[JFettig]

Are any of you interested in a cnc conversion kit for the 7x lathes? I have partially designed one and have the idea in my head mostly. it would actually end up being a 12x or so lathe by the time Im done with it for multiple tool posts

what I need to figure out is what you guys want if I was to do this, leadscrew, basic cheap stuff or ballscrews or even preloaded ballscrews.

I went to price out ballscrews to have it preloaded, steppers, and xylotex drives and all that would come up to be about $350, then there would be the rest of the hardware, that would cost some, I am not so sure about doing one or two, its typically not worth the time to do one offs, then to get enough to do a small production run at work and keep the costs down is also difficult as there are many parts to it.

Basicly what I have designed is a new carrage and cross slide that would have about 6-8" of travel I have to decide on motor sizes and screw sizes to complete the drawing, I have whats important to fit it on the lathe designed.

This is something that I will probably not have time to get to untill summer if I end up even getting to it.

My mill isnt quite big enough to make the larger parts like the carrage and cross slide, so if I was to sell these I would have to do this part at work if we would even find time to do it.

Would there be enough interest to make like 20 of these kits up and sell them?
Basically it would replace the existing carrage and either use the existing leadscrew with a motor mounted to it and that would be the only modification to the lathe becides removing un-needed stuff.

Jon

[kdoney]

I would be interested. On mine no modification to the lathe was needed. I use the existing drive mechanics. One servo is gear belted to the leadscrew and another servo is bolted onto the cross slide. It is as accurate as the manual lathe. (The photo is before I put an acrylic cover on the gear housing and hooked up the drivers.)

[JFettig]

That is very nice man! I was thinking about doing direct drive steppers or something similar, maybe customizable mounts. I would also be using a larger tool post, I already have the larger tool post on my lathe 1/2" tool max and its a little more rigid than the stock one it seems. I would also get rid of the compound slide or just not include it.

Did you just use the half nut for your z axis?

I was thinking I would use a regular nut or ballnuts for that one.
My design also has room for 5/8" ballscrew and possibly preloaded nuts in the cross slide.

Jon

[RotarySMP]

I did my conversion with ACME (actually the metric equivelent), and am just in the process of designing a ball screw conversion as I am not the pleased with the wear and variable backash with the current set up.

I'm using a Phase II AXA tool post on a plynthe without the compound and fina good match to the CNC conversion.

Make sure to address a swarf guard for the Z screw.

[kdoney]

Yes I just used the half nut and lead screw. I would like to go to ballscrew on both axes. I have 2 ground screws long enough but haven't had the time. When you come up with a design, I would like to look at it.
Hey Mark, any photos?

[RotarySMP]

http://www.wrathall.com/Interests/interests_index.htm

[JFettig]

Mark, do you have any updated pictures anywhere? you said you have an enclosure and some other stuff?


Jon

[RotarySMP]

http://www.wrathall.com/Interests/CN...Enclosure3.htm

The enclosure looks like this, but witha green tin wall.

What other stuff did you want to see Jon?

[JFettig]

I was just wanting to take a look at all the stuff you did to it, Your site is kinda hard to navigate and find stuff like that. Do you have a folder with just pictures in it?

I am still trying to decide between leadscrew and ballscrew for mine.

What size stepper motors do you have on there?

Jon

[cncadmin]

How do you guy's handle driving the spindle? You must be able to control the speed for doing threading operations. I thought of using a encoder on the motor OR using a high speed servo motor.

[JFettig]

With turbocnc you can use a 1 rev encoder. At turbocncs site, they have a scematic and all for it. It woudl be better to use a regular encoder, I dont know how the screws will turn out because there will be a little bogging down and it could change a little bit. so who knows how acurate it will be, Although I have seen some threads made with it. Mach2 uses the same thing for an encoder.

So far, I am only working on designing the hardware, havent gotten to the encoder for the spindle yet.

I beleve the scematic and parts are simple and cheap and easy to get ahold of from what I remember.

