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Common Steels Used in Injection Mold Making
2016-07-16 20:57:01

Common Steels Used in Injection Mold Making


When it comes to injection mold making, choosing the right tool steel can make a huge difference. Making an incorrect choice can cause disasters that fly-in-the-face of many hard hours of work.

Making a poor tool steel choice for your injection mold can mean a cracked core or cavity, causing it to wear out long before it is expected it to.  To help avoid this problem ask yourself these questions before making your tool steel choice:

· How many parts is the mold expected to produce?

· Surface finish of the molded part?

· Are there any shut offs that could wear?

· What cycle time is expected?

· Are there any long cores that there is no way of getting cooling into?

· Will there be thin steel areas venerable to cracking?

When in the process of considering which steel to choose for your injection molding process, there are basically two types to choose from although always there will be your exceptions to the rule.  

·    Steel choices for injection mold making include hardened steel and pre hardened steel.     

The commonly used hardened tool steels will contain S-7, H-13, 420 Stainless Steel, while the pre hardened tool steels are comprised of P-20 and mod pre-hardened stainless steel.

Some specialty type steels are Maraging 300 for toughness and PAS 940 for heat transfer.

Choosing The Right Materials is Critical

As with the tool steels - choosing the right materials for other aspects of your injection mold making processes also need to be considered. Mold material selection is well-known to have a dramatic impact on outcomes.

While having proper materials inevitably improves the design, build and repair processes for specialty injection mold making and timely product delivery, it often also saves both time and money. This is what keeps injection mold making able to remain competitive.

When it comes to tracking, maintenance costs, tooling - and when considering wear resistances, part geometry, cooling and part stability - even cycle times - all of these considerations become essential.

Mold makers and tooling specialists alike agree on the huge impact choosing the right materials can make. Each engineer has their own experience of the risks, factors to consider and scope of results obtained when doing their own evaluations of the success of their injection mold making processes. 

Evaluations and materials results can differ from machine to machine and from process to process. Some major manufacturers will swear by the evaluation of their part geometry. 

They also consider the cycle time impact and the nuances of part stability from cooling processes and materials selections. Mold material impact is always reinforced with these outcomes and they also have a big impact when it comes to cooling and water channels.

Other Considerations for Tool Steel When Making Critical Choices

Pre-hardened steels are used for the low production tools.  Many times the mold plate is P-20 steel and the molding can be cut solid into the plates.  Areas of the plate could be inserted with hard steel if needed for shut offs or wear surfaces.

Hard stainless steel tooling would be used to minimize corrosion, either from cooling channels or corrosive materials such as PVC.  Stainless steel will crack quicker than other hardened steels and the thermal conductivity is not good.  Stainless steel will not hold a sharp edge.  Stainless steel will be used for high quality surface finish needed to produce lenses and clear parts.

H-13 and S-7 steels are tough materials.  These materials hold up well to wear and constant pressures of injection and the mold closing.  Special care must be taken for corrosion.  Water channels will rust in time.

PAS940 is used for transferring heat.  The material is not very hard so plating is sometimes used to add surface hardness.

Maraging 300 is used for thin steel areas and for strength and toughness.

If you have any uncertainty at all about which choices to make when it comes to tooling steel, materials or more efficient processes for your next injection molding project - be sure to contact Crescent Industries

This article was composed from notes taken from posts in globalplasticinjecitonmolding.com. Notes were also taken from the article: "Which Tool Steel is Right for Your Plastic Injection Mold?"  Other notes were also taken from the article published in an issue of MoldMaking Technology, on October 12, 2012 called "Becoming a Master of Mold Material."

Contact us to get the BEST materials of H-13/1.2344/SKD61 & S7 - slaes@altaspecialsteel.com

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