Selection of best Injection mold tooling material for tool cavity is very critical part of injection molding tool development. Injection mold tool material creates huge difference on tool cost, tool life and quality of part in the long run. In this article we will discuss various injection mold materials for mold cavity and where to use them.
Factors Affecting the Selection of Injection Mold Tooling Material
Following factors affects the selection of injection mold tooling material. These points are considered to ensure optimum injection mold material selection.
Types of Injection Mold Material
Tools steels can be broadly classified in two categories :
- Heat Treating Tool Steel
- Pre-Hardened tool steel
1. Heat Treating or Hardening Tool Steel
H-13 Mold Steel
H13 material s a through hardening tool steel. It has excellent hot tensile properties, wear resistance, toughness and resists tempering at high operating temperatures. After hardening, H-13 tool steel typical hardness range is approx. 44 to 48 RC. Welding is also possible on H-13 tool steel. H-13 tool steel can be nitrided as well. Read this article for more details on H-13 tool steel.
H-13 tool steel is used in high volume injection molds. For example, Mold insert in H-13 material can give 1 million injection cycles while molding 33% glass filled nylon.
H-13 tool steel material is used for abrasive materials injection molds.
H13 tool steel is more expensive than P20.
Stavax mold Steel
Stavax is a through hardened stainless steel material with good corrosion resistance, polish-ability and wear resistance. Photo-etching and welding is possible on stavax tool steel. Recommended stavax through hardness range is 45 – 54 HRC. Read this article for more details in stavax mold steel.
Good corrosion resistance in Stavax Tool Steel material offers following advantages:
- Lower mould maintenance costs.
- The surface of the cavities maintain their original finish over extended running periods.
- Injection Molds can be stored and operated in humid conditions.
- Water cooling channels are not affected by corrosion. As a result, heat transfer characteristics and cooling efficiency are constant throughout the mold life.
Stavax Tool steel material is used in high production volumes injection mold cores, cavities and stripper rings. It is also suitable for molding corrosive materials such as PVC and abrasive filled materials. Because of good polish-ability, Stavax tool steel material is also suitable for injection molding of optical parts such as clear glass.
Stavax tool steel is more expensive than H13 tool steel materials.
Ramax Heat Treating Mold Steel
Ramax heat treating tool steel material is a through hardened stainless steel with good corrosion resistance. It is supplied with a uniform hardness of 38HRC that is more than P20. Welding is also possible on ramax tool steel with required expertise. Read this article for more details in Ramax mold steel.
This tool steel has application only for parts requiring low to medium polished parts.
S7 mold Steel
S7 is very durable, impact-resistant tool steel material that can be hardened up to 56 RC. It is an air or oil hardening shock resisting (cold work) tool steel offering a unique combination of toughness and wear resistance. Read this article for more details on S7 mold steel material.
S7 tool steel is primarily used in applications that require resistance to shock and impact such as slides and lifters. This material is also used for very tight tolerance and high-volume part requirements.
Stainless steel is a Post hardened tool steel with hardness range of 50-52 Rc
Stainless steel is used for low production volume products.
2. Pre-hardened Mold Steel For Injection Molding
P 20 Mold Steel
P-20 is a pre-hardened mold steel with good polish-ability and photo-etching properties. It is available in hardness range of 28-32 Rc.
P20 mould steel is hard chromium plated for mould reconditioning purposes. It can also be electroless nickel plated for extra corrosion resistance.
It can be welded which is helpful for repairs. It can be flame hardened or nitrided for extra resistance to wear and erosion. A nitride surface also increases the corrosion resistance. Read this article for more details on P-20 tool steel.
P-20 pre-hardened tool steel is used for medium production volume molds. It can not be used with abrasive materials and part finish above SPI B-2 .
P-20 material is mainly used for the mold base but can also be used for core, cavity, gate inserts, sprues and sliding inserts in moulds with low and medium production.
NAK 80 Mold Steel
NAK-80 is a Pre-hardened tool steel, available in uniform through hardness of approximately 40 HRc.
It is super clean, Vacuum-Arc Remelted steel with uniform grain structure, uniform hardness, and excellent dimensional stability. When welded, NAK 80 leaves no witness lines after re-aging.
NAK-80 material machines up to 20% faster than 30 HRC P20 mold steels. It also do not require stress relieving even after heavy machining.
NAK-80 tool steel is used for medium production volume molds. This material can also be polished over welded areas. NAK 80 steel can be used for critical diamond finish applications. For example, Clear lens molds.
NAK 55 Mold Steel
NAK 55 is a pre-hardened mold steel with uniform microstructure. It is available in hardness range of 38-42 HRC. NAK 55 Machines upto 30 to 40 % faster than P20 mold steels. It had good weldability and EDM properties.