Muoviteknologia Teppo Vienamo Joints / attachments Principles of joining plastics parts Mechanical joints / attachments Adhesives Welding

Muoviteknologia Teppo Vienamo Combining functions? Minimizing amount of parts and joints Taking advantage of material properties Suitable material for combined functions DFMA Design for Manufacturing and Assembly

Muoviteknologia Teppo Vienamo Size of series / joint type Large series –Few parts –Integrated functions –Expensive tools –Lot of design work Small series –Simple parts –Minimize design work –Laborious production –No moulds / cheap tooling

Muoviteknologia Teppo Vienamo Mechanical joining Integrated joining parts Screws Rivets Inserts

Muoviteknologia Teppo Vienamo Press Fittings Various materials –thermal expansion of material Plastic in tension Pin in a hole

Muoviteknologia Teppo Vienamo Snap-fit Placing and attachment of a part Permanent or repeating Demanding shapes Avoid tension peaks Bayer snap fit joints manual

Muoviteknologia Teppo Vienamo Living hinge Thin film between thick plastics parts Minimising part amount avoiding hinge parts –Injection moulding –Machining Crystalline plastics polypropylene and polyethylene –10 6 bending 1,5 R 0,25 0,1-0,4 0,15-0,4 R 0,7

Muoviteknologia Teppo Vienamo Separate joining parts Threaded joining parts –Screws –Bolts –Nuts Inserts / out-serts‏ Not threaded joining parts

Muoviteknologia Teppo Vienamo Threads in plastic Rounding in bottom of the thread Male thread is easy Female thread requires often rotating or collapsing core

Muoviteknologia Teppo Vienamo Screws Self threading screw –Thread shaping, requires plastic forming => soft plastics –Thread cutting, not for joints to repeating closure –Wide variety for different use

Muoviteknologia Teppo Vienamo Thread-inserts Repeated attachment Big disengage strength Amounting –ultrasound, fast, good attachment –heat, cheap, slow, good attachment –in-molding, tensions caused by shrinkage, risk of harming the mould –hit-serts, fast and easy, poor attachment, –Expanding inserts, fast and easy tension to plastic –Thread cutting screw insert

Muoviteknologia Teppo Vienamo Screws Flat base screws recommended Conical base causes tension Washer spreads load

Muoviteknologia Teppo Vienamo Sewing Typically textile and thin materials Fast No tooling cost

Velcro Fast joints Attachment by –Sticker –sewing –Ultrasonic welding Muoviteknologia Teppo Vienamo

Muoviteknologia Teppo Vienamo Adhesives Easy Differing materials Equal tension Seal Elasticity Cheap No tools Insulation Easy to repair Aesthetic Chemical fitting Holding Thermal stability Handling the adhesive Poisonous Preparing the surfaces

Muoviteknologia Teppo Vienamo Hardening adhesives Chemical reaction –Epoxy-, polyester- or urethane-based glues –Cyanoacrylate based glues –Anaerobic glues

Muoviteknologia Teppo Vienamo Solvent clueing Dipping the surface in solvent Compression in a jig‏ Solvent evaporates Well fitting surfaces Only for amorphous plastics result ”one part” E.G. trichloroethylene, xylene and acetone Possible to make filling paste of solvent and pieces of plastic

Muoviteknologia Teppo Vienamo Other adhesives Hot-melts Adhesive tapes –Double sided tapes –With or without carrying film UV-hardening adhesives –Fast and expensive

Muoviteknologia Teppo Vienamo Welding plastics Thermoplastics Heat and pressure Be aware –Not to burn plastics –contaminant: release agents, dirt, water

Muoviteknologia Teppo Vienamo Methods Hot gas welding –Melting base- and added material with hot air blower Extruder welding –Like hot gas welding but added material is heated in extruder –Thick materials

Muoviteknologia Teppo Vienamo Fusion welding (Hot plate)‏ Hot plate between parts melts surface Remove heater Press parts together cooling E.G. Tube connections, car lamps

Muoviteknologia Teppo Vienamo Ultrasonic welding Hz vibration Special tool or horn to transfer vibration Moulded ridge of plastic melts by the friction heat pressure Fast method 1-5 seconds Strong attachment

Muoviteknologia Teppo Vienamo Friction welding Typically for rounded bars Rotating part melts by friction and heat Stop and press Strong attachment Vibration

Muoviteknologia Teppo Vienamo Stacking Press molded stud Heat, friction, ultrasonic, cold Materials that don't melt together

Muoviteknologia Teppo Vienamo Laser welding Both lap and butt joints l No heat stress Fast method