When to use hot-plate welding

When considering the common plastics joining methods for assembling a new product, in the mix of options should be hot-plate welding. This low-force method of heating and bonding plastic parts has been around a long time. Contemporary machinery and tooling provide users with exceptional control and consistent weld results.

When would hot-plate welding be a better alternative to other methods? Historically, these would be popular reasons:

• The components are large (this may rule out ultrasonic welding)
• The geometry of the product is complex (this could prohibit the use of vibration welding)
• Excessive or loose particulate (flash) cannot be tolerated
• A-surface part marking is not permissible
• High strength and hermetic seal is required of the assembly
• Assembly/machine cycle time in the 15-25 seconds range is acceptable

These are all excellent reasons to consider implementing the hot-plate welding process. But, consider these additional facts:

• Small assemblies are great applications for hot-plate welding, too. Leading manufacturers offer a hot-plate welder model designed for parts no larger than 6” square.
• Simple geometry components benefit from the low stress, high strength results of hot-plate welding just like complex geometry components
• Even if flash control is not a high priority in a given application, what possible benefit is derived from uncontrolled flash?
• If part marking is the result of a plastics joining process, it’s the result of energy (usually vibratory) going somewhere it shouldn’t be going. At best, it scuffs or blemishes otherwise nicely molded surfaces. At worst, it can cause a rejected assembly due to the obvious, but it can also be a tell-tale sign of inconsistent weld results.
• Even if the application only requires moderate strength and a non-hermetic seal, the performance of the hot-plate welding process generally provides a very robust processing window. That’s good news for everyone on the operational side of the business.
• If hot-plate welding cycle times are not fast enough, consider welding multiple parts simultaneously. Straight-talking technical salespeople and manufacturer application engineers will offer their advice about the feasibility of multiple part welding.

Hot-plate welding, like any of the methods which can be selected to join plastic components, has its pros and cons. For instance, there are certain resin and filler combinations which are extremely challenging – if not impractical to hot-plate weld. Additionally, if the hot-plate welding equipment does not offer velocity, distance, and force control, the user will be limited in process control capabilities. Finally, without suitable coating surfaces on the heated tooling, tool wear and plastic material sticking can be problematic. A reasonably well equipped hot-plate welder with well-engineered tooling can provide an excellent solution for assembling plastics.

Learn more about hot-plate welding.