Precision mold parts performance requirements
1. Strength and toughness
High precision mold and tool components often work under harsh condition. Some usually bear a large impact load, resulting in brittle fracture. Thus, precision molds should have high strength and toughness. It’s to prevent mold components from breaking suddenly during working. And the toughness of the mold and tool mainly depends on the carbon content, grain size, and microstructure of the material.
2. Fatigue fracture performance
The fatigue fracture always happens when the high precision plastic injection mold parts are working. It’s because of the long-term effects of cyclic stress. The forms include multiple impact with small energy, stretch, contact, and bending fatigue frature. In general, this property of custom molding and tooling depends on these factors. Like its strength, toughness, hardness, and inclusions content in the material.
3. High-temperature performance
When the working temperature of precision molding and tooling is higher, the hardness and strength will decrease. And it results in early mold wear or failure by plastic deformation. Thus, the mold material should have high tempering stability. It can ensure that the mold has a high hardness and strength in the working temperature.
4. Resistance to cold and heat fatigue
Some molds are in the state of repeated heating and cooling in the working process. Then, it causes the surface of the cavity to be pulled and stressed, resulting in the surface crack and peel off. As a result, it increases the friction force. Beside, it prevents the plastic deformation and reduces the dimensional precision. Finally, it leads to the failure of the mold. Cold and hot fatigue is one of the primary forms of hot working tool failure.
5. Corrosion resistance
In the working process of some molds, like plastic injection molding, they produce strongly aggressive gas. Because there are chlorine, fluorine, and other elements in the plastic, they decompose and precipitate HCI and HF. They erode the cavity surface, increase the surface roughness and aggravate the wear failure.
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Select proper material for your precision mold components
Current MLS common used materials to manufacture precision mold components include as below.
Sweden: S136, 8407, DF-2 718;
USA: 420, H13, P20, D2;
Japan: SKD61, DC53, NAK80, SKD11, SKH-9 high speed steel;
Germany: 1.2379, 1.2083, 1.2316, 1.2344.
With multiple choices, quality products, fast lead times, excellent customer service and support, MLS will be your first choice of precision machining company.
11 tips to choose the proper material for your precision mold components
1. Precise mold parts definition
Custom molding parts refers to the direct contact with the plastic and injection molding products. For example, cavity, core, slider, insert, oblique top, side pumping.
2. Importance of Mold components material
Precise mold parts material is directly related to the quality and life of the injection molds. Also, it determines the appearance and intrinsic quality of the molded plastic parts. Precision mould part manufacturer has to be careful to choose the material. In general, we select it according to features of the injection moulded product and mold. And all them should base on the contract and customers needs.
3. Mould parts material selection principle
The selection principle of precision mold components is the type of plastic injection molding products. For example, shape, size precision, appearance quality, using rule, quantity, and so on. Also, the precision mould part manufacturer will think of material cutting, polishing, welding, corrosion, deformation, wear-resisting property. At the same time, we need to consider the economy, injection mould manufacturing conditions and processing method to choose different types of steel.
4. Transparent injection mold
If the customer needs molds to form a transparent plastic injection molding product, the mold manufacturer company will help. We use high-grade imported steel with high mirror polishing performance for its cavity and core. For example, 718(P20+Ni class), NAK80(P21 class), S136(420 class), H13 class steel, and so on. Among them, 718, NAK80 is the pre-hardened state, do not need to conduct heat treatment. S136 and H13 steel are in the annealing state, and the hardness is generally hb160-200. After rough machining, it is necessary to conduct vacuum quenching and tempering treatment. The hardness of S136 is generally hrc40-50, and that of H13 steel is generally hrc45-55 (It depends on the specific brand).
5. Mold with high appearance quality product
There are molds with high requirements on appearance quality, long service life and mass production, molding suppliers provide support to choose molded parts materials.
A. The mold cavity shall use high-grade imported steel with high mirror polishing performance. Such as 718(P20+Ni class), NAK80(P21 class), etc., all of which are pre-hardened and do not need to undergo heat treatment.
B. The core use low and medium grade P20 or P20+Ni class steel, such as 618, 738, 2738, 638, 318, are pre-hardened. For the production of small quantities mold and tool, we can also choose plastic mold steel or S50C, S55C and other high quality carbon steel.
6. Mold with general appearance quality product
For the molds with general requirements on the appearance quality of the injection molding products, the selection of forming parts materials is as follows.
A. Precision molds cavity and core are selected from middle grade imported P20 or P20+Ni class steel.
B. Large and medium-sized molds. The molded plastics have no special requirements for steel. In general, mold manufacturer can choose low grade imported P20 class steel or high quality carbon steel S50C, S55C, and so on. Also, they can choose domestic plastic mold steel.
C. For the cavity with pitting grain, it’s different. When pitting pear ground grain, precision mould part manufacturer should try to avoid using the 2738(738) brand of P20+Ni class.
7. No appearance requirement molds
For some internal structural parts, customers have no appearance and quality rule. If there is also no special requirement for mold steel, we can choose the material as follow. At first, for large and medium-sized molds, there arer many choices, such as low-grade P20 or P20+Ni type steel. Also, we use imported carbon steel S55C, S50C, or domestic P20 or P20+Ni type plastic mold steel. Then, for small mold, if the output is high and the structure is complex, we can make the mold cavity can with low-grade imported P20 or P20+Ni type steel. Domestic P20 or P20+Ni type plastic mold steel are also proper. The core can be made of domestic plastic die steel. Finally, for small mold with simple structure and low output, we can use domestic plastic mold steel or high-quality carbon steel for the cavity core.
8. Molding corrosive plastic parts
For the formation of fluorine, chlorine, and other corrosive plastics and a variety of added flame retardant, if the product requirements are higher, can choose imported corrosion steel, general requirements can choose domestic corrosion steel.
9. Precision molding product with speacial properties
For the molding of the steel has strong friction, impact plastic mold, such as for the injection of nylon + glass fiber material mold, it is necessary to choose a high wear resistance, high thermal tensile strength, and high toughness and other advantages of imported or domestic H13 steel.
10. Insert precision moulding
Molding inserts and inserts into the general parts of the same material. For precision mold components that are difficult to cool or parts that require a high cooling effect, the insert materials should be beryllium bronze or alloy aluminum.
11. The selection principles of materials for moving parts involved in molding in the mold
A. The transparent part shall be of high-grade imported steel with good polishing property, such as 718, NAK80, etc.
B. For non-transparent parts of mold, generally should choose the hardness and high strength of the middle grade imported steel, such as 618, 738, 2738, 638, 318, etc., the surface for nitriding treatment, nitriding depth of 0.15-0.2mm, hardness is hv700-900.
C. If the mold requirements are relatively low, can also choose low-grade imported steel or domestic steel, nitriding treatment hardness is generally hv600-800.