Spillage mostly occurs at the tapping position of the mold, such as the parting surface of the mold, the sliding part of the slider, the clearance of the insert, the clearance of the ejector, etc. If the overflow is not solved in time, it will further expand, and the stamping die will collapse partially, causing damage. Overflow of insert clearance and ejection clearance will cause the product to be stuck on the mold and affect demoulding. Then, how to deal with the overflow of the injection molding machine?

1、 Equipment

(1) The clamping force of the machine is insufficient. When selecting an injection molding machine, the rated clamping force of the machine should be higher than the longitudinal projection area of the injection molding product, otherwise it will cause mold expansion and flash.

(2) The mold closing device is poorly adjusted, the elbow mechanism is not straight, and the left and right or upper and lower molds are not balanced, so the mold parallelism cannot be reached. When one side of the mold is tight and the other side is not tight, injection burrs appear.

(3) The poor parallelism of the mold itself, or the installation is not parallel, or the template is not parallel, or the pull rod is unevenly distributed and deformed, which will cause the mold to be loose and flash.

(4) The check ring is severely worn, the spring of the spring nozzle fails, the barrel or screw is excessively worn, and the cooling system at the feed inlet fails, resulting in bridging, insufficient injection volume of the barrel adjustment, too small cushion, etc. If the flash point occurs repeatedly, please timely repair or replace the parts.

2、 Mold

(1) The precision of the parting surface of the die is poor. The movable formwork (such as middle plate) is deformed and warped; There are foreign matters on the parting surface or protruding slip marks around the mold frame; Due to early flash extrusion, the old mold caused fatigue and collapse around the cavity.

(2) The mold design is unreasonable. If the deviation of cavity opening position is too large, the cavity side will be pulled during injection, resulting in flash.

The fluidity of plastics is good, such as polyethylene, polypropylene, nylon, etc. They have low viscosity in the molten state and are easy to enter the movable or fixed gap, requiring high mold manufacturing precision.

On the premise of not affecting the integrity of the product, the quality shall be placed symmetrically as far as possible, and the materials shall be fed in the thicker part of the product to prevent material shortage and flash. When there are forming holes in or near the product, side gates are usually set on the holes.

Due to the high injection pressure, if the clamping force is insufficient and the support force of the mold at this part is insufficient, the mold will slightly warp, resulting in flash. If there are moving parts on the side of the mold, the projected area of the side will also be affected by the forming pressure. If the support force is insufficient, flash may also occur.

The matching accuracy of the sliding core is poor, and the deviation of the installation position of the fixed core and the cavity will also cause flash. If the cavity has poor exhaust, there is no exhaust groove on the parting surface of the mold, or the exhaust groove is too shallow, or too deep, or blocked by foreign matters, it will cause flash. For multi cavity mold, attention should be paid to the reasonable design of each runner and gate, otherwise uneven filling force will be caused and flash will occur.

3、 Process

(1) The injection pressure is too high or the injection speed is too fast. Due to the high pressure and speed, the opening force increases, resulting in overflow. The injection speed and injection time shall be adjusted according to the thickness of the product. Thin products shall be filled at a high speed without injection; Thick products shall be filled at low speed, and the skin shall be basically fixed before reaching the final pressure.

(2) Excessive feed speed causes burrs. It is worth noting that in order to prevent dents, do not inject too much molten material, so that dents may not be filled, but may appear flash. This situation should be solved by extending the injection time or pressure holding time.

A higher barrel and nozzle temperature or mold temperature will reduce the viscosity of the plastic, increase the fluidity, and flash will appear when entering the mold smoothly.

4、 Raw materials

(1) If the viscosity of plastic is too high or too low, burrs may appear. Nylon, polyethylene, polypropylene and other low viscosity plastics should increase the clamping force; The plastic with strong water absorption or water sensitive plastic will greatly reduce the flow viscosity and increase the possibility of flash under high temperature. These plastics should be completely dry. The viscosity of plastics added with too much recycled materials will also be reduced. If necessary, the residual ingredients will be supplemented. If the plastic viscosity is too high, the flow resistance will increase, and the back pressure will increase the cavity pressure, resulting in insufficient clamping force and flash.

(2) When the particle size of plastic raw materials is uneven, the feeding amount changes, the parts are not full, or burrs appear.

The above is about how to deal with the overflow of the injection molding machine. If you want to know more about the injection molding machine, you can continue to pay attention to Liansheng Precision.