Transcript Slide 1
Plastics
Thanks to Mr. Joe Neary of Summerhill
College for this presentation
Types of Plastics
Thermosetting plastic
Thermoplastic
Thermosetting plastic
Is plastic which has been heated to form into a
shape
When the plastic cools and sets, it cannot be
reheated to take another shape as the chemical
process which takes place when it is heated
cannot be replaced
These plastics therefore can withstand high
temperature
Polyurethane and polyester are thermosetting
plastics
Thermoplastics
Thermoplastics can be softened and reshaped by
reheating again and again
Different thermoplastics soften at varying temperatures
Examples:
Acrylic
Polyvinyl Chloride (PVA)
Polythene
Working with Plastic
Plastics can be:
Cut with saws
Filed with planes
Drilled
Edges can be sanded to produce a smooth
finish
Cutting Plastic
Can be cut by hand or on a band saw
Hand saw should be held at a low angle to reduce tear
out
Polystyrene (foam) can be cut with a heated wire
Filing Plastic
Edge of plastic after it is cut must be planed to finish
Work should be held low in a vice to secure the piece
and to support it
File can be used to bring a piece down to a line
Step 1: Piece is cross filed down to the line
Step 2: Piece is draw filed to remove any file marks
Step 3: Edge is sanded to produce a smooth finish
Instead of files a block plane can be used to finish the
edge
Cross Filing
Draw Filing
Drilling Plastic
Can use a wood or metal twist drill bit
Speed of drill should be fast to prevent chipping
however the piece should be drilled slowly
Waste piece of timber should be placed under
the plastic to support the piece, prevent break
out and to protect the bench or drill press
Drilling Plastic
Bending Plastic
Popular with thermoplastics because process can be
reshaped with no ill effect
Important to complete all shaping and drilling of piece
before bending it
Method:
Strip heating ( localised along bend line)
Oven heating (heats the whole piece-curving)
Important not to overheat plastic as it will bubble and
melt and to allow for the bend in the length of the piece
by adding the thickness of the sheet to the length
Bending Plastic
Bending plastic