An Introduction to

RP Processes BY

Anand Khare 142110001

Arun Pandaran 142110002

RP can be defined as the process of manufacturing physicalobject layer by layer manner directly from their CAD modelwithout any human intervention and without using any tools,dies, fixtures, etc.

RP process belong to the generative (or additive) productionprocesses.

In all commercial RP processes, the part is fabricated bydeposition of layers contoured in a (x-y) plane twodimensionally.

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

Part complexity.

Material.

Part quantity.

Part quality.

Cost.

Increasing number of variants of products.

Increasing product complexity.

Production time is reduced.

Form- fit-function test.

Assembly can be made without joints.

Limited material option.

Inaccurate surface finish.

High Cost.

Limited size of prototypes.

Need for support structures.

Generation of CAD model.

Conversion into .stl file.(Tessellation)

Slicing.

Generation of physical model.

Post processing.

a) CAD model

b) .stl file or tessellation

c) Slicing

Generation of physical model.

Post processing. Removal of supports.

Cleaning of part (wiping, rinsing, ... )

Post curing.

Surface finishing.

Solid based

• Laminated object manufacturing.

• Selective laser sintering.

• 3D printing.

Liquid based

• Fuse deposition modeling.

• Stereo lithography.

• Solid ground curing.

Developed by Stratasys, USA.

Material used ABS(Acryonitrile Butadine Styrene), WAX.

Accuracy 0.127 mm

Robotically guided fiber extrusion.

Strengths No post curing is required.

Variety of materials can be used.

Little wastage of material.

Material has large shelf life.

Weakness Surface finish is poor.

Strength is low in vertical direction

Accuracy is less compared to other RP processes.

Developed by Cubic Technologies, Carson, CA (former

Helisys).

Material used plastic, paper.

Accuracy 0.076 mm

Basic manufacturing approach-

Cut and Paste approach.

Paste and cut approach.

Decubing Grid Cutting

Strengths Prototyping time is proportional to surface area.

Cost of machine is one of the lowest.

Material used are least expensive.

Weakness Parts are weak in Z direction.

Prototype (paper) may absorb moisture.

Decubing is time consuming.

Laser spends more time in cutting the grids than useful part contours.

Developed by Daimler Chyrsler in collaboration with IIT Bombay.

• Rapid prototyping is a new tool, which used appropriately ...

– allows the manufacturing enterprise to run smoother

– increases production rate and product quality

•New uses and applications are discovered everyday

• Future areas include new materials directly deposited (metals, ceramics)

K.P. Karunakaran:” Rapid Product Development and

Manufacturing”, IIT Bombay, Chapter no. 15-16.

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