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