Need Help! Tormach 770 3rd gen 4th axis DIY problem....

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Thread: Tormach 770 3rd gen 4th axis DIY problem....

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    Exclamation Tormach 770 3rd gen 4th axis DIY problem....

    Hello guys ,

    In many of my works I needed a 4th axis so I did some researches and figured out I will make one with a harmonic gear my self.
    The machine is 770 3rd gen , as far as I read it's 4th axis plug and play.Just need the proper wiring and a new driver+ motor.


    I've found a same number leadshine motor and driver (for half the price ) and decided to give it a go.
    I've build all the parts on my tormach great result btw you can see from the pictures.


    Problem : machine doesn't command this driver.... I did all the wiring similar to the other axis , when I control my 4th thru another XYZ driver it works....
    Cannot find any differences in the drivers ... pictures attached. Only the PULDIR cable connector was different but I followed the order of wires and tested it in another XYZ drive and it worked....

    Any guesses ?





    Pictures attached LEFT original Tormach , right Leadshine same part number

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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Best advice on these is to work by functional blocks. Your blocks are g-code/interpreter, machine controller, driver/wiring, motor.

    What happens if you swap a functioning driver/motor (X or Y) to the A axis control ribbon connector? If yes, the new driver/motor/wiring is wrong. If not, look at g-code, machine setup, stuff like that. And so on. Be very deliberate, keep good notes, work out what to test and write it down. I always get caught testing and retesting the same thing, while missing the obvious other branch of the path until someone else points it out.

    One quick thought: Can't quite make it out, but are the DIP switches set the same in the one that works and the one that does not? (I assume so, but it doesn't quite look like it).

    Second quick thought. I don't have a 770, but on my 1100 the A axis uses the OLD -not Leadshine- stepper driver. Tormach was quite specific about that. Since they don't sell a separate 4th axis for the 770, I wonder if perhaps the machine control board is expecting the original driver, not a Leadshine driver, and just doesn't provide the right signals.

    Once you get this running, post a description of your design and build. Many of us will be interested.



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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Quote Originally Posted by GLCarlson View Post
    Best advice on these is to work by functional blocks. Your blocks are g-code/interpreter, machine controller, driver/wiring, motor.

    What happens if you swap a functioning driver/motor (X or Y) to the A axis control ribbon connector? If yes, the new driver/motor/wiring is wrong. If not, look at g-code, machine setup, stuff like that. And so on. Be very deliberate, keep good notes, work out what to test and write it down. I always get caught testing and retesting the same thing, while missing the obvious other branch of the path until someone else points it out.

    One quick thought: Can't quite make it out, but are the DIP switches set the same in the one that works and the one that does not? (I assume so, but it doesn't quite look like it).

    Second quick thought. I don't have a 770, but on my 1100 the A axis uses the OLD -not Leadshine- stepper driver. Tormach was quite specific about that. Since they don't sell a separate 4th axis for the 770, I wonder if perhaps the machine control board is expecting the original driver, not a Leadshine driver, and just doesn't provide the right signals.

    Once you get this running, post a description of your design and build. Many of us will be interested.
    I've fixed the problem , after finding the thread about how to locate the Dir/Pulse cables on the connector.
    Once you locate those cables (No 3,4,5 only used from all 6) you can control any driver you like.Also you can hook it a servo motor like Clearpath.

    After you get it running , you need to adjust it to go with your ( non factory ) rotary.

    Then you boot up from Linux go to folder "operator , machine config , into last version of PP and into 770............. .ini file" this is the file that controls the whole machine . Going to "AXIS 3" into the file , there is a parameter called SCALE this parameter is 500 by default for the tormach rotary with 90:1 worm gearbox ratio.
    You adjust/calculate this parameter depending on your drive-train ratio.This is a formula depending on the Pulse setting on the driver used to control the motor with different accurancy of rotation.

    For example I was using 124:1 Harnonic drive gearbox and this same stepmotor as the one on X-axis.I can say it's too slow.
    A hybrid stepper or a Clearpath servo will be better as they can rotate a lot faster.
    I am considering now to modify the back side of the 4th axis mount and install the motor with a positive belt pulley to increase the speed of the rotation.

    Even make my first part today!



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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Terrific!

    And many, many thanks for the configuration file info- you just saved me one hell of a lot of digging and a royal pain setting up a mechanical equivalent of what Tormach hard coded as a ratio. I've had a 160:1 harmonic drive hanging around the shop waiting for me to cut some pulleys to make it look like 90:1....

    Could you post a worked example of how you calculated your scale parameter for 124:1, please? Or is it a simple proportion (500:90::x:124)? More detail, please.



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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Regarding calculating the scale.When you go to linuxcnc website you dig into folder "motor traj" file ( INI Configuration ) there is some formulas how to calculate it. I've tried those but didn't manage to get a close number to 500. Then yes I did it the way you are guessing ( a proportion ).

