Release time：2021-10-22
There are many types of moulds. Only plastic moulds can be divided into:
(1) Injection mold; (2) Blow mold; (3) Blister mold; (4) Extrusion die; (5) Foaming mold; (6) Silicone mold.
Injection molds can be subdivided into:
According to different runner systems, it can be divided into two parts: hot runner mold and cold runner mold;
According to the different ways of channel separation, it can be divided into: two plate mold, three plate mold;
According to the different forms of ejection, it can be divided into: positive mold, inverted mold;
According to the type and quantity of injection molding plastic, it can be divided into two kinds: monochrome mold and two-color mold.
Plastic molding cycle process:
1) Mold closing - the mold closes and generates high pressure.
2) Injection - inject molten plastic into the mold cavity at a certain speed, pressure and metering.
3) Pressure maintaining: after the injection section, the plastic is still injected at a certain pressure for feeding.
4) Cooling - the process of product cooling and shaping.
5) Storage - the screw rotates backward to plasticize a certain amount of raw materials for the next injection.
6) Mold opening - open the mold.
7) Ejection - the product is pushed out after cooling and shaping.
8) Close the mold and start the next cycle.
Five parameters of forming:
1) Pressure: including injection pressure, holding pressure, clamping force, back pressure, ejection pressure, water pressure, etc.
2) Speed: including injection speed, mold opening and closing speed, material storage speed, ejection speed, etc.
3) Temperature: material pipe temperature, mold temperature, cooling medium temperature, original semi drying temperature, etc.
4) Time: injection time, pressure holding time, cooling time, forming cycle base, etc.
5) Position: storage metering position, loosening position, injection section switching position, pressure maintaining switching point, mold opening position, ejection position.
Bad forming analysis:
1. Weld
Cause: multi point glue feeding or glue melting bypasses the broken hole and forms a line mark on the plastic surface.
Countermeasures: (1) improve the mold temperature, especially the front mold temperature; (2) Improve the ejection speed; (3) Increase the holding pressure; (4) Raise the temperature of the feed pipe; (5) Increase back pressure; (6) Expand the gate; (7) Increase exhaust; (8) Add cold wells.
2. Shrink
Definition: dents caused by local excessive shrinkage of plastic.
Countermeasures: (1) increase the holding pressure; (2) Increase glue injection; (3) Reduce the temperature of the feed pipe; (4) Reduce the mold temperature; (5) Expand the gate; (6) Change the gate position; (7) Add more glue; (8) Modify the product structure.
3. Spray mark
Definition: scattered traces of plastic products around the gate.
Countermeasures: (1) raise the mold temperature; (2) Reduce the ejection speed; (3) Adjust the shooting position; (4) Improve gate design; (5) Add cold charging wells; (6) Expand the flow passage.
4. Flow mark
Definition: the strip-shaped white trace formed on the surface during the product molding process.
Countermeasures: raise the mold temperature; Reduce the ejection speed; Raise the temperature of the feed pipe; Increase back pressure; Sufficient drying of raw materials; Expand the gate; Add more glue; Increase flow channels and cold charging wells.
5. Disc print
Definition: a ring-shaped texture near the gate.
Countermeasures: (1) raise the mold temperature; (2) Improve the ejection speed; (3) Raise the temperature of the feed pipe; (4) Increase back pressure; (5) Expand the gate; (6) Add more glue.
6. Unsatisfied mold
Definition: glue shortage caused by insufficient product filling.
Countermeasures: (1) increase the injection pressure; (2) Improve the ejection speed; (3) Raise the mold temperature; (4) Raise the temperature of the feed pipe; (5) Increase the quantity of materials; (6) Expand the gate; (7) Expand the flow channel; (8) Increase exhaust; (9) Increase the material thickness of the product; (10) Increase the liquidity of raw materials.
7. Phi Feng
Definition: excess sheet growing along the parting line in product forming.
Countermeasures: (1) reduce the injection pressure; (2) Reduce the ejection speed; (3) Reduce the mold temperature; (4) Adjust the delivery switching point; (5) Reduce the quantity of materials; (6) Reduce the temperature of the feed pipe; (7) Reduce the gap of the mold; (8) Evenly feed glue.
8. Z-shaped spray mark
Definition: spray marks formed by direct filling of plastic.
Countermeasures: (1) raise the mold temperature; (2) Reduce the ejection speed; (3) Raise the temperature of the feed pipe; (4) Change the gate position; (5) Increase the cross section of the gate.
9. Stress trace
Definition: marks formed on the outer surface of products due to sudden changes in material thickness.
Countermeasures: (1) reduce pressure maintaining; (2) Adjust the injection switching point; (3) Balanced glue feeding; (4) Change the gate position; (5) Increase gate; (6) Increase exhaust; (7) Change the product structure; (8) Secondary processing desalination;
From the perspective of cost and service, the improvement of poor appearance is: 1) adjustment and improvement; 2) Change the mold; 3) Secondary processing; 4) Replace the product.
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