Rigid and Foam Sheet
In sheet extrusion, we seperate rigid sheet and foam sheet. In both processes, which are quite similar, the requirements for extrem good homogeneity of best melt quality is the key of success. Therefore, screws for sheet extrusion are only made by large experienced screw and barrel manufacturer. We got experience in this field for more than 20 years.
The difference for foam sheet and rigid sheet screws are based in temperature control and homogeneity of melt as well as the level of pressure in front of the screws. The pre-heating is basically the same. During the pre-heating, the formulation should be heated up in a homogenic form and then sheared in the compression zone. For rigid sheet extrusion the following vent zone has to have open structured melt so that all gasable parts can be vent of. For foam sheet formulation it is important that the reaction of foam agents do not start first. If this happens you vent of the foam agent. For foam sheet only non reactive gasable parts must be vented. In the metering-zone the rigid sheet screws have to show best homogeneity at high pressure, free of any pumping lines of the twin screws. At foam sheet screws the gasing process of chemical formulation components should start and should be homogenic mixed in the formulation. Creating best homogeneity is highest priority. Only with a best homogeneity you are able to get a fine cellstructure. For both screws sets it is important to find the right structure in the 8to0 adapter.
All GTS sheet screws do have an active oil tempering. Only by controlling the screw tip by oil it is importante to run high output, especially for foam sheets. We deliver GTS screws only including a special sealed oil block system which is able to run years free of leakage.
When you ask for a quote you will get a download with a lot of technical descriptions around your screws.