Goal: Minimize forces on thread flanks
In order to further develop their product portfolio, BIG Daishowa is continuously developing new tool concepts in-house at the MEGA Technical Center. One of the products that emerged from these efforts is the MEGA Synchro tapping holder. It is a “compensation chuck,” which uses elastic components to compensate for the synchronization errors between tooling machines and tools. The basic challenge threads pose is to minimize the differences in length arising from the spindle speed as well as the applied feed rate in relation to thread pitch and thread depth, in order to minimize the axial forces that arise on the thread flanks. High axial forces can have a negative impact on the thread flanks and result in decreased lifetime of the tap holder: “Although modern CNC machines are equipped with synchronous spindles, minor synchronization errors still occur,” says Masayuki Doi, development manager at BIG Daishowa. Even minor deviations immediately create high axial forces on the flanks of the tap holder.
Optimized construction thanks to cutting force measuring
In order to optimize the design of the MEGA Synchro, BIG Daishowa relied on a 3-component dynamometer from Kistler. The piezoelectric cutting force measuring device measures a compact 170×140 mm and can be mounted onto the machine tool table. It is exceptionally rigid and accordingly has a high natural frequency, which allows highly precise measurement of forces per cut even at high rotation speeds. “Due to the precise measurements obtained using Kistler’s dynamometer and the conclusions drawn from those, we have been able to tailor the design to such an extent that the forces on the thread flanks have been drastically reduced,” Doi states. In concrete terms: For tapping with a collet chuck, axial forces exert up to 750 N on the tap. Whereas when it comes to MEGA Synchro this is at max. 60 N. This increases the lifetime of an M12 tap by a factor of 2.4.
"Due to the precise measurements obtained using Kistler’s dynamometer and the conclusions drawn from those, we have been able to tailor the design to such an extent that the forces on the thread flanks have been drastically reduced."
Masayuki Doi, development manager at BIG Daishowa
Doi is self-assured: “Without Kistler’s cutting force measuring device, we would not have been able to develop the MEGA Synchro.” BIG Daishowa has developed unique collets and nuts for their new tapping holder. In contrast to many other tooling manufacturers, BIG isn't using conventional ER collets but their proper slim collets to clamp the tap. This has a positive effect on the runout accuracy. Moreover, their slim diameter nut is avoiding interference with the work piece.