Less scrap – more productivity

As consistent as cruise control

“The revolutionary aspect of APC is that component quality serves as the definitive control variable. Since the APC function acts as correction during each cycle, previously unforeseen possibilities for robust and more efficient injection molding are now open,” says Dr. Reinhard Schiffers, Head of Machine Technology at KraussMaffei. The APC 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 makes it possible to compensate for deviations in the same shot. This leads to significantly lower fluctuations in article weights. In this way, fluctuations in the manufacturing process triggered by external factors such as changing temperatures, climate conditions or batches can reliably be compensated for.

In a figurative sense, APC operates the same way as cruise control for vehicles. As is well known, 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 shot weight specified by the mold setter consistent during ongoing production if, for example, the material viscosity changes due to outside factors. However, cruise control does not replace the driver; similarly APC cannot replace the machine setter. Only after the mold setter has configured the parameters for a high-quality part is APC activated, stabilizing the process and taking part of the workload from the operator.

Faster restarting

Along with improvements to general process stability during ongoing production, APC also provides advantages when restarting production after machine downtime. “The Adaptive Process Control system precisely detects to what extent the material viscosity has changed during machine downtime. The production of reject parts is avoided thanks to the specific adaptation of the changeover point and the holding pressure profile,” says Dr. Schiffers. Even changes in the machine, such as signs of wear on the screw and barrel or the closing behavior of the nonreturn valve, which may lead to irregularities in the plasticizing and injection process, can be compensated for via APC.

Furthermore, the use of APC increases energy efficiency in injection molding production. 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.

Increasing the portion of recycled material

Injection molding machines with an APC function also enable reliable processing of high quantities of recyclate, which often cause fluctuations in viscosity. “Using the APC function here, we can prevent fluctuations in component weight within adjustable limits due to a change in material viscosity. Even if the recyclate quantity increases, the component quality remains consistent. In this way, APC not only supports zero-defect production, but also the use of more environmentally friendly and cost-effective recycled materials,” says Dr. Schiffers.