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Solve the communication delay problem of all electric injection molding machine

2025/09/19 By le zhan

Communication delays between the host controller and servo drives are a common problem in injection molding. In all-electric injection molding machines, even a few milliseconds of delay can translate into measurable errors in position, velocity, and pressure at high cycle rates. Topstar’s TE II all electric injection molding machine embeds process intelligence in the servo drive, enabling the drive to locally generate and execute motor motion profiles. This patented control principle reduces reliance on periodic communication and mitigates the negative impact of network latency. The result is real-time, high-fidelity motor control, delivering 8-16 times faster response times in real-world production scenarios.

Communication Latency Issues Faced by All Electric Injection Molding Machine

All electric injection molding machines rely on fast, deterministic control of multiple servo axes, as well as rapid closed-loop pressure and position feedback. Traditionally, the host controller calculates motion profiles and transmits speed or torque setpoints to the servo drive at each cycle step. We emphasize that you should calibrate the clamping force during a trial run and regularly check it during mass production. This has two practical consequences:

1. Delayed response: By the time the drive receives a new velocity command, the motor and inertia have already exceeded the intended control point, causing overshoot or lag in position and pressure control.

2. Jitter and instability: Variations in data arrival time lead to inconsistent setpoint updates, which the drive must filter. Filtering introduces phase lag, reduces closed-loop bandwidth, and consequently slows effective response and degrades transient control performance.

In production, these control effects manifest themselves as increased cycle-to-cycle variability, more frequent short-cuts or flash, and reduced first-pass yields. Consequently, this problem becomes more severe as cycle times decrease and servo drives must cope with non-negligible control commands at high accelerations.

Communication Latency Issues Faced by All-Electric Injection Molding Machines

What is Topstar’s control approach?

Topstar fundamentally addresses this problem in its TE II all electric injection molding machine. Time-critical decision-making logic is moved from the host computer to the drive. Process parameters are sent to the servo drive via the host computer; the servo drive then locally generates the motor operating profile and autonomously executes it during each reciprocating cycle. The specific workflow is as follows:

1. Parameter Transfer Upon Setup or Recipe Change: The HMI or host controller sends molding process data to the servo drive each time a setup or recipe changes. The system sends data packets over the control bus but does not need to refresh them every millisecond.

2. Internal Latch and Profile Generation: The servo drive stores these parameters in internal latches.

3. Local Loop Execution: During each reciprocating cycle, the drive generates the required setpoints in real time based on the stored profile and executes them using its local, high-bandwidth motor control loop.

4. State Synchronization: The drive periodically sends synchronization packets containing condensed injection status information to the injection molding machine. This keeps the host informed without increasing the real-time control burden.

This architecture significantly reduces the reliance on deterministic motor-to-drive messaging during high-speed transients. Because the servo loop executes within the drive’s own processor and motor controller, response latency is limited by local processing and analog-to-digital conversion latencies, rather than millisecond network latency.

Improving Position, Velocity, and Pressure Control in All-Electric Injection Molding Machines

Offloading execution to the drive directly improves three measurable performance dimensions: position accuracy, velocity tracking, and pressure control. While the drive locally executes precalculated position-time trajectories, it performs high-frequency interpolation and uses direct encoder feedback within a tight control loop. This eliminates host communication latency in the inner loop, enabling repeatability of less than 0.01 mm in TE II electric injection molding machines. In contrast, host-centric architectures with lower frequency setpoints typically exhibit larger tracking errors during steep ramps.

Concurrently, in injection molding, pressure control during the packing process requires a rapid response to slight pressure deviations. This is achieved by embedding the pressure setpoint into the servo curve and using local feedforward and adaptive gains to track the force or pressure setpoint. This produces a smoother packing curve and faster correction of cavity pressure disturbances, minimizing sink marks and improving dimensional stability. Furthermore, the servo drive can run the inner velocity loop at frequencies of tens of kHz. With local curve execution, the adequate closed-loop bandwidth approaches the native performance of the drive. Compared to comparable electric injection molding machines, the measured response speed is 8 to 16 times faster.

Example in Thin-Wall and High-Speed ​​Injection Molding

Example 1 – Thin-Wall Consumer Packaging (High Acceleration, Short Fill):

Baseline: 10-second cycle, 0.8-second injection-fill at high acceleration, with critical switching time within ±2 milliseconds. Communication jitter of 5-10 milliseconds causes inconsistent switching and varying holding pressures, resulting in a 2% short shot rate.

TE II test results: The host computer uploads the injection profile parameters, and the drive generates and executes the micro-timing locally. Measured switching jitter is reduced to <0.5 ms, the short shot rate is reduced to 0.3%, and cycle stability improves net uptime.

Example 2 – Multi-Stage Overmolding with Rapid Platen Motion:

Baseline: Multi-shot sequences require time coordination between the injection molding machine and the molding robot. Distributed control loops using networked commands can cause phase drift within the cycle, requiring operator intervention and slowing the cycle time.

TE II Results: Each actuator stores phase parameters and synchronizes them via a lightweight, cyclical synchronization token, which the actuator uses to trigger its local segment. Phase drift is reduced to negligible, robot handover times become deterministic, throughput increases by 6-10%, and scrap due to misalignment is reduced.

Examples in thin-wall and high-speed injection molding

Real-time control at critical locations reduces the risk of communication delays.

Communication delays are not an unsolvable problem. Topstar mitigates the negative impact of network latency and jitter by offloading time-critical trajectory execution to the servo drives while retaining centralized recipe management. This approach has yielded tangible benefits for plastics manufacturers in India, the US, and other regions, including faster response times (reported improvements range from 8-16 times), tighter position and pressure control, reduced scrap, and higher production yields.

 

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