With the development of science and technology, plastic injection moulds have become an essential tooling of producing plastic products in China plastic products manufacturing industry. In our real life, plastic products have almost captured all fields. Whether it is the parts of aircraft and cars or some of the commonly used toothbrushes and cups in our daily lives. In fact, those plastic products that are commonly used around us are not produced by the manufacturer one by one according to the drawings, but are produced in batches through plastic injection moulds.

Before plastic injection moulding manufacturer produce plastic products, the injection mould of this product will be made in advance. After the injection mould is completed, the manufacturer can mass-produce through this mould. Is the plastic injection mould manufacturing process complicated?

In fact, the plastic injection mould manufacturing process is very precise and complicated, because in the real life, plastic injection moulds are applied to various plastic injection moulding products, and many plastic moulded products must be manufactured accurately, such as plastic bottle mouths and caps. The production of them needs to be very delicate, because if there is a little inconsistency, it can't be combined. Therefore, when making plastic injection moulds, it is necessary to pay attention to such problems. The injection moulds must be made very precise which is possible to make high-quality plastic injection moulding products. Of course, for those plastic products that are relatively large and inexpensive, there is no high process requirement. For example, the mould of plastic basin doesn't require too strict requirements for the manufacturing process.
Plastic Injection Mould Factory

The following problems should be noted when choosing China plastic injection mould manufacturer:
  • Don’t just focus on injection moulding products design, ignore injection mould making.
  • Don't just pay attention to prices. Should have overall consideration from injection mould quality, production cycle, and injection moulding company service.
  • Avoid multi-head collaboration, try to make plastic injection mould making and plastic injection moulded parts processing integration.
The ejector system has a variety of forms. It relates to the shape, structure and plastic properties of the product. Generally, there are ejector pins, jacking tubes, push plates, ejector blocks, pneumatic composite ejectors, etc. The design principles of the ejector system are as follows:
  1. When selecting the parting surface, try to keep the product on the side of the mould release mechanism.
  2. Top output and position balance to ensure that the product is not deformed, not broken.
  3. The thimble should be located where it does not affect the appearance and function of the product.
  4. The use of standard parts as far as possible is safe and reliable for manufacturing and replacement.
  5. The ejection position should be set at a large resistance, not too close to the insert or core. For box type and other deep cavity moulds, the side resistance is the largest and the top surface and side surface should be ejected at the same time so as to avoid deformation of the product.
It is necessary to check and verify the easily damaged plastic injection parts and register them. Reserve the amount of inventory that may be consumed within 4 ~ 5 weeks, and record the damaged parts that have been replaced. Perform the inspection of common auxiliary equipment, and take a photo to record the position of the injection mould assembly.
The most common cause of black streak is the material residue in the injection moulding machine barrel.Residue remains in the plunger injection moulding machine.For valve gated injection moulding machine, the valve-regulated part also tends to remain residue.The air is compressed to a high temperature in the cylinder, with the high temperature gas in the gate, so it will be easy to be black streak.
Black Streaks
Residual gas inside the injection mould is compressed into high temperature state and burn the material.
Insufficient air discharging will cause burn mark.
Insufficient air discharging will also cause material shortage.
Burn Marks
In the nozzle and side slip, cooled resin flow into the mould cavity in a semi-cured state. After contact with the injection mould, the resin immediately cured, and then into a deep cavity formed flow mark.Different thickness of the plastic parts can also cause flow mark.
Flow Marks
Using only one sprue (gate), without confluence the material from two directions, in this way the molded parts generally do not have weld line. If you want to avoid weld lines, you can only change the position of the sprue in the injection mould so that the welding mark will not occur in obvious places.
Change the location of the sprue in injection mould
Same reason with reticular fracture.
If not well demolded, the release pin will apply excessive force resulting in molded plastics whitening.
Whitening refers to stress whitening. We can see from the stress yield curve and crack white perception that it indeed to the energy expended. Just add a little energy will crack after whitening. (Figure A)
ABS material yield curve
Fracture looks like crack, but the essence is different, that the fracture is not like a void defects, coupled with stress in the polymer due to the parallel arrangement direction of itself. If heat the product, it can return to the state without fracture. In this way, we can distinguish the reticular fracture and crack.
Polystyrene has high impact resistance. The rubber particles dispersed in the polystyrene stress concentration point, majority cause tiny fracture. This is because the absorption of deformation energy. ABS is very subtle, so the fracture is very tiny, and has superior impact resistance.
Injection molded parts crackThe residual stress within the product. Moulding conditions should be set towards to elimination of stress. That is to increase cylinder and mould temperature, and when the flow ability of the material becomes a good state, the injection pressure should not be too high.

Pre-heated metal insert can ease the residual stress during injection moulding. In the same principle, annealing after forming the insert is also a method. When setting the moulding condition, reduce the injection pressure is the most effective. If the ejector pins are balanced, release more force when demoulding.
Reason of molded parts deformation (warping, bending, small wrinkles) is the same to cracks. That is the residual stress within the product. moulding conditions should be set towards to elimination of stress. That is to increase cylinder and mould temperature, and when the flow ability of the material becomes a good state, the injection pressure should not be too high.
Eliminate Molded Parts Deformation
To reduce the residual stress, the injection mould should be annealed. Heat distortion temperature below 10℃, heated over 2 hours to eliminate the effect of internal stress. However, due to the high cost, this method is not widely used.

If the cooling water holes of the mould cannot uniformly cool the product, and it also have residual stress, which means that the cooling water hole cannot be too shallow.
Molded parts flash Injection mould parting line, sliding surface, release pin, pad and so on, constitute a variety of slot gap between the moulds. The inflow material will cause flash. The flash looks like wedge-shaped blocks. It is gradually trend to be bigger.

The general principle to eliminate plastic parts flashes is to fix the injection mould. If the flash is caused by improper configuration, we should reduce cylinder and mould temperature, and reduce injection speed, in order to reduce material flow ability. However, it should be noted that cause a residual stress in the plastic parts.

It should be noted that add too much pressure on the injection mould will produce flashes. Foreign matters between the parting surfaces will cause damage to the mould and produce flash.Injection mould material commonly used materials such as S50C or pre-hardening HRC30 special steel, in this way, the parting surface is difficult to produce flash.
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Online tour of our plastic injection mould making factory in Shenzhen China.
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