WEISS North America reviewed Werner Geissler’s test system situation and recommended a conversion to its TO series of direct drive rotary table to drastically cut cycle time. WEISS (Buchen, Germany), and its’ subsidiary WEISS North America, Inc. (Willoughby, OH), is the industry leading specialist for rotary tables and automation.
Werner Geissler GmbH (Elzach, Germany) has been producing precision turned parts for forty years predominantly for the automobile and automotive supply industry. Where as speed is the name of the game in automotive suppliers market, Geissler recently sought out a solution to accelerate cycle times for a test bench that performed the final inspection of precision turned parts. At the heart of the system was a pneumatic rotary indexing table which had reached its limits and was no longer able to produce the desired shorter cycles.
The goal of Geissler’s custom machine building department was to replace the existing pneumatic tables with a more efficient electrical direct drive rotary table – as the automotive industry demands that final inspection results need to be 100%.
PNEUMATIC PRODUCTION PROBLEM
At issue was the case for tension screws for the common rail injection systems for a specialist automotive supplier. The production from 25 CNC automatic lathes runs through a single test bench. A rotary indexing table feeds the components to the test stations, where cameras, lasers, and spreading fingers check the dimensions in 2.6-second cycles. If the machine fails, inspections need to be performed by hand−which is costly, time-consuming, and occurs approximately every four weeks.
This is when regular maintenance of the pneumatic rotary indexing table takes place as the short cycle times push the table to its mechanical limits.
Additionally, after one month the shock absorbers and parts of the mechanics need to be replaced by Geissler’s in-house custom machine building department; which also designed and built the test bench. This frequent maintenance was taken into account during the development as the rotary indexing table was kept easily accessible so that the shock absorber unit could be replaced quickly.
TO 220 DIRECT DRIVE ROTARY TABLE PRODUCTION SOLUTION
Initial WEISS consultation suggested a fixed-cycle, electro- mechanical rotary indexing table from their TC series. This would have easily halved the previous switching time of one second. Upon further investigation, the parties discovered that the direct drive, user programmable TO220 torque direct drive rotary table with a switching time of just 0.3 seconds under current conditions was an optimal solution.
This would cut the cycle time of the test bench from 2.6 seconds to 1.9−generating time-and-cost savings which would recoup the cost of the somewhat more expensive direct drive table within just three months.
Installation of the TO presented advantages as the rotary indexing table is easily accessible and not the core element of the whole system−as often is the case. Although the programmable, gentle approach ramps of the TO eliminate the hard impacts caused by the pneumatics, some unpleasant oscillating motions did occur. The cause of this was quickly identified and remedied. The external arrangement of the rotary indexing table means that the whole construction acts like a torsion spring, which leads to unpleasant undulations because of the direct drive’s larger dynamics. Bracing the substructure solves the problem.
Finally, Geissler’s master electrician leveraged the WEISS Application Software (WAS) which enabled simple and intuitive commissioning of the system’s most important parameters.
The graphic user interface series also provided clear and in-depth programming with a faster (approximately 15 minutes) set-up, and smooth operation−saving valuable time-and-cost. Additionally, it only took a few minutes to connect the inverter to the control system via the Profibus. The easy-to-use WAS also made it possible to optimize the approach ramps and further cut switching times.
The sum of these elements means that the test machine can get back to checking quality on schedule.
TO 220 DIRECT DRIVE CONCLUSION
According to Christian Nemeth, Geissler’s head of custom machine building,
“The extremely fast cycle times and, in particular, the absence of maintenance of the direct drive WEISS rotary indexing tables were the reason for the conversion. The good service and active support during start-up also impressed us.”
Nemeth also noted that he’s already decided that a test bench, which is still under construction, will be converted to a direct drive rotary indexing table. Additionally, he plans to design the next test bench on the basis of a TO from WEISS right from the outset.