UNIVERSAL COLLEGE OF ENGINEERING AND TECHNOLOGY

Final Project PresentationGroup No:12

Design and Fabrication Rotational moulder machine

Prepared by:Group 12• Marshal R Javia 120460119059• Samip N Shah 120460119058• Jainil M Shah 120460119027

Guided by:Mr. Vedprakash SinghAsst. Professor (Mechanical)Universal college of Engineering and Technology. (Internal Guide)

Table of content

• Introduction• Project Description• Literature Review• Patent table• Multiple solution• Work Plan• References

Introduction

What is rotational moulding?• Rotational moulding, known also as rotomolding

or rotocasting, is a process for manufacturing hollow plastic products.

• Rotational molding is best known for the manufacture of tanks but it can also be used to make complex medical products, toys, leisure craft, and highly aesthetic point-of-sale products.

• Rotational moulding is the process of producing hollow parts by adding plastic grains to shell like mould.

• It is then slowly rotated causing the soften material to disperse and stick to the walls of the mould.

• The polymer is then cooled to near room temperature and resulting hollow part is removed. The cyclic process is then repeated.

Fig.1-Rotational moulding process

Introduction

Steps in rotational moulding machine process.• Preparing the Mould• Heating and Fusion• Cooling the Mould• Unloading / Demoulding

Introduction

• Preparing the Mould• The process begins with filling a hollow mould with a pre-determined

quantity of polymer powder.• This powder can be pre-compounded to the desired color.• The mould is preheated by convection, conduction, to temperature ranges

around 260 °C - 370 °C, depending on the polymer used. When the powder is loaded into the mould it is closed, locked.

Introduction

• Heating and Fusion• The mould is bi-axially rotated as the polymer melts and coats the inside of

the mould. • The rotation speed is slow, less than 20 rotations/minute; the process is not

centrifugal. During this phase of the rotational moulding process timing is critical.

• If the mould spends too much time inside the oven the polymer will degrade - this will reduce its impact strength.

• If it spends too little time inside the oven melting of the polymer will be incomplete and it will not fully coalesce on the mould wall, creating large bubbles in the item.

Introduction

• Cooling the Mould• After the melting has been consolidated to the desired level and the timing

is right, the mould is removed from the oven and cooled. Cooling of the mould is typically done with air .

• Cooling allows the polymer to solidify to the desired shape and shrink slightly so that it can then be handled by the operator and removed from the mould.

• It is important that the cooling rate be carefully measured because rapid cooling causes the polymer to shrink too fast and warps the part.

Introduction

• Unloading / Demoulding• When it has cooled sufficiently to be handled and the polymer can retain

its shape, the mould is opened and the part is removed. • The moulding process can then be repeated by adding the polymer powder

to the mould.

List of material used in the mould

• Low-density polyethylene (LDPE)• Linear low-density polyethylene (LLDPE)• High-density polyethylene (HDPE)• Polyvinyl chloride (PVC)• Nylon• Polypropylene• Thermoplastic Polyester Elastomers TPE - Hytrel

Low-density polyethylene (LDPE)

• Low density polyethylene  is a thermoplastic made from the monomer ethylene.

• It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high press process via free radical polymerization.

•  Its manufacture employs the same method today.

•  Despite competition from more modern polymers, LDPE continues to be an important plastic grade. 

Fig.2-LDPE material

Linear low density polyethylene (LLDPE)

• Linear low-density polyethylene  (LLDPE) is a substantially linear polymer, with significant numbers of short branches, commonly made by copolymerization of ethylene with longer-chain olefins.

• In general, LLDPE is produced at lower temperatures and pressures by copolymerization of ethylene and such higher alpha olefins as butene, hexene, or octene.

Fig.3-LLDPE material

High-density polyethylene (HDPE)

• High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a polyethylene thermoplastic made from petroleum.

• It is sometimes called "alkathene" or "polythene" when used for pipes. 

• With a high strength-to-density ratio, HDPE is used in the production of plastic bottles, corrosion-resistant piping.

