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IndustryArena Forum > MetalWorking Machines > Tormach Personal CNC Mill > 4th Axis Issue - Basic Rotary Table
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  1. #1
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    4th Axis Issue - Basic Rotary Table

    The job I bought this for got done another way, but now I have another job where it might be useful. I finally hooked it all up and put it on the machine table.

    Hooked it all up. No issue really other than being quite an exercise is advanced yoga positions inside a full enclosure. Filled it with oil, and filled the oil port. I actually over filled it with oil. I guess I wasn't looking at the moment it passed the site glass and then started pouring out below the table. Then per the instructions I backed out the adjustment screw, and fed it back in until felt a bit of resistance. I felt the motor turn a tiny bit as I took it in another 1/4 turn per the instructions. All seemed good.

    However, there is a problem. When rotating in the A(-) direction (clockwise when looking at the front of the table) it runs great at a screaming 3-2/3 RPM. When running in the A(+) direction (counter clockwise when looking at the front of the table) it sometimes chatters and even stalls.
    Bob La Londe
    http://www.YumaBassMan.com

  2. #2
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    Re: 4th Axis Issue - Basic Rotary Table

    The steps per revo or degree appear to be wrong as well. A simple 360 degree move went much further than 360 degrees.
    Bob La Londe
    http://www.YumaBassMan.com

  3. #3
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    Re: 4th Axis Issue - Basic Rotary Table

    The email sent to Tormach.

    The original job I bought this for was completed another way. Recently another job came in that would benefit from this 4th axis, so today I installed it.

    I hooked it all up. No issue really other than being awkward inside an enclosure. Filled it with oil, and filled the oil port. I actually over filled it with oil. I guess I wasn't looking at the moment it passed the site glass and then started pouring out below the table. Then per the instructions I backed out the adjustment screw, and fed it back in until I felt a bit of resistance. I felt the motor turn a tiny bit as I took it in another 1/4 turn per the instructions. All seemed good.

    ISSUE ONE OF TWO:
    However, there is a problem. When rotating in the A(-) direction (clockwise when looking at the front of the table) it runs great at a screaming 3-2/3 RPM. When running in the A(+) direction (counter clockwise when looking at the front of the table) it sometimes chatters and even stalls.

    ISSUE TWO OF TWO:
    The second issue is that the steps per degree must be wrong. The dip switches are correct. I double checked them before powering it up, and checked it again after realizing there was an issue with steps per degree. It turns 25% further than commanded. With A-Axis referenced to zero and indicator mark set to zero on the rotary table if I enter a G0 A360 at the command line it turns 90 degrees past the zero mark instead of stopping at the zero mark. Yes dip switches 4 and 6 are flipped to the left. All other dip switches are set to the right. The other wires on the drive are set 320 321 322 323 325 324. 325 goes to A- and 324 goes to A+. I even reached in with my camera phone and took quick pics to make sure as needed.

    I suspect both problems are related. Something doesn't match between the mechanical hardware and the electronics.
    FYI: 3-2/3 RPM (1320 degrees per minute) seems incredibly slow. Is that correct? Obviously its actually turning 25% faster than that per issue two of two above.
    Hopefully I get it solved quicker than that, but it seems odd.
    Bob La Londe
    http://www.YumaBassMan.com

  4. #4

    Re: 4th Axis Issue - Basic Rotary Table

    Not sure what the screw is that you are referring too since I don't have one. What happens if you loosen it?

    Sounds like accel setting and steps per degree are off..

  5. #5
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    Re: 4th Axis Issue - Basic Rotary Table

    Quote Originally Posted by number40Fan View Post
    Not sure what the screw is that you are referring too since I don't have one. What happens if you loosen it?
    That would be the backlash adjustment screw as detailed in the instructions. Among the couple items you must do before using your basic rotary table 4th axis to make sure you don't damage it. (along with filling it with oil.) If you loosened it you could potentially lock up the axis. Not a smart thing to do.

    Sounds like accel setting and steps per degree are off..
    DOH! LOL.

    Actually it was kind of funny. In one section they say, "Match DIP switch (see Figure 13) settings on drive as detailed in technical document TD10173 (included)." What they do not say is the dip switch settings in Figure 13 are wrong and you MUST get them from TD1073 which by the way was not included. That was the issue with steps per degree. I felt silly when I found it by downloading TD1073, but setting the dip switches correctly did correct the problem with matching up actual movement with command movement.

