26 February 2018
- Last edited 26 February 2018
Here is the text from Wikipedia.
High frequency welding
High Frequency welding, also known as Dielectric Sealing or Radio Frequency Heat Sealing is a very mature technology that has been around since the 1940s. High frequency electromagnetic waves in the range of Radio Frequencies can heat certain polymers up to softening the plastics for joining. Heated plastics, under pressure weld together. Heat is generated within the polymer by the rapid reorientation of some chemicals dipoles of the polymer, which means that the heating can be localized, and the process can be continuous.
Only certain polymers, which contain dipoles can be heated by RF waves, in particular polymers with high loss power. Among these, PVC, polyamides and acetates are commonly welded with this technology. In practice, two pieces of material are placed on a table press that applies pressure to both surface areas. Dies are used to direct the welding process. When the press comes together, high frequency waves (usually 27.120 MHz) are passed through the small area between the die and the table where the weld takes place. This high frequency, radio frequency heat the plastic, that under pressure welds taking the shape of the die.
RF welding is fast and relatively easy to perform, produces a limited degradation of the polymer even welding thick layers, does not create fumes, requires a moderate amount of energy and can produces water-, air-, and bacteria-proof welds. Welding parameters are Welding Power, heating and cooling time and pressure, while temperature is generally not controlled directly.
If you used a Transient Thermal system, you would need to assign an internal heat generation thermal load to a small volume of the body, since the heat is generated by the dipoles in the plastic itself. You could slice the body and assign different values of internal heat generation.
I don't know HFSS or much more that I just read above about RF welding, so can you provide a value for internal heat generation to the sliced pieces near the die?