Benchtop CNC mill running a Tormach Rapid Turn/4th axis setup

[Roadstercycle]

Hi everyone and welcome back to my nightmare. Actually this time it's a dream come true. Last week I had discovered the Tormach Rapid turn and thought that's a great idea and not as pricey as the other guy running the Servo setup with brake, etc. So I decided to check Ebay and low and behold there was a used Rapid turn with all the goodies for a good price. Bought it on the spot. Now how do I hook this up to my CNC running Mach 3 when all the warnings from Tormach say that it can only run on there magic software and it's made only for the 770 and 1100. Well I called B.S. on that. So here we go.

I started by running a dual VFD setup that I can control manually. This way you have the best of both worlds. By running both the Main spindle and Rapid turn spindle now you can do precision grinding and other things I have not thought of yet. I also installed a switch so I flip flop between the Main spindle RPM and the Rapid turn RPM in Mach 3. The Index seems very solid, I can't wait to cut threads.

Next I installed a 900 in.oz. stepper on the other side directly across from their 3 phase motor using an almost exact copy of there motor mount bracket except for making it fit my stepper, that way all you have to do is swap the belt to the stepper pulley. Easy Peasy. It's a safety thing too, you don't ever want to drive the opposite motor when your working. I used their motor belt pulley on the stepper but had to make a thin tube as the nema 32 stepper has a .500 shaft and the Rapid turn motor shaft was about a .556. No big deal, bore a piece of aluminum tube then cut down to size sneaking up on it, I wanted it perfect.
So that worked great. I did have to replace their junk set screw as it strips right out because it's so soft. I counter drilled the set screw hole and used a 10-32 allen bolt and it worked perfect. It went through the larger pulley as I would not use that pulley for the 4th axis anyway. It's about a 3.5 to 1 ratio so the braking action of the stepper should be fine. I tried it and I could not turn the 4" chuck by hand, it was solid. I could not even get the belt to slip.
So of coarse using a multi grooved belt is suppose to be a huge no no when indexing and I would agree if I was making huge cuts and pushing every limit. For what I'm doing and about 90% of the home machinists I don't think it's a big issue. Scrolling, cutting splines, rotary engraving, making flats etc. I don't see any issue doing these.

The biggest issue I ran into really was just getting the Proximity sensor to work. So I put in a picture of that too. Pulled my hair out until I tried the 1.5K resister across the power and signal. Works like a charm. The drawing is the stock Tormach cable with the end cut off.

OK, The picture with the cutter and splined shaft was a setup picture. Just trying to show what could be possible. I did this splining actually on another 4th axis of mine on this machine with no brake just index with the nema 32
stepper. Actually same stepper, I robbed it for this.

Next step is figuring out a gang tooling setup, that should be fun.

Anyway I hope this helped some people out with running a Rapid turn on a non Tormach. I may put it on my Skyfire VMC2 when it arrives.
The nice thing about the Charter Oaks mill is the bed is long enough to just leave the Rapid Turn on there, still plenty of room for other projects.

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[CS900]

so since you brought it up...

I'm considering mounting a servo on my CNC lathe for indexing similar to the set-up you have here. I however am way too lazy to swap belts every time I want to change over. Have you considered putting a contactor inline with the your stepper motors and having Mach3 turn it on and off with the spindle commands? I would think once the steppers are isolated from any load even when the spindle is running you don't have to worry about any back EMFs damaging the drivers.

That's a great looking set-up you have there, and it's nice to see people hacking the tormach equipment. great job sir!

[Roadstercycle]

so since you brought it up...

I'm considering mounting a servo on my CNC lathe for indexing similar to the set-up you have here. I however am way too lazy to swap belts every time I want to change over. Have you considered putting a contactor inline with the your stepper motors and having Mach3 turn it on and off with the spindle commands? I would think once the steppers are isolated from any load even when the spindle is running you don't have to worry about any back EMFs damaging the drivers.

That's a great looking set-up you have there, and it's nice to see people hacking the tormach equipment. great job sir!

Hi CS900, Yes I thought about going that way, I have a set of 3 pole double throw switches on my Charter oaks so I can turn the steppers on and off for doing hand milling. It does open the contacts and there is no issue with the EMF and the motors turn smoothly. I just decided I did not want the stepper running at over 6000 RPMs. If you have the stock Rapid turn spindle motor running the spindle at 2000 RPMs. There is about a 3 to 1 overdrive then, thus the 6000 RPMs. So I decided the couple minutes or so to swap the belt is nothing compared to taking the Rapid turn off and then putting on my 4th axis and visa versa. The Rapid turn will live or the CNC mill now unless I need to do some long crazy job.

