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Precision injection mold with ordinary mold mold cavity dimension precision is high, is the biggest difference for mold cavity positioning and parting surface accuracy requirement is very high, therefore, the dimensional tolerance of precision injection mold needs to control the tolerance size of the products under a third.Of precision injection molding process prone to shrinkage have thermal contraction, phase change, orientation, contraction, compression shrinkage of these four conditions, 1, thermal contraction is due to the mould temperature and the temperature is too high, lead to actual shrinkage rate increased, therefore in the process of mould processing to strictly control the mold temperature. 2. Phase change shrinkage generally occurs in the molding process of crystalline resin materials. Mold temperature affects the crystallinity, and the crystallinity increases when the temperature is too high. 3. Directional contraction can be avoided by controlling infusion speed; 4. In the case of compression shrinkage and elastic reduction, generally, the specific capacity of the molding products will be reduced by increasing the pressure, increasing the density and decreasing the expansion coefficient, so as to improve the shrinkage rate.

Cost reduction is the hard principle of enterprise survival. However, the mold factory wants to reduce the cost, destock, avoid the production and consumption stagnation is also one of the important links. Destocking: it can reduce the supply by controlling the loss of consumption, and it can also control the reserve amount of actual demand, so as to achieve the purpose of supply/demand simultaneous control. The second is to strengthen technology, improve effective management regulations, reduce sluggish production and active or compulsory consumption, so as to ensure control of sluggish cost. The only way to improve the problem of excessive inventory is to optimize the management of supply and demand and reduce or at least not increase new inventory.As the top priority for cost reduction in inventory, need to multiple comprehensive control for improvement: useful, useless, multi-purpose, using less to strict verification and digital management, avoid excessive inventory, causing problems such as material can't consumption.Secondly, the management control of dull materials is also the key to reduce the cost. Strengthen the concept of technical improvement, reconfirm the inventory to control the sluggish production; Optimize the management and actively turn the sluggish inventory into controllable cost; Then effectively improve the way of consumption or force a sluggish consciousness of consumption.Mould processing plantNot only to inventory, but also to ensure the company's production units operating normally. Supply and demand improve at the same time, promoting the active digestion of existing inventory under the premise of the balance between the two. Inventory reduction should not only bring into play the improvement effect of inventory management, but also clearly reflect the purpose and effect of reducing costs. It is necessary to clarify the direction of destocking and improvement of sluggish management so as to meet the starting point of cost reduction and resource saving. With the direction of developing the staff of the whole company to enhance the awareness of cost reduction, we encourage the whole staff to carry out destocking, wasting stagnation, rewarding those with excellent performance and encouraging other efforts to get ahead! Eliminate the original stagnant restrictive measures, promote reform, and raise the subjective consciousness of personnel destocking, sluggish consumption and cost reduction.

We make pipe mould for Japan has nearly 100 sets, because the mold cavity of stitching is more, high demand for product appearance, the following is the company's engineering department summary of pipe fittings mold design certificate when some of the main points, dear colleagues, please read careful study.1. Cavity layout. According to the geometric structure characteristics of plastic parts, size precision requirements, batch size, mold manufacturing difficulties, mold cost and other factors to determine the number of cavity and its arrangement.2. Determine the parting surface. The position of the parting surface should be conducive to mold processing, exhaust, demoulding and molding operations, surface quality of plastic parts, etc.3. Determine the casting system (shape, position and size of the main runner, runner and gate) and the exhaust system (method of exhaust, location and size of the vent).4. Select the jacking method (jacking rod, jacking tube, pushing plate and combined jacking), and determine the side concave treatment method and core pulling method.5. Determine the cooling and heating modes, the shape and position of the heating and cooling groove, and the installation position of the heating element.6. According to mold material, strength calculation or empirical data, determine the thickness and dimension of mold parts, the shape and structure, and the position of all connecting, locating and guiding parts.7. Determine the structural form of the main molding parts and structural parts.8. Calculate the working dimensions of the molding parts considering the strength of each part of the mould.

