1. The basic composition of the mold
(1) Front mold (master) (fixed mold),
(2) rear mold (mould) (moving mold),
(3) insert (insert),
(4) row (slider),
(5 ) Inclined roof,
(7) gate (inlet)
2. Effect of Mold Product Shape on Products
Wall thickness, geometry, shape shrinkage, mold draft
3. Effect of water inlet on shrinkage of products
Larger inlet size results in smaller shrinkage, smaller size results in higher shrinkage, parallel flow direction results in higher shrinkage, and lower vertical shrinkage.
4. The effect of die wall thickness and wall thickness is too small
Excessive wall thickness: (1) Increase in cost (2) Extend the forming time and reduce the production efficiency (3) The quality is difficult to control, and bubbles, shrinkage holes, depressions, etc. are prone to occur.
The wall thickness is too small: (1) The resistance to plastic flow in the mold is large. If the shape is more complex, the forming will be difficult (2) the strength is poor
If the wall thickness of the plastic part is not uniform, the shrinkage will not be uniform after the forming process, and not only the air bubble, the depression, and the deformation will also have a large internal stress. The junction between the wall thickness and the thin wall should avoid sharp corners, and the thickness should be gradually reduced along the direction of the plastic flow.
5. Fillet (R position)
Set the rounded corner (R position) to increase the strength so that the plastic parts will not be deformed or cracked.
(1) In order to ensure the strength and rigidity of the product without thickening the wall thickness of the plastic parts, reinforcing ribs may be provided at the appropriate parts of the plastic parts to prevent deformation. In some cases, the problem of plastic flow during molding may also be improved.
(2) The thickness of the ribs must not exceed 50% of the plastic parts, usually about 20%.
(3) The ribs should be lower than the plastic parts.
(1) It is easy to produce welding marks around the hole, which reduces the strength of the plastic parts. Note: The distance between holes and holes, holes and plastic parts should generally take more than twice the hole.
(2) The edge of the hole can be used to strengthen the hole strength.
(3) The depth of the blind hole must not exceed 4 times the diameter of the hole.
(4) The screw hole should pay special attention to the hole strength and aperture size. If the hole diameter is too large, it will slip after entering the screw. If the hole diameter is too small, there will be no screws or knocking screws.
(5) The hole is too long (high) should pay attention to poor mold exhaust
(6) The depth of the aperture is preferably not more than 8 times the aperture.
(7) Holes with steps, the cores are fixed on both sides of the fixed and movable molds, it is difficult to ensure the concentricity, and burrs are easily generated at the joint positions of the two cores, so the cores (either ) Increased by more than 0.5MM from the other side of the guide forming
8. Mold inserts, rows, and inclined tops.
Inserts, rows, and angled tops of molds are usually set on the moving mold of the mold. If the fitting is not tight, there will be burrs.