Introduction to Low Volume and Precise Injection Molding


Injection molding is an industrial procedure for the production of plastic parts in huge quantities. But, certain applications need less volume and smaller tolerances. These may be difficult to source in China. This article will cover everything you should be aware of when purchasing low-volume and exact injection molding components and other services from China. In order to produce low-volume production runs Small-sized businesses usually use special injection molding solutions designed for small runs and prototypes. In cases where precision and accuracy is essential, exacting injection molding methods provide extremely tight tolerances

Introduction to Low Volume and Precise Injection Molding

The term “low volume” injection molding means the production of parts in 1,000 pieces or smaller. Intense injection molding is able to hold tight tolerancing of +-0.005 inches and less. Making the right combination of precision and low volume is a challenge, and requires a strong processes and an intense focus on detail.

The reasons to choose low-volume precision injection molding are:

  • The development of new products
  • Manufacturing spare parts
  • Designing molds for testing
  • Short production runs
  • Budgets are tight

China provides low cost, however the process of ensuring quality can be difficult when you are far away. This guide will outline the most effective methods for purchasing low-volume precision parts for plastic injection from China.

Finding the Right Chinese Supplier

Deciding on the most reliable supplier to work with in China is essential to get excellent outcomes. There are a few important aspects to take into consideration:

Specialized Expertise

Looking for companies that specialize in precision and low-volume injection molding is essential. They’ll be equipped with the appropriate technology, equipment as well as quality control.

Tooling Capabilities

The mold maker has the capabilities in-house to design and manufacture precise mold tools. Find out their experience with cavity and core materials, finishing, tolerances and artwork. Make sure they achieve the precise tolerances and requirements for surface finishes crucial for a high-quality plastic component.

Quality Certifications

Check for ISO 9001 or ISO 13485 certification to confirm that the business is using quality control systems that are in place. This certification helps ensure constant manufacturing quality, and pay focus on the details. When it comes to medical products, ISO 13485 is required.

Production Capacity

Review current workloads for production and the schedule with the company. If a site is booked over, it could not provide the proper attention and importance to a small volume precision project. Make sure they have the capacity to dedicate whenever needed.


The ability to write and speak English skills are required in order to avoid miscommunications that could cause mistakes. Make sure that the technical team and project executives are proficient in discussing the specifications and concerns.


Get customer references from customers that have completed similar, low-volume, high precision molding projects. Contact them in detail to inquire about their capability, experience and efficiency.

Checking suppliers’ knowledge on the criteria prior to moving forward helps avoid problems.

Defining Part Requirements

In the case of sourcing small-volume high-precision injection molding from overseas having precise specifications is vital to ensure successful results. Be sure to define:

Part Geometry Offer 3DCAD diagrams and designs that include GD&T callsouts to key functions. Completely detail every dimension as well as shapes and capabilities.

Tolerances Indicate tolerance values in all dimensions that are critical. The tolerance allowed is based on the part’s dimensions and material. The general tolerance for precision molding can be +-0.005 in (+-0.127 millimeters).

Surface Finishes The definition of finishes for surfaces like texture, gloss, or any other coatings that are required.

Materials: Specify candidate plastic material and the most important properties required such as strength, flexibility as well as heat resistance.

Volumes Give the target for production quantities and a the timeframe. Make sure you understand it is a small volume project at the beginning.

Certifications The list of required conformity certificates such as UL, CE, FDA in the event that they are relevant.

Documenting these requirements clearly prior to engaging with a vendor is essential to avoid mistakes or delays later.

Selecting Plastic Materials

The selection of the appropriate plastic is vital to achieve the precision requirements for injection. In conjunction with your molder in selecting the right material that meets your needs as well as molding with consistency within the tightest tolerances.

The best materials that are suitable for small-scale precision injection molding are:

The polypropylene (PP) – Excellent mechanical and chemical resistance as well as fatigue strength. It is easy to mould and has excellent quality and dimensional stabilities. A versatile, cost-effective precision injection material.

