The function of ejector: the main purpose of ejector is to eject the product from the Medical plastic injection mold cavity, and at the same time, it has the function of exhausting the cavity.

The Medical plastic injection mold design principle of the position of the ejector pin 

First, it should be designed in the place with the largest wrapping force on the mold; secondly, in the place with high adhesion force such as deep pits on the product; the ejector pin can also be placed in the place where poor exhaust is easy to occur.

The second principle of ejector position Medical plastic injection mold design: the arrangement of ejector must be evenly distributed, otherwise it may cause ejection out of balance. In the ejection design, the product should be divided into small areas for design, and after the partial area design is balanced, the ejection and exhaust of the entire product should be comprehensively considered.

Design principle 3 for Medical plastic injection mold design of the ejector: The product where the ejector is placed should have a certain thickness. When the product is thin, there may be thimble marks on the side surface of the product without thimble. If it is an appearance part, when the customer cannot accept it, or when the product size is out of tolerance, the ejector cross-sectional area can be considered as large as possible or Use a formed ejector pin (ie: ejector pin cross-section that is the same or similar to the product ejection area).

The Medical plastic injection mold design principle of the position of the ejector pin 4: The ejector pin should be designed to have a large ejection cross-sectional area as much as possible, which not only ensures the ejector pin strength (not easy to break), but also enables the product to be ejected easily.

The ejector rod is generally divided into: dome pin, stepped dome pin, square thimble, jacking tube, etc.

The first point: In general, the dome needle is preferred (because the dome needle is cheap and easy to process). When the diameter of the dome needle is less than 1.2mm: the stepped dome needle should be used, and the dome needle stage should be designed as long as possible. enhance

The strength of the thimble; the diameter of the thimble is generally ≥0.6mm. When the diameter of the thimble must be less than 0.6mm, the plan must be discussed with the superior and approved for use.

 The second point: the square thimble is used to top deep grooves, narrow grooves and other shapes.

The third point: the ejector tube is used to eject the forming hole.

The fourth point: the thimble hole must be designed at the position of the thimble on the Insert. The length of the matching section between the thimble and the Insert is generally 10~15mm; the design principle of the dome pin via: Dome pin = ΦAmm, dome pin via = ΦA+0.5mm.

Fifth point: In order to facilitate the assembly of the square thimble, when there is a round hole on the Insert that passes over to the square hole, the square hole must be designed with a guide section generally: 5mm X 3° or 3mm X 5°; when there is no round hole on the Insert When excessive, the square thimble hole guide section can be used: (3~A)mm X 3°

Note: A=Insert height minus (10~15)mm. At the same time, when designing, it should be noted that the ejector rod cannot be smaller than 4mm or interfere with the cooling water circuit.

Moving mold parting or double ejection: When only ejecting with the ejector pin is not enough to eject the product, or the ejection will cause damage to the product, you can use the moving mold parting, moving mold INSERT floating or double ejection method to eject the product. eject.

When the fixed mold has a tendency to stick to the mold and the product is allowed, the fixed mold should also increase the ejection design; when the product is not allowed, the product should be changed in the moving mold, and measures such as pulling back or modifying the parting surface should be added to ensure the product. stay in the moving mold.

Stripper Plate: It is mainly used for large flat products, or products with deep cavity shells and small volumes that are difficult to place thimbles. The ejection of the top plate can save the number of ejector pins, but the ejection mechanism itself is relatively large, and sometimes it is necessary to add two ejectors.

Insert Floating: Mainly used for complex parts with large wrapping force, and it is difficult to achieve good ejection effect with ejector pins or other ejection designs. The purpose of smooth ejection of the product is achieved by reducing the wrapping force by floating Insert. 

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