Spindle repair: A complex but important process
Machining Center spindle repairs is a complex activity by itself. Being manager of independent spindle repair house, I will always advocate the need to get this repaired from us. But Why? There are solid reasons behind it.
While most of our customers are from automobile ancillaries, they are talented ones. So there is no doubt of their competency on rebuilding spindles. Still, I feel that there some factors which are not known to them.
Which are those factors?
Non-availability of proper tooling and equipment to dismantle and assemble the spindle: High-end spindles like Franz Kessler, Weiss, Makino, Mazak, Okuma, Doosan use shrink fitted lock nuts. These lock nuts are used to lock the bearings and in some cased to lock the rotors as well. One needs special equipment like oil injection pumps to remove such lock nuts. We also need press to dismantle spindles with suitable sleeves. However, this tooling is not available in maintenance departments of respective companies.
Complexities of assembly: There are some elements in the spindle assembly which challenges conventional method. E.g. In one the spindles, we observed that lock nut was tightened on threads by provision of grub screw which has access to it from ID of spindle. In addition to this there are bearing arrangements which are deceptive.
Availability of genuine and right spares in particular bearings: There are numerous precision bearing suppliers all across India. However, one needs to understand that bearing interchangeability is never limited to boundary dimensions of bearings but it also to be checked for geometrical configurations. There are some Makino A series machines which use bearings with holes on the inner ring to facilitate lubrication. Or we have found in one of the Mazak spindle, bearings with groove and holes on outer ring of the bearings. All these special arrangements are provided for some purpose. If we do not use exact equivalent, spindle is likely to fail within no time. Take case of disc springs which is C class item. Still, we are not lucky to have source of consistent quality disc springs. We have to be dependent on foreign suppliers.
Lack of knowledge of critical processes in spindle rebuilding: Machining center spindle reconditioning is not mere replacement of bearings. But there are some auxiliary activities to be carried out for successful repairs. Taper grinding is such an important activity. Many people do have knowledge and tooling to regrind BT or ISO tapers. But new edge spindles with HSK tapers do have complex tooling and process. Not many people are aware of it. Grafting of tapered sleeve is another process which we have mastered.
Testing of spindle: The whole success of spindle repairs activity lies in testing of it. One should have capability to test the spindle to the final parameters. You will find there are many electronic components like encoder, clamp/declamp sensors etc, which are to be checked for its function-ability. It is painstaking process to find that the spindle is having problem once it is put on the machine.
There are few more points which I will try to explain in due course of time. But for all the above reasons, I strongly recommend to get spindle repaired from Independent spindle repair house like Setco.
About the Author:
Rajesh Mandlik is the Managing Director of Setco Spindles India Pvt Ltd with 28 years of industrial experience. He worked with SKF India Ltd and Rollon Hyadualics before starting his own business by name Ultra Precision Spindles. Eventually this business was taken over by Setco USA in 2012. He is an avid blogger and likes to write on social, technical and management issues. He also likes to interact with students to inculcate entrepreneurial among them. He is also a Guinness Book of World Record holder for being part of the longest human chain under salt water which was attempted on December 27, 2016.