The mold industry is the basic industry of the national economy. Molds are the basic process equipment for military industry, machinery, electronics and light industry. With the development of production and science and technology, the intensification of competition in the economic and trade market has prompted the accelerated replacement of products, which has put forward higher requirements on the quantity, quality, cost, delivery time and other aspects of molds. The key to the success or failure of mold development lies in design. It can be said that this is the consensus of our industry insiders, and many units have this feeling-not afraid of processing, but afraid of design. It can be seen that the design difficulty of a mold is much greater than the processing difficulty. The author believes that a successful mold is not only able to complete the predetermined stamping task, but also to minimize the total cost of the mold in a series of processes such as its own processing, adjustment, maintenance, and consumption of wearing parts. This is the highest realm of mold design.
Methods to reduce mold costs The cost of molds is mainly composed of the following parts: material costs, design fees, processing fees (including commissioning costs), packaging fees and transportation fees, taxes, and other costs (such as commercial operations, payment of management fees, etc.). Among them, the total cost of materials, processing fees and taxes should account for at least 80% of the total cost of molds. The material cost and processing cost are determined by the design drawings, what brand of materials to use, how much raw material is needed, what process route is needed for mold parts processing, whether it has good debuggable performance, the number of modifications, etc., all of which depend on the design. Therefore, mold design is the most critical link. Therefore, controlling mold costs must start from the design. To achieve the goal of reducing costs, in summary, the following aspects need to be done well:
1. First of all, the overall design plan should be formulated reasonably, that is, the design concept should be correct, and the relevant principles or rules should be followed from the stamping process, layout to the determination of the overall structure. For example, in the formulation of the layout plan, according to the conventional design rules, the first step is to punch out the guide hole first, and then the second step must set the guide pin for guidance. No matter how small the step is, it cannot be left empty. If it is not arranged in this way, the initial feeding accuracy and the entire mold step accuracy cannot be guaranteed, which is equivalent to losing the positioning reference, and the accuracy of the stamping parts is out of the question.
How to effectively control the processes of punching, bending, drawing, folding and curling of strip materials, and what structure to use to ensure that the blank is formed according to the design intention. The formulation of these plans requires the designer to have a relatively full understanding of the deformation law of the material. At the same time, the current plan should be necessary for proofreading and calculation, such as the size of the unfolded size, the determination of the number of deep drawing, the value of the initial gap, the deviation of the pressure center, the size of the clamping force, the unloading force or the push force, the length and compression of the spring, etc. should be calculated first and used as the theoretical basis for the design. Try to use a more mature structure.
When designing the mold structure, it is best to imagine the future assembly, operation and deformation process of the mold. This can early discover many unrealistic assembly problems or interferences generated during operation, hinder feeding, unstable positioning and other problems from the beginning of the design. Because once a major design error occurs in the mold, it will cause the mold to be scrapped. I have seen such a mold. Its last station has to complete three actions: cutting, 87° bending, and ejecting. The layout is not wrong. However, due to the lack of consideration in the structural design, it only meets the requirements of sharp angle bending. The lower baffle specially set for the swing punch hinders the ejection of the workpiece and cannot work continuously. It complicates a problem that was originally easy to handle, and the mold was eventually scrapped. Later, the new mold changed the structure, the punch was changed to a straight-through type, the die was changed to an inclined surface, and the mold was accepted after the baffle was removed. Therefore, there must be no major problems in the overall plan.
2. Before determining the stamping process route and layout, various plans should be cost-estimated, which can provide a basis for decision-making. For example, a stamping part can be stamped with several single-step dies, or with a skip-step die (progressive die), or with a compound die. Which plan should be adopted? We need to compare which plan has the lowest comprehensive cost.
3. We must implement the promotion and application of standard parts and use as many standard parts as possible. The reason is very simple. Because standard parts can be mass-produced, their market price is relatively cheaper. Another benefit is that it shortens the mold manufacturing cycle and reduces the total workload by at least half. At present, there are a wide variety of mold standard parts on the market, with complete specifications. For example, springs, mold frames, guides, screw plugs, guide hole punches and concave molds, guide pins, detection pins, small pressure plates, floating pins, ejector pins, etc. These parts can be purchased from specialized manufacturers, thus eliminating the need for design and processing. It reduces the pressure on the production link and speeds up the progress, which in turn promotes sales to a certain extent.
