Denford Triac VMC with ATC Conversion / Fix

[andy_con]

bit of a thread hijack sorry.

so when I got the machine it turned on and worked, but every time I started the spindle it tripped the RCD. I notice straight away the main fuse on the sprint drive card had been bridged, so assuming it was a known problem.

after many hours of faffing I took the top cover off the sem motor and it was filled with burnt carbon from the brushes. after a really really good clean and hoover, it worked and didn't trip the rcd.

I also replaced the brushes in the side of the sem motor just for piece of mind.

a problem since I had the machine is you start the spindle at say 3000rpm and it starts to jump around going up and down, by like 300-400rpm. so sent it away for a £500 refurb and it hasn't fixed the problem just changed the problem. now days when I set the motor to 3200rpm, it will go to that speed then after about 10 seconds jumps to 3800 where it will just sit until turned off. its not a big deal I have live spindle feed back so I can account for it, but it shouldn't be doing it.

Space is certainly a challenge with triac spindles.

Andy, what is wrong with your spindle motor/drive?
Mine started hesitating and making what's probably best described as a rumbling noise, followed by tripping the RCD at higher speeds. I took the brushes out, and there's signs of arcing on one of them, and another was sticking in the holder, but giving them a clean never made any difference.
The armature isn't that clean looking, however I won't be able to get the motor apart without using heat to get the pulley of, and I suspect the real problem lies with the drive. For it to trip the RCD, there's either got to be an excess build up of carbon inside to give continuity between the brushes and the case, or the SCRs on the drive are starting to breakdown and shorting to GND.
From past experience with my old lathe, the rumbling noise is consistent with a faulty drive.

If you want a new replacement DC drive, KB Electronics drives aren't that expensive. For basic speed control, a KBIC would work, or if you want to keep the tacho feedback, a KBMM would be needed. You'd also need to add the extra heatsink for either option to get the rated power capacity.
Axis Controls are one of the UK distributors, who I'd happily recommend as they've always been helpful when I've used them - http://www.axiscontrols.co.uk/shop/kb-electronics-dc

I think I'll go and start a new thread about my replacement plans, as I'm umming and arring over the design.

[m_c]

bit of a thread hijack sorry.

so when I got the machine it turned on and worked, but every time I started the spindle it tripped the RCD. I notice straight away the main fuse on the sprint drive card had been bridged, so assuming it was a known problem.

after many hours of faffing I took the top cover off the sem motor and it was filled with burnt carbon from the brushes. after a really really good clean and hoover, it worked and didn't trip the rcd.

I also replaced the brushes in the side of the sem motor just for piece of mind.

a problem since I had the machine is you start the spindle at say 3000rpm and it starts to jump around going up and down, by like 300-400rpm. so sent it away for a £500 refurb and it hasn't fixed the problem just changed the problem. now days when I set the motor to 3200rpm, it will go to that speed then after about 10 seconds jumps to 3800 where it will just sit until turned off. its not a big deal I have live spindle feed back so I can account for it, but it shouldn't be doing it.

That does sound more like a tacho or drive fault. Have you tried monitoring the tacho voltage, to see what it does when the speed changes?
If the tacho voltage is increasing with the motor speed, then it's most likely a drive fault, but if it drops first, then there's a tacho problem.

[andy_con]

I haven't no, you could spend more time trying to fix these machines than machining

That does sound more like a tacho or drive fault. Have you tried monitoring the tacho voltage, to see what it does when the speed changes?
If the tacho voltage is increasing with the motor speed, then it's most likely a drive fault, but if it drops first, then there's a tacho problem.

[Chaz]

bit of a thread hijack sorry.

so when I got the machine it turned on and worked, but every time I started the spindle it tripped the RCD. I notice straight away the main fuse on the sprint drive card had been bridged, so assuming it was a known problem.

after many hours of faffing I took the top cover off the sem motor and it was filled with burnt carbon from the brushes. after a really really good clean and hoover, it worked and didn't trip the rcd.

I also replaced the brushes in the side of the sem motor just for piece of mind.

a problem since I had the machine is you start the spindle at say 3000rpm and it starts to jump around going up and down, by like 300-400rpm. so sent it away for a £500 refurb and it hasn't fixed the problem just changed the problem. now days when I set the motor to 3200rpm, it will go to that speed then after about 10 seconds jumps to 3800 where it will just sit until turned off. its not a big deal I have live spindle feed back so I can account for it, but it shouldn't be doing it.

I had similar issues. Brushes need to be clean and carbon free (And clearly not worn out). I stripped the motor down as far as I could and found that previously someone had put some putty on the wingdings. I Can only assume the motor had basically started to fail and this was a 'plaster' to keep it going.

I would only get around 30% of full current before the motor would stall. It would then overheat and start smoking from the brush area.

I triple checked the setup and verified with the supplier of the drive (they were really good) - KEITH SANSBY <[email protected]> . So clearly the motor was the problem. Symptoms also included 'hunting' around high speed and any loading would make it worse.

[m_c]

put some putty on the wingdings.

I've just got to say, that typo made me smile :-)

Did you get any pics of how the servo fitted?

[Chaz]

I've just got to say, that typo made me smile :-)

Did you get any pics of how the servo fitted?

LOL, I saw that after too but left it.

No, but will sort. I do have some older pics, lemme see if I can find them.

[Chaz]

I've just got to say, that typo made me smile :-)

Did you get any pics of how the servo fitted?

Difficult to show with existing pics. Ill take a vid on the weekend.

Tight squeeze, had to remove some material for it to fit and a pic of the bracket used.

[m_c]

That's certainly a tight fit.
Any idea what size flange is on the motor?

I think a 100mm flange motor would squeeze in, however I couldn't find any with the power I was aiming for, so opted for a 110mm motor, and spacing it up.

[Chaz]

That's certainly a tight fit.
Any idea what size flange is on the motor?

I think a 100mm flange motor would squeeze in, however I couldn't find any with the power I was aiming for, so opted for a 110mm motor, and spacing it up.

Ill share the sizes tonight. Ive got the original flange drawn up as well as the info on the Panasonic 1.5 KW servo.

[Chaz]

That's certainly a tight fit.
Any idea what size flange is on the motor?

I think a 100mm flange motor would squeeze in, however I couldn't find any with the power I was aiming for, so opted for a 110mm motor, and spacing it up.

The plate that goes across for the DC motor is 115mm x 110mm (Depth).

The motor mount bolts are 81mm across from C to C. The recess flange is 100mm.

This is the motor mount for my Thor machine Y Axis (same motor as used on my Denford for spindle here).