Supplier optimizes part cleaning to match changed requirements
When handling a portfolio of around 1,000 different parts it is no easy task to fulfill growing demands on technical surface cleanliness reliably. In order to meet this challenge, the precision part supplier Allweier not only invested in two new custom-equipped cleaning systems but also acquired a set of versatile cleaning tanks built to match the needs of the cleaning process. Thanks to this combination, the machining contractor meets all cleanliness specifications in a forward-looking and tangibly more cost-effective manner.
In the field of transmission engineering, Allweier Systeme GmbH has been a major player for close to 10 years. Allweier Präzisionsteile GmbH was established more than four decades ago as a vendor and system / development partner for machining solutions. The core competencies of this family-owned enterprise headquartered at Überlingen/Germany, on the shores of Lake Constance, lie in CNC turning, milling and grinding services as well as in module and component assembly. The company owns an extensive pool of highly advanced equipment for machining aluminium parts (including castings) in addition to steels, cast iron, cast steel, titanium, and special materials. Its portfolio currently comprises around 1,000 different items for diverse applications in mechanical engineering, plant construction, automotive manufacturing, conveyor technology and robotics, marine and offshore systems, optical and medical equipment, railways and other sectors. In all, Allweier processes around 20 million parts each year.
„Cleaning the machined parts poses quite a challenge, on the one hand, because of the sheer diversity of materials, part geometries and dimensions. On the other hand, demands on the technical cleanliness of surfaces have grown significantly over the last few years. Requirements such as 'zero particles larger than 600 µm' are common today, and steel parts need to be perfectly protected against corrosion as well“, explains Thomas Schmidt, Technology Planner for Rotary Machining Processes at Allweier Präzisionsteile GmbH. In order to reach the specified levels of cleanliness with due process reliability while boosting the efficiency of the cleaning step in the manufacturing chain, the company invested in two Universal 81W cleaning systems from Ecoclean GmbH plus a set of custom-designed cleaning tanks designed and manufactured by Metallform Wächter GmbH.
„We talked to four equipment manufacturers and conducted cleaning trials. Ecoclean not merely gave us excellent advice but also offered the equipment solution best suited to our task“, Thomas Schmidt reports. The Universal 81W has a vacuum-tight working chamber in which its cleaning, rinsing and drying operations take place. Both systems ordered are designed for a basket size of 670 x 480 x 300 mm (LxWxH) and a maximum charge weight of 150 kg. In order to ensure a reliable removal of adhering particles and chips as well as of machining fluid residue, the work chamber is equipped with a high-performance injection flood washing function plus an ultrasonic cleaning system with a power rating of 10 watts per liter of bath volume. The parts are dried by combined hot-air and vacuum treatment. „We also have parts with cavities which often were still moist upon leaving our old continuous cleaning line. Thanks to vacuum drying, these products now come out 100% dry as well“, Thomas Schmidt adds.
The different requirements on cleaning aluminium and steel parts are addressed by tailor-made configuration of the new cleaning systems. Thus, the system for steel parts and steel castings has four flood tanks. This makes it possible to adapt the fluid used in the cleaning step to the given part (i.e., steel or casting). The third and fourth flood tanks hold the rinsing and preservation fluids, respectively. The Universal 81W on the aluminium cleaning line is equipped with three flood tanks. It comprises an additional treatment system for the demineralized rinsing water. The quality of this water is monitored continuously. „With aluminium parts, it is very important to rinse with demineralized water and to ensure quick and complete drying. This ensures that the parts will remain free of stains and discolorations“, the Technology Planner explains.
Around 80 per cent of all parts are cleaned in defined position. Parts are supplied by an automatic feeding system comprising buffer sections at the entry and exit. Appropriate cleaning programs are stored in the system controllers. The part-specific program for each load is selected either by a basket identification system using sensors, or manually by the operator. After the cleaning process the parts pass through a cooling zone from which they emerge ready for immediate packaging.
The fluids from all flood tanks are subjected to full-flow filtration in the supply and return lines alike. While the cleaning fluids are run through bag filters, cartridge filters are used for the rinsing and anti-corrosion fluids. This system yields a highly effective removal of particulate contaminants. Film-type contaminants such as emulsions are removed first by the oil separator and then, for additional cleanliness, by the Aquaclean system. The latter evaporates the fluid from the flood tanks and returns the condensed liquid into the process circuit while collecting the dirt residue in the Aquaclean tank. This fluid treatment method increases bath life while also reducing the equipment outage times necessitated by bath changes.
In order to realize the full potential of their new systems, Allweier invested in a set of new cleaning tanks at the same time. These allow all parts to be variously arranged inside for maximum cleaning and drying performance. The requirement spelled out by the company to its four candidate suppliers was that all parts had to be protected as effectively as possible in the tank, apart from being arranged and secured so as to withstand rotation. After all, the baskets are swung and turned through up to 360 degrees in the cleaning cycle. Moreover, each tank needed to hold a maximum number of parts without restricting fluid or ultrasound access to the product and hence, impairing the system's cleaning action. Ease of handling was likewise high on the priority list. „In the first phase we were looking at tanks for ten different parts. With that objective in mind, all companies received the same documentation from us. Metallform stood out among the other vendors as early as in this bidding phase. For instance, they supplied 3D design drawings of the tanks with product arranged inside, so I was able to imagine at once how the part would be placed and fixed in the basket. Their consulting service, too, was and continues to be excellent. All this is backed by plenty of competence and in-depth analysis", Thomas Schmidt explains his company's decision in favour of Metallform Wächter GmbH.
In addition to a range of rigid, part-specific product carriers for fast-selling parts, a variety of different semi-flexible and fully flexible solutions were implemented. These are designed to be used for different components or component families at the same time and to be quickly and easily adaptable to another part by the operator while production continues. „Metallform is showing us optimum support in reducing the necessary number of part carriers by providing flexible technology. We derive benefit from this not merely by saving investment cost but also through reduced space demand on the shop floor“, the Technology Planner explains. For instance, the range comprises a part carrier for aluminium annular housings measuring between 240 and 320 mm in diameter and between 20 and 100 mm in length. Relocatable prism-type rake supports inserted into the basic carrier allow different parts to be reliably accommodated and secured. At the same time, the part fixtures can be arranged such as to be in contact with the parts at uncritical points only. For disc-shaped parts of diverse diameters, Metallform developed a fully variable system. It consists of two different inserts of which one defines the number of shelf rows while the other defines their depth. It is thus possible to create a part-holding structure in no time, whether in a MEFO box or in the basic rack. Locking is by means of spring-loaded snap engagement bolts.
All part carriers and cleaning baskets are made of round stainless steel wire with an electropolished surface finish. The round wire makes for good all-round fluid and ultrasound access to the parts. In addition, optimum draining properties are ensured while dirt and fluid carryover is minimized. Moreover, the round wire provides a reduced contact surface area. Local sheathing in clip-on Teflon tube sections for additional part protection is an option.
This combination of new cleaning systems and tanks enables Allweier to not only reach, but in fact outperform technical cleanliness standards for all parts in a reliable manner. „We carry out periodic laboratory analyses, and these have shown that we are achieving a much better cleaning result. Unlike our previous continuous cleaning line the system requires no compressed air for drying. Moreover, the cleaning process is so effective now that the parts made in three shifts can be cleaned in just around two. So it goes without saying that we are working more efficiently as well“, Thomas Schmidt concludes.
Author: Doris Schulz