Need Help!- can i perform arc welding on my CNC?

[woonsteel]

Hi fellow engineers, I am using 6M Machine Center. Below are the following 6M boards:

MAIN BOARD A20B 0008 0410/8D
CRT/PUNCHER A20B 0008 0430
BMU A87L 0001 0016/05E
ROM A20B 0008 0480
PC MODEL B A20 0008 0440
POWER SUPPLY A14B 0061 B002
I/O A20B 0007 0040
DRIVER X A20B 0007 0360
DRIVER Y&Z A20B 0007 0361
SPINDLE SANYO DENKI 7.5KW DC MOTOR
SPEC NO: SP-4076F
SERIAL NO: 497164
I suspect the head alone is too heavy for the motor to handle, because it took the motor about 8Amps to move upward (+ position) meanwhile 4Amps for it to move downward (- position) and overheats the z-axis, this triggers alarms 433,436,400 and 401 to appeared where I had managed to solved the problem by changing the 1”x1” square thick 3/8” 16 pin (A-PC06) in the main board which I bought from United States.

From my experience, it’s hard to change the component by desoldering the whole IC out from the multilayer board because chances high possibility of damaging the inside layer of the pcb circuit due to the repetition of the soldering and desoldering process. It is advisable to just trim off the faulty IC leaving only the pin so that you could solder the replacement on to the existing pin without harming the pcb circuit.

My question is, can I add a counter balance to my Z-axis with the hope of getting lower ampere rating?
We are not allowed to drill or tap so arc welding is my only option, what is the proper procedure in performing this task?

What are the consequences if I perform welding with the board attached?

[Dan Fritz]

Before adding any counterweight, find out if the lubrication on the Z axis is OK. Also, find out if there is an electrically released brake inside the Z servo motor that's not releasing. Sometimes these brakes fail to release, putting a higher load on the motor. A brake is only there to prevent a vertical axis from drifting down when the servo's power is off. Usually the brakes release when they are given 100vac power. A blown fuse or a brake that's faulty will stay clamped, making the motor shaft and ballscrew hard to turn.

Hint: put some wooden blocks under the Z axis so it can't drift down very far, pull the fuses on the Z axis servo, then turn the CNC power on. If the Axis drifts down, you will get a CNC alarm, but the Z axis SHOULD drift down if the brake releases properly. At very least, the ballscrew should be easy to turn by hand.

Your machine tool builder probably selected the correct motor for the Z axis load and inertia. Re-engineering the machine will probably just mask your problem.

Who says you're not allowed to drill & tap?

[woonsteel]

hi Dan
Thanks for your reply. I think it works out as you told since I've tested the z-axis driver board (A20B 0007 0361) by disconnecting the fuses on its hardware (S20, S21, S22), also alarm 401, 432 triggered. When i insert back those fuses, no more alarm appeared and the CNC machine work as usual. Am i doing the right thing.?

I apologize on my sentence regarding that drilling and tapping are not allowed. What i actually mean, i previously drilled and tapped on another CNC machine and it turns out just fine, but now i would like to try another method which is purely on arc welding.

I overheard some saying that performing arc welding on CNC is not advisable as it would harm the electronic components, is it true?
If i persist on arc welding , what is the precaution should i take?

[Superman]

IMHO welding would be not advisable, a lot of bearings etc if these arc while welding, they will be ruined, spindle bearings thru to guide-ways.

If, as a last resort, welding is to be done keep the earth close to the weld area and on the same piece of metal, also disconnect the mains to stop earthing thru those cables

[Dan Fritz]

I wouldn't do it. Too risky.

[woonsteel]

Thank you Superman and Dan Fritz for your kind advices. Appreciate it very much.

I think i would try Superman's last resort, which is to keep the earth cable as close as possible and see how is goes.

I'll update the welding progress with some pictures in the future.