Liebherr LC1002 Gear Hobbing Machine
This machine was originally controlled by a Liebherr CNC. Due to it’s age the original system was becoming difficult to maintain, and get replacement parts for. A logical choice was to upgrade the controls to something newer and more reliable since the machine itself was in excellent condition. So MTB performed a complete CNC retrofit with a GE Fanuc 16i-MB equipped with 7 axes of motion, all in the customers plant. The entire electrical enclosure was replaced with a new one, along with all the components inside. All the feedback systems were changed to absolute using either Heidenhain or GE Fanuc systems.
One of the most difficult challenges we faced was the spindle motor conversion. There were tow main issues with this motor. First, the original spindle motor was equipped with a tapered motor shaft. Since GE Fanuc does not offer tapered shafts, we were faced with having to design and manufacture a new shaft for the hob head that would accept a straight shaft motor. We did not want to specially modify a motor to accommodate the machine which would result in an impossible to find replacement, so we elected to modify the machine to accept the GE Fanuc standard.
The second issue with the spindle motor was the power rating. The original DC motor was a high performance system, that on paper at least would outperform any AC spindle on the market in the low RPM ranges. Finding the proper motor that could produce the torque, power and RPM ranges of the original DC motor proved to be quite a challenge, because the physical size of the new motors usually exceeded the space limitations we had available on the hob head. We finally settled on a standard GE Fanuc spindle motor and drive that would do the job, and still fit the space and shaft size requirements.
We always use the latest IEC devices for our electrical panels. We have elected to standardize on integral starters and circuit breakers instead of fuses where possible. This eliminates the need for the customer to stock fuses for every circuit in the machine, and also offers a convenient method of troubleshooting a problem. The integral starters have built in fault contacts that indicate different problems, and the circuit breakers allow quick and easy isolation of branch circuits for locating short circuits or load problems.