What is Precision Injection Molding?
Concept, Characteristics, and Key Factors
The Concept of Precision Injection Molding
Precision Injection Molding is an advanced method of plastic injection molding that significantly surpasses the capabilities and requirements of conventional injection molding processes and machines.
It is defined by its ability to produce plastic parts with extremely tight dimensional tolerances. This technology is essential for the rapid development of polymer materials and the trend toward using precise plastic components to replace high-precision metal parts, especially in the demanding fields of electronics, instrumentation, and micro-technologies.
Two Key Definition Targets for Precision Products:
Repetition Precision of Product Size: The consistency of the component’s dimensions across an entire production run.
Repeatable Precision of Product Quality: The consistency of material properties and performance.
Defining Precision (Dimensional Tolerance)
Strictly speaking, precision injection molding refers to the production of plastic products where the dimensional accuracy (tolerance) is typically achieved between $0.01$ mm and $0.001$ mm.
| Tolerance Range | Industry Term |
| Under $0.1$ mm | Precision Molding |
| Micron grade | Super Precision Injection Molding |
Characteristics and Applications of Precision Plastic Parts
Precision plastic parts are characterized by meeting high-precision requirements while also possessing excellent mechanical properties and dimensional stability.
Why Precision Plastic Parts are Essential:
With the trend toward highly integrated electronic circuits and industrial equipment, parts must be:
High-performance
High-precision
Lightweight
Miniaturized
These parts are widely used across multiple sectors, where they successfully replace a number of precision metal parts:
Machinery
Electronics and Microelectronics
Instrumentation
Communications
Automotive and Aerospace Industries
The Critical Factors for Successful Precision Injection Molding
Achieving micron-level precision is not solely about the process; it requires the perfect synergy of four major factors: the mold, the machine, the material, and the process parameters.
1. Precision Molds (precision molds)
The mold is the most crucial condition determining whether a product meets the design requirements. Precision molds must be designed and manufactured with exceptionally high accuracy, repeatability, and structural rigidity to consistently hold tight tolerances under high pressure and temperature variations.
2. Precision Injection Machines (precision molding machine)
A precision molding machine must be used. Unlike conventional machines, these feature:
High-precision control over injection speed, pressure, and temperature.
Excellent repeatability and stability in all moving parts.
Accurate metering systems to ensure consistent shot size.
3. Selection of Plastic Material
The plastic material selected must have minimal and predictable shrinkage characteristics and excellent dimensional stability. Different polymers have different properties, meaning the precision of plastic parts cannot be directly equated with the precision of metal parts.
4. Process Parameters
Tight control over parameters like melt temperature, mold temperature, injection speed, holding pressure, and cooling time is necessary to manage material shrinkage and internal stress, which are critical to the final dimensional accuracy.