The measuring device can be used to perform the distance measurements required to determine shrinkage values in accordance with DIN EN ISO 294-4. The starting point for measurements "to determine the processing shrinkage and post-shrinkage of thermoplastics" are injection-molded test specimens measuring 60 x 60 x 2 mm in accordance with the DIN standard, for which the values are determined. The shrinkage is measured both in the direction of flow and transverse to the direction of flow.

In conjunction with other parameters such as wall thicknesses and flow paths, this information enables toolmakers and calculation engineers to carry out specific calculations for the most accurate dimensioning of their tools. This applies not only to the production of new molds, but also - e.g. in cases of planned material changes - to the adaptation of existing molds. In any case, the cavity must be designed in such a way that the material shrinkage still present up to 48 hours after processing is taken into account with regard to the final plastic part.

"We had previously determined the shrinkage values using probes," summarizes Grit Müller from the Application Engineering team at Kraiburg TPE. "However, the use of contactless measuring devices proves to be particularly advantageous for shrinkage measurements of soft and very soft materials." The reason: "When using mechanical devices, measurement distortions can occur as a result of minimal pressure loads, which in turn result in minimal deviations from the required dimensions for the plastic part produced after processing." According to Müller, the necessary conditions for the use of the new optical measuring device - namely the expansion of the in-house test plate production by integrating an additional insert into the new master mold (including the internal pressure sensors) - had already been created in the previous year.

Since the introduction of the new contactless measuring device, Kraiburg TPE has been able to determine the shrinkage values for all common compounds in accordance with the DIN EN ISO 294-4 standard - regardless of the Shore hardness of the materials tested. This gives customers and potential new customers the opportunity to make their decisions on the use of new or alternative materials on the basis of even more precise information. This is particularly relevant for the production of one-component materials, as only the TPE starting material shrinks here; however, the influence on shrinkage can also be better assessed in two-component composites.