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IndustryArena Forum > MetalWorking Machines > Shopmaster/Shoptask > Adding stepper power to the chuck.
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  1. #21
    Join Date
    Aug 2013
    Posts
    55

    Re: Adding stepper power to the chuck.

    Well, just to complete this thread I have finished the stepper mount plate and machined a pulley for the stepper.
    With a belt connected the whole thing fits neat and I can spin the chuck under the stepper power from within Mach 3 ...treating it as the A axis.



    If I move the A axis 3.75mm the chuck does a single revolution. If I move the x axis along as well then I can cut threads easily.

    It’s slow and needs some lube on the cutter, but the result is pretty satisfying.

    There are lots of things I can do with this tool, and given the cost and time I’m really happy with it.

  2. #22
    Join Date
    Sep 2013
    Posts
    326

    Re: Adding stepper power to the chuck.

    This was a really fun thread! I wish I had time to maybe wash the truck or the dog! :-) The solid workup are really cool and your work is awesome! Thanks for sharing!

  3. #23
    Join Date
    Jan 2008
    Posts
    458

    Re: Adding stepper power to the chuck.

    Julian,
    Real nice work- I like that finish you put on the bracket. What's with the orange color- is that some trick of lighting? It's a bit late now, but you could have accomplished the same thing by using an electric clutch from an air conditioning pump mounted to the other end of the spindle. Then you could engage/disengage with a switch or a command from Mach 3.

  4. #24
    Join Date
    Aug 2013
    Posts
    55

    Re: Adding stepper power to the chuck.

    Yes Small, I painted the castings when the machine was apart.
    I didn't touch the sheet metal, only the castings.
    Dark blue and orange.
    Silly really, but as I made some steel parts I needed to paint them- so I thought I'd paint the other bits too.

    The jewelling on the surface is a great thing about CNC- you take a blunt tool and a simple repeating pattern and just set the machine going.
    Go make a cup of coffee.
    It takes a while but the machine does not seem to get bored.

    Its a really practical finish to hold a little protective oil and it does not show the scratches and marks.



    Yes, I could have done this project easier.
    But I really wanted to try making some machining wax and then casting with epoxy.
    These are things that will come in handy in the future, and I was intrigued by them having seen them elsewhere in this forum.

    Progress is still being made.
    Making a little upgrade to the Y axis at present.

  5. #25
    Join Date
    Jan 2008
    Posts
    458

    Re: Adding stepper power to the chuck.

    Julian,
    I was thinking of doing the same mod to my machine, but using the clutch to disengage- how is you positioning accuracy? I'm mostly wondering about any backlash under lathe cutting loads.

  6. #26
    Join Date
    Aug 2013
    Posts
    55

    Re: Adding stepper power to the chuck.

    Hi Small, its been a long time since I posted anything on here- but I have been doing things. Last night I did a little thing... my chuck gang sort of makes the tailstock redundant so I made a little wood block to go across the end of the slide way to hold the end of the bellows.
    Actually, something I did... perhaps did not post about it ......was to make a triangulated brace for the Y axis. I felt that the Y axis restraining steel plate hanging off the front of the table - retained by two bolts.... was a possible point of flex, so I re-machined the bracket, fitted a different bearing support and attached a brace either side mounted under the table. Made the whole set-up nice and rigid. Perhaps it was not needed- but its solid now.

    I'm also making up the plates for my Z axis upgrade, so I'm a good way there too.

    As for backlash on the chuck stepper- I've not noticed any. I'm not entirely sure what you mean... backlash when I change direction?
    Given the direct drive nature of the set-up there is little or no backlash when the belt it good and tight.

    I attached a laser pointer to the chuck and marked the point of the beam on the far wall of the workshop. When I rotated the chuck and then sent the A axis back to zero the laser point went back to the mark on the wall.
    I could try that again after I cut a thread- is that the sort of test you want?

    If you give me a clear idea of what you want to know I will measure it for you.

    Anyway, my next project will be to make the fittings for the ball nuts for the Z axis- so I will thread some steel (M25)- and see how that turns out.

    I'll post again soon about that.

    Would you like to see the other mods so far?

