Thread: Boxford 165 HMC

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  1. #41
    First I want to make snails for transporting of plastikbottles on the Machine. All other can wait until this job runs good.

    At the moment I must first to get Linuxcnc running with the mesa7i76E ethernet BOB or better motion controller.
    And change the integrated working but softwareless controller
    to the mesa.

    After that, I want to make the mechanical parts for the X-A
    Bridge. Thats relatively easy, because I "only" need a part
    like the X-slider, 2 blocks for adaptation from my
    Guidance to the tailstocks with a toothed belt drive
    and a ballscrew on the side.

    All the other parts are not so important and I can make it whenever I like it.

  2. #42
    Hello I have got the movements smooth and the correct programmed amount in each axis so now I want to understand how I can program the a axis (rotary) it has a ratchet wheel under the table and it locks every 45 degs but to lock it it needs to move a couple of degrees in the opposite direction.
    so if I program A180. The move is good but it doesn't lock so I move -A180. Then A2. And it locks but the DRO on Mach displays A178. Which is no good as it affects the next move, how do I get round this please?
    chris w.

  3. #43
    Thats the problem with steppers, they have no feedback for direct reading of the position. Eventually you can enter a little false value into the parametres, so you turn maybe 180 with an amount of 185 and 5 back.
    In reality it moves only 184 and back to 180 until the motor stalls.

  4. #44
    Do you mean alter the movement amount on the axis in motor tuning to trick it?
    to let you know how I start up, I move the axis to lock it in the nearest square face of the table in relation to the spindle then reverse it a bit so it's locked then zero the DRO, so now I mdi g0g90a-91. Then table move and next line is a-90. Which leaves readout in right position but not quite locked the table so I need to move to a-89. And it locks and ok but the readout displays 89.62 or another number which makes a program impossible as I don't know how much the next move needs to compensate for the clamp amount,
    should I consider changing the axis motor for a servo but it still needs to clamp before machining and I don't want to be involved with a compressor for a brake........ I dunno,

  5. #45
    Yes, you enter a little bit less then in reality, move so much that you are free, after that you turn back to the nominal amount. So you have always pressure against the ratchet. I don't know if 1degree more is enough, you should test some different parametres, until it runs correct.

    Or you can make a new roundaxe without a ratchet and add a small hydraulik diskbrake from a Bicycle. So you can move in every desired angle.
    But because of backlash unfortunately only in one direction
    Last edited by uli12us; 19-01-2016 at 12:19 PM.

  6. #46
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 7 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,133. Received thanks 201 times, giving thanks to others 5 times.
    Can you fake it by resetting the A machine coordinate to the correct value after each move? Not exactly an elegant solution...

  7. #47
    Hello Neale I think that is my answer or solution for the short to medium term as I tried all the positions on the ratchet locking and it varies about .3 degrees so that stops me from allowing for a fixed error,
    is there a way to reset that coordinate within the g code program?
    (reset DRO)
    (reset DRO)

    that will essentially be indexing incrementally but as long as I remember that it will be fine,
    chris w.

  8. #48
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 7 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,133. Received thanks 201 times, giving thanks to others 5 times.
    Chris, please bear in mind that I have not tried this, but I believe that the sequence you need is, basically:

    G91 (set relative mode)
    G0 A95 (turn axis but deliberately overshoot)
    G0 A-10 (turn back to lock position)
    G90 (switch back to absolute)
    G92 Axx (where xx is the value you want to appear in the DRO display at this point)

    Alternatively, if you are resetting the DRO to the correct position each time, you can probably skip the switching relative/absolute bit. Turn to the required angle plus a bit of overshoot, turn back by enough to make sure that the axis is back on its ratchet stop, then use G92 Axx to reset the DRO to the correct value. Absolute moves should then work OK. Good luck if you want to build this into your post-processor!

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  10. #49
    Yes thanks for that it's been a long time since I used a G92 but I understand it,

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