Ejection and reset mechanism of injection mold

The ejection and reset mechanism of the injection mold, the choice of the product ejection method is affected by the product material and shape, etc. Generally, there are ejector pins, simple sleeves, push plates, air, etc. The ejection methods can be used alone or in combination.

1. Requirements for the ejector mechanism

① The ejection system of the injection mold is based on the principle of ensuring smooth, thorough, and non-deformable ejection of the parts. The mechanism is as simple and reliable as possible, with stable ejection and complete reset. ②Generally, the spring return method is adopted. When the demoulding force is unbalanced due to the structure of the part, the injection mold must have a balance and guide device for ejection. ③The plastic part is left on the half mold with ejector mechanism, usually on the male mold. ④ Plastic parts cannot be deformed and damaged. The ejection force should be applied to the rigid part of the plastic part, such as ribs, flanges, and the side wall of the shell, and the acting surface should be as large as possible. ⑤Shanghai Mulan Injection Mold Factory has plastic parts with high requirements on appearance, and the ejector mechanism is located inside the product.

Two, thimble type ejection mechanism

The ejection and reset mechanism of the injection mold and the processing of the thimble are relatively easy. Even if hardness is required, it is easier to perform quenching and grinding than other methods. It can be configured at any position of the product. It is a type of quality that is widely used. mechanism. Ejector hole processing is also easy, the accuracy can meet the requirements, the sliding resistance is small, the situation of jamming rarely occurs, the damage is good, the interchangeability is good, and the maintenance is easy; the commonly used ejector components include round ejector pins, supported ejector pins, flat ejector pins , Secretary Jane. The ejection position should be set in the square with large demoulding force, not in the thin part of the product, and the force can be changed by increasing the ejection area. The ejection mechanism ejects on a small area, and the ejection stress is concentrated on the formed product, and the release material of the cup and box-shaped products is ejected, and the ejection should cause pressure and so on. In this case, the ejector pin is mostly not used. appropriate.

1. Ejector layout requirements

(1) On the product, first punch the thimble on the four sides, and then punch on both sides of the rib.

(2) No small thimble is used on the large plane, and the ejector sleeve is used at the column hole.

(3) The thickness of the sleeve should be more than 1mm, and the inner and outer diameters should be integers.

(4) The thimble should be arranged at the strength of the product, the effect is good, and it is not easy to be white.

(5) The thimble cannot be arranged under the slider, and if necessary, it must be returned to the mechanism earlier to cooperate.

(6) The thimble should adopt the same specification as far as possible, and one kind of thimble is used to facilitate processing and replacement.

2. Matters needing attention in the selection of thimble

(1) Correctly analyze the size and location of the adhesion of the plastic part to the mold cavity, and select a suitable demoulding device in a targeted manner so that the ejection force is applied to the rigid and strong part of the plastic part, that is, as far as possible on the wall The area under the sides, bones, and columns should be as large as possible to prevent plastic parts from being deformed or damaged.

(2) The ejector mechanism should be reliable in operation, flexible in movement, easy to manufacture the injection mold, easy to replace and have sufficient strength and rigidity.

(3) When the diameter of the thimble is below Φ2.5mm, and the position is sufficient, there must be a supporting thimble; if the wall of the cylinder is below 1mm or the wall diameter ratio of the cylinder is ≤0.1, there must be a supporting cylinder, and the supporting length should be as large as possible.

(4) The effective matching length of the thimble = (2.5~3)D, not less than 8mm.

(5) In general, the surface of the thimble should be 0.03~0.05mm higher than the plane of the core. If there is a requirement for the plane of the glue level, it can be considered to add a sinking platform around the thimble.

(6) Try not to set the thimble at the joint of the insert.

(7) For long ribs with a height of more than 10mm, it is recommended to use a flat thimble to eject.

(8) When the thimble surface is on the slope, the thimble must be positioned;

3. Push plate type ejection mechanism

Ejection and reset mechanism of injection mold, Shanghai Mulan Injection Mold Factory push plate type demoulding mechanism is suitable for demoulding of large cylindrical plastic parts, thin-walled containers and various types of single-shell plastic parts. The ejection plate is characterized by uniform ejection, high strength, smooth movement, and plastic parts are not easily deformed. The design points of the push plate type demoulding mechanism are as follows. The push plate should be tapered with the core, and the inner hole of the push plate should be 0.2~0.3mm larger than the forming part of the core to prevent abrasion and jamming between the two. When using a push plate to push out a large deep-cavity shell-like plastic part without a through hole, it is necessary to add an air intake device to the core.