how to reduce the plastic injection mold cost ?

- Jan 18, 2019-

Six magic weapons to reduce mold costs


   Today, let's discuss with you the control of mold costs. First of all, a basic question, what is the cost of the mold? A friend can answer me without thinking: the mold cost is the mold material fee + processing fee + tax. Of course, there is also a labor fee. We can think that the labor fee is included in the processing fee, and of course the design fee.

   From a narrow point of view, this answer is good, but I have to ask, since this is the answer, in addition to cutting corners and tax evasion, is there any way to control or reduce costs?


   This is my opening remark and I am joking with everyone. To really talk about the cost of controlling molds, we must analyze them carefully and affect various factors of mold cost.

 First, the rational design of the product

    I believe that many people present will not agree with me. Whether the design of the product is reasonable or not, how could it be the biggest factor affecting the cost of the mold. Let's take a look. The first foot, I kicked the ball to our OEM. But if you think about it, if the product design is unreasonable, it is a disaster for the mold company. It is a disaster. I have been working on molds for more than 40 years. This kind of experience has been much more experienced. Sometimes, in order to achieve an undercut on the product, the product engineer and the mold designer do not communicate well, and the cost of the mold will increase exponentially.

    I had the privilege of participating in the design of a car interior for a disabled person in a Shanghai auto company. One of the parts is called the middle partition. According to the original design, this part is very large, and the production cost of the mold is about 4 million RMB. The matching injection molding machine is over 4,000 tons. Later I suggested splitting it into 2 pieces. The production cost of the two sets of molds did not add up to more than 2 million. The matching injection molding machines are all 1,500 tons. Finally, all are happy. There are too many such examples. Therefore, a product designer should try to understand the knowledge of the mold as much as possible, so that the designed product is as suitable as possible for the mold engineering, and do not increase the difficulty and cost of the mold. Under the premise of meeting the assembly of the vehicle, maintaining good communication with the mold department is the most effective and direct measure to reduce the cost of the mold. There is also a philosophical question of productivity and production relations. Some product engineers believe that the cost of mold is a matter for your mold company and has nothing to do with me. However, if the production relationship is recombined, the injection molding company and the mold company are one, what will happen? In fact, this is a social trend. The companies that are operating better now are the combination of injection molding companies and mold companies. One company that exists solely on the basis of making molds can hardly survive. Therefore, if the product design is not reasonable, it will directly increase the cost of the mold.

Second, product design changes

   Mold companies often encounter such a situation. In a certain project, the mold has just been designed, the mold frame has just been ordered back, and the customer's change notice will come. If it is a small change, it will not affect the overall structure of the mold. It doesn't matter, sometimes it's more serious, because the shape of the product changes, the mechanism needs to be added to the mold, and even the mold base must be reordered. This cost has increased. So try to minimize design changes. There are a lot of rapid prototyping methods. Before the mold is made, the 3D will be used to make the whole vehicle assembly, and the 3D of the product can be corrected in time to minimize the cost increase caused by the product design change. I remember that I used to participate in the research and development of Beijing Jeep Cherokee 213. The model that was injection molded in Shenzhen had to go to Beijing to try the assembly. The light plane had tossed dozens of back and forth. This cost is a material fee or a processing fee. It is really hard to say.

Third, whether the mold design is perfect

  Here we have to analyze the situation in two cases. The first is the rationality and processability of the mold design.

   In the mold companies, there must be old and experienced designers in the design team, as well as young engineers who have just come out of school. We can't ask young engineers to design high-level molds independently when they first come to the company. Experienced mold engineers, if the mold structure produced by closed doors, can not be perfect, there will be some details that are not well thought out. One of the most important and effective methods is the collective review. I remember that I bought a German mold book in the 1970s. It seems to call 80 pieces of advanced mold structure. The biggest impact on me is that the book mentions the process of making molds. It must go through many times on the mold structure. Collective review. This has the greatest impact on my mold career, and it really benefits a lot. Now I believe that everyone has a consensus. There are now many simulation methods, such as mold flow analysis, mold structure dynamic analysis, trial products and design 3D comparison analysis, which can minimize the cost increase caused by the irrational mold design.

   The second case is design waste. If the mold user clearly produces 500 samples as long as the mold is used to develop the market, if we design according to the mold with a life of 300,000 molds, the cost will be large, which is a waste of design.

Fourth, try to reduce the number of trials of the mold

  Many mold companies calculate the processing cost of the mold, and calculate the processing fee based on the number of days after the mold receives the order and the product is qualified. If the mold has been tested several times, it cannot be delivered, except for the penalty according to the contract. The more days the mold is in the factory, the more processing costs. Of course, the cost of the test mode is also very considerable. Therefore, multiple or uncontrollable test mode times is a large blind spot for mold cost control.

Let's analyze the reasons why the number of molds is too many.

  The first is that the mold design has not undergone sufficient collective review, and the mold structure is unreasonable, so that the mold has to undergo many improvements after the test, so that the mold cost exceeds the budget.

   If after several improvements, you can get it. It is fortunate. There are many cases that are unsatisfactory. Even if the mold is to be scrapped and reworked, the cost cannot be controlled. There are also some cases where the mold design is very good, but the processing of the mold is not in place, which makes the number of trials increase without any reason, directly increasing the cost of the mold. There is no objection to this problem, so many mold companies have increased their investment in measuring equipment.

   The second is that the model is not selected for the best molding process and the model of the injection molding machine. The mold is well made, but the injection molded product is not ideal. The number of trials is increased without any reason, which directly increases the cost of the mold. This is a common problem in some small mold factories.

   The third is that there is not a sufficient understanding of the physical properties of plastics, and even the shrinkage rate is not accurate. Such a situation occurs from time to time. Therefore, before designing the mold, it is necessary to understand the physical properties of the plastic, in order to effectively reduce the number of trials.

   Fifth, mold materials and standard parts procurement

   Choose a stable, reputable supplier. It is a pity if the mold is out of order because of the greed and the sloppy purchase. This is actually a lot of things. Although the responsibility of the supplier can be pursued, the biggest loss is the mold company and the mold user.

 Sixth, the product is qualified

  If we say, we used 100,000 yuan to request a mold for a car glove box. The plastic used is PA+30% GF, the injection cycle is 30 seconds, and the die life is 300,000. As a result, the mold was made, and the size and physical properties of the sample were also achieved. However, because the injection was difficult during the injection, the injection cycle took 60 seconds, and the mold production of 100,000 pieces could not be used, in order to catch up with the vehicle. Must cast the mold again. According to the original mold situation, it is necessary to cast 3 sets of molds at once. It is also spending so much money, I think the cost of this set of molds is three times or six times the original budget. Do you have a different opinion?

   In summary, in order to effectively control the cost of the mold, it must be done:

   Reasonable product design, minimal design changes, perfect mold design and processing flow, good communication between product engineers and mold engineers.

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