The solution of overflowing material in the head of injection molding machine

Overflow (flying edge)

Overflow, also known as flying edge, overflow edge, phi front, etc., mostly occurs in the mold score fit position. Such as the mold parting surface, the sliding part of the slider, the gap of the insert, the hole of the top bar, and so on. Overflow material will be further expanded if not solved in time, thus embossing the mold to form a local collapse, causing permanent damage. The overflow of the gap of the insert and the hole of the top bar will also make the products stuck on the mold and affect the demoulding.

1. Equipment

(1) The real clamping force of the machine is not enough. When choosing an injection molding machine, the rated clamping force of the machine must be higher than the tension formed during injection of the longitudinal projection area of the injection molded product, otherwise, it will cause mold expansion and appear flying edges.

(2) Poor adjustment of the mold clamping device, the elbow rod mechanism is not straightened, resulting in unbalanced mold clamping or left and right or up and down, the phenomenon of mold parallelism can not be achieved, resulting in a single side of the mold is closed tight and the other side is not close, the injection will appear flying edge.

(3) The parallelism of the mold itself is not good, or not parallel, or the template is not parallel, or uneven force distribution and deformation of the tie rod, which will cause the mold is not tight and produce flying edges.

(4) check ring wear serious, spring nozzle spring failure, barrel or screw wear is too large, the inlet cooling system failure caused by the "bridge" phenomenon, the barrel adjustment of the injection volume is not enough, the buffer pad is too small, etc. may cause the recurrence of flying edge, must be timely repair or replacement parts.

2. Mould

(1) Poor precision of mold parting surface. Active template (such as the middle plate) deformation warpage; parting surface with foreign matter or mold frame around the protruding skid mark burr; old mold because of the earlier flying edge extrusion and fatigue cavity collapse around.

(2) The mold design is unreasonable. The opening position of the mold cavity is too deviated, which will make the mold tension occur on one side during injection and cause a flying edge.

Plastic fluidity is too good, such as polyethylene, polypropylene, nylon, etc., in the molten state viscosity is very low, easy to enter the active or fixed gap, requiring a high precision mold manufacturing.

The premise of not affecting the integrity of the product should be placed as far as possible on the center of mass symmetry, in the thick part of the product into the material, which can prevent the lack of material on one side with the flying edge. When there are molding holes in or near the center of the product, it is customary to open side gates on the holes. This is because under high injection pressure, if the clamping force is not sufficient, the mold will not have enough support force in this part and slight warpage will occur, thus causing flying edges. If the side of the mold with moving parts, its side projection area is also subject to molding pressure, if the support force is not enough, it will also cause a flying edge.

Sliding core with poor precision, fixed core, and cavity installation position offset will also produce a flying edge. Poor cavity exhaust, in the mold parting surface without open exhaust groove or exhaust groove is too shallow, or too deep and too large, or blocked by foreign objects will cause flying edge. The multi-cavity mold should pay attention to the reasonable design of each manifold together with the gate, otherwise, it will cause uneven filling force and produce a flying edge.

3. process

(1) injection pressure is too high or injection speed is too fast. Due to the high pressure and high speed, the opening force of the mold increases, resulting in overflow. To adjust the injection speed and injection time according to the thickness of the product, thin products should be used to quickly fill the mold with high speed, full and no longer into the injection; thick products should be used to fill the mold with low speed, and let the epidermis in the final pressure before reaching the general fixed down.

(2) The amount of material added is too large to cause flying edges. It is worth noting that to prevent depression and inject too much melt, so that the depression may not "fill", but the flying edge will appear. This situation should be extended injection time or holding time to solve.

(3) barrel, nozzle temperature is too high or mold temperature is too high will make the plastic viscosity drop, liquidity increases, in the case of smooth into the mold caused by flying edge.

4. Material

(1) plastic viscosity is too high or too low may appear flying edge. Low viscosity plastics such as nylon, polyethylene, polypropylene, etc., should improve the mold force; absorbent plastic or water-sensitive plastic at high temperatures will substantially reduce the flow viscosity, increasing the possibility of flying edge, these plastics must be thoroughly dried; mixed with too much recycled plastic viscosity will also decline, if necessary, to supplement the retention component. Plastic viscosity is too high, the flow resistance increases, resulting in a large back pressure to increase the pressure of the mold cavity, resulting in insufficient clamping force and producing flying edge.

(2) uneven size of the plastic raw materials will make the amount of material added variable, the parts or dissatisfaction, or flying edge.