Fig.4-HDPE material

Polyvinyl chloride (PVC)• Polyvinyl chloride, more correctly but

unusually poly(vinyl chloride), commonly abbreviated PVC, is the third-most widely produced synthetic plastic polymer, after polyethylene and polypropylene.

• PVC comes in two basic forms: rigid and flexible. The rigid form of PVC is used in construction for pipe and in profile applications such as doors and windows.

• It is also used for bottles, other non-food packaging, and cards .

Fig.5-PVC material

Introduction

Advantages of the rotational moulding machine• A hollow part can be made in one piece with no weld lines or joints• The end product is essentially stress-free• The moulds are relatively inexpensive• The lead time for the manufacture of a mould is relatively short• Short production can be economically viable• There is no material wastage in that all of the material is normally

consumed in making the part• It is possible to make multilayer products• Different types of product can be moulded together on the one machine

Introduction

Disadvantages in rotational moulding machine• Rotational moulding machine is the low pressure process so it has been

hard to reach the areas in the mold.• Product stick in mould when unloading the product.• Uneven wall thickness of moulded parts.• A limited number of resins are successfully proceed.• Moulding cycles are long.• Large flat surfaces are difficult to achieve.• Can not make high tolerance parts.• Bubble formed in the product.

Introduction

Types of Rotational Moulding Machine• Bi-Axial type rotomolding Machine• Independent arm rotomolding machine• Rock n roll type rotomolding machine• Shuttle machine

Rock n roll type rotomoulding machine

• This is a specialized machine designed mainly to produce long narrow parts. Some are of the clamshell type, thus one arm, but there are also shuttle-type Rock & Roll machines, with two arms.

• Each arm rotates or rolls the mold 360 degrees in one direction and at the same time tips and rocks the mold 45 degrees above or below horizontal in the other direction

Fig.6-Rock n Roll rotomolding machine

Fig.7-Rock n Roll rotomolding machine

Bi-Axial type rotomoulding Machine

• Biaxial machine consist 3/4 arms and have a moving oven in which mould is warmed where hot air is used to heat the mould. The Mold is attached on a arm which rotate it in two path hence the process is called as biaxial process

• three arm machine is mainly used in application where the process time for each arm require equal like one heating chamber one cooling chamber and one load/unload area.

• Also available in different application like Four station where one heating, one precooling, one cooling and one loding or unloding area.

Fig.8-Bi-Axial rotomoulding machine

Shuttle type rotational moulding machine

• Shuttle type Rotomoulding machines are specially designed to hold large moulds as well as multiple moulds with various capacities.

• Provision for such  large mould carrier plates and arms are provided for both side support for sturdy and comfortable operation instead of cantilever type station arms  which is a special feature for the shuttle type machines.    

Fig.9-shuttle type rotational moulding machine

Project Description

• Rotational moulding is the process of producing hollow parts by adding plastic powder to shell-like mould.

• It is then heated and slowly rotated causing the softened material to disperse and stick to the walls of mould.

• The mould is then cooled to near room temperature and the resulting hollow part is removed .The cyclic process is then repeated.

• Rotational moulding machine is used to make seamless product for example:-A water Tank.

• In rotational molding, rigid, resilient hollow bodies are formed. • So, In this project there will be designing of a rotational moulding machine

in which one part is moving and one part is fixed. The mould will be attached with the moving part of the machine. There will also be change in the burner design so the mould can get the proper heating.

Rotational moulding process

Fig.10-Rotational moulding process

Roto moulding process products

Fig.11-Roto moulding products

Literature ReviewSerial No. Title Author Description

1 Control of Rotational Molding Using Adaptive Fuzzy System

D.I.Abualdi

R.J.Crawafor

Rotational molding is a method for manufacturing hollow plastic parts. In the work reported here, In this literature review the authors had applied the fuzzy logic technique in the rotational moulding process to control the oven temperature and the fuel supply system by controlling the control valve to the fuel. And this network were gave good result compare to conventional rotational moulding process.

Literature ReviewSerial No. Title Author Description

2 Investigation of the influence of mould rotational speed on the cast wall thickness in the rotational moulding process

Tomasz Jachowicz, Janusz W. Sikora

This paper presents the rotational molding process. The general principles of this polymer processing technology have been described. The main applications have been introduced and leading advantages and typical disadvantages of rotational molding process have been discussed. In this paper the different speed is applied to the rotational mould which affects the cast wall thickness in the rotational moulding machine.

