Lathe electronic lead screw project

  1. Henrik Member

    Following on from this RPM gauge thread http://www.mig-welding.co.uk/forum/threads/diy-rpm-dro.55718/ and this lathe thread http://www.mig-welding.co.uk/forum/threads/long-term-atlas-10f-lathe-restoration-modification.53210 I have started working a little bit on an electronic lead screw project.

    The ELS will replace all change gears on the lathe (handy, as I have none), and it will be able to move the carriage accurately for turning, threading, and boring operations. It will also provide an RPM and Z read outs.

    The plan is to make the interface as simple as possible, so that I don't have to have a computer etc out in the shed. I'm thinking something with a couple of buttons on the front to set feed rates, "stops" and jogging of the axis.

    All the source code is available here: https://github.com/hbilar/arduino-electronic-lead-screw
    It's very much work in progress still.


    Anyway, here's a pic of the setup:
    [​IMG]


    The interface is currently just a 9600bps serial interface, which you can see in the video below.

     
    Kram likes this.
  2. DanielW

    DanielW Member

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    Use an old laptop that can be got for buttons and will only accept windows 98? that way it will run Mach3.

    I have an old laptop thats slow but is capable of running word processor programs and Mach3 and if you're willing to pay the Postage you can have it for free.
     
  3. gerrymoore

    gerrymoore CNC expert (well, getting there!)

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    Not sure Mach3 will run from a laptop...it may now but wouldn't a couple of years ago - not enough oomph from the centronics printer o/p??

    Apparently it will now run with win7 so I'm biting the bullet after Christmas and building a new PC with SSD's and WIn7 as all mine at the moment are still on XP !!
     
  4. DanielW

    DanielW Member

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    I know what you're saying here and it was down to laptops was lower than 5v ouput pin?ie not enough for the signal to the driver board.

    can't remember now what it was but if I remember an external 5v applied overcame this problem,would need to revisit the article I found going back a couple of years?
     
  5. addjunkie

    addjunkie Member

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    Interesting, as youll be using the origional lead screw, how is wear/ back lash accounted for.
     
  6. Will it have a degree indicator on the leadscrew to enable same point starts for threading?
     
  7. Thinking about it won't you struggle to synchronise the headstock and leadscrew start times?
     
  8. rtbcomp

    rtbcomp Moderator Staff Member

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    Also you'd need to correct for small variations in motor speed, otherwise you'll end up with a variable thread.

    Mains frequency can vary from from day to day, so Monday's thread could be a different pitch to Friday's thread.

    The way round it would be to fit an encoder disk to the headstock and use the output to regulate the leadscrew speed, or even use the output to step the leadscrew. You'd need to pay attention to the gearing between the leadscrew and its motor to get a smooth thread.
     
    Wendelspanswick likes this.
  9. DanielW

    DanielW Member

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  10. You'd have to synch the two otherwise you would get discrepancies if you took a heavy cut and the headstock slowed.
     
  11. Henrik Member

    Exactly this. Basically there will be a hall sensor that picks up the rpm, which will then be used to calculate the feed.

    Synchronisation is taken care of by starting a threading feed at the same time after one of the rpm pulses. You could even do multi thread by varying the time offset after the pulse.
    This is the reason I did the rpm display part first, although the code bases are not merged at present.


    Addjunkie:
    The lead screw is being replaced with a new trapezoidal 3mm pitch screw and a Delrin nut.


    I bought a lathe "project", so I never had a complete lathe to destroy, so to speak. No change gears, broken feed nuts etc.

    I know I could do this with mach3 and a laptop, but where's the fun in that? :)
     
    ukracer likes this.
  12. Seadog

    Seadog Forum Supporter

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    It's worth looking at MadModder. There are quite a few topics on the subject that go into the intricacies in detail. Here's a link to one for example: http://madmodder.net/index.php/topic,10585.0.html
     
  13. gaz1

    gaz1 Member

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  14. DanielW

    DanielW Member

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    Eh! fun ya say? there ain't no fun in using Mach3...anyway are yer going to use a cnc manual controller? £27 from china,you won't pay import tax on that just vat.
     
  15. Digger6135 Member

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    In my opinion without a direct physical connection between the headstock spindle, and the leadscrew be it by change gears or a gearbox, any attempt to cut accurate repeatable screw threads would be extremely difficult if not impossible, the slightest variation in relative speeds would be intolerable.

    Digger6135
     
  16. DanielW

    DanielW Member

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    Mach3 has a platform for the lathe for syncronising the spindle speed for repeat threading on a lathe,but the spindle on the lathe needs to be electronically variable
    ,can't remember the info without loading the mach3 on my computer and looking at the instructions of mach3 at what board to link up to the speed controller.
     
  17. addjunkie

    addjunkie Member

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    All this jiggery pokery is the work of the devil in carnate. The mechanical and the electrical stepper motor i get, but this electronics is the work of lucifer.

    I started looking at converting my mill, motors no issue, mechanics no issue, jiggery pokery....scares the be jesus out of me!
     
    decca, Parm and slim_boy_fat like this.
  18. DanielW

    DanielW Member

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    What electronics would this be? or is it hooking it all up to the gear intended be the problem? best place for cnc lathe/mill/machine would be.....

    http://www.cnczone.com/
     
  19. addjunkie

    addjunkie Member

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    Spent many hours reading in there, it was all the break out board stuff and messing with voltages etc.....then of course id need to learn to programe it, and i bet that would fill the scrap bin

    On there the conversion seemed to be more important than what the machines were to be used for
     
  20. DanielW

    DanielW Member

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    There really isn't no magic in connecting up the gear,once you have connected one stepper to the driver board the rest is identicle to the other 2 steppers,then its just a matter of connecting the driver to the breakout board(some driver boards have the BO included) the breakout board is then connected to the computers printer port via 4 wires +&- and transmit in and transmit out or recieve and send as its known.

    The steppers or driver board comes with a simple scematic so you can't go wrong.

    Well it is if the if accuracy is needed for turning parts or milling parts as for the actual CNC machines there's machines and there's playthings.
     
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