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Z Axis constant ZERO mod!

Discussion in 'Original Phlatprinter MODIFICATIONS' started by tvcasualty, Feb 25, 2010.

  1. tvcasualty

    tvcasualty New Member

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    This mod uses a micro limit switch to set the my zero to a constant place each time I use my Phlatprinter, no matter the height of the bit I am using. This irons out all kinds of issues on determining the correct depth on cuts for a variety of bits. Finding a zero was always a very difficult process for me, now it is very simple. Not sure how to make this work using Mach 3, but in ECM you can adjust the 'back off' to any distance. Bit moves in slow to the switch, makes contact closes it, bit then back off to a set distance (clearing the switch so it can be turned on), then the zero is set. If the bit is changed, the process works the same way.

    Pictures say a thousand words, videos are much better:
     
  2. kram242

    kram242 Administrator Staff Member

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    The video is not working for me Erik but this is going to be cool! :)
    Can't wait to see it in action
    Mark
     
  3. tvcasualty

    tvcasualty New Member

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    Invention is the result of necessity I guess. I managed to fix my Z axis after giving a little slop to the guide bars, but have went further in solving my problems... I was really hoping this was the final excuse to buy a MKII but Lauren had better to say about it! :) She is right, as usual, but at least I'm up and running again.

    More tweaking to those original parts and I've got a little more speed out of this old boat too. :)

    The original hose couplings needed work to make them more flexible, I get a pic up soon on them for those who are still using the 'cheap' method of coupling servos to all thread. The original hose was coiled and the shape induced a vibration. I used a knife to trim off the outside layer and use only the inner black part, also the all thread gets forced right up next to the servo and now spins much nicer.

    So far this setup works very well, and I am very happy once again!
     
  4. tvcasualty

    tvcasualty New Member

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    Ha! Horrible buzz is the drier going off in the back ground! Not to worry! :)
     
  5. kram242

    kram242 Administrator Staff Member

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    Erik that is one SWEET mod brother!
    This can be done in Mach as well there is a plugin for it!! This is really going to help a lot of people out
    Thank you for sharing :)
    Mark
     
  6. rayclark

    rayclark Member

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    Very nice mod.

    Mark what is the plugin for Mach? You have a link?
     
  7. 3DMON

    3DMON Moderator Staff Member

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    Great idea Erik!
    Thanks for sharing.
     
  8. meistertek

    meistertek Member

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    Cool! This mod would get rid of my current goofy methods of touching off with a ruler over the slot and then trying to step up to the bottom of the foam, or trying to listen to the bit touching off on the bottom of the foam :lol:
     
  9. rjarois

    rjarois Moderator Staff Member

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    Erik, very cool man...that was one of the reasons i went to the overhead gantry...so i can touch off easier... i suppose monkeys like me aren't to bright, lols. great job man. randy.
     
  10. kram242

    kram242 Administrator Staff Member

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    Hey guys its actually a macro from the existing auto tool zero in mach3, from what I understand.
    You can find out more here. This guy pretty much walks you through it and has even created a screenset with the added features of the auto zero tool.
    http://www.cnczone.com/forums/showthread.php?t=36099
    Mark
     
  11. tvcasualty

    tvcasualty New Member

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    meistertek, that was EXACTLY how I used to do it! I have a clear ruler with all kinds of bit scratches on it! Too funny!

    Randy, I thought you'd be proud of my monkey bracket. :)
     
  12. Tweakie

    Tweakie Member

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    I don't know if this would be helpful to anyone using Mach (because I use a touch plate rather than a switch) but I have been following the threads on the Zone and Mach forums and my iteration of the script (pasted into the Auto Tool Zero button) is shown at the bottom of the page here:- http://www.cooperman.talktalk.net/files/17.htm
    I have included an extra check for the Z Scale DRO so touch off distance is the same no matter what the scale settings of this axis.

    Tweakie.
     
  13. kram242

    kram242 Administrator Staff Member

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    Great info Tweakie! You site is full of super useful projects we can all learn from.
    Thank you so much for taking the time to share these with us.
    Mark and Trish
     
  14. ttraband

    ttraband Member

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    I'm using EMC and built a small touch-off plate for my Mark I PP. I figured out which pins to use to wire it in, but the sticking point for me is that the Dremel bit is not grounded, so I need to attach a wire to the bit or collet each time I use the plate. I found it simpler in the long run to set up limit switches on the Z-axis travel and set the zero point from the lower switch, but at this time I'm only using the "stock" 1/8" bit and never changing it. If the touch-plate were simpler I would use it to zero the Z, and change bits more often - including playing with more different materials.

    So, my question is, how do those doing the touch-plate accomplish the bit side of the connection.

