Whether hydraulic, all-electric or hybrid, injection molding machines rely on precise pressure and flow control to produce high-quality plastic parts. Previously, on/off solenoid valves regulated hydraulic oil flow, resulting in abrupt changeovers and inconsistent process parameters. Today, the integration of proportional valves in injection molding machines has revolutionized process control. Proportional valves can steplessly regulate oil flow and pressure, providing smoother speed profiles, tighter pressure control and faster response times.
Precise injection molding machines pressure control with proportional valves
One of the most significant advantages of injection molding machines equipped with proportional valves is the ability to maintain consistent injection and holding pressures. Conventional solenoid valves can only be fully opened or closed, resulting in pressure peaks and fluctuations during the filling and holding phases. In contrast, proportional pressure control valves dynamically regulate hydraulic oil pressure based on a continuously changing electrical signal. This produces a stable, ripple-free pressure curve, ensuring the cavity receives the precise holding pressure required to compensate for material shrinkage. With proportional valves, the pressure accuracy of Topstar injection molding machines has increased from ±5% to ±1%, minimizing part weight variability, reducing flash and ensuring dimensional consistency of high-precision parts.
Stepless flow regulation for smooth velocity profiles
In addition to pressure, proportional valves have revolutionized flow control in injection molding machines. A smooth velocity profile is essential during melt injection to avoid flow hysteresis and minimize shear-induced polymer degradation. Proportional flow control valves, or servo valves, adjust the oil volume steplessly according to the machine’s control system. This enables a gentle acceleration ramp at the beginning of the filling phase, precise mid-term velocity control, and deceleration during holding pressure transitions. Topstar’s all-electric hybrid machines are equipped with proportional flow valves with flow resolutions as low as 0.5 cc/min, enabling complex, multi-step injection profiles that deliver superior surface finish, lower residual stresses, and optimized mechanical properties in demanding applications such as automotive connectors and medical components.
Make injection molding machines more responsive and cycle times shorter.
Reducing cycle times is essential to keep production costs competitive. Solenoid-based injection molding machines often suffer from hysteresis in pressure buildup and flow changes, during which the valve core must fully open or close. In contrast, proportional valves start regulating flow or pressure immediately after receiving an electrical command, with response times measured in milliseconds. This fast response capability can reduce injection and holding phases by up to 15%, as observed in Topstar injection molding machines. Combined with optimized cooling and ejection sequences, faster valve actuation can reduce total cycle time by an average of 10% to 20%. Over millions of cycles, these savings translate into significant production gains and lower energy consumption.
Improved Energy Efficiency and Sustainability
Proportional valves also improve the energy efficiency of the injection molding machine. Conventional hydraulic systems continuously maintain high pressure to ensure rapid actuation when the solenoid valve opens, wasting energy in heat and fluid circulation. Proportional valves are integrated with variable pumps or load-sensing systems to adjust pump output in real time to meet demand. When low flow is required, pump displacement is automatically reduced, minimizing horsepower waste. In Topstar’s injection molding machines, this intelligent hydraulic architecture reduces hydraulic energy consumption by up to 30%. Less heat loss means smaller heat exchangers and lower cooling unit power, further contributing to sustainable green manufacturing initiatives.
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Enhanced Process Monitoring and Closed-Loop Control
The accuracy of injection molding machines depends on closed-loop feedback of pressure, flow, position and temperature. Proportional valves provide a continuous analog control signal that integrates seamlessly with modern machine controllers. This enables advanced algorithms such as PID loops and adaptive control to fine-tune valve commands in real time, compensating for subtle disturbances such as supply pressure fluctuations or viscosity changes. Topstar’s proprietary software leverages this closed-loop data to maintain optimal melt front advancement, gate freeze detection, and pressure holding optimization. The result is a self-correcting system that maintains process stability over long production runs, ensuring consistently high first-pass yields in mass production environments.
Provides Precise Pressure and Flow Control
Proportional valves redefine the operational capabilities of modern injection molding machines, providing precise pressure and flow control, faster response times, energy savings, and greater process reliability. By integrating proportional technology into hydraulic or electric power platforms, Topstar enables manufacturers to meet today’s high-volume markets’ stringent tolerance and productivity requirements.
