Section 9 - Troubleshooting
Welding Process
Material Choice
A family of thermoplastics is usually compatible with its own type and sometimes with other types. Characteristics to consider are the melting point and coefficient of linear expansion. Even members of the same family may cause problems due to differences in the manufacturing process. For example, an extruded Polyethylene (PE) piece may not weld as well to an injection molded PE piece as it would to another extruded PE piece.
Parameter Effects
Surface Speed
Insufficient surface speed may not allow the plastic to reach its melting temperature. Instead, it may simply erode away part of the material and stick by a clawing effect. The surface speed is determined by both the weld joint diameter and the spin motor speed.
Axial Speed
In conjunction with surface velocity, axial speed determines whether the plastic reaches the melting temperature. Both surface and axial speed are needed to produce sufficient frictional heating. Excessive axial speed may cause one part to scrape away part of the surface and produce a lot of flash but insufficient melt volume.
Weld Depth
Insufficient welding depth may not allow the melt to propagate far enough into the plastic to achieve the necessary melt volume and the required weld strength.
Hold Time
Insufficient holding time may prevent the plastic from solidifying and forming a strong permanent bond.
Troubleshooting
Table
Dukane Manual Part No. | Page 73 |