10 factors affecting the quality of injection molds


Mold manufacturing is a complex process, from design, processing, assembly, debugging and other steps to the final actual use. In the entire life cycle, the main factors affecting mold quality are the following 10 aspects.

1. Mould steel

Steel is the decisive factor of mold quality, and choosing a reasonable steel is the top priority. The criteria for selecting steel are:

①Requirements for injection molding materials

Different plastics should use different steels, such as requirements for high polishing, corrosion resistance, etc.;


Steel can be used as long as it can be used, not the more expensive the better; considering the cost factor of the mold, the mold steel should choose the material corresponding to the mold life to avoid unnecessary waste; the life of the general P20 material is about 300,000; the 2738 material is in 500,000 is no problem, H13/2344 is usually more than 800,000-1,000,000, you can choose according to the situation;

③Surface treatment

The surface treatment of the mold is also very important. Nitriding can enhance the surface hardness of the steel and effectively extend the life of the mold; electroplating can effectively modify the plastic mold steel. For some plastic parts that require high brightness and corrosion resistance, electroplating can be used to enhance and improve the performance of the steel.

2. Structural design

The mature mold structure not only considers the product material properties, shrinkage rate, molding temperature, elastic tensile deformation coefficient, etc., but also considers the cooling water circuit and the speed of mold opening and closing. A reasonable mold structure can effectively extend the life of the mold and ensure the smooth production of the mold, improve efficiency and reduce costs.

3. Mold processing

If a worker wants to do his job well, he must first sharpen his tools. The arrangement of the mould process is particularly important. A reasonable process arrangement can speed up the production cycle, shorten the processing time and effectively save costs. And more importantly, accurate and reasonable processing can ensure the stability of the mold in the production process and extend the life. Some processing errors will cause mold welding, no matter how good the welding is, it is a loss to the mold; in addition, poor processing may also affect the mold operation, reduce the mold life, and cause the mold to crack during the production process. Even break.

4. Standard Parts

The lowest wooden bar determines the capacity of the bucket. Everyone understands this principle, but they often fail to notice when doing it. The same is true for molds. Although standard parts are not directly involved in forming, they control the operation of the entire mold. Good standard parts should be able to wear, hard enough, high precision, and not suitable for deformation. The price difference between standard parts of different brands is very big, so don’t just bargain the price when making molds. Your molds will drop from Mercedes-Benz to the masses.

5. Butt bump (flying model)

Relying on the experience of the mold fitter, the seemingly simple job is the most technical job. The main focus of complex molds is this effort. The flat mold is the simplest, as long as the fractal surface does not have flashing, it is basically ok. For example, auto parts molds are very troublesome. Not only are the fractal surfaces relatively irregular, but also often include multiple sliders and top blocks. At the same time, other problems of the mold can be improved and perfected through the collision, so it is a comprehensive work.

6. Polishing/skin texture

Mold polishing is the last link in mold manufacturing. Polishing is directly reflected on the plastic parts, so this is the most face-to-face job. Polishing can also help and supplement the mold movement, especially for demolding. Often the production of some molds is not smooth because of poor lighting, excessive resistance, difficulty in demolding, and even whitening and topping.

7. Mold assembly

Mold assembly is just like assembling a machine. Every component and every screw must not be wrong, otherwise the consequences will be quite serious, ranging from product defects and affecting production, or completely damaging the mold and causing scrap. Therefore, the assembly work must be very meticulous. Pay special attention to the cleaning of the mold during the assembly process, especially the waterway and screw holes, and the iron filings must be blown out.

8. Hot runner or cold runner

This actually has the least impact on mold quality, because hot runners are generally designated by customers, especially some large customers. Well-known foreign brands are very good in quality and after-sales service, so there is generally no problem in quality. It’s just that the quality of some domestic hot runners is quite different. In order to save costs and strive for price advantages, individual small companies use unreliable heating and conductive parts, which are prone to problems. The main problem of cold runner is how to ensure the balance of injection molding, gate size, injection pressure and so on.

9. Cooling water circuit

Anyone who has mold experience knows how important cooling is to a mold. Due to the increase in prices and human wages, when mass production of products, the profit that does not reduce the injection cycle of one second is unimaginable. However, while accelerating the production cycle, the temperature of the mold will rise. If it is not effectively controlled, the mold will be too hot to form, and even cause the mold to deform and fail. Therefore, good waterway design is particularly important, including the arrangement density, diameter, and mutual links of the waterways.

10. Mold maintenance

Mold maintenance is mainly maintenance and maintenance during the production process. The mold is like a car, if it is not used for a long time without maintenance, it may cause the mold to be scrapped. Therefore, every time the mold is used, a comprehensive maintenance must be carried out, especially the rust prevention of the forming part and the rust prevention of the main moving parts. Because the mold needs to receive water during the production process, it may sleep on the mold during the installation or disassembly process, so you must ensure that the mold is dry, and then brush a layer of oil protection.

Plastic Mold
the authorPlastic Mold