On 2/17/2014 11:41 AM, Len Shelton wrote: > Charles, > > I think you know my vote. > > 1) Never assume the user is anything other than a complete amateur. We > are putting tons of these machines in schools now.
PEBKAM! :) > 2) I believe this is the right way to do this. If the BBB cannot do > this, we will be forced to add a secondary microcontroller in the pulse > stream to apply the logic that we need to do this. Seems kinda silly > since the software could do it. If I only knew more about LCNC > programming, it already would. This is the one thing that's preventing > us from moving all of our machines to the BBB immediately. Yeah, this is the solution I'm leaning towards. I appreciate the concept of gantrykins, but given how LinuxCNC deals with non-trivial kins, I don't think it's the way to go unless you really have a non-Cartesian mechanism. As soon as I'm done with the encoder stuff I'm working on, I'll whip up an N-axis HAL gantry module. My linear-delta printer will make a good test-bed for a 3-Axis gantry. In addition to avoiding the "user racks the gantry in joint mode" problem, the HAL component will fix problems with homing if HOME != HOMEOFFSET, at least for the simple gantry case. If anyone listening in doesn't know what I'm referring to, setup a gantrykins machine with a significant distance between the HOME and HOMEOFFSET positions, home your gantry axis, then watch in horror as one side of the gantry finishes homing and rapids to the HOME location while the other side is still poking around at HOMEOFFSET waiting for the home switch to release. <ouch!> > 3) I am really surprised that this works at all without blowing the > drivers. You cannot guarantee that both motors are identical. Yes, it's a total hack, but it works OK for things like the Z axis of a 3D printer, which moves _really slow_ most of the time. -- Charles Steinkuehler char...@steinkuehler.net
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