If you can control the current settings on the stepper drives, lower the
torque settings and drive the gantry axes steppers
together into the hard stops, set the axes to home, then reset the
torque settings to normal.
Dave
On 2/16/2014 3:11 PM, Charles Steinkuehler wrote:
> With the recent release and general popularity of the ShapeOko V2
> desktop mini-mill, I have several folks who are trying to use LinuxCNC
> running on the BeagleBone as a control. If you are unfamiliar with this
> machine, here's a link:
>
> https://www.inventables.com/technologies/desktop-cnc-mill-kit-shapeoko-2
>
> Invariably, one of the first questions I get is how to setup a
> configuration to deal with the gantry setup of the ShapeOko. I know of
> at least three different ways to control a gantry system with LinuxCNC,
> each with it's own pros and cons:
>
> 1) Use gantrykins, and hope users are intelligent enough not to rack the
> gantry when moving around in joint mode.
>
> 2) Use trivkins and setup HAL to turn one axis into two by craftily
> combining the commanded motion with the homing switch states. This is
> easiest if HAL is doing software stepgen (just mask the step pulses in
> the base thread), but I'm pretty confident I can make this work pushing
> the logic in front of the PRU drive step/dir component (as a bonus, this
> setup would also work with Mesa hm2 cards and other hardware based
> controllers).
>
> 3) Ignore the gantry complexity, and just drive both servo motors from
> the same stepper driver. This works _OK_ for the Z axis on a 3D
> printer, but probably isn't a good idea for something that is actually
> making chips.
>
> Questions:
>
> Did I miss any significant options for controlling a gantry style machine?
>
> Which option would be recommended for novice users new to the LinuxCNC
> and CNC world?
>
> I'm thinking the "Magic HAL Wye / Y Cable" that splits one joint into
> two is probably the simplest for most folks to deal with, but am open to
> suggestions.
>
>
>
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