Both the milling machine's brushed motor and the respective control electronics are quite susceptible. Wear on the carbon brushes and the unprotected circuit caused repeated problems. During the first 5 years, I had to contact the manufacturer on numerous occasions because of erratic motor speeds and complete motor failure. This was unsatifactory. As I had also been informed that the electronics are not included in the warrantee, I began to think about rebuilding the drive system.
A 3-phase AC motor controlled by a frequency converter sounded like a reasonable alternative; but the size of typical 3-phase motors seemed to be an issue. An Internet search revealed that the motor manufactuere Grünhain offers 3-phase motors which are smaller than standard motors of the same power. I ended up ordering a 0.75 kW motor for my milling machine.
The original drive train transmission is no longer appropriate for this motor. While considering to replace timing belts and pulleys, I quickly realized that Wabeco had fitted custom components. Thus, I decided to design a completely new drive train with a multi-rib instead of the standard timing belt and with a pulley which I could machine on my CNC lathe. This should guarantee a smooth-running drive system.
I started with a timing pulley, turning off the profile on the lathe. By shrink-fitting, I attached a sleeve into which I cut the profile for the multi-rib belt, thereby saving myself the work of cutting and fitting a keyway for the drive shaft in the quill.
The motor was fitted with a flange and a new drive pulley and mounted inside the orginal motor compartment.
The original case had to be trimmed in order to be useable for the controls: I took over the original arrangement of switches for directional control, an emergency ON/OFF switch, and for the spindle speed potentiometer.
The frequency converter is housed in a modified computer case.
