How to remove the burrs of injection molding products?
The burrs, also known as flying edge, overflow, overflow, etc., mostly occurs in the parting position of the mold, such as: the parting surface of the mold, the sliding part of the slider, the cracks of the insert, the pores of the ejector rod, etc. If the overflow is not solved in time, it will be further expanded, so as to form part of the embossed mold collapse, causing consistent obstruction. Cracks in inserts and top bar pores also cause the product to get stuck on the mold, affecting the release.
In essence, the cap is the surplus left on the product after cooling after the gap between the plastic material entering the mold matching part. To solve the problem of the tip is very simple, that is to master not to let the melt into the mold fit gap. Plastic melt enters the mold fit gap, there are generally two situations: one is that the mold fit gap is originally large, colloidal is easy to enter it; The other case is that the mold clearance is not large, but because of the pressure of the molten colloid forced into.
On the surface, it seems to be completely solved by strengthening the production precision and strength of the mold. It is necessary to improve the production accuracy of the mold, reduce the mold clearance and prevent the melting colloid from entering. But the strength of the mold, in many cases, can not be infinitely strengthened, strengthened to any pressure, the colloid can not burst into it.
The occurrence of the cap has both the mold and the process reasons. Check the technical reasons, mainly check whether the clamping force is enough, only to ensure that the clamping force is enough, when the tip still occurs, check the mold reasons.
Check whether the clamping force is sufficient:
1) Gradually increase the injection pressure. With the increase of injection pressure, the tip also increases correspondingly, and the tip should mainly occur on the parting surface of the mold, indicating that the clamping force is insufficient.
2) Gradually increase the locking force of the injection molding machine. When the locking force reaches a certain value, the tip on the parting surface will dissipate, or when the injection pressure is increased, the tip on the parting surface will no longer increase. The locking force is considered to be sufficient.
Check whether it is caused by mold production accuracy:
With lower material temperature, lower filling speed, with lower injection pressure, the product is just full (the product has a slight shrinkage). At this time, it can be felt that the ability of melt to break into the mold to match the gap is very weak. If the tip occurs at this time, it can be judged that it is a problem of mold production accuracy, which needs to be solved by mold repair. Can consider discarding the use of technological methods to solve the occurrence of the tip. It should be noted that the above "three low" premise is not less. High material temperature, fast filling speed and high injection pressure will cause the pressure of the mold cavity to increase, strengthen the ability of melt to break into the mold and cooperate with the gap, expand the mold and occur the tip. It is true that the product is not satisfied with the glue at this time.
Analysis of the cause of the occurrence of the tip is based on the premise that the clamping force is sufficient. When the clamping force is not timely, it is difficult to analyze the cause of the occurrence of the tip. The following analysis is established in the case of sufficient clamping force. According to the several situations of the cap, the cap may occur for the following reasons:
The first case: as mentioned above, at low temperature, low speed, low pressure, the product is not satisfied with the glue, the tip has occurred. The important reasons may be: the mold production precision is not enough, with too large clearance;
The second situation: when the product is just full of glue, part of the shrinkage signs, no tip occurs; When the injection pressure is increased to improve the product partial shrinkage, the tip occurs. Possible causes are:
1) Material temperature is too high. If the material temperature is too high, the viscosity of melt is low, the behavior is good, and the ability of melt to break into the mold to match the gap is stronger, it will cause the occurrence of tip.
2) The injection molding speed is too fast, and the injection molding pressure is too large (resulting in oversaturation). Too fast speed, too much injection pressure, especially too much injection pressure, will strengthen the ability of melt to break into the mold and match the gap, resulting in the occurrence of tip.
3) Plastic behaves too well. The better the behavior of the plastic, the lower the viscosity of the melt, the stronger the ability of the melt to drill into the mold to fit the gap, and the easier it is to tip. When the mold production has been realized, the depth of the exhaust groove of the mold and the matching gap of the mold have been finalized, and another plastic with good behavior is used for production, the tip will occur.
4) The strength of the mold is less than. When the planned strength of the mold is not timely, when the mold cavity encounters the pressure of the plastic melt, it will deform and expand, and the colloid will burst into the gap of the mold and the tip will occur.
5) Different product plans. Part of the product is too thick glue, injection compression is excessive, it will cause partial shrinkage. In order to adjust the problem of partial shrinkage of products, it is often necessary to use higher injection pressure and longer injection time to fill and maintain pressure, which results in mold strength less than deformation and tip.
6) Mold temperature is too high. High mold temperature can not only make the plastic maintain good behavior, the loss of pressure is small, but also reduce the strength of the mold, which will also cause the occurrence of peeling.
The second situation is the non-common problems encountered in injection molding production, which can not be solved by all technological means at ordinary times, which is very troubling to injection molding technicians. Regarding this situation, the most important means is to fix the mold. The solutions are:
1) Product part glue reduction. The part of the product shrinkage is reduced, the glue position is reduced, the product shrinkage problem can be improved, the injection pressure will be low, the mold deformation is small, the tip can be inhibited. This is a very effective and often used method.
2) Increase the feeding point. Increasing the pouring point can reduce the injection process and injection pressure, and the pressure on the mold cavity will be reduced, which can effectively solve the occurrence of the tip. Increasing the injection point, especially at the shrinking position, can have an immediate effect on reducing the injection pressure of mold cavity. It's one of the more common methods.
3) Strengthen the mold part. Occasionally, the deformation of the formwork can be strengthened by adding a brace between the moving formwork and the thimble plate.