Today I am working on making a 10" diameter tool holder for the side of my mill head. Easy on and off to be able to hold 8 tools for the Rapid turn and have them be able to index with a stepper motor. It will be a gang of 3/4" holders for the Tormach ATC tool holders, a couple boring setups, cut off tool, threading tool and be able to switch out a couple of left and right hand turning tools. Damn that sounds like a lot of stuff. I've looked at a bunch of ways to do it but a rotary tool setup is the best answer,it's just got to be really rigid. Anyway like I said I'm on it. It could be all in vane. It's the not knowing which makes it fun.

Jack

[brian257]

Nice. I have thought of getting one and replacing their motor with a big servo motor to do both lathe work and indexing. I also started a thread yesterday about the possibility of mounting the Rapidturn not on the table of the Tormach I just got so I can use it like a slant bed lathe. I have also though of doing this on my Bridgeport CNC conversion instead of the Tormach. A while back I was considering getting or making a lathe headstock and mounting it to the vertical column of the mill and using it like a slant bed.

[Roadstercycle]

Nice. I have thought of getting one and replacing their motor with a big servo motor to do both lathe work and indexing. I also started a thread yesterday about the possibility of mounting the Rapidturn not on the table of the Tormach I just got so I can use it like a slant bed lathe. I have also though of doing this on my Bridgeport CNC conversion instead of the Tormach. A while back I was considering getting or making a lathe headstock and mounting it to the vertical column of the mill and using it like a slant bed.

I thought about doing a servo at first too but the cost would be ridiculous for the right setup, then add a break since a servo does not have holding power like a stepper. Since I had an extra nema 34 setup from my old 4th axis it really cost me nothing except a little time making the motor mount and bushing for the shaft. Same belt worked perfect since I copied the motor mount the belt length was dead on. I'm not sure but a 1.5 horse servo and control would be about $1000. Is that correct??? I'm really not that familiar with good servo setups.

Since I got the Rapid turn all that stuff has been running through my head too. Attaching it somehow just above the table solidly would be a great answer to all the configurations then you would have a Smithy setup. Hard to get that out of my mind. I think I just threw up in my mouth a little. The only difference it would not be cheesy and able to last a long time. I was just out there looking at making the revolving tool holder. I really like the idea as it would really make a clean gang setup.

[brian257]

Automation Technologies has a 1.33HP servo with brake and driver for $849. https://www.automationtechnologiesin...and-driver-1k/

Not sure if that would be the best or lowest cost option in servos.

[Roadstercycle]

Automation Technologies has a 1.33HP servo with brake and driver for $849. https://www.automationtechnologiesin...and-driver-1k/

Not sure if that would be the best or lowest cost option in servos.

I saw these the other day the only thing that put me off beside the price is that someone said that even with the servo brake on there was some rocking back and forth. That's when in another post they where talking about the external brake needing to be added. Again I'm not the one saying this nor do I have cardinal knowledge of this. Just from another post of the guy who was originally building the turning and 4th axis setup.

Jack

[CS900]

Automation Technologies has a 1.33HP servo with brake and driver for $849. https://www.automationtechnologiesin...and-driver-1k/

Not sure if that would be the best or lowest cost option in servos.

might be a bit harder to implement as it takea a -10 to +10VDC signal to control speed.

[Roadstercycle]

I think I'm going to stick with the stepper as it's done and works fine. An extra $1000 is not going to get me much if anything.

[Roadstercycle]

I did end up making my own drive pulley as Tormach does not have any in stock and thought it may be a couple weeks. It was easy, just had to make a cutter the right size for the belt grooves. I don't know why I did not do this a week ago. Works good no slippage so I think I nailed the grooves. At least with my own I was able to put in 2 locking set screws. The stock Tormach had 1 and the set screw was soft metal as it stripped the allen out really easy, would not even tighten, I ended up replacing it.

Jack

[skrubol]

The drawback of not using a timing belt for a positioning motor is that over time, the belt will creep a little bit. So on a long 4th axis op you may see your last cuts not quite line up with your first cuts.
The brake on 4th axis units is generally on the shaft of the axis itself. Any couplings, (belts or gears) will have some backlash or give under force/torque. Some use bicycle disc brakes for DIY spindle brakes as they can be found quite inexpensively and are in the right size range.

[Roadstercycle]

I totally agree with you. Since Tormach used a multi-groove belt and are actually cutting threads with their unit I'm not too concerned about belt slippage and so far with heavy cuts the only thing that I find that has happened is that the 5C collet rotated and the belt did not. For some crazy reason Tormach either does not put in the 5C locking tab or they forget to put it back in after sending it back for the 5C collet fix. If anyone knows which it is let me know please. As far as belt wearing, keep your belt tight and check your 360 revolution numbers now and then to make sure your dead on. I should not be needing it as much for indexing in the near future as I have the Skyfire VMC2 ordered with the Harmonic 4th axis so that should be awesome.