Literature ReviewSerial No. Title Author Description

3 A preliminaryStudy on theRotational moulding process

L Slatineanu

The rotational molding is a manufacturing method that allows obtaining parts with hollow form by rotating a mold around two perpendicular axes with the part material in the liquid state. The paper presents some theoretical considerations concerning the conditions for the liquid flow during the rotational molding process. The coordinates of a point belonging to the mold were derived, even for the case where the mold rotates around two perpendicular axes. The main forcesacting on a small volume of liquid material, i.e., gravitational, viscous, and centrifugal forces, were taken into consideration.

Literature ReviewSerial No. Title Author Description

4 A Computer Simulation Method for Mold Optimization of Rotational Molded Objects

Wai-On NG, Ching-Yuen CHAN, Kai-Leung, Hui-ying CHEN, and Chi-w LAM

According to this literature review the temperature of the mould is very difficult to measure at some stages so they are applying the computer simulation technique to easily measure the temperature data without any problem .

Literature ReviewSerial No. Title Author Description

5 Investigation of Melt Flow Index and Impact Strength of FoamedLLDPE for Rotational Moulding Process

PL.RamkumaD.M.Kulkarn V.V.RabhijitcAditya Cherukumudi

In this literature review the authors of this paper is studied about the polythene And carried out about its effects on the product. according to the author of this paper polythene material gave wall thickness, high stiffness, good thermal insulation. Here in this paper the Author compare the two material polythene and the LLDP foam. Here the LLDP foam influence the rotational moulding process Rotational mouldingexperiments are carried out in a laboratory scale biaxial machine. Impact tests and melt flow property are performed on therotationally moulded parts.

Patent Table

SrNo. Title Inventor Description

1 Method and apparatus for manufacturing a spherical hollow bodyUS4294793

Kazuyasu takazawa

Improved method for manufacturing a spherical hollow body are disclosed. The spherical hollow body has a use for a core member for manufacturing a football or a volleyball and is manufactured by cooling a thermoplastic resin contained in a spherical hollow mold which is forcedly circulated along a constant locus simultaneously with the rotary motions on two axes orthogonal to each other.

Patent Table

SrNo. Title Inventor Description

2 Rotational moulding machine US 4028038 A

Douglas John Haigh

A rotational moulding machine comprises six mould carriers mounted at 60° intervals about a horizontal main axis of the machine on a turret which can be indexed about the main axis so as to bring each of the carriers in turn to loading/unloading, heating, and cooling stations of the machine. From this machine mass production can be done.

Patent Table

SrNo. Title Inventor Description

3 Rotational moulding machineUS 4,583,932

Paul V. Meuret, La Seyne-s/Mer,France

In this patent heat insulated part mounted to rotate on a frame about horizontal axis.which gives to mould at least one time to perpendicular axis of rotation.Radiating element are located in front of the wall of enclosure whose radiation are reflected by reflector means towards the central part of the enclosure where mould is located.Heat provide to mould by radiation.

Patent TableSr

No. Title Inventor Description

4 Rotational mold system with multiple stations,US4690626

Horst Krzepinski, Schulstrasse

In this cooling chambers can be arranged circularly around the heating chamber which is Disposed at the center, or theheating chamber can be movable such that an openingthereof can be selectively aligned to one of the coolingchambers. The molds can be moved via the supports from a cooling chamber to the heating chamber and back again. This apparatus optimize component utilization and minimizes cycle times.

Multiple solution

Multiple solution

Change of design

Change in rotational speed

Modification in mechanism

Change in design

• Firstly we would be gathering data on different design of rotational moulding machine.

• Then according to the gathered data, we would be calculating the least cost design.

• Then we would modify the least cost design to get a cost effective rotational moulding machine.

• And also the limitation that comes in the rotational moulding process will be eliminated.

Change in the rotational speed

• From the study of few Literature review we come to the solution that the speed of mold can affect the wall thickness of the product.

