What is plastic injection mold?

What components are made of plastic molds, used for?

What are standard components and non-standard components of the mold?

Which materials are suitable for plastic mold components?

Why the mold components need to be heat treatment?

Why the mold surface finish is important for the mold life?

 

What is plastic injection mold?

Plastic injection mold is the most commonly used for the production of plastic parts. The processing equipment for plastic injection molds is the plastic injection molding machine. At first, the plastic particles are heated and melted in the hot barrel of the injection machine, and then driven by the screw or plunger, the melt enters the mold cavity through the injection machine nozzle and the mold’s gating system, and then the plastic will be formed and cooled to the molded parts with the shape that we need.

Injection molds have been widely used in the production of plastic products because they can form multiple plastic parts with complex structures, precise dimensions and good internal quality at one time. In addition, he has the characteristics of short production cycle and high efficiency, so it is suitable for large-scale production of plastic parts.

 

What components are made of plastic molds, used for?

Forming components: directly contact with the melt and form the plastic part. There are usually mold components such as punches, cores, forming rods and rings, mold inserts and other components. Forming components define the internal and external contours and dimensions of the plastic part.

Core-pulling components: including angle pin, sliders, which are used to pull out the movable core when the mold is opened, so that the product is demolded.

Guide components: guide pillars and bushes to determine the relative position of the mold and ejection system.

Supporting and fixing components: including mold base plate, fixing plate, supporting plate, pad, etc., used to fix the mold or support the pressure in the injection molding.

Ejection components: ejector pin, ejector block, ejection bar to release the plastic molded parts.

 

What are standard components and non-standard components of the mold?

The standard mold components are the basic parts in the mold manufacturing. It has great significance to shorten the mold design and manufacturing cycle, reduce mold production costs, and improve mold quality. There are numerous manufacturers of standard parts on the market: Japanese MISUMI/O standards, American DME/O standards, Spanish CUMSA/O standards, German HASCO/O standards, German FIBRO standards, etc.

Non-standard mold components mean that the size and shape of the parts need to be customized according to the mold structure. In general, these parts have a greater impact on the formed parts and require higher accuracy. For example, mold core, mold insert, slider, lifter, ejection pins, etc.

 

Which materials are suitable for plastic mold components?

With the development of the plastic injection molding industry, the quality requirements for plastic molds are also getting higher and higher. Therefore, the failure problems and influencing factors of mold components muss be seriously considered. Therefore, how to choose a good mold steel plays a decisive role for the main mold components like inserts and slider etc.

Hardness

Hardness is the main technical index of mold steel. The mold must have a sufficiently high hardness to maintain its shape and size under the action of high stress. Cold work die steel generally maintains hardness around HRC60 at room temperature. Hot work die steel is generally required to stay within the HRC40 ~ 55 range according to its working conditions.

Toughness

During the injection molding process, the mold is subjected to impact loads. In order to reduce damage such as breakage and chipping, the mold steel is required to have certain toughness. Therefore, hot working and heat treatment processes must be used to achieve the best combination of wear resistance, strength and toughness of the mold material.

Thermal fatigue resistance

The mold is also subject to high temperature and periodic rapid cooling and rapid heating. The thermal fatigue resistance determines the mold life before fatigue crack initiation. In order to obtain a high life for hot work molds, the mold materials should have high thermal fatigue resistance, low crack growth rate and high fracture toughness values.

Abrasion resistance

The most important factor in determining the mold life is the abrasion resistance of the mold components material. In order to improve the wear resistance of the mold steel, it is necessary to maintain the mold component steel with a high hardness, and to ensure that the composition, morphology, and distribution of carbides or other hardened phases in the steel are reasonable.

 

Why the mold components need to be heat treatment?

In order to make mold components have the required mechanical properties, physical properties and chemical properties, heat treatment process are very essential. Among mold failure accidents, accidents caused by heat treatment are generally 52.3%, so that heat treatment plays an important role in the entire mold component manufacturing. The quality of the heat treatment process has a greater impact on the quality of the mold parts. The purpose is to improve the mechanical properties of the material, eliminate residual stress and improve the machinability of the mold components.

 

Why the mold surface finish is important for the mold life?

The surface quality of mold parts is measured by surface roughness, which is usually expressed in Ra (µm). The smaller the Ra value, the higher the surface quality. The working properties of mold components, such as wear resistance, corrosion resistance, and strength, are greatly affected by their surface finishing quality. The higher the surface quality of mold components, the longer its life. On the other hand, if the surface quality of the mold parts is too high, it will increase the cost of mold manufacturing.

The polishing of mold components is a very important process in the mold manufacturing process. Mold parts with mirrors and high-gloss surfaces have higher requirements for mold surface roughness, and therefore higher requirements for polishing. Polishing not only increases the aesthetics of the workpiece, but also improves the corrosion resistance and abrasion resistance of the material surface. It can also facilitate subsequent injection molding processing, such as making plastic products easy to demold and reducing the production injection molding cycle.

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