Views: 4 Author: Site Editor Publish Time: 2022-08-27 Origin: Site
Phi front, also known as flying edge, overflow edge, overflow material, etc., mainly occurs in the mold's parting position, such as the mold parting surface, sliding parts of the sliding block, the gap of the insert, the hole of the top bar, etc. The overflow material will be further expanded if not solved in time, thus forming local collapse of the embossing mold and causing sexual damage. The phi-front of the gap of the insert and the hole of the top bar will also make the products stuck on the mold, affecting the release.
Phi front is essentially plastic material into the mold fit parts of the gap after cooling left on the product excess. Solving the phi front problem is very simple: to control not to let the melt into the mold fit gap to go. Plastic melt into the mold with the gap. There are generally two cases: one is the mold with the gap is initially large, the gel is easy to enter; another is the mold with the gap was not large, but because of the molten gel under pressure forced into the.
On the surface, it seems that the phi front can be entirely solved by strengthening the manufacturing precision and strength of the mold. Improve the manufacturing accuracy of the mold, reduce the mating gap of the mold, to prevent the molten gel from being completely necessary. However, the strength of the mold, in many cases, can not be strengthened indefinitely, strengthened to any pressure, the gel can not burst into it.
The production of phi-front has both mold-related reasons and process-related reasons. When the clamping force is sufficient and the pips are still generated, check the mold's cause.
(1) gradually increase the injection pressure; with the increase in injection pressure, the phi front also increases accordingly. The phi front is mainly generated in the mold parting surface, indicating insufficient clamping force.
(2) gradually increase the clamping force of the injection molding machine. When the clamping force reaches a specific value, the phi on the parting surface disappears, or when the injection pressure is increased again, the phi on the parting surface no longer increases. Then the clamping force is considered sufficient.
With lower material temperature, lower filling speed, and lower injection pressure, the product is just full (the product has slight shrinkage). At this time, it can be considered that the ability of the melt to burst into the mold gap is feeble. At this time, if the phi front is generated, it can be judged that the mold manufacturing precision problems need to repair the mold to solve. Consider giving up the process to solve the production of phi. It should be noted that the above "three low" conditions are indispensable, high material temperature, faster glue filling speed, and higher injection pressure, which will lead to increased local pressure in the mold cavity, enhance the ability of the melt to burst into the mold with the gap, expand the mold and produce phi. However, the product is not full of glue.
Analysis of the causes of the phi is based on the premise that the clamping force is sufficient. When the clamping force is insufficient, it isn't easy to analyze the causes of the phi. The following analysis is based on the condition that the clamping force is sufficient. According to the several situations in which the phi front appears, the possible causes of the phi front are as follows.
The first situation: as mentioned above, in the case of low temperature, low speed, and low pressure, when the product is not full of glue, the phi has been generated. The main reasons that may arise are insufficient precision in manufacturing the mold, with too large a gap.
The second situation: when the product is just full of glue, there is local shrinkage, no phi; when the injection pressure is increased to improve the local shrinkage of the product, the phi is produced. Possible causes are.
(1) the material temperature is too high. Material temperature is too high, the viscosity of the melt is low, and good fluidity, the stronger the ability of the melt to burst into the mold with the gap, it will lead to phi production.
(2) injection speed is too fast, and the injection pressure is too large (resulting in oversaturation). Too fast speed, and too much injection pressure, especially too much injection pressure, will enhance the ability of the melt to burst into the mold with the gap, resulting in the phi front.
(3) The fluidity of the plastic is too high. The better the fluidity of the plastic, the lower the viscosity of the melt, and the stronger the ability of the melt to burrow into the mold and fit the gap it is easy to produce phi. When the mold production has been completed, the depth of the exhaust slot of the mold, the mold with the gap has been set, change another liquidity of suitable plastic to produce will produce phi.
(4) The strength of the mold is not enough. When the design strength of the mold is not enough, when the mold cavity withstands the pressure of the plastic melt, it will deform and expand, and the gel will burst into the gap of the mold, resulting in phi.
(5) The product design is unreasonable. The product's local glue bit is too thick, and too much shrinkage during injection will lead to local shrinkage. To regulate the problem of local shrinkage of the product, we often need to use a higher injection pressure, longer injection time to fill, and pressure retention, resulting in insufficient mold strength deformation, resulting in phi.
(6) The mold temperature is too high. High mold temperature not only can make the plastic maintain good fluidity, pressure loss is slight, but also reduces the strength of the mold, the same will lead to the production of phi front.
When the second situation is encountered, all the process means are usually used to solve the problem, which is more troublesome to the injection molding technicians. For this situation, the principal means is to solve it by repairing the mold. The solution methods are.
(1) Product localized glue reduction. The product shrinkage of the local reduction of glue, glue position thinning, product shrinkage can be improved, injection pressure will be reduced, mold deformation will be small, and phi can be suppressed. This is the most effective and commonly used method.
(2) Increase the feeding point. Increasing the pouring point can reduce the injection process, reduce the injection pressure, reduce the mold cavity by the pressure, and effectively solve the phi front generation. Increase into the pouring point, especially in the product shrinkage position to increase into the pouring point, to reduce the mold cavity injection pressure can play an immediate effect. It is also one of the more commonly used means.
(3) Strengthen the mold locally. Sometimes the deformation of the template can be strengthened by increasing the support head between the moving template and the ejector plate.
We may encounter various problems in the process of precision mold parts production. If you are interested in learning more about the precision mold parts process, remember to pay attention to our blog, professional precision mold manufacturer Shengqi will continue to share knowledge about the production of precision mold parts.