Pattern Materials

Pattern Materials:-
Usual materials – wood, metals & plastics
Wood-
Adv:- Disadv:-
Easy availability Moisture absorption
Low weight Distortion
Easily shaped Dimensional change
Cheap
Care to be taken – seasoning
Example – Pine, Teak, Deodar
Others – plywood boards and particle boards
Reason – Availability in various thicknesses
Higher strength
No need for seasoning
Use – Used for flat type and no three dimensional contour shapes
Large scale casting
Choice of pattern materials depends on
 Size of casting
 No. of castings to be made from pattern
 Dimensional accuracy required
Metals:-
Advantages- Durability
Smooth surface finish
Light weight
Easily worked
Corrosion resistant
Use - For large scale casting production
Closer dimensional tolerance
Plastics :-
Advantages - Low weight
Easier formability
Smooth surface, durability
Do not absorb moisture
Dimensionally stable
Can be easily cleaned
Example – Cold setting epoxy resin with filler
Polyurethane foam – Light weight
Easily formed into any shape
Used for light duty work for small no of casting
For conventional casting
For single casting
Plastics have low ash content and it can be burned inside the mould.