Joining Processes of Plastics

Ümit TAYFUN

OutlineWhat is joining processTypes of Plastic Joining Process Hot Plate Laser Welding Ultrasonic Assembly Vibration Welding Spin Welding  Mechanical Fastening

Joint Design

What is Joining Process Materials joining is a group of technologies

that includes welding, brazing, soldering, and adhesive bonding of metals, ceramics, plastics, and composites to themselves and to each other. A complete “understanding of materials joining requires a thorough knowledge of processes, materials, non-destructive evaluation, and design.’’

Joining MethodsAdhesives and mechanical fastening

are very useful joining techniques, but fusion bonding or welding is particularly suitable since joining times are often very short, enabling high volume production, and the welded parts are readily recycled or incinerated, easing disposal problems.

Features of Joining Process Joining thermoplastics and thermoplastic composites

involves heating the polymer to a viscous state and physically causing polymer chains to interdiffuse, usually by application of pressure. These processes have several attractive features:

Speed Strong joints Tolerance of contaminated surfaces. Joins difficult substrates, such as polyolefins Improved recyclability or incineration.

Classification of Joining MethodsWelding by Direct Heating(heated

tool,hotgas,resistance wire,infrared,laser)

Induced heating(induction,fusion)Frictional

heating(ultrasonic,vibration,spin)Solvent WeldingMechanical Fastening

Heated Tool Welding

Two fixtures press components into a hot moving platen,causing the plastic to melt at the interface

Hot Plate Welding 

Hot plate welding utilizes a temperature controlled heat platen assembly which is introduced between the two parts to be assembled.

Hot Plate Welding Machine

The ideal assembly solution for medium, contoured, or complex thermoplastic parts.  Designed for versatility and easy tooling changeover to accommodate a variety of parts

Hot gas-extrusion Welding

In hot gas/air and extrusion welding, the weld joint is filled with a partially- or fully-molten polymer, respectively

Hot Gas WeldingThin

Thermoplastic sheets can be hot gas welded using a joint and a thin strip of welding stock

Laser Welding

Laser IRAM is based on the idea of passing light/laser radiation through one plastic component and designing  the second component to absorb the laser light.

Laser Welding Machine The laser weld process can

produce visually pleasing joints on parts with complex geometries, both very large and very small. The process is extremely precise and controllable

Friction Welding In Friction Welding the interface alone is

heated due to mechanical friction caused by one substrare contacting and sliding over another surface.

Ultrasonic WeldingSpin WeldingVibration Welding

Ultrasonic Welding

 Ultrasonic welding utilizes an acoustic tool called a horn to transfer vibratory energy through the part to the joint area, where it is converted to heat through friction that melts the plastic

Ultrasonic Weldabilities for common Thermoplastics

Ultrasonic Welding Machine Ultrasonic plastics

assembly is a fast, clean, efficient, and repeatable process that consumes very little energy. No solvents, adhesives, mechanical fasteners, or other consumables are required, and finished assemblies are strong and clean.

Spin Welding

Spin welding is a process that joins circular thermoplastic parts by bringing the part interfaces together, under pressure, with a circular, spinning motion.

Joints in Spin WeldingCommon joints

used in Spin Welding Process

Spin Welding Machine Spin welders use heat

generated by rotational friction at the joint line to weld thermoplastic parts with rotationally symmetric joints. The machine applies pressure axially while rotating one part against its stationary mate, and the resulting friction generates heat that melts the parts together.

Vibration Welding Vibration or linear

friction welding involves the rubbing of two thermoplastic parts together, under pressure and at a suitable frequency and amplitude, until enough heat is generated to melt and mix the polymer.

Vibration welding Machine Vibration welding

can join all known thermoplastics including materials with up to 45 percent filler content. Vibration welders can also join many dissimilar materials with compatible melting points, composite materials and fabrics.

Microwave Welding

Microwave welding is still a technology in a fairly early stage of development. Microwaves have higher frequencies than either induction or RF (dielectric) welding

Mechanical FastenersA large variety of mechanical fasteners

can be used for joining plastic parts to themselves and to another material

Machine Screws and boltsSelf-threading screwsRivetsSpring fasteners and clips

Advantages of using self-threading screws

Off-the-shelf availability

Low costHigh Production

ratesMinimum tooling

investment

Joint Design

References:www.ewi.orgwww.knovel.comwww.plasticwelders.comwww.specializedassembly.comwww.ultrasonicsforless.com www.branson-plasticsjoin.com www.modernplasticwelding.com.au