4. The processability review of non-standard parts design cannot be ignored. In actual production, the reason for the scrapping of parts is sometimes not the operator, but the unreasonable design. For example, a plate worth thousands of yuan is scrapped due to a crack in a sharp corner of the die hole. In this case, can the responsibility be shifted to heat treatment? Because the wall thickness of the die insert design is too thin, it is deformed after cutting the die hole and is scrapped. Can this be blamed on the slow wire operator? There is also such a situation. If a complex special-shaped hole is designed in a splicing way, the processing of the convex and concave dies is relatively easier, and the tool grinder can ensure the dimensional accuracy requirements. If it is designed as an integral type, it must be processed by a slow wire or coordinate grinder, resulting in a processing cost increase of hundreds or thousands of yuan. Sometimes the punch is designed to be too slender and the impact resistance is too poor, resulting in frequent shutdowns and repairs and replacements during stamping production, increasing costs and delaying production. The above-mentioned phenomena are often encountered. Therefore, for non-standard parts, a process review must be conducted before production, and senior designers or process engineers must check whether their drawings meet the factory's process conditions. For example, the size cannot exceed the maximum stroke of the existing equipment, the benchmark must always remain consistent, the curve (surface) processing must avoid interference, be careful not to have sharp corners that are easy to crack during quenching, the clamping surface must be large enough, the dimensional accuracy and form and position tolerances are easy to control, and for some parts that cannot be designed and finalized at one time, there must be room for modification. With process review and control, a lot of additional costs due to unreasonable design can be reduced, thereby reducing factory losses. In order to make the division of labor clear and facilitate management, some enterprises separate the design work from the process preparation work, and each manages its own, so the internal friction is naturally relatively large.
5. The selection of materials should be appropriate. Now people have realized the preciousness of resources, and the prices of mold raw materials have risen again and again, especially alloy tool steel, some of which have more than doubled. For example, the original price of high-speed steel W6Mo5 Cr4V2 was less than 40 yuan/kg, and now it has risen to more than 80 yuan/kg. The original price of cemented carbide YG15 was 300 yuan/kg, and now it has risen to more than 700 yuan/kg. The price of imported materials is even more outrageous. For example, Japan's ordinary mold steel SKD11 is 70 yuan/kg, cemented carbide D30 is 3000 yuan/kg, and the American cemented carbide CD650 is 3000 yuan/kg, which is more than 3 times higher than domestic materials with the same performance. Therefore, when selecting mold materials, as long as they can meet the performance conditions such as part strength and hardness and achieve the expected life, cheap raw materials should be used as much as possible. Blindly pursuing expensive materials, seemingly to improve mold quality, is actually an irrational use of resources and a waste. Domestic mold materials such as T8, T10, CrWMn, Cr12MoV, etc. are relatively much cheaper, and it is recommended to use them first. Especially when the mold size is large, the selection of materials should be more cautious. For some key parts, if wear-resistant carbide materials such as YG15 must be used, they can be designed in the form of hot inlay or partial welding, and their use can be reduced as little as possible, thus saving a lot of money.
6. The mold must be tested several times before leaving the factory, and the problems found in each mold test must be designed and modified and thoroughly solved within the factory. It is best to debug it to a level of certainty before packaging and shipping. Avoid problems that are exposed after the mold is delivered to the user. At that time, there may be no professional equipment and operators on site to cooperate, and it is extremely difficult for fitters to repair or modify the mold alone. Wasting time and increasing expenses are secondary. If things go wrong, the mold will eventually have to be shipped back to the factory for repair, which will be even more troublesome. These expenses will inevitably exceed the budget. At the same time, it also delays the user's production progress and causes negative effects. In short, the time and workload of adjusting the mold outside should be reduced as much as possible.
7. The design of the drawing should be standardized. The actual size of the graphics on the computer must be strictly consistent with the marked size, and the naming must be unique, and the name and drawing number must not be repeated. This may seem a little troublesome and slow, but it can bring great convenience to a series of subsequent work. Whether it is proofreading, processing programming or checking dimensions, the drawing file can be directly called from the computer. It ensures that the design drawings have a clear guiding role in production. Overall, it not only saves a lot of time, but also improves the accuracy of size and shape expression, which can effectively avoid scrapping or rework caused by misunderstandings by others, and effectively reduce unnecessary losses and waste.