  7. #27
    Join Date
    Jan 2008
    Posts
    458

    Re: Adding stepper power to the chuck.

    Julian,
    Yeah- would like to see any pictures of your mods. What I was wondering about is if the stepper motor has enough holding torque to keep the chuck from back spinning when you are cutting, or if the belts have enough stretch or flex to also cause the chuck to rotate slightly under load.

  8. #28
    Join Date
    Aug 2013
    Posts
    55

    Re: Adding stepper power to the chuck.

    Ah, I understand better now- if I used my setup as a dividing head- would the stepper have enough power and the belt enough strength to hold the chuck rigidly enough to get good machining finish.

    Hmmm. Good question.
    At present I don't have a grinder that I can mount easily on the table to test that- I guess I could mount a router or something to the table and run it along a part in the lathe.... like a barley twist table leg.

    I guess you really want to know if I can machine a neat flat on a bar?
    I'll think about that one.

    In the mean time I'll take some pictures.

  9. #29
    Join Date
    Aug 2013
    Posts
    55

    Re: Adding stepper power to the chuck.

    I added a wooden block to the end of the slideway when I removed the Tailstock.
    This simply holds the bracket for the bellows- so they don't keep falling off the end.



    A shot from further away, for those like me who find the close ups a little disorientating.


  10. #30
    Join Date
    Aug 2013
    Posts
    55

    Re: Adding stepper power to the chuck.

    As for the Y axis.

    First I machined a new plate to mount to the table, designed to accommodate my new shaft bearing.

    It has a bigger opening to the top to provide better clearance so that I can slide T nuts easily into the centre table slot.
    It also has holes on both sides for a the braces.



    I removed the table and glued some steel inserts into the slots under the table. I will use these to ground the braces. I glued these in only after I had pre-assembled the whole thing with the braces in place so everything lined up- initially I used a little epoxy putty to hold then in place.



    Finally, I could assemble the whole lot. It makes the Y axis more rigid under load (I think). The eagle eyed amongst you will notice that I notched the side braces onto the front plate to help make the joint more rigid. I didn't feel the bolted joints under the table needed notches because of the loads on them.




  11. #31
    Join Date
    Aug 2013
    Posts
    55

    Re: Adding stepper power to the chuck.

    I've finished the plates for my Z axis upgrade.
    The plate that mounts the bearing blocks will be painted.
    The other plate hangs on the bottom of the quill.

    Just a quick memory jog where I'm going with this;



    I have to say, with every upgrade on this machine it becomes better and better.
    Its taking me some time, but this machine is really making the most of both the limited space I have and the money I spent on it.



    I've still go a fair bit to make.
    The angle plates to mount the stepper, the pulleys and the special mounts for the ball nuts that go into the big bearing blocks.

    I will post more as I go.

  12. #32
    Join Date
    Mar 2012
    Posts
    90

    Re: Adding stepper power to the chuck.

    The mod to the Z axis looks like a big improvement. Can you share more info? I would like to get an idea what is involved. I am planned to stiffen the 5th column soon by replacing the entire motor mounting plate with a 2x6 tubing and making a new triangulated 5th column that will be stiff in both Z and Y.

  13. #33
    Join Date
    Aug 2013
    Posts
    55

    Re: Adding stepper power to the chuck.

    I haven't finished it all yet- only the big components. I'm actually busy using the machine to make stuff.
    The big problem with the Z is the drift as it goes up and down and its backlash as it changes direction.
    This shows up especially when I approach a z position from different directions or when I cycle the z axis (it runs eccentric).

    At present I get around this in different ways- that's why I'm not so eager to finish the project. But I will- I love the idea of 3d machining and it is essential for that application.
    Not so important for 2.5 d.

    What do you want to know?
    I'll tell you what I can.

  14. #34
    Join Date
    Mar 2012
    Posts
    90

    Re: Adding stepper power to the chuck.

    So the goal of the mod is to move the spindle without any side loads by having 2 ball screws at 180 degrees from each other. Both driven by the one stepper motor. My 1st question where can I get the parts I would need to do the conversion? In particular the ball nuts that can rotate around a fixed ball screw. What the dimensions and cost would be for those. The other parts I could probably make. Ideally having pre-loaded ball nuts or double ball nuts would minimize backlash and go a long way to improving the movement of Z. I think my machine has more than 5 thou of Z backlash and the spindle can get somewhat cocked in the bore when moving.

