HELP. Do I need soft limits set to have the CNC slow down to hard limits
Mach3, Vectric 11, Gecko G540, ESS, both Y axis driven
I am adding homing and limit micro switches to my DIY CNC. Do I also need to set up the Soft Limits to have it slow down as it approaches the Limit and Home switches, or is the slow down feature available in the Homing and Limit switch setup?
Thanks
Re: HELP. Do I need soft limits set to have the CNC slow down to hard limits
Hi,
at Limit switches there is no reduction in speed as the switch is approached. When the switch is activated then Mach does an emergency stop at maximum deceleration.
Its been nearly ten years since I used Mach3...and I do seem to recall that there is a SlowZone option. I use Mach4 now and have for some years, it does not have a SlowZone,
nor does it really need one. You just need to allow an extra 2mm or so between the Limit switch and physical hardstops....you don't really want to slam into them.
One of the problems with a Limit switch activation is the the machine loses Reference as it Estops. That is to say the machine zero will have shifted slightly. You have to
re-Home or Reference your machine to finish the part you were machining. A PITA and prone to error. Ideally therefore you'd arrange it such that the Limit switches NEVER activate.
This is the purpose of SoftLimits. They are only useful once a machine is Homed or Referenced, they describe the boundary of the machine in machine coordinates. Mach knows
never to exceed those boundaries. It it detects a move or a jog call that would exceed the SoftLimits it just ignores it, and so there is no Limit switch activation and therefore no loss
of Reference.
On my machine I have two Limit switches and one Home switch per axis. The Limit switches are about 2mm inside the physical hardstop, I have programmed the SoftLimits to be about 2mm
inside the Limit switches and the Home switch a further 2mm inside that. That make my Home switch about 4mm inside the Limit switch and 6mm inside the hard stop.
Once I Home or Reference the machine I activate the SoftLimits and the Limit switches hardly, if ever, get triggered. They are really only machine safety switches, they should never operate if every thing
else is going well. I have not had a genuine Limit switch activation (except if I'm deliberately testing them) for well over a year. I do however get SoftLimits stoppages if I've placed the material incorrectly
within the machining boundary and the Gcode would exceed the machine boundaries. It too is a PITA, but at least you don't have to re-Home or Reference.
HELP. Do I need soft limits set to have the CNC slow down to hard limits
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