    But I got the harmonic drive from a guy who didn't knew the exact ratio of it and I first had to find it. I made a small sharp edge arrow that i mounted on the harmonic drive shaft via one of the 6 bolts, then scratched a small mark on the aluminium mount and did one full revolution on the shaft. Then looked at how many degrees the software did. In my case is was 496 . Then it was - x= 496*90/360 = 124. This was with the driver set at 1600 micro steps. I did a lot of testing on which microstep setting the motor was starting/working smoother and i finally figured out it was 2000. This again changes the SCALE ratio , so i calculate it again. I think by memory my final SCALE number was 861, How I test it if it's exact 360 degrees per turn: I simply tell the machine to make 6 or more turns and watch the arrow and the mark, if after all the turns the arrow stops exactly at the mark , this means the SCALE is correct and it's not accumulating any big error after a few turns,

    This will be more seriously readjusted with a dial indicator measuring a flat face i do on a square stock.

    This 2000 microstep setting made the motor even slower , but running smother. You can try to increase the speed of the motor from the ini file , but if the speed is above the max RPMs/ratio of the motor - the stepper stalls and the machine is going into E-stop.

    Why having slow 4th axis is a problem.( if you don't have the A-axis homing kit connected ) :

    1.When doing a simultaneous 4th axis milling , after let's you do a multiple dept's contour and let's say to mill this contour the axis do 4 turns , you have to watch it rotate 4 negative turns to find it's exact 0 or at whatever degrees it start the contour at every next dept.

    2. It limits your cutting feedrate. For example I made my g-code with a 500mm/min feedrate and when starting the code , the machine automatically (depending you your max turning speed/scale ) dropped to 15mm/min .... you can imagine this is 33,33 times slower from what is desired, right ?

    I've found info that if you have a 4th axis homing kit it rotates to the closest reference point without making turns : look what i mean

    Didn't tested this yet as I don't have a proximity sensor with DIN 6 connector , but may work on this soon.

    This is why a pulley will be made to make this thing turns at least 10x faster.

    I can post pictures of what you are interested tomorrow.



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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Thanks very much for the detail. And, yes, do post pictures. Remember that this forum is one of the most active at CNCzone, and you are helping a lot of others when you provide detail. The more you document, the more useful for all of us.

    Very nice job.



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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Thanks to the OP - This thread is just what I've been looking for! I've also been contemplating converting a 9" manual Troyke rotab I have to use as 4th axis platform on a Series 3 1100 Now typically I try to stay as close to the OE design as possible to avoid too many problems but when I inquired, Tormach told me they still use a 2 phase drive and bi-polar motor on the 4th axis kits they sell. Hmmm. what to do. I was hoping and it would seem to make sense to simply use another Leadshine 3ND883 three phase drive and 863S68H stepper motor on the A axis same as XYZ but I would like to know it works before buying the stuff.
    So no issues with the machine control board etc??
    If I may ask, where did you guys order the Leadshine drive/motors from?? I found several on Ebay, Stepperonline and elsewhere but a little leery about ordering stuff from China. Looks like 1 month delivery times.
    The ones shipping from US are not Leadshine branded only knockoffs.



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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Hello Paul ,

    My advice is to go with a hybrid stepper.This is what I first got for my 4th axis. It's better it's faster ... shame I had to return it as I was thinking it is not compatible with my mill...... it was only the flat cable making the problem.
    I got it from aliexpress for about 150USD + 50USD shipping. Then I got the same leadshine driver/motor for same price .....

    When I go to my workshop I will post more pictures of how things are connected.



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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Well I got sidetracked on this awhile but ended up buying a Leadshine MA860H
    2-phase drive and a 86HS85D Nema 34 stepper. The motor may be a tad big for the drive but we'll see. Yes a harmonic drive would be really awesome but my goal for now is simply to put my 90:1 manual Troyke to use instead of it taking up 50 lbs of bench space! Based on the posts here and tormach manual 2000 pulse/rev should work perfect. Next mini project is to find the right connection solution for the signal ribbon cable to the drive. The drive I bought has the green plugs that take hard wire direct vs Tormach that have the little rectangular black ones. I could snip the end of the ribbon cable and hard wire it but if anyone knows of an adapter of sorts that would be great. The only other way would be to unsolder the green connector from the drive and solder in the replacement black rectangular (DIN?) one. I'm not afraid to solder but it would be better if there was a plug and play adapter option available.
    For mounting I am considering a couple options.
    1:1 timing pulley arrangement would allow me to tuck the motor behind the table thus making a more compact setup and also have the ability to slap the manual handwheel on for setups.
    The other method would be inline with an adapter same as the Tormach unit. Much simpler and no added backlash but man it sticks way out forward. I 3D printed an adapter yesterday so I'll see how it looks. If it's too obtrusive I may still go with the pulleys if nothing else than for a fun projectTormach 770 3rd gen 4th axis DIY problem....
    This is the Rotab and inline adapter.





