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- Measuring Components

Production measurement technology from BLUM at Christmann

Helmut Christmann GmbH based in Birkenfeld near Pforzheim in the Baden region of south-west Germany has made a name for itself as a contract manufacturer of high-precision parts involving a variety of different production techniques. In order to achieve the necessary precision, and assure process safety in production, the company relies on machine-integrated production measurement technology from BLUM.

"We specialise in high-precision parts involving different production techniques. We turn parts that are just 0.2 millimetres in diameter, and carry out electrical discharge machining (EDM) on wire that is just three hundredths of a millimetre thick," reports CEO Marcus Christmann. "We mass-produce carbide metal with a contour accuracy of plus/minus two thousandths of a millimetre. To assure such levels of precision, we employ workpiece and tool measuring technology on our machining centres." Whereas many other contract manufacturers specialise in one production technique, Christmann operates a large portfolio of machinery covering a wide range of different processes, from milling and turning to EDM and grinding. The company has acquired advanced levels of know-how in the production of high-precision parts over a number of years – including in measuring technology.

In-machine measurement is a common practice in milling processes nowadays. Probes are mounted on tool holders and fitted into the spindle as required. The machine then scans the desired measuring points. The measurement signals are relayed to the machine optically or wirelessly, depending on the design variant. This means complex measuring tasks can be automatically integrated into machining programmes, with no need to unclamp the workpiece, transport it to the measuring room, and clamp it back on. Eliminating the need to remove the workpiece is especially important in the production of high-precision parts, as it is practically impossible to clamp a workpiece twice in an absolutely identical way. In-machine measurement also saves a great deal of time, as well as reducing scrap rates.

The LaserControl NT-H laser measuring system measures tools in the horizontal machining centre.
The LaserControl NT-H laser measuring system measures tools in the horizontal machining centre

Based on their good experience with BLUM, it was logical for Christmann to turn to the measuring technology specialist when the need for in-lathe measurement also arose. Machine-integrated workpiece measurement is less widespread for turning than for milling, because the tools are often mounted on a revolver within the machine's working area. Consequently, the touch probe is directly involved in the maching area throughout the machining process, and is thus exposed to chip impacts, as well as shock impact and vibration, which can be very severe when performing interrupted cutting, for example.

Moreover, external measurement accompanying the turning process was extremely time-consuming. The machine operator had to take a part out of the machine after machining and transport it to the measuring room for measurement. In the meantime, the machine continued producing, which meant that, at a machining time of 10 minutes per part, two additional rejects might be produced while the operator was measuring and discovering an inaccuracy. External measurement also prevented the operator from overseeing multiple machines simultaneously, as for many production orders Christmann has to perform regular measurements. So the operator was continually going back and forth to perform measurements.

Consequently, Christmann began looking for a way to increase its unit volumes. It quickly found that in-machine measurement substantially reduced external measuring times. This enabled one operator to oversee two machines – and eliminated the production of rejects during measurement processes. The BLUM TC54-10 T touch probe proved to be a very good solution to this problem.

Christmann GmbH specialises in high-precision parts involving different production techniques.
Christmann GmbH specialises in high-precision parts involving different production techniques

Christmann also employs BLUM's LaserControl system for tool breakage detection and tool monitoring in machine operation. The system detects and compensates for tool wear in the process for example. Broken or excessively worn tools can be automatically replaced by a matching tool as and when necessary. Another benefit of machine-integrated laser measurement is that the tools are measured at nominal spindle speed and in the actual tool clamping situation. This means, for example, that clamping errors are detected, or factors such as length- and temperature-related spindle displacement are recorded and compensated. Marcus Christmann's appraisal is thoroughly positive: "When we are next planning a new acquisition, we will without doubt again choose a product from BLUM. They simply do everything right. The installation process and staff training were also handled without problem."

With a workforce of 40 people, Helmut Christmann GmbH based in Birkenfeld near Pforzheim manufactures high-precision, often extremely small, fine mechanical components. Its customers are in a range of different sectors, from medical technology to electronics, and lot sizes range from one to 20,000 parts per year. The company was founded shortly after the Second World War by the grandfather of the present-day CEO. The company initially made watch cases and components for watch and jewellery manufacture, based in the city of Pforzheim, which is renowned for its goldsmith trade. In the 1980s Christmann became a contract manufacturer. This also entailed a move into tool-making, and specialisation in complex, high-precision progressive composite dies.