The following is the company's engineering department based on the recent months of mold problems summed up by some experience, colleagues please study carefully.Difficult unloading at gate: in the process of injection molding, the gate is stuck in the cover of gate, not easy to get out. Crack damage occurs when the product is opened. In addition, the operator must use the copper rod tip to knock out from the nozzle, so that it can be loose before the mold can be removed, seriously affecting the production efficiency. This fault is mainly caused by the poor finish of the gate taper hole and the knife marks in the circumference of the inner hole. Also, the material is too soft, the small end of the taper hole deforms or damages after a period of use, and the radius of the nozzle sphere is too small, causing the gate material to produce riveting head here. The tapered hole of the gate sleeve is difficult to be processed. Standard parts should be adopted as far as possible. Tapered holes need to be ground below Ra0.4. In addition, the gate pull rod or gate ejection mechanism must be set.Guide column damage: guide column plays a leading role in the injection mold to ensure that the molding surface of the mold core and the cavity do not touch each other under any circumstances, and the guide column should not be used as the force or positioning part. Injections in the following cases, the dynamic and fixed mode will produce a great lateral migration force:(1) the plastic parts wall thickness nonuniformity, the material flow through rate is big, thick wall place here produce larger pressure; (2) the side of the plastic parts is asymmetric, such as the mold on the terraced parting face, and the opposite two sides are not subject to the same reverse pressure.Dynamic and fixed mold migration: for large mould, due to different charging rates in different directions, and due to the influence of mold self-weight during mold loading, dynamic and fixed mold migration occurs. In these cases, the lateral offset force will be added to the guide column during injection. The surface of the guide column will be brushed when the die is opened, and the guide column will be damaged. In order to solve the above problems, a high strength locating key is added on the parting surface of the mould. The perpendicularity of guide hole and parting surface is very important. In the process is used to move, fixed mold alignment position clamping, in the boring machine last boring, so that the movement, fixed mold hole concentricity, and the vertical degree error is minimized. In addition, the heat treatment hardness of guide column and guide sleeve must meet the design requirements.Flexible formwork bending: during injection of injection mold, the molten plastic in the mold cavity generates enormous reverse pressure, usually between 600 ~ 1000 kg/cm 2. Mold makers sometimes don't attach importance to this problem, often change the original design size, or replace with low strength steel plate, the dynamic template in the mould of material with a plunger, because on both sides of the large span, cause the injection template under bending. So the dynamic template must choose high quality steel, must have the enough thickness, must not with A3 steel such as low intensity, when necessary, or support block should be set at the bottom of the dynamic template shores, to reduce the thickness of the template, improve the bearing capacity.Top bar bending, breaking or leakage: the quality of the homemade top bar is better, that is, the processing cost is too high. Now, the standard parts are usually chosen, and the quality is general. If the gap between the top rod and the hole is too large, material leakage will occur, but if the gap is too small, the top rod will become stuck due to the increase of mold temperature and expansion of the top rod during injection. What is more dangerous is that the top bar is sometimes broken when the top bar is pushed out at a normal distance. As a result, the top bar exposed in this section cannot be reset and the concave die is damaged in the next mold closing. In order to solve this problem, the top rod is resharpened, and the 10-15mm mating segment is retained at the front of the top rod, and the middle part is ground down by 0.2mm. After the assembly of all ejector rods, the mating clearance must be strictly checked, generally within 0.05~0.08 mm, to ensure that the entire ejector mechanism can advance and retreat freely.Cooling bad or channel leakage: injection mold cooling effect directly affect the quality and production efficiency of products, such as poor cooling, product shrinkage, or uneven contraction become warped surface defects such as deformation occurs. On the other hand, the whole or part of the mold overheat, so that the mold can not be formed normally and stop production, serious so that the top bar and other moving parts thermal expansion die and damage. The design of the cooling system, processing to the product shape, don't cry because it is complicated or difficult to machining mould structure and eliminate the system, especially in large and medium-sized mold must give full consideration to the cooling problem.Distance taut institutions failed: the pendulum hook, fastener spacing taut institutions is generally used in die core-pulling or some secondary ejection mould, because such institutions in the mold of the two sides set in pairs, its movement request must be synchronous, namely the clamping buckle at the same time, mould to a certain position at the same time. Without synchronization, it is bound to cause pulled mold template skewed and damage, the institutions of the parts to have higher rigidity and wear resistance, adjustment is hard, short life institutions, to avoid as far as possible, you can switch to other institutions. Can be used in the case of relatively small pumping heart spring launch mode method, the core pulling force is larger when the dynamic model can be used under the condition of the back slide cores, finish core-pulling action again after the structure of the die, the hydraulic oil cylinder can be used on large mould core pulling. The inclined pin slider core pulling mechanism is damaged. Such mechanisms are often appear problem mostly processing does not reach the designated position and the material is too small, basically has the following two questions: Angle A large pin, advantage is that can be generated within shorter cavity travel relatively large core-pulling distance. However, if the oversize inclination Angle A is adopted, when the extraction force F is A certain value, the bending force P of the inclined pin in the core pulling process is equal to F/COSA, which is also larger, resulting in inclined pin deformation and inclined hole wear. At the same time, the upward thrust N=FTGA produced by the inclined pin on the slider is also larger, which increases the positive pressure of the slider on the guide face in the guide slot, thus increasing the friction resistance of the slider during sliding. Easy to cause sliding friction, guide wear. According to the experience, dip A should not be greater than 25 °.Guide groove length is too small, some die because of restricted by template area, the length of the guide groove is too small, the slider on the outside of the core-pulling action after the show guide, so that after the core-pulling and mould reset at the beginning of the phase is likely to cause the slider tilt, especially when clamping, slider reset, make the slider damage, even bending failure. As a rule of thumb, the length of the slider left in the chute should not be less than 2/3 of the length of the guide chute after the core pulling is completed. In design, mold manufacturing, according to the requirement of the quality of plastic parts, the size of the batch, make deadline requirements such as the specific circumstances, can not only meet the requirements of products, in the mold structure and the most convenient and reliable, easy processing, low cost, this is the most perfect mold.