Injection molding tolerances and their impact on part quality

Product performance is driven by quality. The stakes for critical-use applications are higher. If a product fails, it could pose a threat to safety, health, or life of the end-users.

High-level risks can be mitigated by having the greatest confidence in injection molding partners’ experience with tight tolerance injection molds.

Why? Tolerances in injection molding have an impact on part sealing, which has a direct effect on part quality and performance. Incorrect seals can allow fluids or atmospheric elements to enter critical components. They can also allow fluids or air pressure to escape from components. It’s a risk.

injection molding


Expert in tight tolerances, a custom injection moulder understands the importance and prevention of sealing.

  • Variable part flatness, and defective gasket type seals
  • Leakage paths can be created by excessive parting lines in sealing surfaces
  • Clean seals are not possible due to inconsistency in dimensional requirements

Although these issues are common, each industry faces its own seal challenges. Parts with tight tolerances for injection molding may be required by automotive and industrial manufacturers. These parts can seal in fluids such as transmission fluids, cooling solutions, or other abrasive chemicals. To ensure medication dosage and management is correct, medical OEMs may prioritize parts with complex geometries. Consumer OEMs may require a home appliance for water interactivity.

It is important to understand the conditions of use, but it is only a starting point. Your partner in injection molding should be able and willing to validate your design for manufacturing. It is important to plan for a good seal in the design phase. Same applies to the exact manufacturing of mating components for mission-critical parts.

A molder who is well-versed in resins is invaluable to this end. They are able to guide you in selecting the best materials for tight tolerances and withstanding exposure.

You should keep the seal and mating parts at the forefront of your part design and material selection. This will result in robust and precise processes that reduce part shrinkage, maintain tight tolerances, allow for full seal function, and enable you to design parts.

Continuous quality control ensures that every critical-use, injection-molded part works as it should before it leaves the manufacturing plant.


Topworks’s Quality Lab in-house helps us to integrate quality benchmarks into all processes to ensure consistent and defect-free results. The Quality Lab is a place for cross-functional collaboration, extensive testing, and exceptional process and injection molding part management.

Injection molding plays a greater role in the development of industries. As expectations for injection molding tolerances are increasing, so are high-quality, high-performance parts.

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