Precision casting enterprises must conduct a comprehensive review of the production management of castings. The project must start with the management of molds (pressing). The material, accuracy, life and delivery date of molds have an important impact on the quality of castings. Precision investment casting companies generally belong to small batches and a variety of specifications. For example, sewing machine castings include more than 200 accessories, etc., which are more complex castings. Occupies a very important position in mold management. Therefore, our management of molds mainly includes:
- 1. The technical department is responsible for all liaisons with mold design and mold production factories. Strengthen the selection, evaluation and confirmation of mold factories. Choose professional mold manufacturers with advanced technology and equipment as much as possible, and strengthen the management of mold trial work.
- 2. The Quality Control Department is responsible for the inspection of new molds, wax molds and castings, calculation of shrinkage, and judgment of whether the mold is qualified.
- 3. The production department is responsible for the daily management of molds, such as mold registration, daily maintenance, storage, protection, evaluation, and handling of warehouse entry and exit procedures.
The item is to strictly strengthen the quality control of raw materials. The quality of raw materials determines to a large extent the quality of castings. Choosing high-quality materials will not necessarily increase the production cost of castings.
The third item is to pay close attention to quality control in the production process. The complexity of the precision casting process determines that each process in the production process must have a full-time inspector to conduct the “three inspections” system of first inspection, patrol inspection, and completion inspection. First, the unqualified control is transferred to the next process.
The fourth item is the control of the shell making process. Layer number parameters Surface layer: surface layer two, two layers, three or four layers, half layer; paint type: 300/325 mesh zircon powder 200 mesh zircon powder
The fifth item is dewaxing quality control. Many precision investment casting companies use high-pressure steam dewaxing methods. The process requires that the dewaxing steam pressure is between 0.6-0.75Mpa, and the pressure time to reach 0.6Mpa should be less than 14S, and the dewaxing time of the entire shell is completed within 6-10min. Because the thermal expansion coefficient of the mold material is much greater than the thermal expansion coefficient of the shell, too long dewaxing time will cause the mold shell to expand and crack. Therefore, after dewaxing, an inspector needs to inspect the quality of the shell to check whether the wax liquid in the shell is Take off, whether the shell has cracks or expansion.
The sixth item is the quality control of shell roasting, metal smelting and pouring. Shell baking mainly eliminates moisture and impurities in the shell, enhances the strength and permeability of the shell, and its temperature cannot be too high or low. Generally, enterprises use the range of 950-1050°C. One thing that needs to be noted is: the operator should be careful when loading the shell and fork shell to prevent it from collision, squeeze, shell drop, breakage, etc.
The seventh item is the quality control of the post process. The post-processes mainly include shelling, shot blasting, pouring riser removal, repair welding, rough grinding, shaping, heat treatment, sand cleaning, mechanical polishing, pickling passivation, electrolytic polishing, spraying and other processes.
One is to ensure that the quality of castings meet the technical requirements for delivery and acceptance, all inspections must be carried out in accordance with the casting drawings, investment precision investment casting technical standards, and the inspection contract submitted by both parties. Inspection mainly includes appearance quality inspection, internal quality inspection and other quality inspections.