MIM Mold Training

The mold of MIM injection molding is a relatively difficult preliminary process, which is the guarantee of mass production of MIM injection molding. The mold workers must be bold and careful in order to effectively complete the mold manufacturing. Otherwise, facing extremely strict tolerances, they will be afraid of hands and feet, which will affect the mold production efficiency. Generally, the mold is manufactured in about four weeks, but the mold production cycle is different for different projects. For example, the elimination rate of mobile phone communication products is very fast for the MIM parts in mobile phone communication. A mobile phone MIM parts project may take three months from R&D to the end of mass production. For the MIM products with such a fast pace, the mold manufacturing time must be shortened, or even reduced to only five days. That is to say, there is no room for any mistakes during the mold manufacturing, and the progress is very fast. This is a great challenge for MIM mold workers.

A mold inspector needs to carry out a number of CMM inspections when he gets the mold base. High tolerance accuracy, no flash, and super high surface quality are all the requirements that must be met in the manufacturing process of the die casting mold for metal parts. There is no doubt that although there are several metal mold manufacturers that can reach this level, there are few. However, it is profitable for companies to choose this industry. The price of a set of molds of MIM ranges from tens of thousands to tens of thousands. Many manufacturers of injection molds see this opportunity and become mold manufacturers of metal die-casting molds, as long as their service objects are molds for radio communication, medical treatment, electronics, automobile and personal protective products industries.

The structure of the MIM mold * * * is suitable for the production of small and medium-sized parts. The breakthrough of the MIM technology has made great contributions to the medical device industry. The weight of surgical medical devices used in the industry is between 0.15-23.4g. Other parts include watch cover, transmission gear, clamp and chisel. Some of them weigh up to 60g. He said, I know there are larger parts, such as replacement parts of golf club head. In a word, the manufacturing of injection molds and metal die-casting molds requires high quality and service. Today, Lianyungang Dongmu will welcome the production of ten sets of MIM injection molding molds. The mold department staff will learn and train every day. In addition to the basic knowledge of mold, the training pays more attention to the training of psychological state. Every mold maker must self check, the process is fixed, and the people are flexible, so as to achieve the customer's requirements as soon as possible.

First of all, the mold design should have a good plan, which is the basis and key to success or failure. It should include excellent cooling water circuit layout and parting line locking device to prevent dislocation of the mold during processing and production, a pair of mold frames that can well support the mold cavity and core sidewall, and a method suitable for demoulding specific parts. The basic structure of the MIM mold is similar to that of the injection mold, with few exceptions. It includes the selection of die cavity and core steel, closing angle fitting parts and sliding blocks, the design of runner system to make materials have good fluidity, the position of gate, the depth of ventilation, the surface quality of the molding area, and the correct selection of coating applied to the details of die cavity and core.

Because many mold manufacturers generally start to manufacture molds according to the design drawings, they give machinists and mold makers a lot of freedom to design details when making molds. However, this method is generally invalid for the manufacturing of MIM dies. Mold manufacturers and MIM mold makers do not observe the layout of a mold. Their main task is to study and observe a set of detailed drawings. The more time they spend on the detailed design of the front of the mold, the less time they spend on the successful operation of the mold. The detailed design includes the selection of mold part materials, tolerance of mold and mold cavity, surface quality and coating, size of gate and runner, position and size of vent, and position of pressure sensor.

Demoulding and cooling have become the key problems in the successful manufacturing of MIM dies.

(1) The steel used for the cavity/core shall be able to withstand the wear caused by the molding materials. "All steels (including gates and flow channels) in contact with molded composite materials shall be made of tool steels with high wear resistance, high chromium content and high hardness, such as D-2 or A-2 tool steels. H-13 steels can also be used because of their high hardness and a layer of high hardness coating. Any detail parts not in contact with molded composite materials can be made of more standard S-7 tool steels.

(2) Close corner/slider "In the production process of MIM die, flash is a serious problem, which is a substantial problem for die makers. In order to prevent this problem, it is very important to have a good cooperation between all closing angles and sliding areas. Only in this way can a high-quality MIM part be produced. The die manufacturer must calculate the rolling size by using the triangle method, and then use this knowledge to check the closing angles of female and male steel, Ensure that it is within ± 0.0001 tolerance range of other calculated dimensions. " The tolerance that people need to maintain is generally quite accurate for metal molds, because the feeding parts of MIM molds are very sensitive to flash, which is easy to produce flash. "If the plastic part has flash, it is easy to remove the flash, but if it is metal, the flash will cause problems like the blade.

(3) In order to release the internal gas generated by the molding materials in various molds, it is very important to adopt a good vent. MIM mold is very different from injection mold in terms of vent depth. A typical plastic mold may have vents everywhere according to the different molding resins, and the MIM mold will definitely produce flash at the depth of these vents. The vent depth of the MIM mold is generally 0.0001-0.0002in, but it may also vary with the selected molding composite metal materials. The shrinkage of a good feed is very low during the subsequent solidification process. In order to strengthen the shape retention as much as possible, a large number of metal powder fillers are used, which are often close to 70% of the volume. In order to obtain good fluidity of high filling feeding, low molecular weight molecules and adhesives are used to make MIM feeding produce high flash sensitivity, similar to the characteristics shown by many filled nylon materials. Paraffin wax and polyethylene/glyceryl feed have better characteristics than acetyl feed, but will affect their higher flash sensitivity.

(4) Demoulding from the mold cavity area is largely determined by the surface quality of the mold cavity and core tool steel, because its shrinkage is extremely low during the molding process. Shrinkage of metal molded parts will not really occur unless the binder material is extracted through the post molding process. Therefore, the polishing of the molding area is very important. Generally speaking, the molded surface should reach 600 composite finish, and diamond finish may be required in rare cases.

(5) Electroplating a high hardness electroplating layer such as chromium or nickel will enhance the efficiency of the demoulding process of the molded metal parts, combined with the highly polished surface, so that it can produce better results. Some types of chromium and nickel have added release agents to improve their demoulding characteristics. After mastering the basic knowledge, there are still more factors to consider, and then gradually learn. Another challenge of MIM comes from raw materials, generally referred to as supplied materials. Because its interior contains a large number of very fine metal powder, often close to 70% of the volume. "It is the metal powder that makes the final parts. Plastic parts increase the fluidity of the metal powder and remove it completely after injection molding. The powder has a little friction, so it must be processed with a harder tool at a higher spindle speed. Many mold makers have to use ablation processing because they do not have high-speed machine tools. However, they cannot leave behind rough surface quality, because MIM requires close tolerance.

Different metals basically have the same mold manufacturing requirements, unless it is sometimes necessary to insert different shrinkage rates. This is not the shrinkage inside the mold. Shrinkage occurs only when the part is detached from the mold and enters the furnace. In the mold, the shrinkage is almost zero, and the shrinkage per inch is less than 0.001 in. Therefore, the shrinkage in the mold is very small. " In addition, experience shows that some mold factories have already made some molds with poor quality before they realize the challenges they face. No matter when a mold factory manufactures * * * molds for a MIM factory, it has taken a lot of time to design the molds. Generally speaking, the result is that the mold is very good, reaching the predetermined work goal, or after * * * mold trials, only a few changes have been made. It seems easy to analyze the details of * * * molds carefully, but it will generate excessive confidence in the details of molds. It is not unusual to spend a lot of time and money debugging the second mold, sometimes involving rework.

At this point, mold makers understand the hardships of the road, and they will not give up trying to improve in MIM mold. In addition to learning the knowledge of MIM mold at ordinary times, they also need to improve their own requirements and practice more. I believe that the future MIM mold will be better and better.