760-22 axis drive fault

[tstom]

I'm having a problem with my 760-22 with Dx32 control.... Started giving me axis following error when it would home the x axis but I was able to slowly jog it to the middle of the travel and it would start up and run Now I am getting a axis drive fault and it shuts down ...the error code on the X axis drive(inthe cabinet) is a 6 also with the machine sitting idle the x axis began to creep to the neg direction without any control input I had to push the Estop to get it to quit........any help would be appreciated

[machintek]

If a axis drifts (control cannot keep it in place) there is uaually a problem with the position loop. The X axis motor on this machine is on the right side of the table. The encoder cable can be damaged by chips. It also gets hardened by oil and coolant, the outside covering of the cable cracks, it flexes more at the crack and the wires break there.
The bulb in the Heidenhain encoder eventually silvers and does not count any more.
The "cable slep" flexible wire way gets damaged, parts fall off, chips fall in and damage the encoder cable.
I also have seen the axis tighten up, the motor run hot and fry the encoder.

1st thing to do is go to the maintenance page, do NOT turn the drives on, turn the ball screw by hand, and see if it counts. The ball screw should turn with one hand with a rag on it.

Note that X and Y motor are the same and interchangeable. Same for X and Y drives. Z is not.

George

[tstom]

Thanks George
My ball screw will defininetly not turn by hand I have the plates under the table loose I remember you mentioned that in a prevoius thread ...(not cutting like that just seeing if it helped) Where else should I look to find what is making my x axis so tight
I'm thinking the motor getting hot like you said may be where the trouble lies

[machintek]

To get to the ball screw, did you take off or slide back the X way covers on the right side?
By the way, I congratulate you on doing research.
There is a coupling between the ball screw and the motor. Loosen that.
Now see how easily the motor turns, and how easily the ball screw turns.

George

[machintek]

There are also gibs that could be checked. I have had only one case where I did find a gib loose that would bind in one direction as it wedged itself. That was on a VMC1000 and on the Y axis.

George

[tstom]

Yes I do have the slide cover off but did not undo the coupler
I will do that first thing tomorrow

thanks again for your help
Tom

[tstom]

I removed the X axis motor bolts this morning and slid the motor out of the coupler The motor turns free I still can't turn the ball screw without putting a wrench on it but it seems smooth turning it with a 3/4 wrench on the flats on the left end of the screw

I checked the encoder read out on the maintenance page and it is counting
The main motor cable has the insulation pulled out of the steel plug end and there are 2 wires a black and a green outside of the foil jacket that aren't connected to anything the insulation is hard as a brick
Does it sound like cables are my problem? or keep looking

[tstom]

George
I may have found my problem....the lube oil line to the nut on the x axis ballscrew was broken off about 3 in. back from the nut I cobbled it back together and used an oil can to get some oil into it The ballscrew turns noticibly easier I can now turn it with 2 hands I ran it back and forth a bunch of times with the fast jog knob and it didn't fault out I will try running a program tomorrow and see what happens

Are the lube line a metric size?

Tom

[tstom]

Thought I'd report in on this and possibly help someone else down the road

I have replaced all the cables to the x axis (not cheap) and upon starting the machine I have the same problem that being the x axis creeps back and forth without any control input so I got brave and took the cover off of the x axis encoder.... I said I replaced all the cables....all but the short cable from the encoder to the main cable the encoder cover had a fair amount of oil in the bottom and the insulation on the small wires is all rotten I decided I couldn't hurt it any further and peeled the main insulation back about 2 inches
I found two of the small wires burnt together so while I'm not real happy about buying cables I probably didn't need they were in kind of bad shape so I probably saved myself a problem in the future

Does anyone know if those two wires being shorted would ruin the encoder ?and can the cable be purchased seperatley It is a Heidenhain RON 426.0003-3750

At least I think I have found the problem

Additionally I shimmed the clamp plates under the x axis ways .001 "as George described some time ago in another post and I can now turn the ballscrew by hand ....snug but I can turn it I had to have a wrench on it before and it was still hard to turn

[machintek]

Heidenhain can give you the wire colors and what they refer to.
I have seen more than one encoder go bad because when the axis was tight, the motors worked too hard and became so hot that the soft wires inside the encoder can melted and shorted to the inside of the encoder can. I know because I took the encoder apart and found this. These wires are quite small and difficult to solder. The encoder is a delicate electronic device. I am not sure Yours is still good but you have nothing to lose by trying to fix it. What I wonder is if what you found may be caused by a short inside the encoder itself causing it to fail perhaps at this spot due to over current/heat. Needs to be looked at.
On the bright side, you are lucky because a short in the positioning loop typically melts the inductor L1 on the BMDC board used as a fuse for the 5 VDC.

George

[tstom]

These wires were bad where the gland goes through the cover can just below the plastic plug. Looks to me like rot from oil or coolant but the axis probably has been tight since I got this machine about 9 months ago

Should I try just a cable or have the encoder tested?

[tstom]

I seperated the bare wires coming from the encoder and taped them up just to see if the encoder would function and if the axis quit creeping(not trying to run it this way) started the machine and no more creep went to the maintenance page and the x encoder is now counting again... power up the drives and now I'm getting a TLAUF communication error...try to home the machine and it post a AUF communication error

Could this be a result of the shorted encoder cable or have I developed a new problem?