I. Causes of DENTS
1-1 products of different parts thickness
1-2 insufficient internal pressure of mould
1-3 Mould Cooling Insufficient
1-4 deformation due to insufficient cooling time
II. Associated Knowledge
2-1 in the production process, concave marks are the most frequent occurrence of adverse phenomena, injection molding plastics in the cooling of the volume shrinkage, the early cooling part of the surface hardening, the interior will produce bubbles, the so-called concave marks, the slow part of cooling in the direction of bubble contraction produced a conspicuous concave.
2-2 Large shrinkage materials are also prone to dents. When you want to change the molding condition to eliminate the indentation, you should set the conditions to shrink the direction of small. That is, the temperature of the mould, the barrel of the material decreases, and the ejection pressure increases, but it should be noticed that the residual internal stresses can be caused.
2-3 because the indentation is not conspicuous as good, so, if not affect the appearance of the time, there is deliberately on the mold processing into a corrosive appearance, such as stria, granular and so on. Also, if the molding material is hips, reduce the mold temperature to reduce the smoothness also have effect. But once there are dents, it is difficult to repair polished products.
III. Methods of resolution
3-1 Instant: Raise the ejection pressure, prolong the ejection time, reduce the barrel temperature and mould temperature, and force cooling in the place where the dent is produced.
3-2 Short Term: in place where the dent is produced to complement the upper side (Fig a). This part is Bian Hou (Fig. B) when the material of the place where the dent is produced is narrow by the edges.
3-3 Long-term: The thickness of design products should be avoided. The reinforcement of the concave scar is easy to produce, and the narrow shape should be as short as possible.