication method to create

components by precise thermal fusing of powdered materials.

This is durable, economical and fast. The SLS is another form of

rapid prototyping. This selective laser sintering (SLS) is one among the

rapid prototyping which include stereo lithography (SLA). This method has

also been extended to provide direct fabrication of metal and ceramic

objects and tools. With this method we can make required and different

prototype. This SLS can be used as a mass production prototyping.



CONTENTS

1. INTRODUCTION

2. WHY RAPID PROTOTYPING NECESSARY?

3. HIGHLIGHTS OF SLS

4. THE TECHNOLOGY

5. HOW IT WORKS

6. THE PROCESS

7. THE MATERIAL

8. EXPERIMENTAL SETUP OF SLS

9. OVERVIEW OF SLS

10. PROTOTYPES MANUFACTURED BY SLS

11. ADVANTAGES OF SLS

12. LIMITATIONS OF SLS

13. APPLICATIONS

14. CONCLUSION

15. REFERENCE



INTRODUCTION

Rapid Prototyping (RP) can be defined as a group of techniques used

to quickly fabricate a scale model of a part or assembly using three

dimensional computer aided design (CAD) data. What is commonly

considered to be the first RP technique, selective laser sintering was

patented by CARL DECKARD A UNIVERSITY OF TEXAS

GRADUATE STUDENT. The company was founded in 1989, and since

then, a number of different RP techniques have become available. Rapid

Prototyping has also been referred to as solid free-form manufacturing;

computer automated manufacturing, and layered manufacturing. RP has

obvious use as a vehicle for visualization. In addition RP models can be

used for testing, such as well Icrlan airfoil shape is put into a wind tunnel

RP models can be used to create male models for tooling, such as silicone

rubber molds and investment casts. In some cases, the RP part can be the

final part, but typically the RP materiel! Is not strong or accurate enough.

When the RP material is suitable, highly convoluted shape§" (including

parts nested within parts) can be produced because of the nature of RP.

There is a multitude of experimental RP methodologies either in

development or used by small groups of individuals.



WHY RAPID PROTOTYPING NECESSARY?

The reasons of Rapid Prototyping are

• To decrease development time.

• To decrease costly mistakes

• To minimize sustaining engineering changes.

• To extend product lifetime by adding necessary features and

eliminating redundant features early in the design.

Rapid Prototyping decreases development time by allowing

corrections to a product to be made early in the process. By giving

engineering, manufacturing, marketing, and purchasing a look at the

product the design process, mistakes can be corrected and changes can be

while they are still inexpensive. The trends in manufacturing industries to

emphasize the following

• Increasing number of variants of products.

• Increasing product complexity.

• Decreasing product lifetime before obsolescence.

• Decreasing delivery time.

Rapid Prototyping improves product development by enabling better

communication in a concurrent engineering environment.



HIGHLIGHTS OF SLS

It is patented in 1989.

Considerably stronger than stereo lithography.

Laser beam selectively fuses powder materials; nylon, elastomers and

so on metals.

Process is simple.

There is no milling or masking steps required.

Powdering, porous surface unless sealant is used. Sealant also

strengthens the part.

Uncured materials are easily removed after a build by brushing of.

THE TECHNOLOGYDept.of mechanical GPTC, Kottayam


The selective laser sintering is a free form fabrication method to create

components by precise thermal fusing (sintering) of powdered materials.

Parts of complex geometries can build in successive layers that define

subsequent cross sections of the component.

The sinter powder is powder fed to the process chamber from two

cartridges flanking the partly built product. This allows for bidirectional

powder feeding to the roller that lays powder across the top of the product,

thus improving building speed. Unsintered powder is relumed to the

powder feeding cartridges, to be recycled. The process is a C02 type

ol'50watt power. The process chamber is Oiled with nitrogen to obtain safe

materials sintering conditions.

HOW IT WORKSDept.of mechanical GPTC, Kottayam


The SLS technology uses a C02 laser to sinter (fuse) a variety

of thermoplastic and metal powders to "grow" 3D objects layer-

by-layer from 3D electronic data (STL files). Because this is an

additive process, highly complex geometries can be built without

issue; and, because the powder holds the parts, no support

structures have to be added and removed. The key advantage of

SLS is its ability to rapidly produce durable, functional objects for

a wide variety of applications.

• Working parts and assemblies with good detail and surface

finishing

• Variety of material: rigid and flexible plastics, fully dense

metal, rubber like elastomer, foundry friendly patterns

• Capable of living hinges,, high-flex snaps, high stress and

heat tolerance and service as short-run tooling

• Can be finished and painted for presentation,

demonstration and video reproduction

• Dimensional tolerancing with thousandths of a inch

• Delivery of most parts and patterns in just a few working days



• THE PROCESS•

• Selective Laser Sintering (SLS) parts are built with successive

layers'of powder selectively bound by a laser beam. SLS is also a technique

• by which parts are built layer by layer. The basic material consists of

powder with paticle sizes in the order of magnitude of 50 11m. Successive

powder layers are spread on top of each other. After deposition, a computer

controlled C02

• Laser beam scans the surface and selectively binds together the

powder particles of the corresponding cross section of the product. During

laser exposure, the powder temperature rises above the glass transition

point after which adjacent particles how together. This process is called

sintering.

•

THE MATERIAL Dept.of mechanical GPTC, Kottayam


The parts are built in polyamide (PA). The powder being a solid

material has an attractive feature of being self supporting for the, generated

product sections. This makes supports redundant. The polyamide material

allows the production of fully functional prototypes with high mechanical

and thermal resistance. The use of PA powder filled within glass particles

(PA-GF) has a much higher thermal resistance and is typically used in

functional test with high loads.

