Novice engineers will inevitably encounter some problems in the process of injection molding. How to solve these difficult and complicated problems?
FCS provides 9 injection molding questions to help you master the molding points and improve production efficiency and product yield.
1. Briefly describe the working state of check valve in the process of plasticizing, injecting and maintaining pressure:
2. Briefly describe the relationship between injection speed and injection pressure, pressure maintaining speed and pressure:
The relationship between injection pressure and injection speed is as follows:
In the injection process parameters, the velocity is dominant between the velocity and the pressure, and there is no direct relationship between the two.
In production, for example, the injection speed of 100mm/s is set. When the actual injection pressure is less than the set pressure value, the screw is molded at the injection speed of 100mm/s; when the actual injection pressure exceeds the set pressure value, the screw cannot reach the injection speed of 100mm/s.
The relationship between the actual injection pressure and the injection speed is that the faster the speed, the greater the actual pressure value, and the higher the injection speed, the greater the pressure you are required to set. High pressure is also required when the speed is very slow. That is to say, the point with the lowest injection pressure will not be at the fastest speed or the slowest speed.
3. If the product has burnt marks, you need to take the following steps:
4. Briefly describe the influence of mold temperature on product deformation?
In terms of molds, the main factors that affect the deformation of plastic parts include the gating system, cooling system and ejection system.
For the control of mold temperature, in addition to the design of the mold cooling system, different cooling rates of each component should be set according to the characteristics of the product structure. More attention should be paid to the different shrinkage rates of plastics parallel to and perpendicular to the flow direction of molten glue. The solidification of molten glue will also deform due to different cooling rates, different crystallinity and shrinkage differences.
With a sound mold temperature and cooling system, after the product is injected, demolded and ejected, the temperature of all parts of the product is balanced, so that a good product with the lowest deformation amount can be obtained, otherwise the deformation of the product will be out of control.
5. If a product is not completely filled and has burrs during production, what are the possible reasons?
6. Why is it necessary to retract after plasticizing? How to optimize it?
Large or small suction will directly affect the quality of the product. Large suction will easily cause stress marks on the surface of the product, while small suction will easily cause unstable residual quantity, unstable product quality, overflow of mold runner, or silky leakage from runner, etc. The general experience value shall not be less than 5mm.
How to optimize: According to the empirical value, it is necessary to fine-tune the adverse phenomena of the products in actual production until no overflow is generated and qualified products are produced.
7. How does the back pressure affect the product? How is the setting of back pressure generally carried out?
High back pressure:
Low back pressure:
Back pressure setting:
From small to large (for details, please refer to the values given by the material supplier and the structural characteristics of the product)
8. What should you do when you find that the surplus is unstable?
9. How to quickly find out the reasonable clamping force?