Measuring Systems for Medical Engineering Company

1.2 Million of Satisfying Tool Changes

Reliability, speed and precision – these are the features of the LaserControl NT by Blum-Novotest convincing S. + A. Martin since 2002. These manufacturers of surgical instruments in Tuttlingen are using the laser measuring system on four machining centers in unmanned, round-the-clock operation.

Because of their nearly 600 companies specialising in this field in the Baden-Württemberg area, Tuttlingen is often called the „world capital“ of surgical technics. This concentration has its origin already in 1867 when standardisation of production of surgical instruments started. An increasing number of competing resp. complementary companies developed in this field. Today Tuttlingen is characterized by manufacturers and dealers of surgical products as well as by specialised suppliers like special tool manufacturers, burnishing, galvanising and providing companies. Almost 150 years after its commencement surgical technics from Tuttlingen stands as a synonym for high-quality surgical instruments, innovative implant technologies and minimal invasive surgery.

S. + A. Martin GmbH + Co. KG situated in the area of Tuttlingen in Rietheim-Weilheim are also very successful in this field. Founded in 1937 and now in their 3rd generation, this family business with 10 employees produces surgical instruments especially for American key accounts. Bone cutting/punching instruments are in their product range, mainly used for spinal disc operations, forceps to hold vessels and tissues as well as titan acutenaculum which are very light and unmagnetic.

In order to be successful in this competitive field a modern, automated machinery is basically required. With their three Hermle milling machines, two of them are loaded by robots, and their Robotdrill by Fanuc which they bought last year and which is milling a workpiece in half of time as it does their old 5-axis CNC-milling machine, Martin is up-to-date. A very important role has the measuring technology by Blum-Novotest which was installed in 2002. On all four machines they are using LaserControl NT which was specially developed for the rough working conditions in machining centers. The systems are used for simple tool breakage detection and non-contact tool setting in length and radius, single cutting edge control, setting and concentricity control as well as form and wear control. Additionally they are using Blum touch probes  – the TC52 on the FANUC, and the TC50 on two of the three Hermle machines. The probes are almost used for automatic workpiece measurement and have been convincing from their first application due to their speed and accuracy.

The operating tasks at Martin are clearly regulated. Turning parts are externally produced by specialists, Martin is milling, mounting, polishing, grinding and finishing the parts in their works for the endusers. The machining centers are working unmanned, round-the-clock. This is possible thanks to the Blum laser system. Each used tool is measured with this system in µm. If e.g. a new tool is changed-in it is measured first and the defined length and radius values are transferred into the tool correction memory. Error sources as typos belong to the past and nobody wonders about the fact that the available tool presetting device is not used.

Martin are using different tools. These can be very small drills up to a diameter of 0.8 mm but also e.g. shaft milling cutters, sawing blades and radius milling cutters. Except of tool setting the system is also used for tool control between the machining steps. Concerning the sawing blades Martin executes a single cutting edge control, the drills are checked for breakage within seconds. The shaft and radius milling cutters, however, are scanned in single cutting edge control. They are defining a wear tolerance in the cycle. If the system realises the wear limit it is replaced by a sister tool. The specialists of Martin are following an intelligent measuring strategy: The tool control is executed after machining. If the tool is ok they know that the workpiece is ok, too. If the laser realises that the tool is broken or blunt or that a sawing blade has a breakout the complete pallet is taken automatically out of the machine and a new pallet is changed-in. In this case the FANUC machine gives an error message. The reason therefore is that it is not equipped with a robot system.

Otherwise Martin has the problem with some tools that a built-up edge arises material-conditioned on the milling cutter – then it must also be exchanged. This is also detected by the laser system as its length or radius values are out the tolerance given by the operator. „We only have the phenomenon of a built-up edge with steel. With titan we don’t have this problem. During machining we are checking the tool for wear and breakage. If the laser system detects an error this is no problem as there are each 2 milling cutters in the tool magazine of the machine,“ explains Ludwig Martin, surgical mechanic at S. + A. Martin.

High-precision measurement in polluted surroundings means an enormous challenge. Coolant is absolutely necessary for the production, however, at the first sight it is a risk for serious measuring errors. “In order to avoid pollution of the optics, the measuring system is sealed mechanically against coolant during operation by a pneumatically operated piston. Furthermore the rotating tool is cleaned with air pressure before measurement. During measurement barrier air protects against pollution. In order to avoid early trigger signal generation and faulty measurement by falling coolant drops, since 2002 the systems are equipped with the patented NT-Technology. By means of this technology and the usage of an integrated micro-processor the measuring system can carry out a so-called “pulling” measurement which eliminates interferences by coolant” explains Erhard Strobel, technical sales of Blum-Novotest.

The system is not used for tool control only but also for thermal machine compensation. If the machine was not in operation during the weekend or if there are thermal variations in the production hall the machine experiences a change after commissioning which causes dimensional deviations on the workpiece. „This problem can be solved by calibration with the laser system. A calibration pin with known dimensions is measured with the laser in X/Y- and Z-axis direction and the deviation to an already reference measurement is defined. The actual deviation is then compensated in the control as additive workpiece zero offset,“ explains Winfried Weiland, technical sales engineer at Blum-Novotest.

The probe systems by Blum have also delivered an optimal performance at Martin concerning zero point detection. The device is changed-in, then the part is clamped and the 3-4 programmed points on the workpiece, i.e. on the part which must be milled, are approached with the probe. Then the values are transferred automatically to the memory and the workpiece zero point is available. This cycle including the complete retrofit is done efficiently and without any problem within a few minutes. „Considering the way many companies are still working we have essential advantages thanks to the measuring systems by Blum: on the one hand we are essentially economic as workpiece setting is automatic and very fast. On the other hand such a system is much more precise than e.g. a simple edge probe which can be seen in the high quality of our surgical products“, explains Ludwig Martin.

Training and practice through Blum are very positively judged by Martin. As the systems are very reliable they had not many contacts to the service department but their questions have always been answered quickly. The best example were the problems with the circular saw blades in 2003: these special saw blades couldn’t be checked by LaserControl NT at that time because of their large number of teeth. In consequence Blum adapted the measuring cycles especially considering this application.

„LaserControl NT is not only a basic building block – it is essential! Without the measuring system unmanned operation would not be possible. And though we are working on a machine since 2003, 5.5 days a week in 3-shift-operation we never had any trouble. In this period we had approx. 1.2 million tool changes where the system was used – and absolutely no breakdown. For myself it is absolutely sure that we will buy the next machine with Blum systems,“ Ludwig Martin says very satisfied.





Editors´s notes:

Established in 1968 and based in Ravensburg, Germany, Blum-Novotest GmbH is recognized worldwide as a developer of leading-edge measuring and testing technology for international machine tools, aerospace and automotive industries. The family firm has more than 250 employees working in Germany, Great Britain, Italy, France, USA, China, Japan, Taiwan, Singapore and Korea. Together with skilled dealers (due to their technical competence called "system integrators") and regional sales offices they guarantee comprehensive service for thousands of Blum systems applied all over the world.




For further information:
 
Blum-Novotest GmbH
Production Metrology
Postfach 1202
D-88182 Ravensburg
Germany

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