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KIA SKT21LMS Repairs

npolanosky

Cast Iron
Joined
Apr 9, 2016
Location
USA, FL
Hi there,

Working my way through repairing a used KIA SKT21LMS I picked up. Got a 3ph generator for doing some troubleshooting while I wait for my shop to be ready for move-in.

The machine is a 2003 with a Fanuc 0i-TB

I've worked through a bunch of alarms and after fixing a lot of little things now I'm back to the original issue the machine was purchased with- The B axis (Subspindle linear) won't move, and because the sub isn't at home I can't do anything else.

The servo amp for the B is giving an alarm 436 "Soft Thermal (OVC) when I press standby and enable the axes. This is one of two things, as far as I can tell-
(A): The servo amp or motor is bad
(B): The axis is bound up.

I am thinking the latter- I cannot turn the ballscrew by hand with the machine powered off, whereas I can move Z by hand. There isn't a brake on the motor, so unless there's a brake elsewhere in the system I think something is stuck. The machine has been sitting for a few years, and they had this problem before they sold it to me and simply opted not to fix it since this was their oldest machine and it had already by superseded by newer ones.

What would cause the axis to completely bind up? I don't see any obvious damage to the linear rails or ballscrew, and the rest of the machine looks good aside from the typical peeling paint and rust from age and use (~30,000hrs on time, 12000hrs cut time).

I have hydraulic pressure, plenty of way oil, the B servo definitely sounds like it's being energized.
 
Shipping bracket? Build up of swarf? Stray dropped part wedged in some were?

Failing that a seized ballscrew bearing, servo bearing or a seized way truck.

Would be tempted to get a indicator and see what will move even if just a few tenths with some pushing and pulling.
 
I didn't see any obvious debris, but I'll take a look. I can get about a 1/16 turn of the leadscrew, but no apparent movement on the sub itself. I'll have to get out the indicator and see if it's going anywhere. The servo bearings are definitely good- I had the servo out and actually replaced one of the bearings which appeared to be damaged. The previous owner had the servo out (probably trying to solve this same issue) and had jabbed a screwdriver through the front seal for the servo. In the process, they dented the shield on the bearing. Not knowing it's condition otherwise, I popped a new bearing and seal in there just to be safe. $40, whatever, easy to do.


If the way trucks or ballscrew are the problem, are those straightforward to replace or is there going to be a major operation? Happy to break out the wrenches and engine hoist, but don't want to get in over my head.
 
Big hammer/vise grips worked great. Just some gunk on the rails. Broke it free and got some lube in there. much happier now.


Finally I have one remaining problem:

I am getting a 500 OVER TRAVEL +B and a 410 SERVO ALARM: B AXIS EXCESS ERR on the Fanuc Oi-TB.
Video below.
KIA/WIA SKT21LMS B Axis Alarm 41 and 5 - YouTube

I am not on any overtravel switches, and the switches are reading properly.
I am fairly certain that my problems come from the fact that the motor+encoder for the B axis were removed and then replaced, and the encoder no longer knows where it's origin location should be.

I have tried the Shift+P+Cancel procedure to disable software overtravel, which clears the 500 alarm. I tried the procedure to reset the origin location using param 1815 bit 4, but I may have done this wrong upon further reading.

When I try to zero return the machine it doesn't do it, but if I manually jog the Z axis for example, the B axis will jump back about 1" and then throw the 410 alarm. It will do this as many times as you can reset it until it hits the hard stop. I cannot manually jog the B axis as far as I can tell, else I get the alarm before I get much movement. Without B at home, the rest of the machine seems to be nonfunctional (likely for understandable safety reasons.


I just need to know if this is a software problem, a servo amp problem, a servo problem, or an encoder problem. Servo seems good, it happily moves until I get the error. The encoder counts position as I turn it by hand, seems smooth and consistent.


If all else fails, does anyone have a really good fanuc tech who could give some phone support or who is in the central FL area?
 

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