First, the control of mold design
1. First of all, we must fully understand the technical requirements of the mold structure, material, hardness, precision, etc., including whether the shrinkage rate of the formed plastic material is correct, whether the 3D size of the product is complete, and reasonable processing analysis.
2. Full consideration should be given to various places that have an influence on the appearance of shrinkage, flow marks, draft inclination, weld lines and cracks of injection molded products.
3. Simplify the processing method of the mold as much as possible without impeding the function of the injection molded product and the shape of the pattern.
4. Whether the selection of the parting surface is appropriate, and careful selection should be made for the mold processing, the forming appearance and the deburring of the forming part.
5. Whether the pushing method is appropriate, whether the push rod, the unloading plate, the push-top sleeve or the like is used, or whether the position of the push rod and the unloading plate is appropriate.
6. Whether the side core pulling mechanism is suitable for use, the action is flexible and reliable, and there should be no stuck phenomenon.
7. Which method of temperature control is more suitable for plastic products, and which structure is used for temperature control oil, temperature control water, coolant, etc., and the size, quantity and position of the coolant holes are appropriate.
8. The form of the gate, the size of the material channel and the feed port, and the position and size of the gate are appropriate.
9, the impact of various types of modules and core heat treatment deformation and the selection of standard parts is appropriate.
10. Whether the injection volume of the injection molding machine, the injection pressure and the clamping force are sufficient, whether the nozzle R, the nozzle sleeve diameter, etc. match properly.
These aspects are prepared for comprehensive analysis and should be strictly controlled from the initial stage of the product.
Second, the control of process manufacturing
Although comprehensive consideration and arrangement have been carried out in the design stage, there are still many problems and difficulties in actual production. We should try our best to meet the original intention of the design in production and find out that the actual processing is more effective and more economical. Craftsmanship.
1. Select economical machine tools for 2D and 3D processing.
2, can also consider the appropriate fixtures for auxiliary preparation in production, the rational use of the tool, to prevent deformation of the product parts, to prevent fluctuations in the shrinkage of the product parts, to prevent demoulding deformation of the product parts, improve the precision of mold manufacturing, reduce Small errors, prevent mold accuracy changes, etc., a series of production process requirements and solutions.
Third, the usual production control
The occurrence of geometrical fluctuations after the forming of plastic parts is a common problem and is a phenomenon that often occurs:
1. Control of material temperature and mold temperature
Different grades of plastics must have different temperature requirements. The poor fluidity of plastics and the use of two or more kinds of mixes can be different. It is usually easy to control the plastics within the optimum flow range. However, the control of the mold temperature is more complicated. Different geometric shapes, sizes and wall thickness ratios of the formed parts have certain requirements for the cooling system. The mold temperature largely controls the cooling time; therefore, the mold is kept as much as possible. In the allowable low temperature state, in order to shorten the injection cycle, increase the production efficiency, and change the mold temperature, the shrinkage rate will also change, the mold temperature will remain stable, and the dimensional accuracy will be stable, thereby preventing deformation of the molded part and poor gloss. Defects such as cooling spots make the physical properties of the plastics optimal. Of course, there is a debugging process, especially the multi-cavity moldings are more complicated. Therefore, the mold temperature cannot be arbitrarily changed during the production process, and the mold temperature should be set within the recommended temperature range of the material.
2. Adjustment and control of pressure and exhaust
Appropriate injection pressure, the matching of clamping force should be determined when the mold is adjusted. The air in the gap formed by the mold cavity and the core and the gas generated by the plastic must be discharged from the exhaust groove outside the mold. If the gas is not smooth, there will be insufficient filling, causing weld lines or burns; these three forming defects sometimes appear in the same part, and when there is a thick wall around the thin part of the formed part, the mold temperature will be too low. Shrink marks, if the mold temperature is too high, there will be burns. Usually, weld spots will appear at the same time in the burned part. The exhaust groove will be neglected, and it is generally in a small state. Therefore, as long as no burrs are generated; The depth of the air shoulder is as deep as possible, and a large venting groove is formed at the rear of the shoulder so that the gas passing through the shoulder can be quickly discharged outside the mold, and if there is a special need, the venting groove is opened on the ejector. It is the same, one is that there is no flash, and the other is that it can work very well.
The depth of the exhaust shoulder is as deep as possible, and a large venting groove is formed at the rear of the shoulder so that the gas passing through the shoulder can be quickly discharged outside the mold, and if necessary, the vent groove is opened on the ejector pin. The reason is the same, one is that there is no flash, and the other is that it can work very well.
3. Supplementary shaping control of the size of injection molded parts
Due to the difference in shape and size of some plastic parts, deformation and warping may occur in different situations with the change of temperature and pressure loss after demolding. At this time, some auxiliary fixtures can be adjusted to make the molds quickly after the mold is released. Take remedial measures, and after it is naturally cooled and shaped, you can get better correction and adjustment effects. If strict management is ensured throughout the injection molding process, the size of the injection molded part is very well controlled.
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