Mill 2 axis conversion

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Sep 24, 2009
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Inspired by Chuck , Steve and Barry and with much help from many I am going to attempt a cnc conversion on my old mill. It started when a co worker gave me some stepper motors from his Tormach mill that he upgraded and also threw in a couple of micro step drivers. I have learned a lot so far asking questions and studying various web sites on the subject.

It may be a slow process as I gather the other components needed and solve the problems as I go, not to mention the few hundred dollars for components and software down the road. So here goes............
I found information needed to make a power supply on the Gecko web site.
A simple transformer, bridge rectifier and filter capacitor. They had all of the data needed to calculate what you need. I wanted to end up with a 48 volt dc system, so I needed approx 36 Volts ac to supply it. I had a heavy transformer core. I removed the winding, calculated the volts output per turn and wound a secondary winding to get 36 volts. I used cotton string to hold the winding in place and will coat it with an insulating enamel.

Here is also a photo of the old mill I will be using.



Just a bit of a concern: You show 36V RMS. 36V RMS is 50.904v peak. Subtracting out the rectifier (1.4v) leaves 49.504v. Can your system handle the extra 1.5V? This voltage will also fluctuate depending on the load conditions in your house as well.
I am not familiar with the tormach mill stepper drives, what is the torque rating of the drives? I see that you have a servo drive on your mill now.
Are the Tormach going to provide enough power to be of any use?
You do know that unless you install ball screws and a number of other things. The inherent friction in your mill will overload improperly sized drives, and cause locating errors.
I appreciate your interest and suggestions.
The drives should handle 50 volts no problem. With the rectifier and capacitor I get around 49.5 volts, which will drop with any load.
The smallest of the two stepper motors is 670 oz in torque and the mill I have is fitted with ball screws already and they are very smooth, almost no backlash and turn very easy. I am still torn on whether to drive with timing sprockets and belts at reduced ratio or direct drive. My mill table isn't that much larger than a tormach. I will probably try direct drive first and if they won't carry the load gear them down with timing gears and belts. I am not looking for a high capacity high speed machine, I just want to be able to machine shapes and curves.
I am almost ready to breadboard the whole set up and give it a bench test. Just need the time to do it. I can't retire for another 5 years!!!!
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One step forward and a couple back
I wired up all of my components for a test run. I had a little trouble with the breakout board manual, one of the axis had the pin configuration two different ways in the manual, but with some experimentation I got that figured out.
I was disappointed in that 2 of the 3 stepper driver boxes did not work, but the motors worked well and I was able to test both axis with the one good driver.
I ordered a couple of new drivers today.

[FONT=&quot]I got my new Chinese micro step drivers[/FONT] model Ma860H[FONT=&quot] ones that Barry has had good luck with. It took me awhile to figure out that even though they are marked the same as my old ones that I had to reverse the polarity on the pulse, direction and enable in Mach3 to get them to work. After that they seemed to function just fine.

So I am ready to start putting it all in a box and adapting the stepper motors to my mill.
Nothing too exciting, but something accomplished. I had an old DRO box that I modified, (made it taller) to house all of my cnc components.
Now I just have to bolt the parts in and wire them.

Got a few minutes shop time this week.
Most of the wiring is complete. I will do another bench test then start machining the motor mounts and timing belt pulleys on the mill.

Another micro step forward.
The control box is complete with motor cables and connectors installed on the motors. After making a few adjustments in Mach3 everything seems to work as it should. Next step, mount the motors and drive system on the machine.

I removed the dial off one end of the x axis and fit a 50 tooth timing gear in it's place. Next is the motor mount and plate, stay tuned


Finally got one axis roughed out and mounted. I connected Mach 3 and it functioned better than expected.
Now to do the other axis

They are used motors from a Tormach machine. The one in the photo is about 600 oz/in of torque. Close to a Nema 34
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I was able to spend another few hours in the shop the other day. This is my solution for the mounting plate for the stepper motor on the cross feed.
It is a curved surface, so a little more challenge. I first machined a plate with the holes drilled for the tap drill size. I then clamped it to the mill with a piece of aluminum angle and used it for a drill guide. The plate has set screws next to the holding bolts to level the plate to the mill. I worked very well.
The last photo shows the mounting plate in place and the timing belt pulley mounted in place of the dial



I was able to make another motor adapter and mount it with a belt to the other axis.
I calibrated both axis and tweaked the motor adjustments in Mach 3.
I wrote a program to cut a 4" circle in CamBam and posted it to Mach3.

Everything worked better than expected. See the short video of it cutting the circle in plastic on it's maiden voyage. I am pleased with the results.
Maybe a Z axis in the near future.

Special thanks to those that offered advice and helped me solve problems with the build, Chuck Fellows, Barry Thomas, Steve Hucks.

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