[HaasStudent]

So, we have fixed the spindle drive controller, but we are still concerned as the spindle when spinning up to any RPM is now hesitating at the beginning, as though it is fighting its own rotation, it was not doing this before the drive controller was replaced, and it is not throwing any alarms, but we are not running it in fear of breaking somthing else. Any insight to this?

[Haas__man]

The first thing to check is that the spindle drive is grounded properly. Make sure all groung leads are to chasis or ground - and have good contact.
What is the year of manufacture on the machine?
When you say you fixed the spindle drive unit - how did you do this and what was wrong with it? Did you remove the drive from the machine to do this?
Also - does the spindle load meter work correctly?

[Wizzard of H]

There are some things that should be cleared up here:
1) If this were caused by an encoder, you would get an encoder alarm because the encoders are self-tested.
2) In a mini-mill or TM, there is no box called a vector drive; there is an axis amplifier as they supply enough current for the smaller spindle motor.
3) Grounding is that old "easy to blame thing" but a lack of ground does not give this kind of symptoms. (A lack of ground WILL cause electrical shock!)
4) A hesitation at start could be caused by an open wire from drive to motor.

[HaasStudent]

I am working with the shop manager on this, so the best I can do is relay what I have been told to me.

The machine is a 1997 VF-4.

The Spindle Drive controller drive had the IGBT replaced, and with a slightly dissimilar model, we were assured by the Haas rep and Mitsubishi that it was compatible with our drive controller. The Mitsu. Rep had us change a drive startup parameter to try to fix the jerky spindle problem. The Controller was removed, torn down and the Blown IGBT confirmed and replaced.

The spindle Load meter reads about 110% on accel and when it has reached its set RPM never drops below 50%.

I have been told that the motor wiring has been checked (which sounds like a visual inspection) and nothing is corroded.

[Haas__man]

The spindle encoder on this particular machine (VF4) are not self tested because the spindle drive is not a vector drive or a minimill power supply. It is a Mitsubshi drive unit. The spindle encoder is only used for rigid tapping on this machine.
HAASSTUDENT - I will see if I can get some drawings of wiring connections to the spindle drive unit so that you can check that everything is wired up ok. You did not mention if the drive was removed from the machine for repair? Grounding to the spindle drive unit could definately be causing your problem - but could also be wired up incorrectly.

[Wizzard of H]

I am sorry but Haas_Man is mistaken.
All of the encoders used on Haas machines since 1991 have had an electronic self-test performed on them to insure consistent signals and consistent count or position information. If the encoder is not working properly, it always gives an encoder alarm.

[micro-tech]

I had a similar issue with the spindle hesitating and rocking back and forth on an SL10. After all day of diagnosing it turned out to be the "Delta Y contactor". This is the one that you hear click when you ramp up the spindle rpms. It had a loose jumper from the factory on mine, but I'm sure they wear out eventually. It gives the spindle more torque in the lower rpms.
Just something else to check.