Welcome to Our Community

Some features disabled for guests. Register Today.

Question on setting up limit switches

Discussion in 'CNC Mills/Routers' started by pitzerwm, Sep 14, 2016.

Tags:
  1. pitzerwm

    pitzerwm Well-Known
    Builder

    Joined:
    Sep 10, 2016
    Messages:
    20
    Likes Received:
    1
    I have a openbuild machine and the builder didn't add the limit switches. I've watched a video on this and have a couple of questions.

    To get the GRBL to know that the switches are installed, and react correctly when hitting one, do you JUST change $21 to 1, or are there other steps?

    Once the switches are installed and GRBL knows that they are there, does the home feature automatically work?

    I'm using Bcnc with a Raspberry Pi3.

    Any direction would be appreciated.
     
  2. pitzerwm

    pitzerwm Well-Known
    Builder

    Joined:
    Sep 10, 2016
    Messages:
    20
    Likes Received:
    1
    I am surprised that there wasn't any help on this thread, but I'll post what I have ended up with. I placed switches at each axis extreme, wired with the NO contacts in parallel to the controller. You need to make $21=1, $22=1, $26= 250, $27=5.0, $24= your machine's safe speed.

    When you test the home cycle, take out your router, if working correctly, the machine will rise to the Z limit first, then the Y limit and then the X limit. It will hit the limit switch back off a bit, re hit the switch slowly, then back off the amount in $27. It will be at the rear right part of your machine.
     
  3. Giarc

    Giarc Master
    Moderator Builder

    Joined:
    Jan 24, 2015
    Messages:
    954
    Likes Received:
    465
    Thanks for the info. I hadn't got around to hooking mine up yet because I haven't finished building the bench that the machine will be permanently mounted to (with the controllers and power supply below and inside) so I do not know how long to cut my wires yet. I need to do it soon, though. Every once in a while when I type G0 X200, I accidentally add an extra zero. :banghead: Luckily I have installed my emergency off button.:rolleyes:
     
  4. Keith Kimura

    Keith Kimura Journeyman
    Builder

    Joined:
    Jun 26, 2018
    Messages:
    31
    Likes Received:
    4
    When executing a "Home" command $H the Z-Axis rises and hits the Limit Switch then grinds for about 30 seconds then generates an Error and informs me to increase the travel distance. Attached are my GRBL Settings. I've been dealing with this and a slew of other problems for the past 30 hrs. I've had this machine for almost a month and still haven't made a successful cut! Quite disheartening. Hopefully things can get turned around.
     

    Attached Files:

  5. Giarc

    Giarc Master
    Moderator Builder

    Joined:
    Jan 24, 2015
    Messages:
    954
    Likes Received:
    465
    Are your switches NO or NC? For what it is worth, I have been cutting with mine for a couple years and I haven't bothered with limit switches. They are unnecessary. I would get it cutting properly before throwing in more variables and potential for failure due to electrical noise.
     
  6. Keith Kimura

    Keith Kimura Journeyman
    Builder

    Joined:
    Jun 26, 2018
    Messages:
    31
    Likes Received:
    4
    Being a 'newbie' I can only go by what I've read on the myriad of CNC posts here and elsewhere. And the consensus is that Limit Switches are an essential aid in a "production process" application. My intent is to use my Workbee as the foundation to a production line application for my new business/product where it will be repeating patterns of three or more different models constantly. So, given this kind of application where repeatability is essential, you're saying that Limit Switches may still be unnecessary?
     
  7. Keith Kimura

    Keith Kimura Journeyman
    Builder

    Joined:
    Jun 26, 2018
    Messages:
    31
    Likes Received:
    4
    Oh, and by the way, the switches are NO.
     
  8. Giarc

    Giarc Master
    Moderator Builder

    Joined:
    Jan 24, 2015
    Messages:
    954
    Likes Received:
    465
    Limit/homing switches would be helpful for you. A temporary work around that could be done, is to pick your X and Y zero point, and always return to that point. The next day, when you turn on Grbl Panel, immediately zero out X and Y. Z will always change with the cutter length or variations in material thickness.

    When I want to do repeats of an item, I put some scrap in the front left corner where I like to zero my x and y. This is at x and y front left extremes of my machine. I then cut an L shape with the endmill I plan to use - for example a 3.175 mm (I prefer mm to inches because for me it is so much easier to design parts with mm than fractions). Now I put my stock piece in this corner bracket and using two other 3.175 mm endmills (a use for broken ones) as spacers on each edge of the bracket, I know my stock piece is just inside the extreme front and left of my cutting area. Now I know that I can use my full 665mmX1270mm cutting area without the slightest possibility of a crash. Once the L piece is milled and attached, I can zero the work piece faster than the machine can. If for some reason the coordinates get messed up, I just jog the bit back to the corner of that bracket. AN example with pictures of this L-bracket method is here from when I cut out plates for my laser cutter.

    Now that I am using Estlcam, what I mentioned is obsolete due to the various probing functions. But, before you try that, you should figure out how to use the machine productively and consistently with GRBL Panel.
     
    Fety Mann and GrayUK like this.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice