Understanding Metal Selection for Molds
There are a myriad of different metals that can be used to make molds. The most suitable choice for one job may not be the ideal choice for the next. There are both short-term and long-term costs that you should consider. Certain molds and tools may be cheaper to build but are more costly to maintain, while for other molds, the reverse is occurs. When selecting the metal for the mold, it is essential to strike a balance between these two factors. What balance is best to strike might not be obvious due to the fact that certain metals react differently with different resins.
Common Metals Used in Mold Making
| Steel Grade | Typical Hardness (HRC) | Main Applications | Key Advantages | Key Limitations | Best For |
|---|---|---|---|---|---|
| P20 | 28-32 | General purpose molds, large molds | • Good machinability • Cost-effective • Widely available | • Moderate wear resistance • Limited corrosion resistance | • Large injection molds • Medium production runs • Non-corrosive plastics |
| H13 | 38-52 | Die casting, hot stamping | • Excellent hot hardness • Good thermal shock resistance • High toughness | • Higher cost • More difficult to machine | • Hot work applications • Die casting molds • High-temperature molding |
| S7 | 54-56 | Heavy-duty molds | • Superior impact resistance • High toughness • Good crack resistance | • Moderate corrosion resistance • Higher cost | • High-impact applications • Heavy mechanical loads • Complex shapes |
| 420 SS | 48-52 | Medical, corrosive materials | • High corrosion resistance • Excellent polishability • Clean processing | • Lower wear resistance • Higher cost | • Medical components • Corrosive materials • High-polish requirements |
| NAK80 | 38-42 | Optical parts, high-end molds | • Superior polish ability • Uniform hardness • Excellent surface finish | • Very high cost • Limited size availability | • Optical components • High-end products • Mirror finish requirements |
| A2 | 57-62 | Long production runs | • High wear resistance • Good stability • Deep hardening | • Limited toughness • Moderate machinability | • Long production runs • Abrasive materials • Precision parts |
| D2 | 58-64 | Wear-resistant applications | • Maximum wear resistance • High compressive strength • Good stability | • Lower toughness • Limited polishability | • Highly abrasive materials • Wear-critical applications • High-volume production |
| P20+Ni | 30-35 | Automotive, large molds | • Better toughness than P20 • Improved through-hardening • Good polishability | • Higher cost than P20 • Limited wear resistance | • Automotive parts • Large components • Better surface finish needs |
Aluminum Molds
If you are looking for tools with lower volumes, Aluminum is an affordable option. This is due to the fact that aluminum is cheaper and is able to reduce time-to-market by allowing for faster time for cooling during production. Tools are made quicker with aluminum than other metals. In the case of production that is high volume the hardened steels for tooling are generally the better option. It is resistant to wear and has less thermal conductivity. While these steels don’t require a coating or treatment to decrease wear, one could be added if one is desired.
Hardened Steel and Stainless Steel Properties
Steel that is hardened is durable and generally low maintenance. The processing of glass-filled materials can result in faster erosion and wear. Since stainless steel is impervious to corrosion, it is the ideal choice for projects that require such hard-wearing materials. Other alternatives can be utilized instead that of stainless steel however they need special treatment to reduce the threat of corrosion. In contrast to other types of steel that are wear-resistant, carbide inserts possess high thermal conductivity. However, their cost can be prohibitively high , and they may be hard to repair.
Detailed Material Analysis
Aluminum Characteristics
Molds made of aluminum can aid in keeping costs for building down , and also accelerate the cycle time. Numerous variations of aluminum are utilized in molding. It is a mistake to assume that just because they are alike, it means they can be interchangeable is an extremely mistake. Each one of the aluminum varieties have different structural and thermal characteristics. It is an extremely soft material, and for any design that is made in aluminum, it’s important to take extra care to ensure that the structure is strong enough. If you are looking for high-volume components that require cosmetics or require accurate measurements, using aluminum isn’t advised. The use of aluminum in prototype tools could be beneficial for testingpurposes even in the event that the final tool will be constructed out of a different material. If the design you’ve created hasn’t been proven and major changes have needed to be implemented, then it’s best to make a low-cost aluminium tool till you’ve demonstrated the concept.
Metal Alloys
Alloys are much more durable than aluminum, and many of them have superior thermal conductivity. They come in a wide range with various hardness levels, which is particularly useful when molding specific materials. When the hardness of the alloy increases, the thermal conductivity of it decreases. Based on the material that is moulded, this could be negative or positive. The cost of alloys is higher than aluminum, but they aren’t prone to breaking, cracking or warp as readily. Carbide inserts, like those mentioned in the previous paragraph, are typically alloys composed of the mineral tungsten.
Steel Types and Applications
Steel is a flexible metal to mold. Similar to aluminum, it is available in a variety of forms and are not considered as being the same. Steel molds are able to be used effectively for low-volume and high-volume components. In general, steel needs to be protected from erosion using an application of a coating or the process of surface hardening. It can be a challenge in terms of maintenance and manufacture, depending on the needs of the project. The most commonly used steel at the middle is P-20. When working with plastics without Abrasive additives, this type of steel or one with similar characteristics, is typically the preferred option. If you are looking for high-volume, high-torque parts the best choice is S-7 steel. It is durable and durable in the process of heat treating.
Specialized Steel Properties
S-7 steel expands and contracts more than other alloys similar to it, which allows for a more comfortable maintenance of tolerances. When it comes to creating medical tooling or high polished cavities, stainless steel is the best choice. It can also be utilized to make PVC because stainless steel is impervious to corrosion. The most popular version of steel used for these purposes is H-13. The stainless steel does not need protection from erosion like does other varieties of steel however it is susceptible to erosion in certain conditions.
Manufacturing Considerations
If a tool isn’t tempered appropriately, it may experience increased wear. Sharp edges of tools are more prone to such imperfections. To reduce the risk of damage, pockets for lifters and slides, they should be smooth in their internal edges and radii in certain cavities. Since the majority of CAD models do not include these radii and the importance of cosmetics to the quality of your product, working an experienced and skilled molder is the best option to ensure proper manufacturing. Let me know if you’d like any adjustments to the heading structure while maintaining the original content!