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I'll bet the feeling of satisfaction is only surpassed by the feeling of relief!
Congrats.

Cheers

Isn't it so much rewarding to finally see it in action

I like the G251 - it almost makes steppers sound like servos. Still not on all speeds though.

Dan

jrslick22
I have to say that's a top job! looks mighty professional indeed.
I've been following this post with interest, I have the same lathe that I will convert once I get some more time. I have to ask, Why didn't  you use the existing lead screws on the lathe?
We all know bath ball screws are better but when you have the lead screws there already , why not utilise them?
Well Done
Katoh

Simple, accuracy. I have put this on the dial and get about .03 - .02 mm accuracy, you have no hope of getting those sort of results with the standard screws in fact i would be surprised if you could get it within .2.

I sill have a lot to do on this machine before its finished, if i was doing it again i would do a lot different. most of the things I'd do different wold be the enclosure not the machine.

Not quite so. Lead screws can be very accurate. Not sure what are the numbers you measured. It is common to speak of a ball screw in terms of accuracy over a given length. Thus, for instance, a C5 accuracy grade would mean about 0.03mm acceptable error in travel over 300mm. Accuracy grade definition varies from one manufacturer to another, so the above example is not dictated by a standard.

Lead screws can easily hold those accuracies. So, when using ball screws it's not really an accuracy demand. Ball screws allow you to have minimal backlash (practical zero), which is often desired in a CNC application. Also, ball screws run quieter and higher speeds can be achieved without the risk of heating the nut and wearing it. Of course they wear slower. Theoretically you can have a lead screw set up to have zero backlash, but it will hardly last.

Dan

EDIT:

Forgot your lathe was Chinese, so the original screws may have been poor quality and not as accurate

Thanks for the reply, yes I can see you have put a heap work in the enclosure, was it planned or a do it as it comes job?
I haven't even opened my lathe up yet its still sitting in the crate wrapped in plastic, so not really sure where or when to start.
I will probably sort all the mechanical out first, drives, motors screws, ect and get it to a fully working unit before thinking about enclosures.
If you dont mind, save me going through all the post again what size steppers did you use? and how did you go changing the x lead-screw to ball screw?
One thing that I dont know if anyone has look into is the Igus lead screw nuts to replace the existing, they are polymer, have zero backlash, and are dust and dirt resistant. I use Igus liner's (polymer type) on my router and they are extremely impressive, very accurate and still operate under a ton of dust. Mind you you need a lot more grunt to push the gantry, but still it cruises at 3m/min and rapids at 5m/min.
not bad for a 150kg gantry on polymers.
Backlash can also be controlled in Mach.
Many thanks for the Info and again you have done well!
Cheers
Katoh

Yeah plastic nuts might work, I've got a set of them but have not yet used em.
X axis was very very hard as the clearances are really tight, I think if I were doing it again i would make a whole new slide that was say 50mm thick as apposed to the standard 20mm I think it is, but then again I think if I were doing it again I would build the whole thing from scratch.
I sort of had an idea that i wanted a fully enclosed lathe, they look way cool and for me keeping the mess in and out was a must apart from that I just maid it up as I went along. tip: Next time i would get the sheet metal cut and folded first then build the frame inside the sheet metal, this way you can use the sheet to keep everything square. mine is square but it took a hell of a lot to get her there.
I got my steppers from http://www.homanndesigns.com/store/index.php?main_page=index&cPath=25 i used the 269 for the X and the 287 for the Z with 1:1 timing pulleys, it does 3.5mps on rapids (speed was important)


Hope this helps

Again thanks for the info. With the X axis ball screw would a smaller screw worked better? say a 12 or even a 10mm.
for the z I see there's plenty of room to use the 16 or 20mm screws.
Have you got a set of the Igus polymer nuts? Do you think they would work if you just used the original screws? I still haven't found time to even unpack the lathe, its not at the top of the to-do list, if I can get enough information now I could good things ordered and here ready to go instead of start- stopping waiting on parts.
Cheers
Katoh

For the money I would just replace the screws, why bother spending the time.
Yes i think a 12mm one would work, mines 16mm. i would go 20mm for the Z, mines 16mm.
I got mine from Chai in hong kong her ebay contact is: http://myworld.ebay.com.au/linearmotionbearings2008/

cheers

I was looking at the same people for the screws but there's a bloke here in Aus as well that's pretty competitive, I'm definitely going to look at putting a 12mm BS in the X, Do you think 20mm in Z could be overkill?
Finely unravelled some of the plastic wrapping tonight, trying to get some specs of the motor, well mine doesn't even have a motor! The original motor was it 2 pole 2880rpm or 4 pole 1440rpm. I have found 1hp 4pole 3phase motor on ebay for $10.00 with a small footprint, could be absolutely perfect. The other thing is what sort of drive pulley was on the motor, that's missing as well.
Thanks
Katoh