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 .00025 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 http://www.mcelroymfg.com/fusion/flash/fusion101.html

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???