When I figure out what I want to do for screws, I'll design a hard copy.

Jon

[kdoney]

I just use a Optek optical switch (OPB620) and a disk with one hole on the spindle in it to trigger the switch. littlemachineshop.com has a kit if you don't want to do it yourself. You would have to tape over the holes which are not needed in his kit.
Kevin

[RotarySMP]

My image folder on the web site whon't help, as it has about 1000 photos of the kids, trips, lathe, etc.

Sorry if navigation is differcult. It seemed like a good idea at the time, and I'm too far down a track to change direction now

TurboCNC is only set up for a 1/rev encoder count, so using a regular 400 count encoder will gain you nothing. The opinion of the authors is that increasing the encoder resolution increases the computational overhead significantly.

If you run plenty of acceleration, turboCNC threads fine.

Go Ball screws.

[RotarySMP]

Sorry, I forgot to answer your question Jon.

I am using NEMA23 double stack Vexta PK268-2.0A 187Ozin motors for both Axis. If you take the chance while the lathe is disassembled to address the variable bed thickness, these motors are good for about 100-120 IPM rapids with the gibs quite tight. I didn't, so I have to limit rapids to about 50IPM so it doesn't stall out on the tight spots of the bed. Geared down 2:1 through 4 and 3mm pitch leadscrews, they have ample power at cutting speeds. The spindle motor power is the limitation here.

Addressing the bed thickness is really the right thing to do. You could just muscle the saddle around with a bigger motor, but it won't fix the saddle being a bit sloppy when tweaked up snug on the tight spots. Rick Kruger did a great write up here:

http://warhammer.mcc.virginia.edu/ty...s/Bedways.html

Did I mention to get ball screws? I didn't and am now redesigning to retro fit ball screws.

[JFettig]

Your right, the bed is a little messed up, I do notice this when moving from end to end. Mainly what I am looking to do is make a kit thats easy to strap on and go, that is if I ever decide theres a market for these to sell.


Jon

[DragnsBane]

sounds like something i would be interested in. if things don't work out for building them are you goin to put them up as shareware or just let it die? summer is about the time i am looking at for the purchases of my machinery so it would work out great.

[JFettig]

If I dont ever make this, I will post the drawings I have. Right now they are basic simple idea scale drawings

Jon

[JFettig]

Well I have designed and built a kit. Very simple kit, bolt on bolt off, easily convertable and unconvertable without any drilling of holes or anything. Just removing about 4 simple parts, total of 5 or 6 screws.

What kind of interest do I have in a kit like this? If there is interest, I will make up a few and put them in the classifieds and see how it does.
Also, what size motors? Nema 23 or 34, I think 23 is all you need really, I have some underpowered 34s on there right now.

The kit uses the existing hardware, existing leadscrews and uses the halfnut. I quickly measured .010 in x and z axis stock leadscrews and nuts. Its not bad if the gibs are tight.

Im uptight about my own designs, so I choose not to post pictures right at this moment.

Jon

[minilatheman]

Jon,

Whew! I think my timing couldn't be better. I just got a grizzly mini-lathe for x-mas. Ive been thinking of buying one for a long time, everyone was bugging me about what to get me for x-mas so I told them... and poof there it was. I couldn't be happier.

anyway I would like to convert it to cnc asap and am very interested in what you have to offer. I saw and read the thread for the stirling conversion plans but have no cnc "building" experience. Mechanically speaking I can make anything I need to convert one but I Am completely lost electrically and electronically.

any help you can offer would be greatly appreciated. If you have a bolt on kit that would be awsome.

please get back to me, Mike

[JFettig]

The offer I am and have been origionally considering is not the electronics, It can actually be quite simple if an xylotex kit, 24v power supply and some 150+oz/in motors are aquired and a little reading.
I personally cannot afford to build complete kits for the lathe, If I coudl I would. I may consider building one on request if time is there, but I will be starting my second semester in college in a few days and I dont know how much time there will be.

Jon