Top Quality by Radio

To automate its manufacturing process for shredding rollers, HSM GmbH & Co. KG has installed Blum-Novotest’s TC63-30 radio touch probe on a turning and milling centre from Gildemeister. New BRC radio technology ensures reliable data transmission, permitting a reduction not merely in set-up and machining times.

Even secret services such as the CIA or the FBI put their trust in HSM Level 6 document shredders, which convert one page of A4 paper into 15,000 individual particles only 1 x 5 millimetres in size. They therefore far exceed standardised security levels, which at level 5 permit particles of 0.8 x 12 millimetres. Now HSM is making document shredders which cut paper into 0.65 millimetre-wide strips. HSM also has the right equipment for high throughputs – conveyor belt document shredders can swallow complete files and shred them as required.

In addition to the document shredders, HSM’s range includes two other product groups: baling presses are used to compress paper, sheeting, board or other materials into compact bales, for example in supermarkets, where the method is used to prepare packaging material for disposal. Smaller presses are designed in the form of vertical presses, in which the pressure ram presses onto the material from above and forms the bale; here the pressing force ranges from 5 to 60 tonnes. For larger volumes, channel baling presses are offered into which the material is thrown from above, following which the horizontally placed ram compresses the material to be pressed horizontally. This produces a virtually continuous bale which, depending on the customer’s requirements, is tied off to a specific length. Hydraulic pressures between 8 and 120 tonnes are used.

Every supermarket now has a PET bottle reverse vending machine which immediately compresses the bottles collected. HSM supplies the appropriate PET crushers to the vending machine manufacturers and is thus de facto the market leader. The crusher perforates the bottle and compresses it in such a way that the perforations hook inside one another and the bottle remains flat.

In the spotlessly clean workshops of HSM’s Production Department in Salem the first thing that strikes you is the volume of bar stock ready for machining. Whether document shredders or crushers, a large proportion of the products manufactured here have rollers which draw in and shred the material. A complete range of machining centres is available for manufacturing these rollers, some of which are deeply grooved and mesh with each other when fitted or are equipped with knife edges. The machining centres are fitted with bar stock and then run their program more or less automatically.

“The demands on the quality of the rollers are very high: if two rollers with 0.65-millimetre wide grooves are meshing with each other to cut up paper into the finest strips, the smallest tolerances are required – after all, the rollers are not designed to touch each other when rotating. To achieve these accuracies, the rollers are first rough-machined, then this initial cut is measured and the adjustment parameters for final machining calculated”, says Marcus Winter, foreman in the Mechanical Production Department and Divisional Head of Turnery. This is carried out for every individual roller – previously, the machine had to be stopped in the middle of machining as well and the door opened, only then was machining continued. One alternative would have been to finish machining completely with no measuring and re-adjustment, but then scrap would have been higher. Last but not least, the enforced stoppage of the machine disrupted the workflow and costs time, because at HSM one worker operates two, and in the case of large-run production, even three machines.

Today, the TC63-30 touch probe from measuring technology specialists Blum-Novotest of Ravensburg is kept in the tool shop. If a measurement has to be performed on an automated basis before or between machining stages the touch probe is simply exchanged like a tool and the relevant measuring points collected. “Data is transmitted not, as is otherwise the norm, by infrared but via radio. The Blum probe is supplied with power via two lithium batteries which, at a normal capacity utilisation of 5%, provide power for approximately four months. The readings are relayed via infrared or – as is the case at HSM – via radio to a receiver in the workroom”, explains Winfried Weiland, Marketing Director of Blum-Novotest.

HSM had also been working for many years with Blum laser measurement systems, for example for checking tool cutting edges in unmanned production or for the length and radius measurement of tools. For almost three years now, probes have also been used in the machining centres – at the start with infrared transmission. These are reliable but, especially in the machining centres on which the rollers are produced, placing the infrared receiver is very difficult. As the turning and milling centres have swivel heads, it is virtually impossible to guarantee free line of sight in every position between the touch probe and the receiver. This is why the specialists ordered the first radio probes a few months ago.

Instead of transmission via the channel hopping method or channel allocation, which is the market norm, the TC63-30 transmits its data using the BRC technology promoted by Blum. The advantage of this technique lies in the fact that every bit of a radio signal is transmitted over a large frequency range, making the transmission particularly immune to parasitic inductions. Otherwise, the Blum technology scores thanks to its very short transmission time. “Radio touch probe systems usually require ten milliseconds and more to transmit the switch signal. In practice, however, what happens is that users measure with a different measuring speed than the one with which the system was calibrated, as a result, significant measuring errors can occur. The reason for this can either be the user’s fear of a collision with the workpiece or the mistaken belief that a lower measuring speed means a more precise measurement. As BRC technology only requires 2.5 ms for the transmission, this error can be virtually eliminated”, explains Erhard Strobel from Blum-Novotest’s Technical Sales Department.

This is confirmed by HSM’s experts, who enjoy absolutely interference-free transmission using the radio probes. It also has a direct payoff, because if the data transmission fails to work the system comes to a halt and the operator would then have to intervene manually. HSM aims to generate the complete test record while machining is being carried out and to file it in SAP so the rollers would not have to be taken first to the Quality Assurance Department to check for machining errors but could continue to be machined directly.

For HSM, geographical proximity to Blum-Novotest is a big advantage. When they accidentally dropped a probe on the floor at their factory they received a replacement extremely quickly and, as a result, only suffered a very brief downtime. This happened despite the fact that in their experience Blum probes withstand considerable wear and tear and are more robust than other probes they had already used. This is especially the case since Blum probes are resilient not only to mechanical stress but also during the measurement process. Because the saying 'First clean, then measure' is actually true. However it does not matter for a Blum probe, it will not be affected by cooling lubricant. In addition, the probes can be used flexibly thanks to their modular construction and can be used with very light extensions made of carbon even at measuring points which are very difficult to access.

“Our entire collaboration with Blum-Novotest is very positive. Set-up times have fallen considerably due to the Blum probes, in some cases by over 50 per cent. Previously, for zero point recording and measurement of the initial cut, the machine had to stop and the operator had to measure by hand and enter the values into the machine control, a process which was also prone to error. Now measurement is integrated into machining and we can manufacture extremely efficiently in three shifts with multi-machine operation”, sums up Marcus Winter.


For further information:

Blum-Novotest GmbH
Production Metrology
Kaufstrasse 14
88287 Grünkraut
Germany

Tel: + 49 (0) 751 6008-0
Fax: + 49 (0) 751 6008-156
E-Mail: vk@blum-novotest.com
Web: www.blum-novotest.com