Whether in building construction, civil engineering or mining, whether you’re a DIY enthusiast or a professional, when exact measurements are required, precise measuring tools are essential. Users must be able to rely on the accuracy of their measuring instruments when it comes to reading off a specific position, length, depth, distance, angle or circumference. Friedrich Richter Messwerkzeugfabrik GmbH & Co. KG, based in Speichersdorf, has over 90 years’ experience in the manufacture of high-quality measuring tools. This pioneer in the field of measuring tools ships its products to over 40 countries worldwide. The family-run business, now in its third generation, is also valued by customers for its ability to produce small batches and bespoke solutions. For example, it has even manufactured a tape measure with an impressive length of 1,200 metres.
It all began with the wooden folding rule, which is now complemented by many other measuring tools made from plastic, aluminium and special steels. As the product range has expanded and the instruments are used in a wide variety of conditions, the demands placed on their marking have also increased. Whether it is the printed scale or the product marking, both must withstand the rather demanding life of a measuring tool. Durable printing requires careful preparation of the surface to ensure that the applied ink adheres properly.
The following discussion focuses on the spirit levels produced by Richter in 11 different lengths and countless variants. A large number of these spirit levels are made from aluminium profiles, which must be thoroughly oiled before the recesses for the vials are punched out. However, this oil film – which is necessary for machining – must be completely removed before printing, as otherwise good print adhesion is impossible. Consequently, the profiles are first degreased; in a second, manual cleaning step, the surface to be printed was previously also cleaned of any remaining oil residues using a solvent. This manual, solvent-based process needed to be replaced for reasons of occupational health and safety, environmental protection (VOC Directive) and process reliability. A search was therefore conducted on the market for a cleaning technology that operates without solvents, can be integrated into the production line and delivers consistently good results. During his research, Jochen Kümmerl, Production Manager at Richter, came across the atmospheric plasma technology offered by TIGRES GmbH. He considered it suitable due to its compact design and the ability to integrate it into the existing production process.
At the TIGRES GmbH premises in Marschacht, the first aluminium profiles were precision-cleaned and then printed at Richter. The print quality and its adhesion were excellent on the spirit levels that had been cleaned using plasma, so a large-scale trial was carried out on the production line under series production conditions.
“During ultra-fine cleaning with atmospheric plasma, the thin film – invisible to the naked eye – that remains on the surface after degreasing is removed. In this process, the organic compounds are broken down, converted into the gas phase and mainly converted into CO₂,” explains Marcus Cardiello, a sales representative at TIGRES GmbH. “This is a dry chemical cleaning process that is carried out immediately before the printing run.”
Two Plasma CAT nozzles were integrated to cover the full width of the side surface. The treatment width of a single nozzle head is 25 mm, meaning that the entire area to be printed was fully covered (see Figure 1). From the first test in the series to the last, the results of the adhesion strength tests were very good and convincing.
“From the Tesa test and the abrasion test right through to the dreaded fingernail test, all the tests were passed and the future pre-treatment method for this application was finalised,” reports Jochen Kümmerl. “When purchasing our products, our customers expect ‘Quality Made in Germany’, which we can now guarantee even more reliably thanks to this new cleaning method.”
The cleaning system was integrated into the production line in no time at all and reliably cleans spirit levels ranging from 20 to 200 cm in length. But it is not just process reliability that has been improved. By replacing the manual and time-consuming cleaning step, cleaning time has been reduced by 50 per cent.
Richter Messwerkzeuge not only supplies products ‘Made in Germany’, but also ensures that its suppliers are ‘Made in Germany’. “For us, short distances to our suppliers, as well as quick response times in the event of downtime or for spare parts deliveries, are very important. In TIGRES, we have found a reliable partner in this regard, including for future projects,” explains Jochen Kümmerl.
This application demonstrates once again that the surface to be printed must be extremely clean in order to produce intricate print images, such as small text and barcode labels (Figure 2). The fewer organic contaminants that are ‘trapped’ between the substrate and the ink, the better the bond between the two.