Acrylonitrile Butadiene Styrene (ABS) – Solid engineering plastic with excellent quality and dimensional stabilities. It is often used to prototype because of the ease of cutting.

PC (PC) – Clear and optically smooth. Stable in dimension and has good impact durability.

Nylon (PA) – Strong but flexible. The material is very easy to mould and well holds the shape of details.

The polyoxymethylene (POM) – Stiffness Low friction, wear resistance. Useful for tiny precision molded components.

Thermoplastic Elastomer (TPE) Flexible material that has similar properties to rubber. It is useful for sealing, grips and molding, and over-molding.

Choose a material that moulds continuously into a stable dimensional component. Beware of materials that are susceptible to warping, shrinkage or deformation.

Designing and Machining Precision Injection Molds

The design of the mold tool and the machining is crucial to achieve precise injection outcomes. Molds must be able of hitting repeatedly precise tolerances, each time.

Important mold design factors comprise:

  • Generous fillet/radii on edges
  • Angles of draft on walls
  • Thin sections and minimal projections
  • Wall thickness uniform
  • Gates strategically placed
  • A robust temperature control system

The tool steel used for molds is required to be highly wear-resistant and machined with precision. Most commonly, the choices for tool steel include P20 for core and cavity, H13 for the ejector pins. The precision of grinding as well as EDM (EDM) yield the most effective outcomes.

Chinese mold makers could make excellent quality precision injection moulds when given the proper design guidelines prior to. Plan in-person design review sessions and testing shots prior to full production.

Addressing Key Manufacturing Challenges

Clamping Force If you are working with delicate, small components, ensure that the injection machine are precise and have the most effective clamping force. A high force could damage delicate part details in the mold.

Injection Speed Injection rates that are high and pressures may cause flash, warp and mold defects. More controlled, slower speeds let the resins molten to be injected into tiny mold parts.

Temperature Consistency Variations in the mold, barrel, and melt temperatures could result in dimensional changes. A strict process control and monitoring is vital for precision.

Material Handling High-quality resins may be sensitive to moisture as well as contamination. Be sure to follow the appropriate storage, drying and materials handling practices.

Tool Wear Keep track of the total production processes and monitor for small-scale wear, corrosion or wear and tear on mold cores, cavities and other components. A regular maintenance schedule will help preserve the precision of your mold.

Measurment Utilize the correct measurement equipment, method and sample size to determine statistically whether tolerances for dimensional dimensions are in place.

Constant communication and monitoring are essential to detect and fix any issues with precision manufacturing promptly.

Performing Part Inspection and Quality Control

Quality control are vital when it comes to low-volume precision injection molding. Incorporate these steps into the process you are using:

The First-Article Inspection Conduct an initial sample approval for the initial production run prior to ramping up. Make sure that all specifications are met.

Dimension Verification Make use of precision instruments such as optical comparators or CMMs to determine the most important features from a small sample of the parts of each lot.

Visual Inspection Complete a detailed inspection for flaws on each part. No flaws are allowed to pass through.

Test: Tests that can be conducted such as leak testing of seals, or pressure testing for important elements.

Control Charts Monitor key dimension and properties by using graphs of statistical process control for identifying the differences.

Trackability Label clearly the production batches and mold tools utilized. This helps in the analysis of root causes to resolve any issues that may be found.

documentation: Fully document the outcomes of each step in the inspection by using photos, drawings video, checklists, etc.

A thorough inspection and quality control is essential to ensure precision in-line molding results on offshore.

Conclusion: Finding Low Volume Precision Molding Success in China

The process of low-volume injection molding with high precision in China is not without its own challenges, but is possible to accomplish it successfully adhering to the best practices in:

  • Choose suppliers who have proven their high-precision capabilities
  • Give complete and detailed specifications
  • Make use of materials that mold uniformly and precisely.
  • High tolerance, robust design molds
  • Make sure you control the process thoroughly and keep an eye out for problems
  • Measure, inspect and record all of it completely

If you manage your business well and close supervision, you’ll get great outcomes and benefit. Working with the best Chinese supplier can make low-volume precision injection molding cost-effective and feasible.


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