On-Machine Measurement Ensures Quality Production

Contract manufacturer Helmut Christmann GmbH has earned its reputation as a premier manufacturer of high-precision parts by employing a variety of different production techniques and carefully monitoring parts with sophisticated on-machine measurement technology. In order to achieve the necessary precision and assure process safety in production, the company relies on machine-integrated production measurement technology from Blum-Novotest (Erlanger, KY).

In addition to Blum’s touch probe, Christmann uses its laserControl laser measuring system for on-machine measuring on its horizontal machining centers.

With a workforce of 40 people, Helmut Christmann GmbH, based in Birkenfeld near Pforzheim in the Baden region of southwest Germany, manufactures high-precision, often extremely small, fine mechanical components. Its customers are found in a wide variety of manufacturing sectors, from medical technology to electronics. Lot sizes can vary from one to 20,000 parts per year.

The company was founded shortly after WWII by the grandfather of the present-day CEO, Marcus Christmann. The company initially made watch cases and components for watch and jewelry manufacturers. Historically, Pforzheim is renowned for its goldsmith trade. In the 1980s, Christmann became a contract manufacturer, which entailed a move into toolmaking and specialization in machining complex, high-precision, progressive composite dies.

“We specialize in high-precision parts involving a number of different production techniques. We turn parts that are just 0.2 mm in diameter, and carry out electrical discharge machining [EDM] on wire that is just 0.03-mm thick,” said Marcus Christmann.

“We mass-produce carbide metal with a contour accuracy of ±0.002 mm. To assure such levels of precision, we employ workpiece and tool measuring technology on our machining centers,” said Christmann. Whereas many other contract manufacturers specialize 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 as well as in the measuring technology that is so important to production of quality precision parts. Today, in-machine measurement is a common practice in milling processes. Probes are mounted on toolholders 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 and model chosen.

Christmann specializes in manufacturing high-precision parts and relies on precision measurement involving different production processes.

The result is that complex measuring tasks can be automatically integrated into machining programs without the 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.

Based on their successful experience with Blum’s measuring technology using both touch probes and lasers, Christmann turned to the measuring technology specialist when the need for in-lathe measurement 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 in the machining area throughout the machining process and is thus exposed directly to chip impacts, as well as shock impact, and vibration. The machining environment can be very severe and damaging to workpieces 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, for example, 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. For many production orders, regular measurements are required, so that the operator had to continually go back and forth to perform the 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 also employs Blum’s LaserControl system for tool breakage detection and in-machine tool monitoring during operations. The system detects and compensates for tool wear in the process, and broken or excessively worn tools can be automatically replaced by a matching tool as needed 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 that 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, and the installation process and staff training were also handled efficiently and without any problems.”