Hidden Die Casting Industry Problem Identified & Solved

New technology for vacuum system filtration helps boost profits for Aluminum Die Casting Foundries.

The high-tech die casting industry relies on traditional steel wool pad filters for vacuum systems, which jeopardizes the process’ overall stability and security. Without an alternative, this causes unnecessary and prolonged machine downtimes as well as excessive cold and warm scrap ratios. Dexwet Filters, a revolutionary and patented new filtering technique utilizing Dexwet SUPER-APF, solved this market gap (Aluminum-Particle-Filters). Leading US and European technology companies have embraced this new approach, and others are progressively understanding the necessity to adopt this profit-maximizing technology as a new process standard in order to preserve their industry competitiveness.

AT A GLANCE

Over the last two decades, vacuum support systems for die casting units have become commonplace in the manufacturing of contemporary and complicated aluminum structural components for the automotive industry. The greater the demand to evacuate the tool form, not only from air and gases, but also from other substances applied to the tool throughout the process, the larger, thinner-walled, and more intricate the automobile parts – from power drains to cassis parts or battery housings – In principle, what does not exist in the form prior to the injection of the liquid aluminum cannot result in a component deficit.

Many parts nowadays cannot be manufactured without a deep vacuum of 10-20 mBar to ensure quality and an acceptable scrap ratio. The first foundry in Germany contacted Dexwet Filters in 2017 to investigate a filter problem caused by old-tech steel wool pad filters used in the vacuum suction line to protect the vacuum valves and pump from debris that is sucked off.

THE INDUSTRY BLIND SPOT

These vacuum filters are typically updated preventively once every shift, with an average machine downtime of 30 minutes. With 20 shifts per week, this aspect results in a weekly loss of up to 10 hours of production time. When the machine resumes operation, three warming shots are typically performed, resulting in 60 “warm-scrap” components that must be melted in again, resulting in a loss of total production time and energy waste.

A further in-depth examination of the incidence of parts with quality defects revealed that the ratio of quality deficient parts identified by final quality control departments using x-ray increased in the second half of the shift, indicating that vacuum filter malfunction might be the underlying cause.

SOLVING THE PROBLEM

Dexwet Filters developed their aluminum particle filter technology from APF1 to APF2, and the final industry solution, SUPER-APF, over three R&D stages for the technology leader vacuum system supplier, Pfeiffer Vacuum.

Dexwet SUPER-APF vacuum filters provide a sturdy filter inlet, 9 filter layers, and a sophisticated and patented design. The first two APF versions allowed the die casting unit to run continuously for 2-3 days without downtime, while the third and current version, which employs Dexwet SUPER-APF filters, substantially doubled its efficacy. Dexwet SUPER-APF is routinely swapped once per week during the service shift, with no more than one filter exchange per week. Because such guidelines cannot take into account the individual circumstances and emission behavior of each die casting unit, such preventative filter exchange is mandated by the vacuum system itself, rather than by any general work direction, as is now standard.

WHY OLD-TECH FILTERS DETERIORATE OUTPUT PERFORMANCE

The severe circumstances within the vacuum suction line when the vacuum valve opens are the source of changes in output part quality induced by “old-tech” steel-wool pad filters. The particle speed strikes the sonar wall at 671 mph near the bottleneck of the suction line. To safeguard the vacuum valve, the most crucial component of any vacuum system, air and gases must be allowed to pass through while any greasy particles and hot liquid aluminum particles must be collected. When a vacuum valve breaks, the die casting units may be out of commission for many days until new components are supplied, which is why each suction line has two filter housings and cartridges.

When utilizing steel pads as filters, the orientation of the steel fibers fluctuates from shot to shot, resulting in oscillations in the filters’ throughput behavior. As additional material is collected by the form-side filter over the shift, the vacuum system’s ability to consistently create the same under pressure conditions within the form deteriorates, resulting in quality variances.

ROI WITHIN ONE YEAR

Dexwet SUPER-APF implementation is a one-time investment with a guaranteed ROI in less than a year. When it comes time to replace Dexwet filter cartridges, users simply remove the dirty cartridges and clean them at a central cleaning station, rotating the cartridges in the foundry between their three places (1 in the machine, 1 at the machine, and 1 clean in the central cleaning station). This reduces waste, but more importantly, it enables users to gain vital insights from analyzing the filtered material or filter cake, which was previously not feasible.

WORKFLOW OPTIMIZATION

For quick and easy filter exchange, a single set of replacement filters is always provided in a transport box right at the die casting unit. If the vacuum system alarms for preventative filter exchange, the machinist can easily replace all filter cartridges with a machine downtime of 5-15 minutes. The clean filters are removed from the box, and the dirty ones are replaced. This brief downtime of fewer than 15 minutes prevents warming shots, and the die casting unit can immediately resume production of quality parts.

This eliminates the necessity for warming shots and scraps due to vacuum filter exchanges during the shift week. If there was a filter exchange alert at the conclusion of such a shift, the worker returns the transport box with the dirty filters to the cleaning station, where a designated box with clean filters is always given, so they may transfer that back to the die casting machine for the next exchange.

FILTER CAKE ANALYSIS AND PROCESS GAINS

The personnel assigned to the filter cleaning station are vital to reap the greatest value from this unique technology. Because these filters are in operation for three days to a whole shift week, the quantity and quality of the debris in the filter cake must be viewed like a drilling core throughout the duration of its operation. This filter cake is composed of aluminum particles with a maximum particle size of 0.5 mm and various types of oily or waxy particles derived from tool fats, separation liquids, silver fat, and other sources. After a few weeks of filter cleaning, the worker assigned to the task will be able to distinguish between typical filter cakes and those with aberrant or strange compositions. Such deviations must then be communicated to the machinist, allowing for early fault diagnosis in the tool and other system parameter calibrations and dosing.

Dexwet SUPER-APF technology was meticulously created to provide vital data to machinists in order to maximize the overall performance of each die casting unit. This contributes to and improves process stability and security. All of this equates to extremely appealing benefits for the entire foundry. It contributes to an increase in the weekly output of high-quality components for each die casting unit while decreasing energy and manufacturing time waste.

REAL COSTS OF LOW-TECH STEEL-WOOL PAD TECHNOLOGY IS AN INDUSTRY BLIND SPOT

The true costs of “old-tech” steel wool pad filters are an industrial blind spot since the direct expenses of these low-cost filters were not included in a foundry’s total cost structure. Georg Fischer (GF+), a technological leader, embraced the technology early in 2017 and has now applied the filters in all of their foundries globally for very good data-based reasons. Dexwet Filters has just entered the US market with its comprehensive product suite, which covers many different sectors and applications. For the aluminum die casting industry, sales have started to provide the technology to North American markets.

OFFERED AS A STANDARD OEM COMPONENT

Dexwet Filters collaborates with Pfeiffer Vacuum, the world’s top producer of vacuum systems. Their innovative two-tank vacuum technology is the only one on the market that enables for precise and accurate pressure monitoring within the form over the whole microsecond injection cycle. While the first tank sucks from the injection chamber’s side, the second cycle begins at the same time the first shuts, delivering the entire vacuum capacity of the second tank throughout the shot curve. They have been selling Dexwet SUPER-APF technology with their cutting-edge systems since 2018, since they were the only vendors to be able to assess the advantages of vacuum building inside the form utilizing Dexwet SUPER-APF technology compared to the previous tech.

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