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Home / Hydraulics Learning Hub / Injection Molding / Material Flow and Backpressure Control

Material Flow and Backpressure Control

Proper material flow and backpressure control is vital in plastic injection molding. Domin servo valves help regulate the injection’s cylinder speed and pressure ensuring consistent production of plastic components.

How Servo Valves Maintain Proper Material Flow and Backpressure

Domin servo valves meter hydraulic flow to precisely control the melt flow rate and screw backpressure throughout the injection, pack, and hold phases of the molding cycle.

  • Material flow control: Servo valves control how firmly plastic enters the mold by controlling the speed and pressure of the cylinder driving the feed screw. This ensures consistent and dependable filling of complex cavities. Learn more about how servo valves optimize velocity-to-pressure control in injection molding.
  • Backpressure control: Backpressure is built in the injection cylinder as material moves through the injection nozzle and into the mold. Adequate backpressure control is important, as it affects the product’s density, size, and shape. Servo valves are responsible for regulating the injection speed and pressure, as well as the mold cycle time.
  • Injection speed: Consistent, optimized injection speeds promote uniform cavity filling and reduce flow marks, voids, and uneven material distribution.
  • Injection pressure: If the injection pressure is not regulated properly, higher pressures can increase overall backpressures. Additionally if injection pressure is too high, it can overpower the clamping force needed to keep the mold closed. Explore how servo valves maintain proper clamping force in injection molding.
  • Mold cycle time: Valves with fast  response and adequate flow control can decrease mold cycle times, which can help contribute to lower backpressure build up in the injection cylinder. 

Comparison of S6 Pro and P6 Pro Valves Technical Data

The S6 Pro and P6 Pro are excellent models for proper material flow and backpressure control in injection molding applications.  With low hysteresis and fast response, these models provide stable backpressure and uniform, repeatable melt flow into the cavity.

Our Recommended Valves

The Domin S6 Pro is recommended for highly dynamic backpressure control and system relief control. The Domin P6 Pro (proportional valve) is recommended for smaller or less dynamic systems, as the flow range (5 to 40 lpm), response times (10 ms), and frequency response (100 Hz) are lower.

S6 Pro Valve

P6 Pro Valve

Hysteresis

<0.2%

<0.2%

Leakage

<0.3 gpm (<1.1 l/min)

<0.13 gpm (<0.5 lpm)

Mass

1.36 lbs (0.62 kg)

1.39 lbs (0.63 kg)

Frequency Response

>250 Hz

>100 Hz

Rated Flow

5-16 gpm

2.6-10.6 gpm

Response Time

<3.5 ms

<10 ms

FAQ for Material Flow and Backpressure Control

The S6 Pro offers very high bandwidth (around 200 Hz) and response times under 3.5 ms for precise control of injection velocity profiles, pack/hold transitions, and backpressure ramps with minimal overshoot. 

Additionally, the S6 Pro has flow rates up to 16 gpm at 1,015 psi, making it well-suited for controlling injection flow and screw backpressure for medium sized injection molding machines.

Compared with the S6 Pro, which is optimized for ultra-fast response and very high bandwidth in more demanding, high-dynamic applications, the P6 Pro offers a slightly gentler dynamic profile with response times under 10 ms. This metric is still more than sufficient for most industrial injection cycles. The P6 Pro is suited for small to medium sized injection molding machines.

 Schedule a demo for the Domin’s S6 Pro or P6 Pro for your press

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