    The other is a little more touchy feely. I went through all the mechanical adjustments and still had issues with chatter in counter clockwise rotation. You twist the motor and motor mount to engage and disengage the worm drive mechanism. Fully clockwise and the table will free spin. Counter clockwise and the motor must turn the table. There is a locking lever that keeps the worm drive from disengaging. I think there are actually two issues here. The point where the backlash adjustment screw engages the drive is not perfectly concentric around its axis of rotation. Firmly engaging the locking lever to keep the drive engaged distorts things a little bit. With the table rotating at its screaming fast 3-2/3 RPM I loosened the locking lever and let it find its own best location for the drive mechanism engagement. When snugging the engagement locking lever back up I tightened it less firmly.

    If my assumptions are correct it will improve as it wears in.

    Tomorrow I will setup a job to test it as it is now.
    Bob La Londe
    http://www.YumaBassMan.com

  6. #6
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    Re: 4th Axis Issue - Basic Rotary Table

    Well, I ran 18 successful parts with it, but only because there wasn't any tight tolerance requirement.

    CONS: Setup (after hook up and initial testing) was rather a pain.
    1. The tail stock is pretty generic to be able to work with several different 4th axis or rotary tables which made setup for this one kind of a pain.
    2. The face of the plate is not flat.
    3. The backlash adjustment screw mating surface is not concentric (close) around its axis or rotation.
    4. It only turns 3-2/3 RPM flat out.
    5. The push against t-slot markings on the tailstock and rotary table point in opposite directions.
    6. The 18mm MT 1 adapter sleeve did not fit in the 18mm bore of the tail stock. I had to ream the tail stock.
    7. Set so the tail stock and rotary table point at each other either the motor points towards the control cabinet, or the knobs and levers for the tailstock are on the side away from the operator.

    PRO
    1. The bore of the rotary table is very nice fit for the MT/ER32 collet chuck I decided to use with it.
    2. The bore of the rotary table seems to be pretty concentric and parallel with its axis of rotation.

    Purchases to do the job where:
    Rotary Table
    Tail Stock
    MT1 Adapter Sleeve
    4th axis driver kit

    From other vendors
    MT1 carbide tipped half dead center.
    MT1 *live 3 jaw chuck
    MT2/ER32 Collet chuck


    I am glad I went with an MT collet chuck. I would have been quite frustrated if I had gone with a bolt on chuck or collet chuck.

    Overall... I found this combination of parts to be adequate, but I probably would have gone another way if I knew everything I know now.

    * Some people would claim a live chuck is one that is under power. I won't quibble over terminology. Live is often commonly used to simply refer to a free spinning tail stock hardware such as a "live" center. This is functionally the same except it has a small tommy bar operated 3 jaw scroll chuck on it instead of a pointed center.
    Bob La Londe
    http://www.YumaBassMan.com

  7. #7
    Community Moderator Jim Dawson's Avatar
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    Re: 4th Axis Issue - Basic Rotary Table

    I'm a little late the the game here, but I had a similar experience when I powered my rotary table. It started out life as a 6 inch Vertex Super Spacer. It was tight and the stepper would barely drive it in one direction, but the other direction was pretty good.

    What I found is that the worm shaft was binding against the thrust surfaces, just steel against cast iron. Installing ball thrust bearings on either end of the worm shaft completely solved the problem.
    Jim Dawson
    Sandy, Oregon, USA

  8. #8
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    Re: 4th Axis Issue - Basic Rotary Table

    Quote Originally Posted by Jim Dawson View Post
    I'm a little late the the game here, but I had a similar experience when I powered my rotary table. It started out life as a 6 inch Vertex Super Spacer. It was tight and the stepper would barely drive it in one direction, but the other direction was pretty good.

    What I found is that the worm shaft was binding against the thrust surfaces, just steel against cast iron. Installing ball thrust bearings on either end of the worm shaft completely solved the problem.

    I just broke it all down and put it in a drawer a little while ago. I may use it again, but I am seriously thinking about finding a splash down motor for my mini lathe and using it on the table instead next time.
    Bob La Londe
    http://www.YumaBassMan.com

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