• If the speed is to high than the wall thickness will decrease and if the speed is low than the polymer is not spread properly and polymer does not stick around the wall properly.

• In the rotational moulding process moulding cycles are long so speed of mould should be uniform during the process.

Modification in Mechanism

• Currently the rock and roll mechanism is the most effective .• As one of the multiple solution we can change the gear mechanism .• And for the changing the speed we can also use A.C. or D.C motor

with different r.p.m with that gear mechanism.

Motor specification• RPM: 20 at 12V• Voltage: 4V to 12V• Stall torque: 28 Kg-cm at stall current of  1.3 Amp. • Shaft diameter: 6mm• Shaft length: 22mm• Gear assembly: Spur• Brush type: Carbon • Motor weight: 143gms

Heating cycle time

• Here it is necessary to control the heating cycle in the rotational moulding machine.

• There are three distinct segments to the oven cycle time. • The first is the time needed to get the mold to the required temperature. • The second is the time needed to coalesce and densify the polymer against the

mold surface. • And the third is the time needed to ensure that the polymer is fully fluid and all

bubbles have collapsed.

• So the equation used to find the cycle time is, Where, mold mass is mm, heat

capacity of is cp

Qmold = mm cp (Tfinal . -T0);

Charge weight

• To get the charge weight for a desired wall thickness, it is simply necessary to work out the volume of material in the end product and multiply this by the density of the plastic.

• The volume of the plastic is obtained by taking the volume of the inside of the mold and subtracting the volume of the air space inside the plastic part.

• For a molded cylinder of outside diameter D, length L, and wall thickness h, where ρ is the density of the solid plastic. This equation will give the charge weight for any desired wall thickness, assuming the other outside dimensions of the cylinder are known.

Charge weight

• W=Charge weight• ρ=Density• D=Diameter of mold• L= length of mold• h= Wall thickness

Heating the mold

• Rotational molds are traditionally constructed of relatively thin, high thermal conductivity metals such as aluminum and steel

• The mold absorbs substantially more energy than the plastic. ρ Cp t dT/dθ = h(Tair . T)

• Cp is its specific heat, • ρ is the density of the mold material,• t is the mold wall thickness,• T is its instant temperature, • θ is time,• Tair is the environmental temperature and• h is the convection heat transfer coefficient

Design and calculation

• After analyzing many design of the current rotational molding machine we conclude that for our project the rock and roll machine design is the most suitable.

• So we made changes to the rock and roll rotational molding machine design so we could get better output.

• So we changed the mechanism of the rock and roll rotational molding design which was earlier a lot complex as well as expensive.

• We made two ends for holding the die, one end is the fixed end and the other end is the moving end.

• The die will be greased inside and then it will be filled with the proper amount of raw material.

• The die is greased inside so the product is easy to remove from the die.

Design and calculation

• The fixed end is attached with a DC motor which has low rpm.• The moving end is connected with a screw so we can turn the screw to move the

screw forward and backward.• Both the fixed end and the moving end will be mounted on the main frame.• The main frame will contain the pipe and the burners which will be used for

providing heat to the rotating die.• The one end of the pipe will be closed and one end of the pipe will be supplied with

fuel for burning.• The main frame will be supported on the base frame, the base frame will be larger

than the main frame to support the whole weight of the machine.• The main frame will also tilt up to certain angle so this tilting will help the melted

plastic to flow and reach both the end of the die.• The main frame will be supported by the side springs so it stays in its original

position.• The tilting of the main frame will be done manually.

