Injection mold ejection system design
After the product has completed a forming cycle, the mold is opened and the product is wrapped on one side of the mold and must be removed from the mold. This work must be done by the ejector system, which is an important part of the entire mold structure. Generally consists of three parts: ejection, reset and ejection.
Injection mold ejection system design process
1, the design principle of the ejection system
The ejector system has various forms, which are related to the shape, structure and plastic properties of the product. Generally, there are ejector pins, jacking pipes, push plates, ejector blocks, and pneumatic composite ejector.
The design principles of the ejector system are as follows:
1 When selecting the parting surface, try to keep the product on the side of the demoulding mechanism.
2 The top output and position balance ensure that the product is not deformed or broken.
3 The thimble shall be located at a location that does not affect the appearance and function of the product.
4 Try to use standard parts safely and reliably for manufacturing and replacement.
5 The ejection position should be set at a large resistance and should not be too close to the insert or core. For the box-shaped iso-cavity mold, the side resistance is the largest, and the top surface and the side surface should be simultaneously pushed out to avoid the deformation of the product.
6 When there are thin and deep ribs, the ejector is usually placed at the bottom.
7 At the product inlet, avoid setting the thimble to avoid rupture.
8 For thin meat products, the product can be taken out by placing a thimble on the runner.
9 The thimble and the thimble hole are generally matched by a gap. If it is too loose, it will easily produce a burr, which is too tight and can cause a jam. In order to facilitate the processing and assembly, and reduce the friction surface, a matching length of 10~15mm is generally reserved on the movable mold, and the remaining part is reamed by 0.5~1.0mm to form an escape hole.
10 In order to prevent the thimble from rotating during production, it must be fixed to the ejector plate in a variety of forms, which must be determined according to the size, shape and position of the thimble.
2, the principle of selection of the ejection type
In the injection mold structure, the design of the ejection mechanism directly affects the quality of the finished plastic product. If the design is not good, the plastic part will produce a series of defects, such as warping deformation, cracking and whitening of the plastic part. The determination of the ejector type is the most important part of the ejector design. The optimised design of the ejector type, quantity and ejection position is based on the ejection force and the release resistance.
The ram is the simplest and most common form of ejector. Because of its convenient manufacturing and repairing, the ejector effect is good and it is the most widely used in production. However, the circular ejection area is relatively small, which tends to cause stress concentration, topping through the product, and deformation of the product. In the tubular box-shaped products with small draft and small resistance, try to avoid using them. When the jack is relatively elongated, a stepped ejector pin is generally provided to enhance rigidity and avoid bending and breaking. Pole structure,
(2) Pipe jacking
The top tube, also known as the cylinder or the cylinder needle, is suitable for rings, cylinders or products with a central hole. It is ejector that the contact force is uniform throughout the week, it will not deform the product, and it will not easily leave obvious marks of ejector, which can improve the concentricity of the product. However, it is avoided for the thick and thin products of the surrounding area, so as to avoid damage caused by difficulty in processing and weakening of strength.
(3) Push board
Push plates are suitable for a wide range of containers, boxes, cylinders and slim, thin-walled products with a central hole. It has a smooth, uniform ejection and a large ejection force, leaving no trace of ejector. Generally, there will be a fixed connection to prevent the push plate from being pushed down during production or demoulding, but the push plate may not be fixed as long as the guide post is long enough to strictly control the demolding stroke.
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