Denford Software & Machines

Hi folks, just when I thought I was getting somewhere my ATC unit died!
Stripping the unit down I found that it had stripped a tooth on the input gear and that all the others on it were badly worn. I had read only the other week about this happening to someone else but searched and searched but couldn't find the thread.

Anyway knowing that I had seen RS part numbers on several drawings for machines and that the gear box had 60 stamped on it I figured it was a 60:1 reduction.

SO RS supply them

441-5119 £45.73
http://uk.rs-online.com/web/p/products/441-5119/

OR Farnell do them

1761265 £41.54
http://uk.farnell.com/maxon-motor/11045 ... dp/1761265

OR CPC (part of the farnell group) do them and are the cheapest!

MC01825 £38.81
http://cpc.farnell.com/1/1/90730-gearbo ... motor.html

Now the output shaft will need drilling for the roll pin to fit in, also the box itself will need drilling for the 2 power wires to pass through. But there you have it.

I read on a CNC forum that the motors that drive these are susceptible to burn out and the boxes to teeth wear due to them driving forwards at full voltage then going into reverse and stalling against the pawl at half voltage. A user on there said he had put a current limit circuit to reduce this problem. I may look into this at a later date.

Admins sorry if I shouldn't have put this up as Denford may still supply the units but it is weekend and wanted one for Monday so I can try and sort out if I should buy Quickturn 2d or not.

Hope that helps anyone who runs into the same issue.

I appreciate your posts with regard to the Orac ATC. I'm curious to know whether you followed up on the modification to limiter to reduce risk of motor burnout and other wear.

Also, do you (or does anyone else) know of any source for replacement motors?

Thanks!

Hi, sorry no, I didn't do anything more with it. I became to frustrated with the DOS control and have decided I will convert to VR turning. I would be a lot further along with this BUT I decided (forced into due to rotten chassis) to rebuild my Landrover, do major work on the house, be thwarted with constant poor quality parts for the Landrover. So the lathe is more of a trip hazard at the moment and will be for about another 12 months before I can get to working on it.

Pete

I think we have a couple of motors in stock at Denfords if you are interested?

The new Toolchangers we build now have stepper motors fitted but we did modify the toolpost control card on the older machines to limit the power to the motor. I will see if I can locate the drawing when I am next in the office showing the mods. It was only fitting a couple of resistors from what I remember.

Thanks Martin, Hope you guys are doing ok there.

On a slightly different point, I noticed on later ATCs they had 2 pawls, was there an issue with the earlier single pawl units wearing resulting in an inaccuracy/reliability in alignment on tool changes. I remember there was a member who had problems and they had to replace the pawl. Is there any specs on the pawl size? I was having some issues with setting zeros and then on a tool change it being out the next time it was selected.

Thanks

Pete

Hi Pete

Hope you are well.

We changed to 2 pawls as we found that the single pawl was being distorted over time with the grub screw pushing in to it which then caused the centre height to be out. At the same time they were made slightly larger as well.

Thanks Martin,
I thought that must have been the case, do you have the specs on the original pawl size when you are back in. Not that I'm going to be doing anything with it still for a while just if they are on here it would be great when I come to it.

Pete

I'd be interested in any electrical and mechanical changes with regards the Orac ATC. I'm not going to apply any mechanical changes to mine any time soon as I've already stripped and rebuilt it with new bearings, they seemed OK but as it was apart they were cheap enough so changed them. The pawl was slightly burred but easily cleaned up with a small stone, the gearbox was knackered so it was replaced. I found someone selling them on ebay, apparently used but when I inspected the first one I couldn't see any sign of use so got a couple of extra as spares. The motor seems to be OK as the ATC now work well.