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Important steps before mold making -- die selection
May 08, 2018

Important steps before mold making -- die selection

When making moulds for silicone products, the first thing to consider is the selection of raw materials for moulds. According to the quality, quantity and structure of the product, the material selection of the mould is decided. Mold material selection is a very important link in the whole mold manufacturing process. Mold selection needs to meet three requirements: first, the mold to meet the wear resistance, strong toughness and other work needs; secondly, the mold to meet the technological requirements; again, the mold should meet the requirements of economic applicability.

(1) die meet the requirements of working conditions

1. Wear resistance

When the blank is plastic deformation in the mold cavity, the surface of the cavity flows and slides along the surface of the cavity, which causes the sharp friction between the surface of the cavity and the blank, which can cause the die to fail because of the wear. Therefore, the wear resistance of materials is one of the most basic and important properties of dies.

Hardness is the main factor affecting the wear resistance. Under normal circumstances, the higher the hardness of the die parts, the smaller the wear volume, the better the wear resistance. In addition, the wear resistance is also related to the type, quantity, shape, size and distribution of carbide in the material.

2, strength and toughness

Most of the working conditions of dies are very bad. Some of them often suffer from large impact loads, resulting in brittle fracture. In order to prevent the die parts from breaking suddenly at work, the mold should have higher strength and toughness. The toughness of the mold depends mainly on the carbon content, grain size and microstructure of the material.

3. Fatigue fracture properties

During the working process of the die, fatigue fracture is often caused by the long-term effect of cyclic stress. Its form is small energy, multiple impact fatigue fracture, tensile fatigue fracture, contact fatigue fracture and bending fatigue fracture.

The fatigue fracture properties of the die mainly depend on its strength, toughness, hardness, and the content of inclusions in the material.

4, high temperature performance

When the working temperature of the die is higher, the hardness and strength decrease, resulting in early wear or plastic deformation of the die. Therefore, the mold material should have higher resistance to tempering to ensure that the mold has higher hardness and strength at working temperature.

5. Resistance to cold and hot fatigue

Some moulds are in the state of repeated heating and cooling in the working process, making the surface of the cavity under the action of tension and stress, causing surface cracking and peeling, increasing friction, hindering the plastic deformation and reducing the size accuracy, resulting in the failure of the mold. Cold and hot fatigue is one of the main forms of failure of hot working dies.

6. Corrosion resistance

Some moulds, such as plastic moulds in the work, because of the existence of chlorine, fluorine and other elements in the plastic, decomposed and precipitated HCI, HF and other strong erosive gases after heating, eroding the mold cavity surface, increasing the surface roughness and aggravating the wear failure.

(two) the mold meets the requirements of the process performance

Mold manufacturing generally has to undergo forging, cutting, heat treatment and other processes. In order to ensure the manufacturing quality of the mold and reduce the production cost, the material should have good Forgability, machinability, hardenability, hardenability and grinding property; it should also have small oxidation, decarburization sensitivity and quenching dehiscence tendency.

1. Forgability

It has lower hot forging deformation resistance, good plasticity, wide forging temperature range, low cold forging cracking and precipitation of net carbide.

2 craft

Spheroidizing annealing has wide temperature range, low annealing hardness, small fluctuation range and high spheroidizing rate.

3, machinability

The cutting parameters are large, the tool loss is low, and the machined surface roughness is low.

4, oxidation and decarburization sensitivity

When heated at high temperature, the oxidation resistance is good, decarburization rate is slow, insensitive to heating medium, and has little pitting tendency.

5. Hardenability

After quenching, it has uniform and high surface hardness.

6, hardenability

After quenching, a deeper hardened layer can be obtained and quenched with a mild quenching medium.

7, the tendency of quenching and dehiscence

Conventional quenching has small volume change, slight warpage, slight distortion and low tendency of abnormal deformation. The sensitivity of conventional quenching is low, and it is not sensitive to quenching temperature and workpiece shape.

8, grindability

The relative loss of grinding wheel is small, and the maximum amount of grinding without burn is large. It is not sensitive to grinding wheel quality and cooling condition, and is not easy to wear and grinding cracks.

(three) the mold meets the economic requirement

When selecting materials for moulds, we must consider the principle of economy and reduce manufacturing costs as far as possible. Therefore, under the premise of satisfying the performance, the first choice is to use low price carbon steel instead of alloy steel.

In addition, when selecting materials, the production and supply of the market should also be considered. The selected steel grades should be as few as possible and centralized, and easy to purchase.

Knowing the knowledge of mold selection can make the advantages of mould better. To produce better and better mold


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