BS EN ISO 294-4:2019 pdf free.Plastics – Injection moulding of test specimens of thermoplastic materials.
BS EN ISO 294-4 This document specifies a method of determining the moulding shrinkage and post-moulding shrinkage of injection-moulded test specimens of thermoplastic material in the directions parallel to and normal to the direction of melt flow. For the determination of shrinkage of thermosets, see ISO 2577[2]. Moulding shrinkage as defined in this document excludes the effects of humidity uptake. This is included in post-moulding shrinkage and thus in total shrinkage. For cases when post-moulding shrinkage is caused by the uptake of humidity only, see ISO 175[1]. Moulding shrinkage as defined in this document represents the so-called free shrinkage with unrestricted deformation of the cooling plates in the mould during the hold period. It is considered, therefore, as the maximum value of any restricted shrinkage.2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 294-1:2017 Plastics 一Injection moulding of test specimens of thermoplastic materials 一Part 1: General principles, and moulding of multipurpose and bar test specimens ISO 294-3:2002, Plastics 一Injection moulding of test specimens of thermoplastic materials 一Part 3: Small plates.Select the change-over point, between the injection and hold periods carefully to avoid a depression in the time against pressure curve (see Figure 1, Curve c] and to avoid a peak that, during the 1 s following the change-over point, exceeds the cavity pressure at hold by more than 10 % (see Figure 1, Curve b).Due to the inertia of the injection-moulding machine, the effective change-over time is longer than its nominal value. The correct change-over point shall therefore be adjusted individually for each value of the injection speed and for each material under test.NOTE Peaks in the cavity pressure lead to transient overloading of the cavity, followed by partial backflow of the melt. Thus, the mass of material injected into the cavity is not clearly defined and the orientation of the material near the gate will be perturbed. Keep the hold pressure constant during the hold period. BS EN ISO 294-4 pdf download.