I started my Mill to CNC converstion. Here is a pic of the parts

Why not go with direct drive, and turn you some flexable disk couplings ?

Because of the motor being in the way.

Is that how you did it?

Yeah, I mounted them on roughly 2-1/2"x 0.50" Al standoffs, to accomodate the couplings, directly to the saddle and table.
The z axis, I mounted off to the right of the column utilizing the same standoffs.

I could have used some old motor mounts that came with some NSK ballscrew assemblies, but opted not to becuase they were too long, and I didnt want to cut them(might find a use for them in the future)

I was just wondering why you decided to go with what looks like(cant really tell from the pic) to be a 4:3 ratio on 20 TPI leadscrews that come with the MIcromark mill?

Seems it would be pretty slow using steppers, and you would get very low rapids with it(alot of torque though)

If you run your motors at a higher voltage than specified, youll not lose much torque anyway.

IMO a stepper system really has no need for a gear reduction.......this is best used for a servo system where you have >1000 RPM motors.

Just my opinion though.
And Im ,by no means, a pro at this stuff.............just an addicted hobbiest!

I'm really want the torque, and I plan on using 10 tpi ballscrews. The pulley's are used to allow me to mount them off to the side of the bed. I was doing to go the direct route, but I did'nt want the NEMA 34 steppers in the way of the bed. I got the Idea from a website that converted the same machine as mine.

Well I got my ball nuts and ball screw and will start maching them. I will post pics as I convert my machine to CNC. Stay tuned.

wHAT DOES SOMETHING LIKE THIS COST TO DO, RUFFLY? I have a homier mini mill and might do this in the future....

The ball and screws cost me 100.00.

Hey I recognize some of those parts. Werent they made at a place called L.S. Tool ?

Yes they were :) .

Well I start to lathe my ballscrews and learned a thing or to about positive and negitive rake angles. I have to buy some cutter's to make my life easier. So once I get the right cutters I will see how well my 7x10 lathe cuts. Stay tuned!

Still like your 7x12? I stilll havent got one yet. I have access to a 9inch south bend lathe. But want something here at my home. Was looking at that or a 9x20. I like the idea the 7x12 are more easy to move around..

I'd like to get the converstion the littlemachines has to make it a 14" lathe.

My little lathe will not cut hardened steel, I will have to get machined on a bigger lathe. So i'm waiting to do that.

Next week, I'm going to try to complete the machining to the screws and I have to make a addon to hold the thrust bearings. I will post pics of the rest of the converstion.

Paul wrote:
My little lathe will not cut hardened steel,
Time to look at mounting your Dremel on the tool post.
Start at http:/mini-lathe.com/ for info :)

robotic regards,

Tom

I have a question, do you guy thing I should use a belt drive to drive my screws or direct drive?

The steppers I'm using have about 250 in oz of torque. I was going to belt drive it to get more torque out of the system. I plan on cutting steel and alum.

Here is why I question myself-

http://www.cnczone.com/links.php?s=&action=viewlink&linkid=54

It would make my life easier to do it this way. HELP!

My plan is to belt drive, with a 2:1 ratio. But that is because I am going rack/pinion, and I need to gear down the servo a little. The smallest pinion is 1.7" per revolution (0.00425").

After further research, it looks like the feature that I thought added accuracy actually divided it out. The G340 has a step multiplier, but that means it sends the equivalent of 2/5/10 pulses to the servo for each input step.

I need the opposite, more resolution, not less. I guess I could find encoders with more counts.



I know the Shop-bots do a 3.5:1 gear down on their steppers.

Zeph

Zeph, if I understand you correctly, you should be getting more resolution, because your servo has to turn more times to move the same distance. How can this not work in your favour?

Where are your encoders mounted?

Well the feature in the G340 looks like it is designed to remove steps to soften the load on the software. For each step the software sends, it can be programmed to move the servo up to 10 steps. That could be useful if your steps translate to 0.0001" or less, but was not the feature that I thought it was.

I got an email from Dan Mauch who reminded me that the G320/G340 have quadrature encoders, which effective quads the resolution. That makes my 1.7"/rev with a 500 CPR encoder translate to 0.00085" per rev., which should be fine for my work.

I could still use a 2:1 gear ratio (which would increase torque), but no longer HAVE to just for resolution reasons.

I'm planning on the servos from Dan Mauch, which have the encoders on the back of the shaft.

Thanks-

Zeph

Great z conversion-

http://metal.duncanamps.com/mini_mill_z_axis.php

Hi Paul, could you tell me the supplier website from whom you bought your ball screws and their specifications? I need to buy some for my CNC.
Cheers

I got the screws and balls from Roton 317-821-4400 the part numbers are
59321-36 ball screw 29.95 ea
19193 ball nut 19.40 ea
to make them pre loaded 9.65 ea

Well with the help of my friends machine shop, I got one screw machined and a thrust bearing holder done. I will post pics of these parts.

Here is a pic

Poketing of the bed

Finally I going to get back to my retro of my milling machine to CNC. I need some ideas to make the Z axis move, any ideas out there?

Pics of the machine's head?

Have you seen this http://www.kdntool.com has kits for all types of mills, might be able to find some ideas here.



Nathan

DId you ever get the Z axis done? if not I got some pictures for you.


Jon

I have a RongFu Clone Round Column Mill that I am thinking of retrofitting to CNC.
Does anyone here have experience at doing that?
If so -what size Steppers/Servo's, controller, etc. was used?
Any problems with the head moving? (I would probably retrofit the quill feed for the Z and not move the head - for what I would be machining on it - mostly hobby parts and stuff).

Thanks for any input.

Joe Comunale
Romeo, Michigan USA