Ultrasound-based fine cleaning of carbide and high-speed steel cutting tools

A cleaning process for optimum coating adhesion

In machining technology, the trend is towards ever increasing speeds, accuracy and tool life – and the KOMET GROUP addresses these requirements with innovative tool developments relating to, e.g., indexable inserts, drills and the associated coatings. A special cleaning process developed by UCM AG of Switzerland helps to optimize coating adhesion.

Established in 1918, the KOMET GROUP is a leading full-range supplier of high-precision tools and an internationally acknowledged technology and innovation expert. The group headquartered in Besigheim/Germany views itself not just as a toolmaker but as a creative partner covering the entire machining process chain. Its core competences lie in the development, manufacture and sale of customer-focused solutions and forward-looking services meeting worldwide demand from, e.g., companies in the automotive and aircraft manufacturing, mechanical engineering, shipbuilding and agricultural equipment industries as well as from the energy technology sector. The KOMET GROUP serves their needs with the aid of 22 subsidiary companies and 50 agencies around the globe.

Cleaning – a critical determinant for coating quality

The cost-efficiency, productivity, precision and durability of machine cutting tools are key criteria in KOMET's development work. To achieve such performance the company relies on advanced production technologies. On the other hand, it employs new alloys and materials as well as coatings applied by the PVD and CVD processes.  For optimum adhesion of the coating layer, the parts are subjected to aqueous cleaning before the coating is applied. This involves the residue-free removal of contaminants from prior machining processes, e.g., oils, emulsions, polishing pastes, chips and abraded particles. A cleaning system fitting this bill was in place at the company's Cutting Materials product center where it handled indexable inserts and rotationally symmetric parts such as drilling, boring and ID turning tools made of carbide and high-speed steels.  However, this system was getting on in years and prone to breakdowns, so it came up for replacement in 2012.

Not just equipment but a complete process

„In making our choice, it was important to us that the vendor should be knowledgeable about the task of cleaning cutting tools. Also, what we wanted was not just equipment but a complete cleaning process. The cleaning chemicals should preferably be available from our proven supplier, and the system should be appropriately equipped or the process parameters adjusted accordingly', reports Timo Maier, head of production grinding at the KOMET GROUP's Cutting Materials product center, who oversaw the "New Cleaning System" procurement project.

In the bid phase, five equipment manufacturers were involved and cleaning trials were conducted at two of them. The specification called for a "ready for coating" level of part cleanliness. Moreover, there had to be no corrosion of parts consisting of high-speed steel, nor any cobalt-leaching from carbide tools in the cleaning process.

The winning bid was presented by UCM AG of Switzerland, a SBS Ecoclean Group company. 'What convinced us about UCM, on the one hand, was the way their process was designed in cooperation with our existing chemicals supplier. On the other hand, we liked their high-grade mechanical engineering and the workmanship quality', Timo Maier justifies his company's decision.

Cleanliness "as needed" and extended bath life

The cleaning system devised by UCM comprises seven immersion tanks. Of these, two are used for cleaning with an alkaline and acidic fluid, respectively, one is for preservation of the high-speed steel parts and the remaining four are dedicated to rinsing operations. In the last rinse, de-mineralized water is used to obtain stainless part surfaces. Both cleaning tanks and the preservation tank are fitted with ultrasound units of variable output to match the specific part characteristics. 'Every cleaning station has its dedicated oil separator to remove film-type contaminants from the cleaning fluid straight away. This makes for a long bath life", adds Marius Knoll, head of KOMET GROUP's production coating and testing department which actually runs the cleaning system. Particulate matter is removed via cartridge filters.

Another feature contributing to the good cleaning performance and long bath life is the four-sided overflow system developed by UCM, which is used at all stations. In every tank, the cleaning or rinsing fluid is introduced from below, moves upwards, and then flows out over the rim on all sides. Foreign matter and particles dislodged from the product are thus discharged from the tank without delay. This avoids re-contamination when the parts are lifted out of the bath and prevents the formation of dirt pockets in the tanks. At the same time, a uniform and intense cleaning action is thus ensured. The parts are dried with hot air.

Fully automatic operation – for high throughput

Indexable inserts and boring tools are arranged in part carriers for the cleaning cycle. The customer's own part carriers are placed in the machine racks which circulate continuously on a conveyor. Accordingly, they remain in the system while part carriers are loaded and unloaded, and are picked up by the transfer unit in defined positions. Every load has its own punch card determining the part-specific cleaning program. For a future automatic program selection, UCM has prepared the system so as to support the use of RFID chips. 'Integrating the RFID functionality is not yet required as we get along with two cleaning programs at this point', Timo Maier explains. In its standard version the system is capable of storing 16 programs.

To meet the need for high throughput rates, the system is equipped with two transfer units. The first of these moves the load to the center of the line and then returns for the next load, while the second transfer unit handles the flow of parts through the dryer and beyond. ‘We've been using this system for about two years now and are very satisfied with the cleaning result. Moreover, the process has become more cost-efficient, not least because of its high availability rate of over 99%’, Marius Knoll sums up his company's experience.

Author: Doris Schulz