Switch to parallel mold piping now
Switch to parallel mold piping now
How to reduce energy costs for mold temperature control by a third
Mold temperature control has a decisive influence on both the quality of the resulting parts and the efficiency and energy consumption of the manufacturing process. A simple way to improve quality consistency while significantly reducing the energy costs associated with temperature control is to switch from serial to parallel tubing for the injection mold.
Serial mold piping is significantly more common in injection molding facilities than parallel piping. The reason: Serial piping is easier and faster to install and requires fewer meters of tubing. However, during operation, this setup leaves much potential for efficiency and quality improvements untapped.
Using a test setup, WITTMANN clearly illustrates the difference between the two piping configurations.
The injection mold is simulated using two analog flow controllers. The sight glasses allow the influence of changing parameters to be observed with the naked eye. For comparison, one flow controller is piped in series and the other in parallel.
The setup includes a Tempro plus D100 dual-circuit temperature control unit with frequency-controlled pumps and a Flowcon plus digital flow controller. In practice, the Tempro plus D and Flowcon plus work together to ensure a constant temperature and flow rate and provide uniform heat distribution within the mold.
Shortly after the Tempro plus D and Flowcon plus are turned on, a difference becomes noticeable between the two water distribution manifolds with different piping configurations. Although both temperature control circuits operate at the same pump speed and all valves are fully open, the flow rate in the water manifold with parallel tubing is nearly three times as high as in the manifold with serial tubing – and this is achieved with a pump pressure reduced by two-thirds.
For the application, this means that with parallel piping, they can significantly reduce the temperature controller’s output to achieve the same total flow rate as with serial piping. The flow rate is less prone to disruptions with parallel piping, for example, when cooling circuits become clogged by deposits from the cooling medium. This results in uniform temperature distribution and, consequently, consistent component quality. Positive side effects include reduced wear and energy-efficient operation, which directly improve the CO₂footprint and unit cost calculations.
Parallel Piping
Low operating pressure: high flow rate
Uniform temperature distribution: consistent part quality
Reduced wear: long maintenance intervals
Low energy consumption: competitive unit costs
Serial Piping
Increased operating pressure: reduced flow rate
Uneven temperature distribution: increased risk of rejects
Premature wear: frequent replacement of spare parts
Increased energy consumption: high production costs
The graphs show the operating pressure (top graph) and the pump’s energy consumption (bottom graph) for both serial and parallel tubing configurations in a specific practical example involving a temperature controller.
Serial connection:
3 bar
13.5 l/min
550 W/h
Parallel connection:
1 bar
30 l/min
350 W/h
Serial connection:
3 bar
13.5 l/min
550 W/h
Parallel connection:
1 bar
30 l/min
350 W/h
Calculation Example
Based on 24-hour operation over a five-day workweek and an electricity price of 15 cents per kilowatt-hour, the electricity costs for a single temperature controller with a serial connection to the mold amount to 495 euros per year. Switching to a parallel connection reduces electricity costs to 315 euros. Taking a medium-sized injection molding plant with 20 machines, each equipped with at least two temperature controllers, as an example, the total savings amount to more than 7,000 euros.
