Analysis of excessive burr of the hottest injectio

Analysis of excessive burr of injection molded products

too much burr occurs on the parting surface, that is, between the moving mold and the static mold, the sliding part of the slider, the gap of the insert, the hole of the ejector rod, etc., flows into the melt, forming redundant flash burr on the workpiece. Such flash burr plays a leverage role during molding, which will further increase the flash burr, resulting in local depression of the mold, When forming, the flash and burr enter a vicious circle of increasing. Therefore, if flash and burr are found at the beginning, the mold must be repaired as soon as possible

there are several reasons for burr

1. Insufficient clamping force

compared with the projection area of the molded part, if the clamping force is small, there will be a gap between the dynamic and static molds due to the effect of injection pressure, so flash burr is bound to appear. Especially when the side gate is placed on the hole near the center of the workpiece, because this molding gate requires a large injection pressure, it is very easy to have burrs. This defect can be eliminated by reducing the injection pressure or increasing the clamping force. Sometimes it is also very effective to use plastic with good fluidity and low-pressure molding according to the specific situation

2. The mold is not tightly matched locally

first of all, the problem of loose clamping of the dynamic and static mold is discussed. Although the mold itself is tightly closed, when the injection machine with elbow bar type mold locking mechanism is used for molding, it is often caused by poor parallelism of the mold or poor adjustment of the mold locking device, such as mold locking on the left and right sides. The phenomenon of balance, that is, only one side of the left and right sides is locked, and the other side is not closely attached. At this time, the pull rod (two or four pullers) must be adjusted to make it evenly spread. Secondly, there is also a lack of tightness due to poor research and matching of the mold itself. Especially when there is a forming hole in the center of the workpiece, due to the supporting effect of this part, burrs are also easy to appear when the clamping force is insufficient

in addition, the sliding core is an action mechanism, which often produces burrs, so the cooperation of the sliding core is very important. Especially for the left and right split Halff mold, the projected area of its side is also affected by the forming pressure. If the design cannot fully withstand this pressure, burrs often appear. As for the gap of the insert and the hole of the ejector rod, it will not only produce the phenomenon of increasing the vicious circle of burrs, but also increase the ejection resistance

3. Mold deflection causes

if the mold is not original enough, it will deflect under the action of injection pressure. At this time, if there is a hole near the center, 3. The total profit of China's paper industry will decline, and burrs will appear around the hole; In addition, when the center hole is used to open the

side gate, burrs will also occur around the hole and the gate. The burr caused by this reason is caused by the poor manufacture of the mold, so it is difficult to repair. The burr can be reduced by strengthening the mold

4. It is understood that the fluidity of plastic is too good

it is simply due to the fluidity of plastic, which is not the cause of burrs in theory. However, when the plastic fluidity is too good, even tiny cracks can be drilled into the plastic, so it is very easy to have burrs. To eliminate this kind of burr, you can reduce the melt temperature or injection pressure, and also reduce the mold temperature or injection speed,

5. Inject too much melt

this is not the direct cause of burr. In order to prevent shrinkage, it is wrong to inject too much molten material. It should be molded by increasing the injection time or pressure holding time (refer to shrinkage)

6. There are foreign bodies on the mold surface

there are foreign bodies on the mold clamping surface, which will inevitably produce burrs. To solve this problem, it is obviously necessary to clean the mold surface so that the mold closing surface can be closely pasted