What You Need to Know When Making an Injection Mold?

What You Need to Know When Making an Injection Mold？

When it comes to making an injection mold, there are two key factors that significantly impact both the cost and performance of the mold: mold material selection and cavity layout design. Understanding these aspects not only helps you make informed decisions but also allows for potential cost savings.

1. Mold Material Selection – Choose Right, Not Just Expensive

One of the most important considerations is the choice of mold material. Why? Because it has a direct impact on the mold’s cost and lifespan.

For example, standard P20 steel costs around $10 per kilogram, while high-grade stainless steel like S136 can be more than double that price. However, the decision should not be based solely on cost — it should focus on selecting the right material for the job.

P20 steel, although economical, typically supports up to about 300,000 molding cycles. If your production volume exceeds this, using P20 may lead to frequent maintenance or premature failure. On the other hand, higher-end materials like S136 or NAK80 offer longer life and better corrosion resistance, making them more cost-effective in the long run for large-volume production.

Moreover, product characteristics play a crucial role in material selection. For general plastic parts with no special surface requirements, P20 is usually sufficient. But if the product requires a high-gloss or mirror finish, a material with excellent polishability — such as NAK80 — becomes necessary.

In summary, the right material depends on:

•Production volume: High-volume runs justify investing in premium materials.

•Product specifications: Surface finish, chemical resistance, and dimensional accuracy all influence material choice.

The golden rule is: choose what fits your needs, not just what's expensive.

2. Cavity Layout Design – Balancing Cost and Efficiency

The second critical factor is the number of cavities in the mold. In simple terms, each cavity corresponds to one part being formed during a single molding cycle.

Accuracy is essential — cavity dimensions must match the product shape and structure within tolerances as tight as ±0.01 mm. The number of cavities directly affects:

•Molding efficiency

•Production capacity

•Mold cost

More cavities mean higher output per cycle, but they also increase mold complexity and cost proportionally. Therefore, cavity count should be carefully designed based on production demand.

Example:

Let’s say you use a 1-out-of-4 (1x4) cavity mold, and each molding cycle takes 10 seconds. That means you can produce up to 34,560 units per day under continuous operation. If you need higher output, increasing the cavity count to 6 would raise the daily theoretical output to 51,840 units.

However, if such high capacity isn't required, opting for a 6-cavity mold could result in unnecessary cost increases — a 6-cavity mold may cost 50% more than a 4-cavity one.

So, when determining the number of cavities, consider:

•Total production quantity

•Monthly or annual output expectations

•Cost-performance balance

It is not always better to have more cavities — the goal is to meet production needs without wasting resources

Final Thoughts

Both mold material and cavity design are relatively easy-to-understand concepts, even for those without deep technical expertise in mold-making. These two areas also offer significant opportunities for cost optimization.

While there are certainly other factors that affect mold cost and performance — such as cooling system design, ejection mechanism, and mold base type — they often require more specialized knowledge. For non-experts, focusing on material selection and cavity planning is a practical and effective way to ensure value for money.