Precision Injection Molding Machines: Selection Guide

precision injection molding machine

Precision molding is a complicated process, and it is an injection molding method that requires high precision. The concept of precision injection molding is mainly different from "traditional injection molding". The precision plastic parts produced are often used to replace high-precision metal parts in the fields of instruments, electronics, optics, and medical equipment.

In this article, you will learn about:

What is precision injection molding
Benefits of Precision Injection Molding
Characteristics of precision injection molding
Main Variables Affecting Precision Injection Molding
How to choose a precision injection molding machine

What is precision injection molding

Precision molding is the latest technology in the field of plastic injection molding. Precision injection is an injection molding method whose precision far exceeds the requirements of conventional injection molding processes. It is based on the rapid development of polymer materials, replacing high-precision metal parts with precision plastic parts in the field of instruments and electronics.

Precision molding is a type of plastic molding, and precision molding is the most expensive and complex mold design process on the market. It is only used on small and rare occasions in the manufacturing process when product development requires exceptionally precise plastic injection molded forms.

Benefits of Precision Injection Molding

When a project requires parts to be used in high-tech applications and requires high volume production, precision injection molding may be a wise choice for the following reasons:

Cost-effective

Automation and repeatability of precision injection molding helps reduce labor costs while increasing productivity

Complexity

High level of detail can be mass produced

Strength

By adding fillers or compounds, the plastic used can be very strong, even at reduced cost

Efficiency

Precision injection molding is much faster than other traditional molding methods and allows more parts to be made with only one mold

Design freedom

Precision molds are custom made to project requirements, allowing for greater customization and control

Requirements for precision injection molding

The most important technical index of precision injection molding products is the precision of injection molding products (dimensional tolerance, shape tolerance and product surface finish).
The parts have high precision and small tolerance, that is, the precision dimension limit is high.
The product has high requirements, and it is required to maintain dimensional stability for a long time.
The rigidity of the mold is good, the dimensional accuracy of the cavity, the smoothness and the positioning accuracy between the templates are high.
Adopt precision injection machine to replace traditional injection machine.
Using precision injection molding process.
Select materials suitable for precision injection molding.

Main changes affecting precision injection molding

The precision of precision injection molding machine

High temperatures affect the viscosity of the hydraulic fluid in the molding machine, which can create speed and pressure increases during the molding cycle. This variation can result in inconsistent dimensions from shot to shot during the molding process.
Material Consistency

Many plastics are hygroscopic, meaning they absorb moisture on a molecular level. Therefore, the material needs to be dried in a drying system before molding. Any moisture absorbed by the material in the forming equipment after drying can negatively affect the consistency and physical properties of the material as it hydrolyzes during the forming process. The higher the humidity, the more difficult it is to keep dry material. This is a major issue for quality, high-precision molding.
Thermodynamic control of the mold

In general, high factory temperatures and temperature variations make precise mold temperature control very difficult. Injection molds are designed with waterlines to thermodynamically balance heat loss from the plastic material to achieve a specific plastic shrinkage and thus part size. The mold operates with a separate water temperature controller to achieve the desired temperature. Consistent control of mold temperature and resulting plastic shrinkage is critical for high-precision injection molding. Ambient temperature changes undermine the goal of consistency.

How to choose a precision injection molding machine

The injection pressure of the precision injection machine is high, and the rigidity of the mold clamping system is large. The parallelism of moving and fixed templates is controlled within the range of 0.05-0.08mm.
It requires the protection of low-pressure molds and the control of clamping force precision. Because the size of the mold clamping force will affect the degree of deformation of the mold, which will eventually affect the dimensional tolerance of the part.
The mold opening and closing speed is fast.
Plasticizing parts: screw, screw head, non-return ring, barrel, etc., should be designed in a structural form with strong plasticizing ability, good homogenization degree, and high injection efficiency. The screw drive has a large torque and can be infinitely variable.
It is necessary to be able to stably control the repeatability and mass repeatability of the product.
Due to the high speed requirements of precision injection molding machines, it is necessary to emphasize the response speed of the system. the
Precision injection molding machines must be high-pressure, because it affects the precision and quality of precision products and improves injection molding efficiency.