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How to solve the problem of slow response of servo injection molding machine？

2025/07/23 By Topstar

Servo injection molding machine 3-1

Up to 30% of the cycle delay in servo injection molding machine is attributed to control and drive lags, resulting in a slow response speed and a direct impact on production and product quality. Topstar uses a self-developed unified control system that integrates injection units, clamping units, auxiliary machines, and automation peripherals through a single HMI interface. This unified architecture ensures that all components communicate on a deterministic real-time bus, reducing command delays by up to 50%. This integrated control enables instantaneous adjustments to speed, pressure, and position for the entire injection molding machine. Combined with automatic mold opening position compensation, the injection molding robot can grasp parts with milliseconds of consistent response speed. Let every link bring swift response and high-precision injection molding.

Integrating unified control on servo injection molding machine

A common bottleneck in servo injection molding machines is the disconnection of the control loops between the injection, clamping, and auxiliary systems. For example, traditional systems require separate control commands to start the injection screw, clamping cylinder, and robot removal device, resulting in cumulative delays. Operators must frequently copy parameter changes between modules manually, which slows system response. Therefore, we replaced this multi-node control with a unified self-developed control language, thereby achieving synchronous command transmission. At the same time, all system parameters are displayed on the HMI to facilitate unified adjustments, thereby allowing for immediate recalibration of the entire plastic injection molding machine configuration. The upgrades reduced the injection molding machine’s response time to cycle start commands from 120ms to under 40ms, boosting part repeatability and cutting cycle times by 5%.

injection molding machine 25-1

Automatic compensation for mold opening of the servo injection molding machine

Another key to addressing the slow response of servo injection molding machines is to compensate for the mold opening position automatically. In addition to the standard mold opening time, we also monitor the template position with an error of no more than ±0.01 mm and dynamically adjust the injection molding robot approach trajectory. The injection molding robot starts part removal as soon as the mold safely releases the parts. I installed a position feedback loop on the moving template, using a high-resolution linear scale, and connected it to the real-time controller of the servo drive.

Combined with the motion controller of the injection molding robot under a unified control system, synchronous drive is achieved, which increases the grasping time from a lag of 150 milliseconds to less than 50 milliseconds. In addition, a predictive algorithm based on cycle history enables the system to pre-adjust for thermal expansion and wear, ensuring consistent cycle response even under varying production temperatures and mechanical loads, significantly improving response speed.

Paired with tilted double-shot cylinders and linear guides

Mechanical response also determines the speed of overall injection molding. Topstar’s servo injection molding machines feature tilted double-shot cylinders for mold clamping and ejection, mounted on precision linear guides. The tilted mounting reduces the hydraulic path length by 30%, thereby reducing the travel time of the slide valve. Active voice: I used precision linear guides for the injection unit to reduce mechanical clearance to less than 2 microns. Additionally, the use of double-acting cylinders enables simultaneous opening and ejection movements, further reducing mechanical sequencing delays. The tilted cylinder orientation, combined with high-precision guides, reduces mechanical inertia and friction, allowing for faster mold clamping, opening, and screw reversal speeds. As a result, the injection molding machine can complete the transition between the injection and ejection stages in 80 milliseconds while maintaining the alignment tolerance of precision-tolerance components.

Proportional back-pressure control on servo injection molding machines

The fast response to start injection commands also depends on the accuracy of pressure control. High-response servo valves dynamically adjust screw back pressure during plasticization to maintain consistent melt density and reduce hydraulic overshoot. Our system integrates a 2ms proportional valve directly controlled by the servo drive. This configuration stabilizes the injection pressure within 1 bar of the set value, eliminating pressure fluctuations and ensuring that the forward movement of the screw starts on time. Additionally, the adaptive back pressure curve automatically adjusts to accommodate different injection volumes, thereby improving melt uniformity. Accurate and stable injection curves accelerate cycle conversion and enhance part quality by minimizing fluctuations, flash, and compression deviations in the final molded parts.

Proportional Backpressure on Plastic Injection Molding Machines

Bringing a fast response

Solving the problem of slow response of servo injection molding machines requires a holistic approach, using a unified control architecture, unified HMI adjustments, mold opening compensation related to robot coordination, inclined cylinder and linear guide upgrades, and proportional back pressure control, which can reduce cycle start delays by 30% to 60%, improve part quality consistency, and increase the output of injection molding machine production lines.

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