Burr occurred mostly in the sub-surface, that is, between the dynamic mode and the static mold, sliding parts of the slider, insert the gap, ejector holes into the melt, etc., in the workpiece to form excess flash burr .
This burr flash burrs, in the molding lever from the role of the flash burrs will be further increased, resulting in local depression of the mold, the formation of the flash burr into a vicious circle increases, so if the beginning of the discovery The flash burr, you must trim the mold as soon as possible.
Burr generation for the following reasons
1. Clamping force is not enough
Compared with the projected area of the molded parts, if the clamping force is small, there will be a gap between the movable and static molds due to the injection pressure, so the flash burr will inevitably occur. Parts near the center of the hole, because this kind of molding gate requires a larger injection pressure, so prone to glitches.
Reduce the injection pressure or improve the clamping force can eliminate this defect, according to the specific circumstances to switch to good liquidity using low pressure plastic molding, and sometimes very effective.
2. Mold with the local tight
First of all, to discuss the dynamic and static mold clamping problem, despite the tight mold itself, when using the toggle lever clamping mechanism injection molding machine, often due to poor mold or mold clamping device to adjust poor, resulting Such as the phenomenon of uneven clamping on both sides of the left and right sides, that is, only the left and right side is locked, the other side is not close, then you must adjust the rod (two or four pull skewer) to balance the exhibition.
Second, there are also due to poor research and development of the mold itself caused by the lax close.Especially the center of the workpiece has a molded hole, because of this part of the supporting role, when the clamping force is not sufficient when the burrs are prone to.
The other is the sliding core, because the mobile core is the action mechanism, often have glitches, so with the sliding core is very important, especially for the right and left parting Huff mode, the side of the projection area is also affected by the forming pressure, Burrs can also occur if the design does not fully withstand this pressure.On the insert gap and mandrel porosity, not only will there be a vicious cycle of glitches, but will also increase the ejection resistance.
3. Mold deflection caused
If the mold original enough, by the injection pressure will produce deflection, then if there is a hole near the center of the hole will have burrs; Also use the center hole to open the side gate, hole and runner around will also produce Burr. Burr caused by this reason, is caused by poor mold making, it is more difficult to repair. To take reinforcement mold, burr can be reduced.
4. Plastic liquidity is good
Purely because of the plastic flow is too good, in theory, is not the cause of burrs. However, when the plastic flow is too good, even if it is fine cracks in the plastic can be drilled into, so prone to glitches. To eliminate this Burr, can reduce the melt temperature or injection pressure, but also reduce the mold temperature or injection speed,
5. Inject too much melt
This is not the direct cause of glitches.It is wrong to inject too much melt in order to prevent shrinkage and should be molded by increasing injection time or dwell time (refer to shrinkage cavity).
6. Mold surface foreign body
There are foreign objects in the mold clamping surface, will inevitably produce burrs.To solve this problem, it is clear that the net mold surface should be cleaned so that the mold can be close to the surface.