南工大塑料成型加工2015窦finishing, adhesion, assembly.ppt

Finishing, Adhesion, and Assembly Material removal Traditional Cutting, Drilling, Milling Surface finishing Issues Heat transfer Peck drilling Skip-tooth saws Increased cutting speed Slower cutting advance Hole size (shrinkage) Cutting fluids Brittle/soft Composites Traditional Machining Used to make minor shaping corrections Used to trim excess material Used often in thermoforming and blow molding Sometimes parts are molded oversized so that they can be machined to exacting tolerances Material removal – water jet Typically used with the more difficult materials (composites, very hard plastics) Water-jet can cut most materials, even composites effectively Material removal – lasers Laser cutting burns the material away In clear materials, holes can be cut between surfaces without affecting the surface Focus adjustment can reduce kerf, heat distortion and depth of cut Material removal – hot wire Traditionally used for foams Can cut any thermoplastic Material may flow back together Joining Adhesive joining Definitions: Adherends/substrates – pieces to be joined Adhesive – glues Applicator – the device used to put on the adhesive Adhesive Joining (Adherends) Surface preparation Cleaning Chemical etching Flame treatment Corona treatment Plasma treatment Coupling agents Mechanical abrasion Especially important for some materials (PE) Adhesive Joining (Adhesives) Liquids, pastes or solid films In all cases the adhesive goes through a liquid phase Chemical change Structural Hot melt Pressure sensitive Water based Radiation cured Non-Traditional Joining Fusion Heat materials and force them together Ultrasonic Vibrate the materials to soften them and force them together RF (radio frequency) Similar to Ultrasonic at a different frequency Spin/Friction stir Material is not raised in temp to the Tm Some of the strongest joints Non-Traditional Joining Induction Electromagnetic heating Requires some metallic filling in the plastic to be joined Mechanical Joining and Assembly