+86 17727725162 jqj014950@topstarltd.com

Home / How do you avoid mold sticking problems in injection molding machines production?

How do you avoid mold sticking problems in injection molding machines production?

2025/02/03 By Topstar

injection molding machines 95-12

Injection molding machines enable precise batch production of plastic parts in the production of plastic products. However, one problem that often plagues operators of actual output is mold sticking. That is molded parts stick to the mold cavity or core during the ejection process. This problem not only affects production efficiency but also increases scrap rate and maintenance costs. Therefore, solving the problem of mold sticking is crucial to providing consistent product quality. In this guide, we will explore several possible strategies to prevent mold sticking problems, emphasizing best practices for optimizing injection molding machine performance.

Optimizing injection molding machines mold design to prevent mold from sticking

A well-designed mold is the first line of defense against mold sticking problems. Injection molding machines rely on molds with precise geometry, surface finish, and cooling systems to ensure smooth part release. For example, an insufficient draft angle (taper applied to vertical walls) can create suction that pulls the part back into the mold. Topstar recommends a minimum draft angle of 1–3°, depending on the material type and part complexity.

In addition, polishing the mold surface reduces friction, while textured finishes may inadvertently trap molten resin. Proper venting is equally essential – trapped air or gas can increase internal pressure and cause parts to stick. Topstar’s injection molding machines use a self-developed control system that monitors mold conditions in real-time, enabling pressure and temperature adjustments before sticking occurs.

injection molding machines 95-1

Control injection molding machine temperature settings

Poor temperature management is the leading cause of mold sticking. Injection molding machines must maintain precise thermal control of the barrel, nozzle, and mold. Overheating the molten plastic can degrade the material and produce a sticky residue that sticks to the mold. Conversely, low temperatures can cause incomplete filling or premature cooling, which increases ejection resistance.

For temperature control, Topstar’s fourth-generation mold temperature controller can ensure an accuracy of ±1°C. For example, semi-crystalline materials such as polypropylene require higher mold temperatures (40-80°C) to minimize shrinkage and sticking, while non-crystalline plastics such as ABS perform best at 50-70°C. Calibrate thermocouples regularly and use thermal imaging cameras to identify hot/cold spots in the mold.

mould temperature controller 81-1

Fine-tune ejection parameters

Ejection force and time are key to avoiding sticking. Too fast an ejector speed or a misaligned ejector pin can deform the part or damage the mold. The injection molding machine must synchronize ejection with the cooling phase – too early ejection risks tearing, while a late ejection causes the part to shrink and seize the mold.

Topstar’s servo-driven ejection system allows programmable force distribution, which reduces stress on delicate components. For example, a two-stage ejection process (gentle initial movement followed by full retraction) minimizes sticking in deep-cavity molds.

Choosing compatible materials

Material properties directly influence the risk of sticking. Hygroscopic resins absorb water, leading to gas formation and sticking. High-viscosity materials, such as polycarbonate, require higher injection pressures, which increase friction.

Topstar’s injection molding machines support a material database that automatically adjusts settings for optimal flow and cooling. For example, adding 0.1-0.5% lubricant to polyolefins can significantly reduce sticking. In addition, always dry hygroscopic materials to ASTM standards before processing.

Keeping injection molds clean

Contamination is the main culprit for sticking. Dust, degraded resin, or residual release agent can cause uneven surfaces that trap molten plastic. While making suitable equipment parameter adjustments, Topstar also emphasizes daily cleaning procedures for injection molding machines, including cleaning the barrel with a specialized cleaner before changing materials. Mold maintenance is equally important. Ultrasonic cleaning can remove microscopic debris on textured surfaces, while laser ablation can repair pits or corrosion. Implement a preventive maintenance plan to replace worn parts, such as springs or bushings, which will cause the ejector mechanism to misalign if not replaced in time.

Mold-Cleaning-Final2

Better Solutions for Sticking Problems

By optimizing mold design, temperature control, ejection system and material selection, Topstar can help customers achieve perfect production operations. Remember, every minute saved in solving sticking problems means higher profitability and customer satisfaction.

Prev: Injection molding machine for medical device production: key factors

Next: How to solve the problem of communication delay in electric injection molding machine?

TRENDING POSTS

HOT TOPIC

Get A Quick Quote