Adaptive Process Control eliminates fluctuations during injection molding

2009
  • UPDATE: new APC calculator shows potential financial savings 
  • First installations among US plastics processors
  • System compensates fluctuations and intervenes automatically
  • APC function is offered for all machines

KraussMaffei is now offering the opportunity to calculate financial APC savings online by means of the new APC calculator. The first step for the processor is to enter the parameters shot weight and cycle time. This produces the throughput rate. In the second step the price for new material is entered in euro/kg. The processor can now freely select the reduction in the reject proportion and the increase in the recyclate proportion. The APC calculator then automatically calculates the annual savings in euros.

For example: tube shoulders. With a throughput rate of 27 kg/h, a new material price of 1.10 euro/kg, a 1.5% reduction in the reject proportion and a 2% increase in the recyclate proportion, this produces annual savings of 4,207 euros, according to the company.

The APC calculator is available online in five languages: German, English, Spanish, Russian and Chinese.

Link: APC calculator

First installations among US plastics processors

Woco IPS (Waco, Texas) and Intralox (Harahan, Lousiana) are among the first American plastics processors where the new APC machine function has been installed:

“In Texas we’re subjected to extreme climate fluctuations during production. We are convinced that by using APC, we’ll be able to compensate for these fluctuations reliably and ensure constantly high product quality,” explains Alexander Wein, Global Project Manager Railway at Woco. The location in Texas acts as a supplier primarily for the railway and transport industry and is currently applying for ISO certification for the automotive industry. “The APC function will surely provide us with more support in implementing the high quality required here,” Wein adds.

“We have about 600 different molds in use. Per day we have about 40 mold changes. The APC function yields enormous savings potential for us,” explains Tom Moore, Technical Project Manager at Intralox. In addition to this, the technical project manager praises the easy installation of APC: “The KraussMaffei AX 130-750 injection molding machine was equipped with the APC function in a completely straightforward and intuitive manner. Ongoing production was not impeded in any way.”

 Tom Moore, Technical Project Manager at Intralox

Tom Moore, Technical Project Manager at Intralox

External factors negatively influence process

In injection molding, process stability plays a critical role with respect to the quality of the manufactured components. This is the reason why injection molding machines have to operate with a high repeatability rate over a long period of time. However, various external factors such as room temperature, humidity, wear and the use of recycled materials, can lead to fluctuations during the injection molding process  and negatively influence the process. The injection molding machine does continue to operate with typical precision, but is unable to compensate for the fluctuations from outside the process. This leads to quality defects and possible production waste.

To compensate for these fluctuations, the two companies KTW Kunststofftechnik Weißenburg and KraussMaffei Technologies began a joint project about 2 years ago aimed at reducing the rejection rate in the injection molding process. A new machine function was developed: the Adaptive Process Control system (APC).

KTW: specialized in automotive exterior and interior components

KTW is a medium-sized automotive supplier with sales that have almost tripled in the last five years. The company specializes in high quality exterior and interior components, such as finishers, paneling, covers, air ducts and wheel house shells, which are manufactured using both the standard injection molding process and through special processes involving multicomponent technology, over-molding of film or fabric and variotherm technology.

The company processes approximately 5,000 tons of thermoplastic per year on a total of 21 injection molding machines. Since 1998, the company solely employs KraussMaffei injection molding technology. Since then, 14 fully automated machines in the clamping force range of 80 to 2300 tons have been installed. In 2011, as part of a larger package, KTW acquired the MX 2300, which produces wheel house shells from recycled materials for a large German automaker.

Albert Burghart, Plant Manager of KTW in Weißenburg

Albert Burghart, Plant Manager of KTW in Weißenburg

Albert Burghart, Plant Manager of KTW in Weißenburg, states: “The use of the APC function enabled us to substantially improve continuous monitoring of melt quality, significantly reduce the subsequent rejection rate and guarantee precise traceability of the components down to the individual shot.”

System compensates fluctuations and intervenes automatically

In order to eliminate these fluctuations to a large extent, the MX 2300 machine of KTW was equipped with the APC process control system. The polyolefin recycled material produced by KTW for wheel house shells is stored in 80-ton silos. Depending on their origin, the recycled materials vary in terms of grain size, consistency and bulk density, leading to substantial fluctuations in viscosity. KTW uses the Adaptive Process Control system to intervene automatically, within specified limits, so that a change in material viscosity does not lead to fluctuations in component weight. The APC function, integrated into the MC6 machine control system, analyzes the current process state in each injection process. The system adjusts the changeover point and the holding pressure profile to the current melt viscosity and current flow resistance in the mold. This makes it possible to compensate for deviations in the same shot. As a result, the injection molding machine is capable of keeping the product quality stable, even if the viscosity of the material or the flow resistance in the mold change due to external factors.

After changing materials in injection molding machines without APC, significant fluctuations in component quality can arise (top). APC, on the other hand, makes it possible to achieve uniform component quality (bottom)

After changing materials in injection molding machines without APC, significant fluctuations in component quality can arise (top). APC, on the other hand, makes it possible to achieve uniform component quality (bottom)

The APC function is offered for all machines, both hydraulic and electric, and can also be easily retrofitted in existing machines (MC5 and MC6 control systems).

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