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The requirement for prototype parts that are fit for functional product testing in production intent materials is ever increasing. At RP Technologies, we’re also seeing an increase in secondary processes being bought in for effective testing and development.

Hot plate welding at prototype stage is one of the increasingly requested processes and we can provide this service in-house for prototype projects and low volume production.

What is Hot Plate Welding?

Hot Plate Welding is a thermal welding technique capable of producing strong, air-tight welds in thermoplastic parts. When using thermal energy in a tightly controlled manner, thermoplastic parts can be heated to molten temperatures very quickly and then joined together.

Hot plate welding is used for a variety of applications but we typically see it being used on automotive expansion tanks, it’s the ideal process for tanks that need floats or sensors placing inside prior to welding for a hermetic seal.

The process is tailored to suit each project by manufacturing custom nests to accurately hold the components in position. The hot plate which contains cartridge heaters has mirrors bolted to each side of it which are profiled to suit the parts being welded.

To start the process the components are loaded into the nests, a hot point moves between the two parts before they move onto the hot plate.  The melt time elapses and the parts move apart with the hot plate moving away. The two melted parts are then brought together and as they cool down the plastic welds together. Once cool the welded components are removed from the nests.

Design Considerations

When designing parts that require hot plate welding there are a few points to consider.

It’s important that additional material is included in the component design to allow for sufficient melt to take place to achieve a suitable weld joint. As this varies for each component RP Technologies and Machine Techniques will look at each project individually and make a recommendation suited to your project.

If there are internal components fitted within the parts being welded the internal components will be subject to heat from the hot plate during the welding process. This means the internal components must be in a material that can resist this heat. RP will provide further information upon quotation of your project.

Joint Design

There’s a variety of joint designs that can be used depending on if aesthetics are important to your component design.

Straight Butt – this is the simplest but leaves the weld visible on both the inner and outer of the weld joint.

Flanged Butt – this has the weld internally on two legs meaning after the weld is completed it can’t be seen from either the inside or outside of the welded part.

Recessed – this creates an invisible weld from the outside of the product, ideal when aesthetics matter.

We will discuss joint design with you for each project to ensure the final welded part suits the application requirements.

Thermoplastic Materials

The most suitable material for hot plate welding is polypropylene. Acetal and glass filled

nylon can also be welded using this process if the time between melt and joints coming together can be reduced to less than 2-3 seconds.