Fusion, Friction, & RF Welding Shawn Andres, James Szymanowski, & Dario Kis PLET 370

Purpose To familiarize the class on the joining of composite plastic parts Specifically fusion, friction, and RF welding

Presentation Outline Plastics Welding Generalities RF Welding Introduction Theory and Background ADV/DISADV Basic Operation Procedure Equipment Used Design Requirements Examples Conclusion Fusion Welding (same) Friction Welding (same) Extra Info

Plastics Welding Generalities Definition: Uniting parts by joining their heated surfaces and allowing them to flow together Welding terminology Thermowelding Heat sealing Dielectric heating Cannot be used on thermosets Best for semicrystalline materials with good heat stability Different than adhesion bonding

Welding Generalities Cont. Importance when combining plastic components over Molded in components Simple assembly Material Compatibility Issues Melt Temperature/Degradation Mechanical Properties Melt Strength Others

Generalities - Influence of Additives/Fillers Can add or detract w/ respect to weldability Glass fillers Colorants/Lubricants Talc filled

Generalities - Methods of Heat Application Gas Electric Gun Heated Tool Induction Heating Friction (spinning)

RF Welding (sealing) Introduction Also known as Dielectric welding High Frequency Welding Definition Process of fusing materials together by applying radio frequency energy

RF Welding Theory & Background History WWI and WWII detecting underwater subs with radio waves 1963 First application to rigid thermoplastics First application Joining film in the 1950’s 1963 Applied to rigid thermoplastics

RF Welding Advantages/Disadvantages Advantages Only heated during RF generation RF tooling is usually run “cold” Clean, fast welds Economical Resultant joint strength = parent material(s) Disadvantages Joint design Application contingencies Material-to-material differences

RF Welding Basic Operation & Process Process High frequency emission Alternating current switches polarity Causes back and forth molecular movement In turn causes localized heating/bonding

RF Welding Equipment Equipment Machined brass die RF machine (Platen) Mech NRG to vibration NRG converter Horn Stand Programmer

Pictures of RF Welding Machines

RF Welding Design Requirements - Material Characteristics Melt Temperature Similar between materials Ex) PE cannot go with PS Modulus of Elasticity More rigid, easier to weld Low modulus mat’ls (PP & PE) can be welded, need proper horn positioning

RF Welding Design Requirements - Material Characteristics Cont. Impact resistance of composite part Strong weld necessary Coefficient of friction Similar and higher is better Thermal conductivity Similar and high or low depending on wall thickness

Example Materials Used in RF Welding PVC PU PE Acrylic Polychlorotriflouroethylene Others

RF Welding Examples of Common Applications Where fluid-proof seal is necessary Medical industry Health care industry Industrial applications Consumer products

RF Welding Conclusion Polar and non-polar plastics can be joined w/ special equipment Materials as thin as in w/ special equipment Economical Fast

Fusion Welding Introduction Definition Portions of the parts to be joined are heated to softening and pressed together Types Plate Bonding Butt Welding (Uniform bead) Electrofusion (Coupler)

Fusion Welding Advantages & Disadvantages Advantages Welds stronger than parent components Simple joints Disadvantages Butt joints Only used for pipes

Fusion Welding Basic Operation Procedure Initial heating Pressing Video

Fusion Welding Equipment Used Equipment Welder Warming Collar Clamping/Holding Equipment

Fusion Welding Design Requirement Pictures Correct Welding Incorrect Welding Considerations during Fusion welding –Localization of heat at selected area (deformation of other areas) –Use materials with wide melting range

Fusion Welding Examples

Fusion Welding Conclusion Used for joining pipe Clear weld areas Warming time Warming surface depth Joining time (pressure application)

Friction (Spin) Welding Introduction/ Theory and Background Definition Heat required to soften and fuse two materials achieved by friction generated from two materials moving while in contact Component-to-component similarities Mechanical properties Physical properties Geometry First application – sealing water filled compasses

Friction Welding Advantages & Disadvatages Advantages Oxygen is excluded from the joint (direct contact) Weld strength=parent material Good appearance Disadvatages Configuration limited to circular parts Flashing

Friction Welding Basic Operation Procedure Component rotation Pressure Contact Heat Production Concluded by Forge Force

Friction Welding Equipment Equipment –Standard shop equipment –Lathes –Drill presses

Friction Welding Design Requirements/Considerations Smooth surfaces Low melting temps. Surfaces are free of contamination Large surfaces are difficult to weld Circular areas can be molded in

Friction Welding Considerations Cont. – Weld Quality Factors Joint geometry most important Surface velocity Contact Pressure Coefficient of Friction Heat transfer capacity of material(s)

Friction Welding Examples Floats Aerosol bottles Joining studs to plastic parts Automotive Electronics Furniture Toy Appliance Industries

Friction Welding Conclusion Flashing may occur Must be circular weld joints Good weld strength No air entrance Inexpensive tooling

Extra Info - Other Methods of Welding Plastics Sheet Hot air/gas Track Speed Tractor/Machine Linear Vibration Induction/Electromagnetic

Extra Info - Weld Testing Importance of joint strength Factors that affect joint strength Test Methods/Tools/Ops

Questions???