    Thanks,

    Tom
     
  15. Ampair

    Ampair New Member

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    Perhaps you could make a small wire brush (10 wires [3/4",20mm] snipped from a hand wire brush and crimped into a small copper or brass tube or a crimp eyelet) and mount that under the deck below the touch plate. It should contact a 1/16" tool just before it reaches the sideways home position allowing it to be all ready to sense the instant of contact with the touch plate.
     
  16. tvcasualty

    tvcasualty New Member

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    Originally I had the limit swith on the bottom of the Z travel. The plan was to come up with the touch off distance for each bit and set it when ever I changed. The result never worked like that. I had constant problems trying to set it up so the zero was constant. The stop must be at the end of the bit and able to account for different lengths to get the most out of the machiene.

    The touch plate would be the way to go, I agree, but due to the grounding problem, why not just use a limit switch instead?
     
  17. kram242

    kram242 Administrator Staff Member

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    I love the idea of the switch it solves the grounding problem completely
    Mark
     
  18. rayclark

    rayclark Member

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    If anyone does this in Mach using a switch, please post instructions how to do it. I'm confused as to what needs to be done with the mach software.

    Thanks
     
  19. Tweakie

    Tweakie Member

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    As I see it Ray - If you wire your (normally open contact) switch, one side to ground and the other side via the breakout board, (which I am assuming here is configured with the LPT input pins pulled high) to any spare input pin on your parallel port, say pin 15 then when the switch is closed (tool contact) pin 15 of the parallel port, is pulled low.
    Within Mach set (Config / Ports & Pins / Input Signals) 'Probe' / Enabled / Pin Number 15 / Active Low. Many have also added an LED to their main screen to visually indicate the switch closure. (If you do choose to modify your screen you can download ‘Screen4’ or ‘MachScreen’ from the bottom of the page here http://www.machsupport.com/downloads.php but be sure to save a copy of your screen .set before you start, just in case you trash the original).
    If your BoB has the LPT pins pulled low then one side of the switch is connected to +5V via a series resistor and the other side to Pin 15 and Mach ‘Probe’ set Active High.
    Then once the macro is pasted into the ‘Auto Tool Zero’ button away you go.

    Tweakie.
     
  20. Tweakie

    Tweakie Member

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    Hi Tom,

    To answer your question, from just one perspective – On my machine, I use a 3 phase spindle driven from a variable frequency drive (VFD). As high frequencies can cause the stray flux to create a charge on the rotor, which would otherwise discharge / arc through the bearings and cause pitting, a carbon brush is fitted, internally, to connect the shaft and the body of the spindle to ground. I think this was probably done to reduce RFI but it is a bonus for me and using a touch plate probe.

    Tweakie.
     
  21. ttraband

    ttraband Member

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    Thanks for all the replies.

    I'd love to have the variable speed spindle, but the dremel is "double insulated" so doesn't have the grounded bit. To make matters worse, I used schedule 40 PVC for my X roller, so the roller height is just a bit higher than it ought to be. This means I can't just set a touch-plate across the gap, as that doesn't really represent the correct zero height. I've seen the mods for adjusting the height or building up the table, but haven't made a final choice. It hasn't been a deal breaker with the 1/4" foam sheets, but as I graduate up to thicker/stiffer materials I expect I'll have to get the table into the "correct" alignment.

    For the touch-plate, I thought about doing a "permanent" brush or spring against the collet or bit, but was afraid of the effect that the constant rubbing, especially with foam dust acting as an abrasive, might have over time. The spring brush idea at the end of Y travel solves that issue. I also thought about a simple alligator clip to the bit, but then you're still having to manually connect each time.

    Since I already have the Z (and Y) limit switches in place, I may just add another switch (instead of the probe) wired in as a Z home. I just need to decide where to put it. I did the "original" belt mod with the rollers inside the case so I have lost some Y travel to that, and I have included about .25" of "negative Y" travel when setting the Y home position relative to the Y limit switch. I am worried about losing any more Y travel, but I'm even more worried about running the spinning bit into the switch. Maybe the thing to do is set the "home" switch high enough above the table so that it is less likely to be in the way during an actual cut and include the correction factor in the EMC configuration.
     
  22. tvcasualty

    tvcasualty New Member

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    Exactly! :)
    Mine could be higher but I'm not concerned about grinding my switch at this point.
     
  23. ttraband

    ttraband Member

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    The switch method would also allow for other non-conductive tools like grinding wheels to be used. Although I can't currently think why I'd want to, its always nice to have options.
     
  24. rayclark

    rayclark Member

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    Has anyone made a screen set that uses the Phlatprinter screen set but with the AutoZero Tool function added in. I've been trying and just have not been very succesful at creating it. :(
     
  25. Tweakie

    Tweakie Member

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    Ray,

    If you let me have a copy of your screen .set file, I will add the button for you.

    Tweakie.
     

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