Why Are Injection Molds for Medical Products More Expensive?

Why Are Injection Molds for Medical Products More Expensive?

Injection molds are widely used in the production of both daily necessities and medical products. However, compared to general household items, medical product molds tend to be significantly more expensive.

For example, if two products are similar in size — one being a consumer item and the other a medical component — the mold cos for the consumer product may only be around ¥10,000–20,000 RMB, while the medical version could reach ¥40,000–50,000 or even higher. This price difference is due to several key factors: material selection, design complexity, machining precision, surface treatment, quality control, and maintenance requirements.

Let’s take a closer look at why medical injection molds are priced so high.

1. Material Requirements

Medical-grade molds must be made from materials with high corrosion resistance, wear resistance, heat resistance, biocompatibility, and sterilization compatibility. These properties prevent harmful substances from leaching into the final product, ensuring patient safety.

A commonly used material for medical molds is S136 steel. The domestic version costs about ¥20–70 per kg, while imported versions can go up to ¥90–120 per kg.

In contrast, molds for daily-use products often use standard tool steels such as P20 or 718H, which are selected more for their cost-effectiveness and machinability rather than high performance. P20 steel, for instance, costs only ¥8–10 per kg, and 718H is around ¥10–15 per kg.

2. Design Requirements

Structural Design:

Medical molds typically require sterile design, meaning they should have no dead zones, gaps, or rough surfaces that could harbor bacteria (e.g., fully sealed structures and rounded transitions). They may also include metal inserts or complex sealing structures, demanding high positioning accuracy.

To avoid contamination, these molds often adopt a no-release-agent design, relying on mirror-polished surfaces and sufficient draft angles (usually ≥2°) for smooth ejection.

On the other hand, daily-use product molds focus more on aesthetic design — such as textures and curved surfaces. Parting lines can be adjusted more flexibly, and minor flash or seams are acceptable. Fewer complex inserts are involved, and mold release agents are often used to assist in demolding.

Runner and Gate Design:

Medical molds often use hot runner systems, which are more costly. Gate placement must not interfere with product function — for example, on a medical tube, the gate must be hidden and not affect fluid flow. The inner walls of the runners must be polished to a mirror finish to prevent residue buildup and material degradation.

Daily-use molds usually employ cold runner systems, which are cheaper. Gate design prioritizes cost and molding efficiency (e.g., submarine gates or pin-point gates), with less concern about residual marks.

3. Precision and Tolerance Requirements

Medical molds require extremely tight tolerances, often within ±0.05 mm. For example, the fit between a syringe plunger and barrel must be precisely controlled using advanced CNC machining and EDM processes.

Geometric tolerances like flatness and perpendicularity are also strictly controlled. For instance, a medical tray's flatness tolerance is often below 0.1 mm, to ensure proper assembly and effective sterilization.

In comparison, daily-use molds typically allow tolerances above ±0.05 mm, as long as the part meets functional and visual requirements. Tight dimensional coordination is less critical, and machining difficulty is lower.

4. Surface Treatment

Medical molds require mirror-like polishing, with cavity surface roughness Ra ≤ 0.2 μm, sometimes even Ra ≤ 0.05 μm (e.g., for syringes). This reduces bacterial adhesion risks. Additional treatments like hard chrome plating or nitriding are often applied to improve corrosion resistance, wear resistance, and ease of cleaning after sterilization.

Surface finishing for daily-use molds is more diverse — options include matte, textured, or glossy finishes — depending on the product appearance needs. While aesthetics are important, sterility and hygiene are not major concerns.

5. Quality Control and Inspection

Medical molds undergo full dimensional inspection, along with biocompatibility testing (e.g., cytotoxicity, sensitization tests) and sterilization validation (e.g., D-value testing for moist heat sterilization). These tests are costly and time-consuming.

Moreover, trial runs are more frequent — typically 5–10 times — simulating mass production conditions to verify consistency. Production data from each batch must be recorded.

In contrast, daily-use molds mainly require visual inspections (for burrs, sink marks) and basic functional tests (such as seal integrity or strength). Trial runs are limited to 1–3 rounds before entering full production.

6. Maintenance and Service Life Requirements

Medical molds must be thoroughly cleaned after each production run, using methods like alcohol wiping or ultrasonic cleaning. Regular checks are required for wear, especially on parting lines and ejector pins. They must also be stored in temperature- and humidity-controlled environments to prevent rust or deformation. A typical service life expectation is over 1 million cycles.

Daily-use molds are cleaned on an as-needed basis, with fewer environmental controls during storage. Their expected lifespan varies based on product demand and may not necessarily reach the million-cycle mark.

Conclusion

As we can see, medical-grade injection molds are subject to much stricter requirements across all aspects — from material selection and design to processing, surface treatment, inspection, and maintenance. This explains why their prices are significantly higher than those of molds used for everyday consumer goods.