In the plastic injection molding industry, the mold is equally as important as the material used to make the plastic parts. Working with a weak or improper mold typically results in poorly produced parts, excessive expenses, and lost profits. As such, choosing the right material for creating the mold itself is a vital part of the success of your injection molding project.
In this article, we will examine the most common materials used in manufacturing plastic injection molds. We will also go through their strengths and weaknesses, giving complete context to help make the selection process simpler.
Injection Mold Tooling Material Comparison
There are numerous plastic injection mold materials in the market today, each with its unique properties that make it viable for specific projects. Let’s look at this mould material selection list that outlines their strengths and where they excel.
| Material | Properties | Benefits | Main Application |
| Aluminum | Excellent heat transferLightweight | No post-heat treatment neededEasy and fast to moldFaster heating and coolingFast cycle time | Injection molds for automotive and electronic products |
| Carbon Steel | Maintains hardness at high temperaturesDurable | Wear resistanceAbrasion resistance | Injection molded components for automotive and consumer goods |
| P-20 Steel | Excellent machinabilityHigh strengthHigh toughnessPre-hardened steel | Long tooling lifeEasy and fast to moldNo heat treating neededGood wear resistanceGood corrosion resistance | Best for molds with smaller cavitiesUsed in a diverse line of parts and components |
| H-13 Steel | Excellent durabilityGreat mechanical fatigue resistance | Long tooling lifeTighter dimensional toleranceHigh wear resistanceResists thermal fatigueHigh abrasion resistance | Parts made from plastics with additivesHigh-precision moldsIdeal for larger cavities |
| S-7 Steel | Excellent durabilityGreat mechanical fatigue resistanceHigh toughness | Long tooling lifeTighter dimensional toleranceHigh wear resistanceHigh impact strengthHigh hardness levels | High-stress moldsHigh-precision moldsGreat for smaller cavities |
| 420 Stainless Steel | Exceptional corrosion resistanceHigh strengthGood wear resistanceGood fatigue resistance | Longer tooling lifeHypoallergenicExcellent heat conductivityConsistent product qualityHandles greater stress | Ideal for high-volume injection moldingPerfect for parts used in the medical, pharmaceutical, and food industries |
| Beryllium / Copper Alloys | Good thermal andelectrical conductivityHigh strength and wear resistance | Rapid mold coolingCan withstand multiple usesImproved part quality | Used to make high-wear components |
| Titanium | Excellent corrosion resistanceHigh strengthLightweightBiocompatible | Extended mold lifeResistant to wear, cracking, and bendingMaintains strength and stability at high temperatures | Injection molded parts for aerospace and medical useUsed for making complex, high-precision parts |
| Magnesium | Low densityGood thermal conductivityElectromagnetic shielding | LightweightFaster mold coolingPrecise and repeatable molds | Manufacturing of electronic product casings and automotive parts |
| Ceramic | High hardnessHigh temperature resistanceDeformation resistance | Long service lifeTight tolerancesSmooth surface finishHigh pressure tolerance | Ideal for high-purity products |
Materials Used for Making Injection Mold
Aluminum
Affordable and easy to mold, aluminum is a go-to material for making injection molds that require fast tooling and prototyping. Additionally, with its great heat transfer capabilities, cycle times are greatly reduced, leading to faster production times. Aluminum is typically used in making injection molds for parts that require fast heat dissipation.
However, as aluminum is softer than steel, the molds wear out faster than other types. It also struggles when handling high clamping pressures required for large parts. Some plastics, like PEEK and PSU, won’t work well with aluminum molds, as they can’t maintain the necessary high heat to process these plastics.
Carbon Steel
Carbon steel comes in all types and properties, with some types used in creating molds for plastic injection molding. This material is typically chosen for its high wear and abrasion resistance, as well as its capability to maintain hardness when exposed to high temperatures.
Conversely, carbon steel has low corrosion resistance and toughness, making it prone to cracking when extreme pressure is applied. It also needs constant maintenance to properly function, which may lead to higher operational costs.
P-20 Steel
As a general-purpose tool material, P-20 steel exhibits great flexibility that can be used in a wide variety of parts and components for different industries. It also balances cost, production time, quality, and dimensional stability, making it a go-to material for many injection molding projects without specific requirements.
While offering a lot at an affordable price, P-20 steel doesn’t excel in a specific parameter. Some of its pain points include lower hardness levels, lower wear resistance, and a potential for developing hard spots. It’s also not ideal for high-volume production, as it breaks sooner than other harder steels.
H-13 Steel
If your injection molding project requires precision tooling or you need to mass-produce parts, then H-13 steel is one of the best materials to use. It has high durability and wear resistance, allowing molds made from H-13 to produce up to 1 million parts with tight dimensional tolerances.
When considering using the material, remember that crafting injection molds with H-13 steel may take longer to produce. The mold will need heat treating to fully form after machining, extending the mold production process. Another factor to consider is the price, since H-13 steel costs more than other steel alternatives.
S-7 Steel
S-7 steel shares similar characteristics to H-13 steel, mainly its exceptional durability and capability to handle high pressure from larger mold machines. This material works best for molds with smaller cavities and can be heat-treated via air quenching to achieve good dimensional stability.
On the flip side, S-7 steel also has the same challenges as H-13 steel, namely its longer production time and manufacturing cost. Additionally, it doesn’t have great abrasion resistance, especially when handling plastic materials filled with glass or mineral resins.
