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РусскийSelection of material for shaping parts
Everyone who has ever connected his life with the production of products knows that the full cycle, from the drawing to the manufacture of the product, must be entrusted to professionals who are masters of their craft. Correctly composed terms of reference, based on efficiency, functionality, and design of the future product contributes to the first step towards designing and manufacturing of a mold or die. Your tool is your investment. Payback of the product and return on investments will depend on the right choice of materials for the manufacture of mold, die elements and timely maintenance. The competent operation and maintenance will prolong the service life of the tool, and also maintain the quality of the products. Your product will be competitive, and therefore in demand. So, first of all, you need to choose the material for the future tooling. Materials used for the manufacture of injection molds must withstand pressures and forces occurring during the casting process. To such materials high requirements are imposed, they should provide: good heat transmission, high wear resistance, high corrosion resistance, high dimensional stability and better workability. Such materials, depending on the chemical composition, are carbon and alloy steels.
In general, the correct choice of steel grade for shaping parts depends on the type of polymer material being processed and output of manufacturing range. If you are going to process aggressive materials such as PVC, you need to choose stainless steel grade 40X13, 30X13 for production of shaping parts, if the polymer material does not contain aggressive components, fiberglass, and if the output is small, then you can fix on cheap steel grade P20 with a hardness of 28-30 HRC. For the processing of abrasive materials, as well as for the production of a large volume of products (up to 1 000 000 units), it is necessary to use 4Х5МФС tool die steel with a hardness of 50-52 HRC with the possibility of wear-resistant coatings. The hardness of steel also depends on the heat treatment.
Tests on injection molding machines
Finally, tooling is assembled, passed test of hermeticity of cooling system and ready to pass acceptance test at production shop of plastic products on injection molding machine with locking force, specified in the terms of reference. During tests, the technological process is tried out to this grade of polymer material, the quality applicable to the product is achieved, if necessary, the mold is modified, all corrections are fixed and recorded in the project documentation. Reference sample is made for the part, a passport is made for the mold, where throughout the life cycle of the mold information about maintenance, repair of the tooling, and the number of products produced is entered.
Mold should be mount on injection molding machine with rated locking pressure. Locking pressure is calculated as relation of max length of a material flow path to a wall thickness of a product (average pressure in mold cavity), multiplied by project surface area of future casting. Too high locking pressure will lead to failure of mold, as well as to defects of product.
Die is mounted on press with not less than estimated pressure.
Before the beginning of mold operation, it is necessary to learn its units and the principle of work.
Thermostatic control of mold
Mold should preferably be thermostated, prevent it from thermal shock, which can lead to fallout- micro cracks, followed by destruction. Thermostatic control of mold helps to reach high figures when developing technical process: the best extraction of a product, high physical and mechanical properties of product, the best spill, and naturally the best physical form (depend on the cleanliness of surfacing processing of shaping part) and etc. The temperature of thermostatic control is set, depending on polymer’s property and reaches high figures more than 100 0С. Most often, heat transfer liquid, depending on the temperature is water or oil. The significant property of cooling (the temperature of mold is lower than the melt temperature) during the long-term usage is consistency. It is necessary to provide uniform cooling of casting. It is important that the temperature of rubbing elements of mold varies not more than 5 0С during the operation. Change of linear dimensions and geometry under changes of the temperature can lead to scores on rubbing elements and blocking of mold.
Well-timed maintenance of mold
During the operation a mold undergoes significant changes. Careful maintenance and timely repair of operated mold is necessary. To ensure permanence, servicing and scheduled repair are necessary for molds and dies.
Maintenance of tooling can be divided into three stages: maintenance during operations, after the disassembling and before sending for storage. Do not forget to provide toolmakers with the latest defective products – this facilitates rapid orientation in the problem and finding the cause of the defect, respectively, rapid repair.
Maintenance during the operation:
- inspection before launching of shaping parts for scores, cold work- hardening, changes in geometry of the signs and pushers, carbon deposit, and also the presence of run on the mold (tightness of cooling system). If it is necessary, clean air channels.
- check lubricants in easy of access places (pushers, guide pillars, bushings, sliders). Remove the old lubricants; apply fresh lubricant Litol-24, trying to apply evenly a thin layer, so that the lubricant not falls on the shaping parts.
Maintenance after the disassembling:
- inspection, maintenance diagnostics;
- cleaning and lubrication;
- resetting of small faults, changing;
- cleaning, flushing the cooling system;
- tightening of loosen knots.
For a long period of storage, molds and dies are preserved, applying to shaping parts lubricants from preservative consistence. Keep molds and dies better on racks, protect from moisture, dust and dirt, if necessary cover with a polyethylene film. All tooling should be identified for quick search.
Scheduled repair includes:
- current maintenance with partial disassembly/assembly with replacement of elements; grinding and polishing of shaping parts.
- general maintenance with full disassembly and replacement of all worn parts. Parameter recovery according to the drawing.
We provide with all necessary documentation, carry out preventive maintenance of molds and dies. In our work we are eager to make your tooling work for a long period.