End Stops on MiniRambo?

I know that the Rambo supports the dual endstops and auto squaring. But does the Mini-Rambo with the non-dual endstop firmware support endstops on X and Y? The firmware Ryan included on the board I bought has Homing functionality enabled, and I’ve activated it a few times and had the gantry run into the end and grind on the belt until I could get to it.

If I were to install end stops and wire them up to the board, would the firmware know to stop when it hit them? Or would I have to rebuild and re-flash the firmware to enable it?

If they are working, what about wiring two endstops up in series between the two sides of the machine for a poor mans auto squaring? As long as the machine is nearly square, I wouldn’t have too much wear on the belt.

  • The non-endstop software has the min endstops available by default, the maxes are disabled in configuration.h. Note that things are not going to stop when hitting an endstop unless you are currently homing, and if you home all the Z will drop down into your table until physically restrained or you hit an E-stop. To use them to home a machine you'd ask for a home X and home Y separately. That's why we typically don't bother to use them for CNC operations, you almost never need to go to 0,0,0.
  • Not likely to work... Even in series there's nothing to stop the side that hit first while driving to the other side. If you're out of square it's easier and safer to mount hard stops and pull the machine square manually against them before powering up the steppers. (Better yet is to square the machine during assembly. :))
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I squared the frame to within an inch of its life when I assembled it. But at 36x60 inches, there is enough play between the sides for the two ends of the gantry to get out of square if it gets pushed around when not in use.

Any suggestions on how to print and install hard end stops?

I’d use pieces of wood, you just need something that sits in the way when moving the (unpowered) gantry to a fixed position. Don’t move things too fast, the steppers will act as power emitters and can provide more oomph than your controller expects.

So, with the hard stops in place, move the gantry to 0,0 and pull both ends of the X and Y axis to the stop. While holding it like that use something like Repetier-Host or your display to move the Z up a couple of mm. That energizes the steppers and it should stay.

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This would mean having multiple pieces of wood that are all exactly the same size (or at least 2 pairs that are the same size), right? Since the gantry doesn’t move all the way to the corners anyways (the center and Z-axis are in the way), it seems like printing and clamping stops onto the pipes would work.

Ding! I just realized the point you were making here. Unless the end stop switch is accompanied by a hard stop that prevents the gantry end from moving, it would just blow through the end stop switch and keep going. My brain is moving slow this afternoon.

Both my machines only have endstops on one end. I have hard stops on the other side at the square position. If the other side hits first, it just skips steps until the endstop side catches up. Other way around there’s a gap, so I manually twist the geared pulley to drive it into position. Endstops have been enabled from the beginning. Steppers are in series though.

That sounds like what I was thinking. Only difference is that I was thinking of hard stops on both sides with end stop switches attached to each. That way it can square up either way. Once one side hits the hard stop, it will close the switch, but that won’t register until the other side also hits the stop and trips the switch.

Probably not good for the switches.

In what way? Electrically or mechanically?

I am planning on using something like this for squaring mine. I can print multiple things much more precisely than I can cut them. https://www.thingiverse.com/thing:2519039

Mechanically.

What is your concern re: the switches? The limit switches I have have a fair bit of play in the leaf portion. Enough that You should be able to situation them so that they strip right before the gantry impacts the hard stop. That should minimize any physical stress on them, shouldn’t it?

No. You are betting on a very imprecise method to stop within 1mm or so? Just use hard stops by hand, switches are going to do no good only on one side.