Manufacturing of PMMA Cam shaft

by Rapid Prototyping

Manoj Kumar Kuna

Introduction to Rapid Prototype.Definition.Types of Rapid Prototype. Stereo Lithography ( SL ) Selective Laser Sintering ( SLR ) Fused Deposition Modelling ( FDM ) Laminated Object Manufacturing ( LOM )Cam Shaft ProductionConclusion

.

Over view

Rapid Prototyping is a process which is used to create a prototyping of a newly created design in order to carry out further advancement or changes in the design.

It is an additive manufacturing process.Cam shaft which is produced by conventional and

other un-conventional machining process,requires a series of process to obtain a product.

It is proposed to produce the camshaft by an additive manufacturing process using rapid prototyping.

Introduction

The term Rapid Prototyping (RP) refers to a class of technologies that can automatically construct physical models from Computer-Aided Design (CAD) data

RP process belong to the generative (or additive) production processes unlike subtractive or forming processes .

In all commercial RP processes, the part is fabricated by deposition of layers contoured in a (x-y) plane two dimensionally.

The third dimension (z) results from single layers being stacked up on top of each other, but not as a continuous z-coordinate.

RP can be classified into two fundamental process steps namely generation of mathematical layer information and Generation of physical layer model.

RAPID PROTOTYPING

Classification of RP:

In this process photosensitive liquid resin which forms a solid polymer when exposed to ultraviolet light is used as a fundamental concept.

A SL machine consists of a build platform (substrate), which is mounted in a vat of resin and a UV Helium-Cadmium or Argon ion laser.

The laser scans the first layer and platform is then lowered equal to one slice thickness and left for short time.

This process helps in reducing recoating time, smoother surface and reduced trapped volumes.

Stereo Lithography

Stereo lithography

In Selective Laser Sintering (SLS) process, fine polymeric powder like polystyrene, polycarbonate or polyamide etc. (20 to 100 micrometer diameter) is spread on the substrate using a roller.

The laser is modulated in such away that only those grains, which are in direct contact with the beam are affected.

Once laser scanning cures a slice, bed is lowered and powder feed chamber is raised.

Reduces the thermal distortion and fecilitates the fusion to the previous layers.

The un-used powder cleaned away and can be recycled once the model is complete.

Selective Laser Sintering

Selective Laser sintering

In Fused Deposition Modeling (FDM) process a movable (x-y movement) nozzle on to a substrate deposits thread of molten polymeric material.

The build material is heated slightly above (approximately 0.5 C) its melting temperature so that it solidifies within a very short time (approximately 0.1 s) after extrusion and cold-welds to the previous layer.

Movable nozzle which has only X-Y direction movements deposits a molten polymeric material on to a substrate.

The support material is relatively of poor quality and can be broken easily once the complete part is deposited and is removed from substrate.

Fused Deposition Modeling

Fused Deposition Modeling

The slices are cut in required contour from roll of material by using a 25-50 watt CO2 laser beam.

A new slice is bonded to previously deposited slice by using a hot roller, which activates a heat sensitive adhesive.

A layer of adhesive coated material is in turn glued out to obtain the components shapes using laser .

Once one slice is completed platform can be lowered and roll of material can be advanced by winding this excess onto a second roller until a fresh area of the sheet lies over the part.

Sealed with a silicone fluid or epoxy resin to prevent later distortion of the paper prototype through water absorption.

It is 5-10 times faster than other R.P

Laminated Object Manufacturing

Laminated Object Manufacturing

Model of a cam shaft developed in a CAD software for RP production

Explaining the modification done in RP process

 

Fig showing the tool holder which is provided with paths for the movement of the laser tool

Fig showing the 3 dimensional representation the modified RP machine

Fig showing the side view of the modified RP machine

..

Fig showing the layer feeder with leveling roller

Fig shows the of the arm hydraulic cylinder with pistons for the movement

 Fig showing the arm which moves the tool holder in x and y axis direction

 Fig explaining the multiple tools used for manufacturing multiple

cams.

 

 

            

 

property   symbol unit Poly methyl Cast iron 

        methacrylate     

Young’s modulus   E GPa 2 83   

Yield Strength   σy MPa 70 45   

Ultimate strength   σu MPa 344 66.16   

Percentage elongation   %EL - 0.9691 2.47   

[=% strain at failure]             

Glass transition temperature   Tg oc 105 -   

Ceiling Temperature   Tc oc 220-230 -   

Critical weight  mc

-27500 -

  

       

Entanglement Weight   - Da 5900-7900 -   

Water Absorption   % - 2.0 -   

Modulus of elasticity   E GPa 3.3 -   

Sheer Modulus   G GPa 1.7 -   

Poisson’s ratio   V - 0.38-0.40 -   

Density   P g/cm3 1.190 at 20oc -   

Tensile strength   σy MPa 70 -   

Critical Strain   % - 0.8-1.30 -   

               

  Comparison of properties between poly methyl methacrylate and cast iron

Thus the R.P metal addition 3-d printing process of SLS can be adopted for mass production of complex parts.

Advancements in this technology increases in production rates.

This consist of increasing the number of platforms and the number of laser points to be directed on the material.

CONCLUSION

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