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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Mounted





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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Alrighty. With the help of some prior posts here and the internet, I was able to wire it up temporarily today and it appears to work nicely! I'll need to buy all the proper cables and receptacles for the panel. I did find the same CPC plugs/receptacles tormach uses in its 4th axis kit online but it looks to be a pita having to buy all the little pins, sockets etc and crimp everything. Automation Direct has some neat pre-made 16 ga multi-pole control cables with pre-wired molded plugs and receptacles. I had one 4 pole panel receptacle on hand so I'll just buy the rest of the stuff. Then I'll make a junction box for the motor with a receptacle for the cable plug, that way the cable can be removed from the rotab for removal and not get in the way. The motor leads and power connections were fairly straightforward however it was a bit of a head scratcher figuring out the signal connections from the Tormach control board (IDC ribbon cable connector) into the drive. Really wanted to avoid frying something. As expected the rotation degrees on the table coincide perfectly with the A axis readout in Pathpilot display so thats good. The only thing I noticed is the motor seems very warm. Initially I had the dip switches set at the peak current 7.2A but lowered it to 6.5A for now.
    In case its of help to anyone else doing this in the future- Here is the physical wiring (obviously a temp rig) from the ribbon cable to drive.






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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Its alive.....Tormach 770 3rd gen 4th axis DIY problem....




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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    In looking at your motor coupling I was wondering if it could wind/unwiind as the load changed, causing positioning error?



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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Hmmm. Possibly. I suppose it could and does to some small degree. There may be a better coupler design than the one I used. What does Tormach use Oldham or Lovejoy style maybe?? I'm thinking that at 90:1 reduction it won't amount to much at least not my intended application.
    The weak link I see on these types of 4th axis rotabs is the gear wear and backlash trade off of the worm gear design. I don't have it filled with oil at the moment since it leaks out like a sieve so for now keeping the test rotating to a minimum.
    BTW I put a thermocouple on the motor and it shows 120F with only some quick jogging. I can put my hand on the motor at that temp but much more and it would be pretty uncomfortable. To those with more experience with steppers I have to ask Is this typical? If you guys see anything obvious I may have done incorrect please shout.



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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Try twisting and untwisting it with your fingers. You may be surprised how easily it winds and unwinds.



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    Default Re: Tormach 770 3rd gen 4th axis DIY problem....

    Quote Originally Posted by georgimirov View Post
    Regarding calculating the scale.When you go to linuxcnc website you dig into folder "motor traj" file ( INI Configuration ) there is some formulas how to calculate it. I've tried those but didn't manage to get a close number to 500. Then yes I did it the way you are guessing ( a proportion ).

    But I got the harmonic drive from a guy who didn't knew the exact ratio of it and I first had to find it. I made a small sharp edge arrow that i mounted on the harmonic drive shaft via one of the 6 bolts, then scratched a small mark on the aluminium mount and did one full revolution on the shaft. Then looked at how many degrees the software did. In my case is was 496 . Then it was - x= 496*90/360 = 124. This was with the driver set at 1600 micro steps. I did a lot of testing on which microstep setting the motor was starting/working smoother and i finally figured out it was 2000. This again changes the SCALE ratio , so i calculate it again. I think by memory my final SCALE number was 861, How I test it if it's exact 360 degrees per turn: I simply tell the machine to make 6 or more turns and watch the arrow and the mark, if after all the turns the arrow stops exactly at the mark , this means the SCALE is correct and it's not accumulating any big error after a few turns,

    This will be more seriously readjusted with a dial indicator measuring a flat face i do on a square stock.

    This 2000 microstep setting made the motor even slower , but running smother. You can try to increase the speed of the motor from the ini file , but if the speed is above the max RPMs/ratio of the motor - the stepper stalls and the machine is going into E-stop.

    Why having slow 4th axis is a problem.( if you don't have the A-axis homing kit connected ) :

    1.When doing a simultaneous 4th axis milling , after let's you do a multiple dept's contour and let's say to mill this contour the axis do 4 turns , you have to watch it rotate 4 negative turns to find it's exact 0 or at whatever degrees it start the contour at every next dept.

    2. It limits your cutting feedrate. For example I made my g-code with a 500mm/min feedrate and when starting the code , the machine automatically (depending you your max turning speed/scale ) dropped to 15mm/min .... you can imagine this is 33,33 times slower from what is desired, right ?

    I've found info that if you have a 4th axis homing kit it rotates to the closest reference point without making turns : look what i mean

    Didn't tested this yet as I don't have a proximity sensor with DIN 6 connector , but may work on this soon.

    This is why a pulley will be made to make this thing turns at least 10x faster.

    I can post pictures of what you are interested tomorrow.
    How do you increase the speed of the motor in the ini file? All axis' in my ini file have a feed rate above the max velocity except for Axis_3. The only thing I have been able to do to change the motor speed is change the scale. That obviously screws up the correct positioning.



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Tormach 770 3rd gen 4th axis DIY problem....

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