The polyamide SLS parts have excellent long term stability and are

resistant, against most chemicals. They can be, made water tight by

impregnation. The PA material is used as bio compatible, food safe and not

harmful to health or environment.



EXPERIMENTAL SETUP OF SLSThermoplastic powder is spread by a roller over a surface of a build

cylinder. The piston in the cylinder moves down one object layer thickness

to accommodate the new layer of powder. The powder delivery system is

similar in function to a build cylinder. Here a piston moves upwards

incrementally to supply a measured quantity of powder for each layer.

A layer beam is then traced over the surface of this tightly

compacted powder to selectively melt and bond it to form a layer of the

object. The fabrication chamber is maintained at a temperature just below

the melting point of the powder so that heat from the laser need only

elevate the temperature slightly to cause sintering. This greatly speeds up

the process. The process is repeated until the entire object is fabricated.



After the object is fully formed the piston is raised to elevate it. Excess

powder is simply brushed away and final manual finishing may be carried

out. No supports are required with this method. Since overhangs and under

cuts are supported by the solid power bed. It may take a considerable length

of cool down time before the part can be removed from the machine. Large

parts with thin sections may require as much as two days of cooling time.



OVERVIEW OF SLS

This overview bypasses many intricacies of the processes involved.

Selective laser sintering is very similar to Stereo Lithography (SLA) with

the exception of using powdered raw material rather than photo-sensitive

liquid as the build material. The system consists of an X-Y axis controlled

laser, a Z axis controlled table, and a bed of powdered raw material that is

maintained at a constant level. Prototypes are created with the table initially

positioned below the surface of the powder a distance equal to (The

thickness resolution (or the part. The laser traces a two dimensional cross-

section of the item at that level, fusing the powder touched by the laser. The

table then descends a distance equal to the thickness resolution and

powdered media is replenished over the solidified layer. This process

continues until the entire prototype has been solidified. At this time the

model is lifted out of the media bed. cleaned of loose material and

smoothed to remove the Z axis stair-steps created by the process. "Trapped

volumes" are not a problem for SLS models. Support structures arc

generally not required. A good selection of materials is available for this

process, ranging from a rubber-like polymer to hard plastic.



PROTOTYPES MANUFACTURED BY SLS

(a) AIRFOI (b) PAINTBALL-MASK (c) IMPELLER



ADVANTAGES OF SLS

• It offers the key advantage ol'making functional parts in essentially

final materials.

• The system is mechanically more complex than SLA and most other

technology

• The method has extended to provide direct fabrication of metals and

ceramic objects and tools.

• Since the objects are sintered, they are porous.

SLS are

Fast

Economical

Durable and functional parts Large and complex parts Small

series, produced in one building process No support

Structure' necessary



All kinds of finishing degrees can be made water light

LIMITATIONS OF SLS1. Surface finish: The surface of an SLS part is powdery, like the base

material whose particles are fused together without complete Melting. The

smoother surface of an SLA part typically wins over SLS.

2. Dimensional accuracy: SLA is more accurate immediately after

completion of the model, but SLS is prone to residual stresses that are

caused by long term curing and environmental stresses. Both SLS and SLA

suiler from inaccuracy, but SLS is less predictable because of the variety of

materials and process parameters.

3. Accuracy: the accuracy of a rapid prototype is dependent on many

factors. Upon completion of the prototype the SLA provides greater

accuracy than SLS.



APPLICATIONS

Selective Laser Sintering is the ideal solution for fully functional

prototypes and series. Rapid Manufacturing.

Fully functional prototypes and series

1. Parts for mechanical and thermal tests

The polyamides material allows the production of strong, durable parts

that can be used tor extensive functional testing. Sintered products have

mechanical properties comparable to those of injection molded PA 12

parts, typical applications are snap fits but it is also possible to produce

working hinges.

Polyamide parts with glass filling have a much higher thermal

resistance and are perfectly suited for lighting elements and ventilation

systems or products that require high thermal loads. Apart from their use as

test products, the functional SLS parts often also need to be used at the

same time for a visual/csthetical control or dimensional check.



2. Scries of small plastic parts

SLS is an interesting and cost-effective alternative to injection molding

(Rapid Tooling). With the P 700 machine which has a large build area, a

series of small pieces can be built in one single laser sintering process.

This dramatically decreases the price, as the cost of an SLS part depends on

its volume. Or in other words, the cost is defined by the amount of powder

it takes to build it and not by an initial investment in an injection molding

tool. Moreover, series of SLS parts are available in a few days. So no need

for high start-up investments, no long lead times to produce a mould and

injection mould the parts, no difficulties in case the parts are complex .



Component of a vacuum cleaner, buiii on the EOSINT P700 with a build

volume of700x380x580mm

3, Large and complex functional parts

The EOSINT P 700 machine can build large, complex geometries in

one piece, up to 700x380x580mm. The number of layers to be built is

significantly reduced as large parts can be built horizontally, which

considerably shortens the building process. Parts exceeding the P 700'

maximum dimensions .can be built in multiple pieces and put together

afterwards. The process of gluing sub-parts and assembling components

can be done in the most accurate and secure way using the Rapid Fit

system. Rapid Fit allows to firmly position the parts on a unique support



system with individualized fixtures, supporting the part on well positioned

points.

CONCLUSION

Selective laser sintering provides exact representations of yotir

complex designs in just days. This means that without delay, you receive a

superior design communication tool. Using the physical prototype, you can

detect errors early and correct them before it's too late. It all adds up to

hitting aggressive deadlines critical to time-to-market reductions.


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