Is the inspection environment of the plastic case and any defective points?

2021-03-23 14:50:25 admin

Compared with metal, stone and wood, plastic products have the advantages of low cost and strong plasticity. They are widely used in the national economy. The plastic industry occupies an extremely important position in the world today. For many years, the production of plastic products has developed at a high speed all over the world. Of course, it is also an area where quality is very error-prone. This requires quality monitoring. Do you know the inspection environment of the plastic shell and the points where there are bad defects?




   1. Inspection conditions and environment




  The inspection conditions and environmental rules are as follows:




  1, distance:




  The distance between the human eye and the surface of the measured object is 300mm~350mm;




  2, time:




  The inspection time for each piece does not exceed 12s (if the defects that cannot be inspected within 12S are acceptable);




  3, location:




  The viewing surface is 45° with the desktop, and it rotates 90° up, down, left, and right (to ensure that all defects on each surface can be seen);




  4, lighting:




  100W cool white fluorescent lamp, the light source is 500mm~550mm from the surface of the measured object, (illuminance reaches 600 Lux~800Lux).




   2. Poor plastic material defects




  1, point defect:




   has a point-shaped defect, the largest diameter shall prevail when measuring the size.




  2, heterochromatic point:




  The color that appears on the surface of the plastic part is different from the surrounding dots.




  3, bubbles:




  As the raw material is not sufficiently dried, there are shrinkage holes inside the product after molding.




  4, multiple glue points:




   There are small plastic bumps on the surface of the product due to mold damage.




  5, shrink:




   When the plastic melt passes through a thinner section, its pressure loss is very large, it is difficult to continue to maintain a high pressure to fill the pits formed in the thicker section.




  6, bright spots:




   For non-glossy plastic parts, due to uneven wall thickness, local shiny phenomenon occurs at the sudden change of wall thickness.




  7, hard scratches:




   There are deep scratches on the surface of plastic parts due to the friction of hard objects.




   8. Fine scratches:




   There are no deep scratches on the surface of the plastic part.




  9, flash:




   Due to injection molding parameters or mold reasons, plastic scrap edges are generated at the edge or parting surface of the plastic part. .




  10, weld line:




When plastic melt flows in the cavity, when it encounters obstacles (cores and other objects), the melt cannot fuse well after bypassing the obstacles, so an obvious line is formed on the surface of the plastic part. It is called a weld line. k) Warpage: Plane deformation of plastic parts caused by internal stress.




  11, top white/top convex:




  Because of the large tightening force of the plastic parts, the ejector area is subject to the white print or bulge caused by the strong ejection force.




  12, insufficient filling:




   Due to insufficient injection pressure or poor exhaust in the mold cavity, the molten resin cannot reach a certain corner of the mold cavity, resulting in insufficient injection.




   13, silver bars:




  The silver-white streaks appearing on the surface of the plastic part along the resin flow direction.




  14, flow pattern:




  The annual ring-like stripes on the product surface centered on the gate.




   15, burnt:




   Local plastic coking and blackening appearing on the surface of the plastic part.




   16, drag flowers on the side:




  Due to excessive injection pressure or uneven cavity, the edges are scratched during demolding.




   17, rupture:




   product cracks or small cracks caused by internal stress or mechanical damage. s) Color difference: The color difference between the surface of the product and the standard sample is called color difference.




   18. Impurities:




  There are foreign matters mixed into the raw materials, etc., and spots appear on the surface of the product after molding.