420 Stainless Steel
420 stainless steel offers great toughness, strength, and versatility as an injection mold material, making it a viable option for different projects. What sets it apart from other materials, however, is its excellent corrosion resistance and its non-porous nature, preventing bacteria and other particles from growing on its surface. These properties are ideal for injection molded parts for medical, pharmaceutical, and food and beverage use.
Despite its great features, 420 stainless steel can be quite difficult to weld, with a risk of cracking and distortion. It also significantly shrinks during the cooling process, leading to warping or deformity. Additionally, it doesn’t conduct heat that well, affecting cycle times.
Beryllium / Copper Alloys
Copper alloys and high-demand injection molding go hand in hand, thanks to the metal’s great thermal and electrical conductivity. Copper alloys also exhibit higher machinability and corrosion resistance than other steels. Due to its high wear resistance, copper alloys are greatly utilized in making molds for injection molding, specifically for parts that are exposed to constant wear.
However, extra care is needed when using beryllium copper alloys, as it has certain properties that require special considerations. They also rank lower on strength and hardness levels compared to other steels, making them unsuitable for heavy-duty or large molds.
Titanium
Highly regarded for its corrosion resistance and high strength-to-weight ratio, titanium is considered a premium metal for making injection molds. Partnered with its high resistance to wear, tear, cracking, and bending, titanium molds also boast extended service life. Titanium molds are typically used to make complex injection molded plastic parts for the medical and aerospace fields.
These perks come at a cost, though, as the metal can be quite expensive compared to other steels. They can also be difficult to machine due to their hardness, and their low thermal conductivity can make the injection molding process take longer to complete.
Magnesium
Magnesium molds have a high strength-to-weight ratio, great heat transfer, and exceptional stiffness and wear resistance. It also has great precision and durability, allowing for the mold to be used thousands of times with consistent quality and output.
One of the cons that magnesium molds have includes their poor corrosion resistance, which can limit their service life when used with corrosive materials. Another is its volatility, as it requires specialized tools and knowledge to create molds with magnesium. Moreover, magnesium as a metal can be expensive, and the need for additional alloys to improve its performance may add to the overall costs.
Ceramic
Ceramic is one of the modern materials used in making plastic injection molds and is selected for its high dimensional accuracy and surface finish. Compared to metal plastic injection molds, those made from ceramic have a longer lifespan when properly made and handled. It also specializes in creating injection molded parts with high purity.
A downside of ceramic is its high manufacturing cost due to the steep price tag associated with the material. Creating ceramic molds also takes time to make and has a limited design capability, making it undesirable for projects with short lead times. And as a brittle material, ceramic molds are prone to chipping and breaking under high pressure.
Tips for Choosing Materials for Injection Mold Making
Now that we have a better grasp of common materials used for making injection molds, it’s time to know which material would work best for your project. Proper material selection will ensure that the mold will be maximized, and parts produced will be of top quality.
Part Dimensions and Materials
First, consider the specifics of your plastic injection molded parts. These would include the part dimensions and any precision requirements the part will need, like complex designs and the like. The plastic material will also play a big role in choosing the mold material, as some materials have better resistance to corrosion and abrasion.
Production Quantity and Timeline
Next, factor in the production volume for your project and when you need the parts to be completed. Some materials work better for high-volume production, while others fit low to medium-volume parts manufacturing, so it’s important to choose the right one. Moreover, certain mold materials support faster cycle times, which makes them ideal for projects with shorter lead times.
Additional Factors
Drilling further into the specifics of your plastic injection molding project, take time to list if there are any pressure or heat requirements in manufacturing the parts. These have to be factored in, as certain materials have low heat tolerances and don’t take on pressure well. The production environment also needs to be added to the equation, as some materials aren’t as corrosion-resistant, significantly affecting their service life and the quality of the completed parts.
Available Budget
Then, there’s the cost to consider when choosing your injection mold material. Materials like magnesium and ceramic, while having exceptional properties, are quite expensive and may need significant investment. Conversely, aluminum and certain steels are more affordable, at the cost of lower properties or shorter service life.
Fox Mold – Your Experienced Injection Mold Manufacturer in China
For 13 years, Fox Mold has been manufacturing world-class injection molds used by thousands of brands across the globe. We’re dedicated to elevating your business through our comprehensive mold making proficiency and commit to reliable results.
From mold design to production, our extensive industry experience and exceptional production capabilities can complete your project within a week. This is backed by a state-of-the-art manufacturing facility strategically located in Guangdong, China, known for its manufacturing expertise. Our precision parts manufacturing guarantees 90% approval of our molds upon first testing, turning from sampling to production in a few days.
Along with tight tolerances of +/-0.01mm on each mold, we also carry an extensive line of plastic injection mold materials that match your diverse requirements. We also keep finished molds for up to four years, with free maintenance and a warranty coverage that ensures they stay in perfect condition.
Wrapping Up
Plastic injection molds are crucial to the success of an injection molding project. As such, it’s important to select the right material in making the mold to maximize its performance and service life, among others. While there are several injection mold steel material available, it all boils down to what your project needs, production timeline, and available budget.Need to have an injection mold done or revised for your upcoming plastic injection molding project? Get in touch with the experts at Fox Mold and see how we can bring your ideas to reality. Book a free consultation today.
