Basic ways to improve mold quality

Update:11-06-2020
Summary:

First of all, the design of the parts should be reasona […]

First of all, the design of the parts should be reasonable, and the best structural scheme should be selected as much as possible. The designer of the parts should consider the technical requirements and the structure of the parts must conform to the manufacturability and feasibility of the mold manufacturing.

 

The design of the mold is the most important step to improve the quality of the mold. Many factors need to be considered, including the selection of the mold material, the usability and safety of the mold structure, the processability of the mold parts, and the convenience of mold maintenance. At the beginning of the design, it should be considered as carefully as possible.

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1. The selection of mold materials should not only meet the customer's requirements for product quality, but also need to consider the cost of the material and its strength within a set period. Of course, it also depends on the type of mold, the working method, the processing speed, and the main failure Factors such as form to select materials. For example: the main failure mode of the punching die is blade wear, you must choose a material with high surface hardness and good wear resistance; the punching die mainly bears periodic loads, which is easy to cause surface fatigue cracks and lead to peeling of the surface layer. The material with good surface toughness; the material with a particularly low friction coefficient should be selected for the drawing die; the material with strong thermal fatigue should be selected due to the cyclic thermal stress; for the injection mold, when the plastic part is ABS, PP, PC For such materials, the mold material can be pre-hardened and tempered steel. When the plastic parts are high-finish and transparent materials, corrosion-resistant stainless steel can be selected. When the batch of products is large, quenched and tempered steel can be selected. In addition, it is also necessary to consider the use of mold materials with low affinity to the parts to prevent the mold from aggravating the wear of mold parts and affecting the quality of the mold.

 

2. When designing the mold structure, try to make the structure compact and easy to operate, and ensure that the mold parts have sufficient strength and rigidity; when the mold structure permits, the corners of the surfaces of the mold parts should be designed as round corners to avoid stress Concentration; for concave die, cavity and some punches and cores, combined or inlaid structures can be used to eliminate stress concentration. For elongated punches or cores, appropriate protective measures need to be taken in the structure; for cold punches, It should be equipped with a device to prevent clogging of parts or waste materials (such as: ejector pins, compressed air, etc. At the same time, we must also consider how to reduce the impact of sliding fittings and frequent impact parts on the quality of the mold caused by long-term wear.

 

3. In the design, the range of disassembly and assembly must be reduced when repairing a part, especially when the wearing parts are replaced, the disassembly and assembly range should be reduced as much as possible.

 

The manufacturing process of the mold is also an important part of ensuring the quality of the mold. The processing methods and processing accuracy in the mold manufacturing process will also affect the service life of the mold. The accuracy of each part directly affects the overall assembly of the mold. In addition to the influence of the accuracy of the equipment itself, it is necessary to improve the processing accuracy of the parts and the technical level of the fitter in the mold grinding process to improve the processing accuracy of the mold parts. ; If the overall assembly effect of the mold does not meet the requirements, the chance of the mold operating in an abnormal state will be increased in the trial mold, which will have a great impact on the overall quality of the mold. Therefore, in order to ensure that the mold has good original accuracy-the original mold quality, in the manufacturing process, we must first choose a high-precision processing method, such as EDM, wire cutting, CNC machining, etc., and pay attention to the accuracy of the mold, Including the processing accuracy and assembly accuracy of the mold parts and the comprehensive inspection of the mold accuracy through the trial mold acceptance work, it is also necessary to use high-precision measuring instruments during the inspection. For those mold parts with complex surface curved surface structures, ordinary straight The ruler and the cursor card cannot achieve accurate measurement data. At this time, precision measurement equipment such as a coordinate measuring instrument needs to be selected to ensure the accuracy of the measurement data.

 

The surface of the main molded parts of the mold is strengthened to improve the surface wear resistance of the mold parts, thereby better improving the quality of the mold. For surface strengthening, different strengthening methods should be selected according to different molds. For example: punching die can use electric spark strengthening, hard alloy surfacing, etc., to improve the wear resistance and compressive strength of the surface of the mold parts; die-casting molds, plastic molds and other hot-processed mold steel parts can be nitrided (hard nitrogen Chemical) treatment to improve the wear resistance, heat fatigue resistance and corrosion resistance of the parts; the drawing die and bending die can be treated with sulfurization to reduce the friction coefficient and improve the wear resistance of the material; carbonitriding (Soft nitriding) can be applied to the surface strengthening treatment of various molds. In addition, a technology called FCVA vacuum diamond coating developed in recent years can form a layer on the surface of the part that is extremely strong and very smooth, even and dense. The protective film is particularly suitable for mold surface protection. Treatment is also a significant way to improve the quality of the mold. Of course, if the part is a trial product or the production volume is quite small, it is not necessary to carry out the surface strengthening treatment of the mold part.

 

The correct use and maintenance of the mold is also a major factor to improve the quality of the mold. For example, the installation and debugging of the mold should be appropriate. In the case of a hot runner, the power supply wiring must be correct, the cooling water circuit must meet the design requirements, and the parameters of the injection molding machine, die casting machine, and press in the production of the mold must meet the design requirements. When using the mold correctly, regular maintenance of the mold is also required. The guide posts, guide sleeves and other parts of the mold that have relative motion should be filled with lubricating oil frequently. For molds such as forging molds, plastic molds, die casting molds, etc. Before molding, lubricant or mold release agent should be sprayed on the surface of the formed parts. Planned protective maintenance of the mold and data processing during the maintenance process can prevent problems that may occur in the production of the mold and improve the efficiency of repair work.