The zero-defect production approach in injection molding

  • Adaptive Process Control compensates fluctuations in injection molding process
  • System adjusts changeover point & holding pressure profile in each cycle
  • KraussMaffei at #Fakuma

Fluctuations in the injection molding manufacturing process caused by external factors such as changing temperatures, climate conditions or batches are omnipresent. A new system allows to compensate for deviations. The new APC (Adaptive Process Control) machine function developed and patented by KraussMaffei adjusts the changeover point and the holding pressure profile in each cycle to the current melt viscosity and current flow resistance in the mold. This compensates for deviations in the same shot which leads to significantly lower fluctuations in article weights. APC is offered on all electric and hydraulic series from KraussMaffei.

As consistent as cruise control

In a figurative sense, APC operates the same way as cruise control for vehicles. Cruise control systems automatically control the supply of fuel to the engine so that the vehicle does not drop below or exceed a speed defined by the driver, even in changing road and wind conditions. Similarly, APC is able to keep the specified shot weight consistent during production if, for example, the material viscosity changes due to external factors. However, cruise control does not replace the driver. Similarly APC cannot replace the machine operator. Only after the operator has set up the parameters, APC is activated, stabilizing the process and taking part of the workload from the operator.

KM graphics

This graphic illustrates fluctuations in component weight, which are greatly diminished when APC is used. This improves the Cpk value (process capability index) significantly and reduces the expected scrap rate substantially (source: KraussMaffei)

Faster start-up and increased energy efficiency

APC also provides advantages when restarting production after machine downtime. The system precisely detects to what extent the material viscosity has changed during machine downtime. The production of reject parts is avoided due to the specific adaptation of the changeover point and the holding pressure profile. Even changes in the machine, such as signs of wear on the screw and barrel or the closing behavior of the non-return valve, which may lead to problems during plasticizing and injection, can be compensated for.

In addition, the use of APC increases the energy efficiency. In practice, the barrel temperature and the back pressure are frequently set higher than needed to ensure stable melt quality. But this increases energy consumption and prolongs cooling and cycle times. Since injection molding machines with APC function can compensate for deviations in viscosity, these procedures are no longer required. As a result, less energy is used and the cycle time is shortened.

Reliable processing of recycled material

Injection molding machines with APC function also enable reliable processing of high quantities of recycled material. Fluctuations in component weight due to a change in material viscosity can be prevented. Even if the recyclate quantity increases, the quality of the produced part remains consistent. In this way, APC not only supports zero-defect production, but also the use of cost-effective recycled materials.

Main Picture: After a material change, injection molding machines without APC show significant fluctuations in output quality (top) whereas constant good quality can be achieved with APC (bottom)

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