Heller MCH250 Spindle Upgrade

Heller MCH250 Spindle Upgrade

Our customer owned several Heller Cat 50 taper horizontal CNC milling machines set up for cutting aluminium at high speeds. They received an order to mill cast parts and found the spindles were failing frequently during the production run. The OEM gave them the option of purchasing new spindles with a high price and long lead time. We sat with them and reviewed their process and the spindle issues they were having.



1) The feed rates had to be reduced to get the spindles to last more than a month. This made the cycle times far to long to remain profitable making the part.
2) When we evaluated the spindles we found the retention force on the tool holder was significantly lower than it should be. We found the tool was being pulled out of the taper during cuts. This caused taper damage (bell-mouthing and uneven wear). This also caused damage to the gripper fingers adding to the retention force issues.
3) The taper damage caused tool runout which in turn shortened the life of the tooling. It also caused chatter on the part.



Northland Tool redesigned the spindle’s drawbar system and brought the drawbar force from 2200 pounds to 4800 pounds. We also redesigned the bearing complement to increase the load capabilities in the axial and radial positions.


After reassembly of all components, adjusting bearing preload, and undergoing break-in and testing procedures, this spindle passed our final quality inspection before being returned to our customer with a 1-year warranty.

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