How to Choose a Mould-Making Technique?
What’s the best mold-making technique for a given application? It depends on a couple of important factors, including the desired end-part material, the intended manufacturing process, the geometry of the model, and the production volume.
A simplified, step-by-step approach to choosing the best technique for your manufacturing project is covered in stages below:
1. Outline the Development Criteria for Your Project
A manufacturing master plan can help create clear-cut details of what is to be expected from a project, its development timeline, and the available budget. Whether you’re planning to create custom parts or mass-produce thousands of the same item will define what options to pick in the next steps. The development criteria might vary depending on the project, but generally include the design of the part, size, material, quality, required tolerances, timeline, required production volume, cost constraints, etc.
In product development, the initial document that answers many of these questions is often the product requirements document (PRD), while the bill of materials (BOM) is the comprehensive list of parts, items, assemblies, and other materials required to create a product.
2. Select the Manufacturing Process
The right manufacturing process for a certain part is largely dependent on the development criteria. In some cases, multiple production processes can be used to create any given design. As a rule of thumb, choose the process that can produce the given part with the required quality, at the lowest costs, while fulfilling the rest of the development criteria. The material choice and manufacturing volume are likely the most important factors driving your decision.
For plastic parts, you can read our guide to manufacturing processes for plastics.
3. Select the Mold-Making Technique
Once you settle on the right manufacturing process, the type of mold for the process is also largely defined by the development criteria. While the exact factors are dependent on the manufacturing process, here are some of the most important considerations when choosing a mold-making technique:
Design of the part: Try to simplify the design as much as possible and align it with the design rules of the given manufacturing process to be able to choose the technique that can achieve the lowest costs. Simple designs might only require molds that can be created with manual techniques, while complex designs often require multi-part molds and digital manufacturing tools like 3D printers or CNC machining to create.
Production volume: Large-volume production runs require durable molds that can accurately replicate models without wearing out after a few uses. However, fabricating such tools comes with high costs and lead times. For one-off parts and lower volume batches, it might be more efficient to choose cheaper molds that can be created faster, such as sacrificial molds or soft molds that can be discarded when they begin to show signs of irreparable wear.
Quality: Tighter tolerances require more precise molds and tools to create, such as digital manufacturing tools, and need to be more durable to ensure consistent part quality over multiple cycles.
Timeline: Producing complex metal molds often takes months through a service provider. If you’re working on a shorter timeline, try to look for alternatives that can shorten the lead time, such as 3D printed rapid tooling.
Material: Materials that have a higher melting point or are more abrasive will require molds that are more durable and can create the required volume of parts without degradation.
Mould Material Description | |||||||
Material | Material characteristics and Application | ||||||
S136H | It is high grade non - embroidered tool steel. Excellent corrosion resistance, polishing rotation, wear resistance, machinability, EDM can obtain ultra mirror processing effect and high quality surface, quenching with excellent stability. The surface of the cavity remains smooth after a long period of use. Molds do not need special protection when they are operated or stored in a damp environment. Recommended for injection moulds and corrosive plastic moulds with high polishing requirements. | ||||||
718H | It is vacuum melted chromium-nickel-molybdenum alloy steel, modified pre-hardened plastic die steel, which has been hardened and tempered before leaving the factory. There is no risk of cracking and heat treatment deformation. It can be nitrided and flame hardened without heat treatment to improve the surface hardness and wear resistance of the die. Excellent polishing performance and improved wear resistance. Used for injection and extrusion moulds for thermoplastic materials, plastic moulds with high surface finish, blow moulding moulds, forming moulds, structural parts, shafts. | ||||||
P20 | P20 die steel is a type of plastic die steel, because its machining performance is better, has a certain abrasive. As for its hardness range, it should be able to reach 285-330HB, which can be converted into 30-36HRC, so it can meet the general needs. | ||||||
NAK80 | Pre-hardened steel (36-43 HRC), without heat treatment, can be directly machined; Surface and center hardness is uniform, good machinability; Excellent discharge machining, grinding after discharge machining is very easy, because the surface hardness of discharge machining is uniform and the hardness of white layer is low; Good mirror polishing; Good weldability; Good etching property; Stable size, suitable for precision parts and mass production. Due to the influence of its chemical composition, the material is brittle, and it is easy to crack in the place where the processing stress is concentrated when used in the more complex mold. High thermal sensitivity, it is necessary to preheat during welding, heat preservation and post-welding heat and de-stress tempering, otherwise there will be the risk of welding failure. It should be noted that the size changes will occur when the processing temperature exceeds 520℃. | ||||||
8402 | At high and low temperatures, it has good wear resistance, excellent toughness and ductility, stability and excellent processing and polishing rotatory, excellent high temperature strength and thermal fatigue resistance, excellent hardenability, small size deformation of heat treatment. Used for metal hot forging die, aluminum extrusion die, plastic die, aluminum die casting die, etc. | ||||||
8407 | 8407 special steel is a chromium, molybdenum and vanadium alloy tool steel. It is a steel with high purity and fine structure obtained by special steelmaking technology and strict quality control. The isotropy (isotropy) of 8407 is better than that of H13 in the general traditional steelmaking system. This is more valuable for the mechanical fatigue resistance and thermal stress fatigue resistance of molds, such as die-casting molds, forging molds and extrusion molds. Therefore, the die hardness of 8407 can be 1-2hrc higher than that of ordinary H13 without sacrificing toughness. High hardness can slow down the occurrence of hot cracking and improve the service life of the die | ||||||
ASP-23 | It is chromium-molybdenum-vanadium powder steel, high wear resistance (abrasive wear resistance), high compressive strength, excellent hardenability, good toughness, good dimensional stability of heat treatment, good temper softening resistance. Asp-23 is especially suitable for thin materials to be processed and forming, or die failure due to mixed abrasive wear and adhesion wear, or knowledge abrasive wear, and the risk of surface plastic deformation is also high. For example, blanking of medium or high carbon steel, blanking of hardened steel plate or cold rolled steel strip, plastic mold containing glass fiber. | ||||||
XW-42 | It is a kind of high carbon and high chromium alloy tool steel containing molybdenum and vanadium. Wear resistance and toughness, excellent quenching properties, is often recommended for use in molds that require good wear resistance and appropriate toughness (impact resistance). Such as: precision hardware mold, semiconductor mold, precision parts and so on. | ||||||
#45 Steel | #45 Steel is a high-quality carbon structural steel with low hardness and easy cutting. It is often used as formwork, shoot, guide post, etc. in the mold, but it must be heat treated. The quenched and tempered parts have good comprehensive mechanical properties and are widely used in various important structural parts, especially those connecting rods, bolts, gears and shafts working under alternating loads. However, the surface hardness is low and not wear-resistant. The surface hardness of parts can be improved by quenching and tempering + surface quenching. fold |
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#50 Steel | The steel has medium machinability, low cold deformation plasticity, poor weldability, no temper brittleness during heat treatment, but low hardenability. The critical diameter in water is 13-30mm, and it tends to crack during water quenching. This steel is usually used after heat treatment such as normalizing, quenching and tempering, or high-frequency surface quenching., It is suitable for manufacturing die parts with high wear resistance and large dynamic load and impact |