Retrofit 7x14 lathe 2axes with Theading.

[rruybal]

I'm thinking of buying a 7x14 lathe, (no matter where you buy) it's the same lathe with different finish, (paint, or whatever). I want to use servo-motors, buy the hardware and elcetronics. I bought BobCam, but that's another story. I want to turn small parts, (Big Secret) and I don't want to go through all the manual stuff. I need to know where I can buy Quality parts, at a reasonable price. I'll take care of the spindle TIR by turning collet blanks on the lathe. They,ll run as true as the bearings. But what I'm looking at is repeatability. I can do this by seting up indicators to track all movement or go CNC. I think I want to go CNC. So you expeiranced guys out there, Please give me a hand. I've been reading your posts and I'm impressed.

Would Greatly Appreciate it.

[daedalus]

What you are talking about is a sieg 7x14 lathe, sieg are the company that make them in china, although they are sold under dozens of brands. http://www.siegind.com/
You should be able to find a fair few existing conversions in the project logs section of this forum.

I dont have the same lathe, so i cant really comment on the hardware, but here is a rough list of the electronics requirements.

There are literally hundreds of options, but assuming you have a budget, this would be a reasonable place to start:

Power supply
Two popular approaches:
Build a linear power supply
Cobble together a load of cheap PC psu's

The linear one would be the better option, but the pc psu approach is very cheap, more efficient power usage wise. Personally i have built linear psus for my mill and lathe, they are pretty easy to hook up, and there are countless guides on the forum on how to do so.

servos / encoders
Ebay is your friend for sourcing these, you regularly see servos going for cents on the dollar. You are looking for brushed DC servos, with encoders included. You can get encoders seperately, but its a pain to fit them, and usually you can get motor+encoder on ebay for less than the encoder costs new.

servo drives with step direction inputs
You will have trouble sourcing these second hand, as industrial drives tend to use analog or pwm control signals. There are quite a few different hobbyist targetted brands around, and geckodrive seem to get a good reviewm although i havent used them myself http://www.geckodrive.com/product.cfm?pid=14

breakout board / pc interface
This is what hooks the servo drives to the PC, a good quality opto-isolated parallel port breakout should be all you need. I got mine from www.cnc4pc.com.

Spindle speed measurement
Basically you use a beam break sensor to read index pulses from the spindle, so you can drive the servos with electronic gearing for screwcutting. I have one from cnc4pc above that includes everything you need.

PC
Something thats reasonable with a printer port, ideally dedicated to being the lathes pc, you will probably have to strip down a copy of XP, so its best that its dedicated. Laptops are ok, but some have out of spec printer ports on them, so its something to watch out for.

NC software
Mach is a good choice, its pretty cheap, windows based, and has a massive amount of community support (see the forum section here).
EMC2 would also be good, its based in linux (but does come with a bootcd release), has community support, and is free software.

[salzburg]

HI rruybal,
You could look up DAK engineering website and read his article on his minilathe
conversion, very interresting and informative. Also look up the Minilathe website,there
you will find a conversion kit from Ron Steel. I bought that one and I am in the
process of installing it. Wheter you are going with servos or steppers look at the
Gecko drivers site.

[rruybal]

Now I know in which direction to go. I do have a screamer of a PC it's a Dell XP with a 3.6 Gb. CPU and loads of HD space and 4gb of ram. Do you think it's best to use a stand alone computer? Is there a possibility that their would be some sort of problem with incompatible software on my HD? Or is it just good practice to use a dedicated computer? I have no problem getting another computer if that's best. I'll check out the leads you bave me. And once again thanks for your helpful input.

[rruybal]

Thanks Salzburg
I'll look into it today.

[daedalus]

it is best to have dedicated. The reason is that mach3 needs precise timing when bit-banging the step/dir signals through the parallel port, and its usually a good idea to have a fresh install of XP with some services turned off for running mach (there are tutorials on how to do this in the mach section of the forum). Whilst you can do this by setting up dual boot on your own pc, with the cost of second hand hardware relatively low there is some convenience of having them as seperate machines.

[Al_The_Man]

One other method between manual & CNC is by DRO.
Al.

[rruybal]

Thanks daedalus,
It's no problem to get a cheap Generic computer, especialy if it will have only minimal software. Can I load it with a CNC Mill as well, or is it best to have each machine as a stand alone sysrem? And what about bobcam?

[rruybal]

DRO would be great if it were a prototype project, but if this thing takes off as I hope it will, I'll have a lot of parets to make. As it stands right now I'm looking at 500 parts at least. So you know why I want to go the CNC route. I used DRO's for many years and I like them. But I'm tryinf to avoide the manual part of it especially when I may have to tweek the dia.'s and angles. Instead of moving the the cross-slide to a new angle I'll just modify the program. If the dia. has to change the same applies. Thanks for the input

[daedalus]

rruybal: i have one machine with mach on for both my lathe and mill, and just swap the cables over. Only downside is i can only run one machine at a time, but you can always get another machine if / when you need to run both machines simultaneously.

[rruybal]

Thanks daedalus,
I think with a fast machine to do programming and then verify part, in bobcam, and then send it to the generic computers for running the lathe and mill. Yes I have also looked at a medium size mill for other projects. I've looked at some of the sites you recomended and there's a ton of stuff out there. I will be asking for more advise as I go along. Once again Thanks