Design

Fig.12- AutoCAD design of machine

Design

Fig.13 AutoCAD design of machine with mold

Design

Fig.14 AutoCAD design Live center and dead center

Design

Fig.15 AutoCAD design of burners

Calculation

P=2𝜋𝑛𝑇 / 60 P=Power T=torque

30=2𝜋(20)𝑇 ⁄ 60

T=180/4 π

T=14.32 Nm

T=F.r

F=T/r

F=14.32/0.1

F=143.2 N

Diameter of the corn shaped die holder =2.5 cm

T= πτ𝑑3/16

τ=16T/ π𝑑3

τ=4.67 N/𝑚𝑚2

τ=P/A P=tangential force

P= τπ𝑑2/4

P=22.92 N

T=60P/2πN T=twisting moment

T=22.92*60/40π

T=10.95 Nm

σ𝑏= Bending stress

σ𝑏=P/A

σ𝑏=22.92*4/π𝑑2

σ𝑏=4.66 N/𝑚𝑚2

M=bending moment

M= πσ𝑏𝑑2/32

M/I = σ𝑏/y

M= I*σ𝑏/y

M= 2πσ𝑏𝑑4/64d

M=πσ𝑏𝑑3/32

M=π*4.66*2.53/32

M=7.148 N.m

Charge weight W=ρቂπ𝐷2𝐿4 − πሺ𝐷−2ℎሻ2ሺ𝐿−2ℎሻ4 ቃ ρ=Density

D=Diameter

L=length of mold

h=Wall thickness

W=0.926ቂπሺ10ሻ2(12)4 − πሺ10−2(0.5)ሻ2ሺ12−2(0.5)ሻ4 ቃ W=0.926ሾ1021.01− 63.61(12)ሿ W=0.926ሾ257.60ሿ W=238.54 gm

Weight of mold=Density*weight

Density of aluminium=2.70 g/𝑐𝑚2

Volume of aluminium= V

V= π𝑑𝑜2L/4 - π𝑑𝑖2L/4

V= πL/4(𝑑𝑜2 - 𝑑𝑖2)

V=12π/4(102 - 72)

V=3π(51)

V=480 𝑐𝑚3

Weight of mold =2.70*480= 1296 gm

Conclusion • After analyzing conventional rock & roll rotational moulding machine design the

project design of rotational molding machine design have more advantages like • Higher thermal efficiency- After studying research paper heat efficiency is affected by rotational speed so

motor speed used in this project is optimum and due to that more heat is gained on surface area on mold so the time required for molding is decreased.

• More durable product-Product durability is depend on the heat gain or heat given to the mold , as there is higher thermal efficiency the product will be more durable.

• Cost effective-By using less and easy mechanism in this project the machine becomes cost effective.

• It is also cost effective and also easy to operate. From the theoretical and practical analysis obtained design of the machine is satisfactory to eliminate the errors in the product. 

Work PlanJuly 2015

Aug 2015

Sept 2015

Oct 2015

Nov 2015

Dec 2015

Jan 2016

Feb 2016

Mar 2016

Apr 2016

Literature review

Design

Analysis

Fabrication

Modifications

Conclusion

References[1] http://www.rotomachinery.com/machines Accessed on 30/9/2015[2] http://www.rotoline.com/index.php/maquinas-para-rotomoldagem/open-flame

Accessed on 30/09/2015[3] http://www.theplasticprofessionals.com/rotational-molding/rotomold-materials.htm Accessed on 1/10/2015[4]http://www.rotomachinery.com/machines/special/hrm-rock-roll Accessed on 1/10/2015[5] http://www.naroto.com/About%20Rotational%20Molding.htm Accessed on 1/10/2015[6] http://www.rotationalmoulding.ca/materials/pvc.htm Accessed on 1/10/2015[7] http://www.rotationalmoulding.ca/materials.htm Accessed on 1/10/2015 [8] http://gvlpoly.com/roto-poly/roto-molding-process/ Accessed on 1/10/2015 [9] http://gvlpoly.com/roto-poly/industries/ Accessed on 1/10/2015 [10]

http://www.lyondellbasell.com/techlit/techlit/Brochures/Guide%20to%20Rotational%20Molding%205717.pdf Accessed on 1/10/2015

References[11] http://www.ias.ac.in/sadhana/Pdf2014Jun/625.pdf Accessed on 1/10/2015 [12] http://iieng.org/siteadmin/upload/9853E0114075.pdf Accessed on 1/10/2015 [13] www.astrj.com/pdf-190-177?filenamepdf Accessed on 1/10/2015 [14] https://macsphere.mcmaster.ca/bitstream/11375/6524/1/fulltext.pdf Accessed on

1/10/2015