Temperature settings for cylinder and mold
Optimum settings of the correct temperature are not only important for an easy and unobstructed processing. The correct processing temperature can also have, depending on the TPU – grade, a high influence on the final physical properties of the parts. The following graphs show exemplarily the stress at 100% strain, the ultimate tensile strength and the ultimate elongation as a function of the processing temperature. The study was done on an injection molding machine with 30mm screw diameter.
Valuation of clamping force
Clamping force ≥ mold opening force in kN =
surface in cm2 • mean cavity pressure in
The actual clamping force required is determined first and foremost by the two variables included in the formula. Over and above this, the clamping force is influenced by other factors, such as the rigidity of the machine and the mold, the design of the molded part, the permitted breathing, the processing parameters and the molding compound itself.
As a guideline from the experience, it is assumed that the mean cavity pressure is between 300 and 700 bar.
-Projected surface = sum of all the surfaces subject to pressure projected on to the plane of the clamping platen Example: truncated cone-shaped disc
For material grades with very good flow behavior, it may be necessary to use the higher pressures (greater clamping force) in order to prevent flash formation.