With a spectrum of around 1,000 different parts, it is not easy to reliably meet the increased requirements of technical surface cleanliness. To meet this challenge, Allweier invested not only in two new cleaning machines with customized equipment, but also in cleaning baskets that are especially suited for cleaning and can be used flexibly. With this combination, the contract cleaner meets the cleanliness values in a future-proof manner and cleans significantly more economically.

Allweier Systeme GmbH has been active in drive technology with its own developments for around ten years. Allweier Präzisionsteile GmbH was founded more than 40 years ago as a supplier and system and development partner in machining production. The core competencies of the family-owned company based in Überlingen on Lake Constance are CNC turning, milling and grinding as well as the assembly of subassemblies and components. The company has extensive, state-of-the-art machinery for machining parts made of aluminum as well as cast iron, steels, gray iron and cast steel, titanium and special materials. The range currently includes around 1,000 different parts from mechanical, plant and vehicle engineering, materials handling and robotics, the marine and offshore sector, optics and medical technology, as well as rail transport and other industries. All in all, Allweier processes about 20 million parts a year.

“On the one hand, the cleaning of the processed parts is a challenge due to the different materials as well as the most varied part geometries and dimensions. On the other hand, the requirements for technical surface cleanliness have increased significantly in recent years. Specifications such as no particles larger than 600 µm are common today, and optimal corrosion protection is also indispensable for steel parts,” explains Thomas Schmidt, Technology Planner Rotation at Allweier Präzisionsteile GmbH. In order to achieve the specified cleanliness values in a process-safe manner and at the same time making the cleaning production step more efficient, the company invested in two Universal 81W cleaning systems from Dürr Ecoclean GmbH and in new part-specific cleaning containers designed and manufactured by METALLFORM Wächter GmbH.

Customized plant technology
for higher efficiency

“We talked to four equipment manufacturers and carried out test cleanings. Dürr Ecoclean not only gave us excellent advice, but was also able to offer the best system concept for our task,” reports Thomas Schmidt. The Universal 81W has a vacuum-proof working chamber in which the cleaning, rinsing and drying processes take place. Both systems are designed for a basket size of 670x480x300 mm (LxWxH) and a maximum batch weight of 150 kg. To ensure reliable cleaning of adhering particles and chips as well as residues of machining media, the working chamber is equipped with devices for high-performance injection flood washing and ultrasonic cleaning with a power of 10 watts per liter bath volume. Parts are dried by combined hot air and vacuum drying. “We also have scooped parts that were often still damp after cleaning in our previous continuous system. Thanks to vacuum drying, these workpieces now also come out of the system completely dry,” says Thomas Schmidt.

The new cleaning systems meet the different requirements for cleaning aluminum and steel parts with tailor-made equipment. For example, the system for steel and cast steel parts has four flood tanks. This allows the medium for the cleaning process step to be adapted to the workpiece (steel or cast iron) in each case. The third and fourth flood tanks contain the rinsing and preservation medium. The Universal 81W of the aluminum cleaning line is equipped with three flood tanks. A deionized water treatment system has also been integrated into this system for rinsing. The water quality is continuously monitored. “The rinsing with deionized water and the fast as well as complete drying is very important for the aluminum parts. It ensures that they are stain-free and that no discoloration forms,” explains the technology planner.

Around 80 percent of the parts are cleaned as set goods. Feeding takes place via an automatic loading device with buffer sections in the infeed and outfeed. Appropriate cleaning programs are stored in the plant controls. The part-specific program for the respective batch is selected either via a basket recognition system with sensors or manually. After the cleaning process, the batches pass through a cooling zone so that they can then be packed immediately.

The media from all the flood tanks are passed through a full-flow filtration system in both the forward and return flow. Bag filters are used for the filtration of the cleaning baths, and cartridge filters for the rinsing and corrosion protection media. This enables a very effective discharge of particle contaminations. Filmic contaminations such as emulsions are removed by the Aquaclean system in addition to the oil separator. It evaporates the liquid from the flood tanks, the condensate is returned to the process circuit, and the remaining dirt is collected in the Aquaclean tank. This treatment extends the service life of the baths and plant downtime for bath changes is reduced.

Flexible baskets
designed for cleaning

In order to fully exploit the potential of the systems, Allweier has also invested in new cleaning baskets. The parts can be positioned in these containers to ensure maximum cleaning and drying performance. The task with which the company approached four manufacturers was: The parts must be placed and fixed in the basket in the best possible way for protection and rotation. This is because during the cleaning process, the baskets are swiveled and rotated by up to 360 degrees. At the same time, each basket should hold the largest possible number of parts without impairing the accessibility of the medium or the ultrasound to the parts and thus the cleaning effect. Also on the list of priorities was ease of handling. “The first phase involved containers for ten different parts. The companies received identical documents from us for this purpose. Even in the offer phase, METALLFORM clearly stood out from the other suppliers. For example, we received 3D design drawings of the baskets with parts in them and I could immediately imagine how the part would be placed and fastened in the basket. The consultation was and is also excellent. There is a lot of competence behind it and everything is properly thought out,” Thomas Schmidt explains the decision for METALLFORM Wächter GmbH.

In addition to various rigid, part-specific workpiece holders for so-called high demand parts, different partially and fully flexible solutions were realized. These are designed in such a way that they can be used simulaneously for different components or component families and can be quickly and easily adjusted by the operator during operation for the respective component to be cleaned. “METALLFORM provides us with optimum support in reducing the required number of workpiece holders through flexible solutions. We not only benefit in terms of investment costs, but also in terms of space requirements,” reports the technology planner. This includes, for example, a workpiece holder for ring housings made of aluminum with diameters between 240 and 320 mm and lengths of 20 to 100 mm. Here, displaceable prismatic plug-in rakes, which are inserted into basic carriers, enable the various parts to be securely held and fixed. At the same time, the part holders can be positioned in such a way that the workpieces only rest at non-critical points. METALLFORM developed a completely variable system for disk-shaped components with a wide range of diameters. It consists of two different inserts, one of which determines the number of compartment rows, the other the compartment depths. In this way, compartments can be formed in no time at all to securely hold the parts in a MEFO-BOX or the base frame. They are fixed in place by spring-loaded locking pins.

All workpiece holders and cleaning baskets are made of stainless steel round wire with an electrolytic polished surface. The round wire makes the parts easily accessible for medium and ultrasound from all sides. At the same time, optimum dripping behavior is achieved, thus minimizing dirt and media carryover. In addition, the round wire reduces the contact surfaces. And these can be selectively sheathed with Teflon tube in the form of clips to protect the components.

Better quality and
higher efficiency

The combination of the new cleaning systems and baskets enables Allweier not only to achieve the required technical surface cleanliness for all parts in a process-safe manner, but also to go below it. “We regularly carry out laboratory analyses and these have shown that we achieve a significantly better cleaning result. Compared to the continuous cleaning system, we no longer need compressed air for drying. In addition, the cleaning process is now so effective that the production from three shifts can be cleaned in just under two shifts. As a result, we naturally also work more efficiently,” Thomas Schmidt summarizes.