    I never did lock down my Z when cutting and I think that would help a lot, but would be a PITA compare to not having to do so. I discovered that the lock down bushing that pressed on the spindle was not machined right. After I took off about 10 thou on the lathe I could actually use the Z lock down lever.

  15. #35
    Join Date
    Aug 2013
    Posts
    55

    Re: Adding stepper power to the chuck.

    You are totally correct Blacki. No twisting moment from the single ball screw. Where can you get the parts? Ebay- from China. These parts are pretty standard. The nuts that rotate around a fixed ball screw are just ordinary nuts mounted to a collar with the pulley on the end.
    I've made all the bits on the machine so far.
    As for costs and dimensions- well hmm. I'm not sure what they would cost you but I can let you know my shopping list and all the dimensions you need- there is no secret.

    Whether you should do it... hmm I'd wait till I finish mine and I will let you know how good it was.

    At present the mods I've done so far have taken the pressure of me to improve further.
    The big benefit to me with this final mod would be that I can 3d machine much better.
    I've been using my machine a lot over the last year- I really like it. I'm building a band saw for cutting lumber- and machined many of the bits on the Patriot.
    Plus loads of quick jobs on the mill and lathe.

    Only problem I've had so far was the cooling fan in the electrical cabinet- it stopped working.
    When I replaced it I found it was 24v but was running on a 48v supply. I guess it could only take that for so long. Anyway- $8 later and a 48v one was fitted.

    I should note that I'm presently engaged in making a new bench as I have a problem with the original because its feet do not line up with the beams in my wooden floor.

    I figured I'd fix that first because I've found that the floor is bouncing quite a bit.

  16. #36
    Join Date
    Mar 2012
    Posts
    90

    Re: Adding stepper power to the chuck.

    Any dimensions and the types of parts you are using would be appreciated.

    For 3d machining I would think that reducing the X and Y backlash would also be needed. I'm getting about 3 thou on them. Any thoughts on improving them?

  17. #37
    Join Date
    Aug 2013
    Posts
    55

    Re: Adding stepper power to the chuck.

    I agree that X & Y are the first thing to do- even for machining simple things like circles and them no being oval.

    Once I was below 0.1mm (4thou) backlash on X&Y I found that the issues tended to become more numerous.

    To get down to 0.1mm there were a couple of things I did that really improved things.
    Less than 0.1mm and there were lots of little things that all contributed.

    An example would be stepper drive belt tension.
    Bearing backlash at the ball screw mounts.
    On the Y axis I discovered that the mount plate that hangs off the front of the table was bending.
    Gib adjustment, even the oiling on the ways had an impact on the stickiness of the movement.

    Anything less than 0.05mm (2 thou) and I'm content. I don't mill much that needs more accuracy.

    For example I milled a simple bit of 1mm mild steel plate the other day into a very complicated shape- so I could bend it into a special bracket (8 bends).
    It would have taken a long time to do this by hand or with a manual mill.
    I drew it up while indoors with the wife then simply created a cam file, put a piece of wood in the vice, skimmed it, screwed the plate on, installed a 3mm cutter and set the machine going.
    And went and made me and the wife a coffee.

    Came back and it was done- simple!
    A bit of de-burring and some bending and I had a solution to someone's problem.

    Person who wanted the bracket was really happy with the prototype and I'll simply subcontract out the volume he wants.
    I'm not sure how much easier this could have been.

  18. #38
    Join Date
    Sep 2005
    Posts
    127

    Re: Adding stepper power to the chuck.

    Julian,
    I know this is an old thread, but I'm wondering if you ever finished up your Z axis mod. I've got an old Bridgemill which I think has a similar mill head to yours. I'm wanting to upgrade to ball screws, and I have some pictures of a Bridgemill Chuck modified years ago with a dual ball screw on the mill head. Unfortunately there is a lot of detail missing from the pictures, so I was hoping if you finished your project you might be willing to share. I don't think JT offers the ball screw kit for these anymore, so I'm guessing you wouldn't be cutting into his business if you shared!

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