Failure of injection mold and its exclusion?
The structure of injection mold and mold processing quality directly affect the quality and production efficiency of plastic parts.The most common in the production of injection mold and plastic products, some of the most common mold failures and their main causes are analyzed as follows.
It is difficult to remove the material.In the process of injection molding, casting [1 stick inside the gate set, not easy emergence. Khan die, products appear crack damage. In addition, the operator must use copper bar from the nozzle tip on, to loosen the rear can release, the serious influence production efficiency. This fault is the main reason gate taper hole finish is poor, inner hole circumference direction mark. The second is the material too soft. Use for a period of time after the cone Kong Xiaoduan deformation or damage. And the nozzle spherical radian is too small, the gate is expected to produce riveting head here. Gate set of cone hole is more difficult treatment, should as far as possible using standard parts, if you need to processing,You should also make or purchase a special reamer. The taper hole should be ground to ra0.4mm. In addition, you must set the sprue bar or gate top out.
Damage of the guide column.The guide pillar plays a leading role in the mould, so as to ensure that the forming surface of the core and cavity is not mutually touching in any case, and the guide column can not be used as the force part or positioning piece.Injections in the following cases, the dynamic and fixed mode will produce a great lateral migration: plastic parts for non-uniform wall thickness material flow rate is big, thick wall place here produce larger pressure;The side | side of the plastic parts is asymmetric, such as the mold of the stepped parting surface, and the opposite pressure is not equal to the two sides.
The large mould, due to the different charging rate, and the influence of the mold's self-weight in the loading mode, generate dynamic and fixed mode deviation.In the above situations, the lateral offset force of the injection will be added to the guide column, the surface of the guide column will be pulled and damaged when the die is opened, and the guide column will be bent or cut when it is serious, or even the mold can not be opened.In order to solve the above problems, a high intensity positioning key is added on the mold parting surface. The most convenient and effective is the use of the cylindrical key.The vertical dimension of the guide hole and the parting surface is very important.In the process of processing, when the position of the moving and fixed die alignment is clamped, the boring machine can be finished in the last time, so as to ensure the concentricity of the moving and fixed die hole, and minimize the verticality error.In addition, the heat treatment hardness of the guide column and guide sleeve must meet the requirements of the setting.
Bend the template.Mold, injection mold cavity molten plastic produce a great pressure, generally is 600 ~ 600 KGF/cm mould 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 span is big, cause the injection template under bending.So the dynamic template must choose high quality steel, must have the enough thickness, must not with low intensity plates. When necessary, or support block should be set at the bottom of the dynamic template shores, to reduce the thickness of the template, increases bearing capacity.
The top rod is bent, broken or leaking.The quality of the self-made top rod is better. It is that the processing cost is too high, and now the standard parts are generally used and the quality is poor.If the gap between the top rod and the hole is too large, there will be leakage, but if the clearance is too small, due to the high mold temperature rising at the injection time, the top rod will expand and die.Even more dangerous is the fact that sometimes the top of the rod is pushed out of the top of a distance and it is not moving at the top. (11 is broken, and the end of the top bar that is exposed when the next closing time is not reinstated.In order to solve this problem, the top bar is reworked, and the mating segment with 10 ~ 15mm is retained at the front end of the top bar, and the middle part is grinding 0.2mm.After assembly, all the top rods must be strictly checked for clearance, generally 0.05 ~ 0.08mm, to ensure that the entire ejection mechanism can move back and forth smoothly.
Poor cooling or water leakage in the channel.The cooling effect of the mould directly affects the quality and production efficiency of the products, such as defective cooling, large shrinkage of products or uneven shrinkage of the products.On the other hand, the mold or local overheating can prevent the mold from being formed normally, so that the top rod and other movable parts can be damaged.Cooling system design, processing to the product shape, don't cry because it is the mould structure complex or add 1: difficult and save the system, especially in large and medium-sized mold must give full consideration to the cooling problem.
The fixed distance tension mechanism failed.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.In the case of a relatively small core pulling force can adopt the method of spring launch mode, the core pulling force is larger dynamic model can be used under the condition of backward sliding core, finish core-pulling action again after the structure of the die, the hydraulic oil cylinder can be used on large mould core pulling.
Today some die because of restricted by template area, guide groove length is too small, the slider outside the core-pulling action after the show guide, so that at the beginning of the core-pulling and mode after reset stage are likely to cause the slider tilt, especially when clamping, slider reset, make the slider damage, even bending failure.According to the experience, the length of the sliding block should not be less than 2/3 of the length of the guide slot after pulling the core.