Email Us

Why Do Products Made by Injection Moulding Need Draft Angles and What Determines Their Size?

Injection moulding mold mechanical polishing is a very delicate manual work, so the polishing technology of injection mold is still the main reason affecting the quality of mold polishing. In addition, it is also related to injection mold materials, surface conditions before polishing, and heat treatment processes. High-quality mold steel is a prerequisite for obtaining good polishing quality. If the surface hardness of the mold steel is uneven or the performance is different, various inclusions and pores in the mold steel are not conducive to polishing, and even the experienced masters cannot achieve satisfactory polishing results.

The effect of injection molding finishing is also different. Although the hardness of mold steel increases the difficulty of grinding and consumes more polishing time, the roughness will decrease and the polishing effect will be better after polishing. At the same time, as the hardness increases, the possibility of surface differences caused by excessive polishing also decreases. Why do products made by injection moulding need to have a draft angle? What factors determine its size? Let's take a look together.

The reason why products made by injection moulding need to have a draft angle

Generally, injection molding mould need to be processed by corresponding molds. After an injection molded product is formed and solidified, it is taken out from the mold cavity or core, which is commonly called demolding. Due to molding shrinkage and other reasons, plastic products are often tightly wrapped around the core or stuck in the mold cavity, and cannot be automatically released from the mold after opening the mold. In order to facilitate the release of products made by injection moulding from the mold and prevent the surface of products made by injection moulding from scratching during demolding, when designing injection molds, an appropriate draft angle must be ensured on the inner and outer surfaces of products made by injection moulding along the demolding direction.

Factors affecting the size of the draft angle of products made by injection moulding

  • The size of the draft angle depends on the performance and geometry of products made by injection moulding, such as height or depth, wall thickness, and cavity surface conditions, such as surface roughness, processing patterns, etc.

  • Hard plastics require a larger draft angle than soft plastics.

  • Plastic parts with complex shapes or many molding holes require a larger draft angle.

  • For products made by injection moulding with large height or deep holes, a smaller draft angle should be used.

  • As the wall thickness of the products made by injection moulding increases, the force to wrap the inner hole on the core increases, so the draft angle should be larger.

The pre-processing technology of injection moulding mold also has a certain influence on polishing. During the cutting of mold steel, the surface layer will be damaged by heat, internal stress, and other factors. The cutting speed and feed rate must be relatively uniform to avoid affecting the mold polishing effect. The surface of electric spark machining is more difficult to polish than ordinary cutting or heat treatment, so electric spark adjustment should be performed before electric spark machining is completed, otherwise a hardened layer will be formed. The hardness of the hardened layer is higher than that of the steel body, and it should be removed as much as possible to lay a good foundation for subsequent polishing.

Keyplast Injection Molding

Other Injection Molding News

Contact Us
Office: NO. 3609 Wuyue Office Building 11, Huangyan, Taizhou, Zhejiang, China, 318020
Factory: No 328, Xiaoliqiao Beiyang Huangyan, Taizhou, Zhejiang, China 318020