CHRISTIE PACIFIC CASE HISTORY: Cycloidal Transmission Rebuild.

A number of rolling presses that we maintain are equipped with a Japanese gearbox or transmission that is extremely compact and powerful.

The cycloidal discs in the transmission roll around the ring gear and rotate at a much slower speed than the input shaft, providing high torque, low backlash, and a high degree of rigidity.

Here is some History

Cycloid technology traces back to the German engineer and designer Lorenz Braren [de]. In the 1920s, he developed an innovative gearbox that eventually became known as the Cyclo. He received a patent for this cycloid gearbox invention in 1925. Subsequently, in 1931, he founded his company, Cyclo GmbH, in Munich and began serial production of cycloid gearboxes in the 1930s. Thanks to a licensing agreement in 1937 with a Japanese company, now part of the Sumitomo Heavy Industries group, the first Cyclo drives were also produced under license in Japan starting in 1939.

One such transmission had a very noisy failure, and we were able to strip and rebuild it without much difficulty.

After separating the electric motor from the Cycloid, our first challenge became evident.

Due to the high load and great amount of torque needed to drive the rolling mill, the keyway between the 22KW electric motor and the cycloidal transmission was chewed up.

This is what the key should look like on the left

Replacing the damaged unit with a spare. We rebuild these transmission so that there is always a spare for "just in time maintenance" like this.

The shaft and keyway on the electric motor were also damaged, and that would require refurbishment.

After splitting the cycloidal transmission we found the cause of all the noise.

The main shaft bearings had collapsed.

The deep groove ball bearing had disintegrated, allowing the balls to roam freely in the transmission. Very noisy, and by some miracle, did not seize or damage the other moving parts.

Remnants of the bearing cage can be see all over the transfer rollers and the cage.

We started with the electric motor by removing the armature and rebuilding the shaft. Machining the shaft to size and milling a keyway came next. Here we have completed and induction and resistance test on the windings. All OK!