Limits and Homes
30 May 2016 22:46 #75270
by BrassCat
Limits and Homes was created by BrassCat
Hello the Forum, I am thinking on using Linux CNC for an engraver I found in a scrap yard, minus electronic. That's probably good, it is - well- not THAT old. Three axis, heavy aluminum castings, stepper driven. Anyway, from motion control software I did back 15 ~20 years ago, home, CW limit and CCW limit were all wired in separately, now I see all three tied together. Well, if the machine had hit a limit sw, knowing which side allowed the operator to jog in only one direction until the limit condition ended. In homing, the operator must then take care that a limit was not hit instead of a home sw.
So I ask, is bringing all three signals, separately, per axis to the controller now considered extreme? It seemed to be the correct method back then. Then I wonder if it is just not enough FAST dedicated pins to connect all these signals individually?
Thanks, Stan
So I ask, is bringing all three signals, separately, per axis to the controller now considered extreme? It seemed to be the correct method back then. Then I wonder if it is just not enough FAST dedicated pins to connect all these signals individually?
Thanks, Stan
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30 May 2016 23:17 #75272
by andypugh
Replied by andypugh on topic Limits and Homes
if you have enough pins, then separate limits is better.
But, in practice, once homed the machine should not be able to get to the limits. And with a stepper machine you might well be able to just disable the drives and push the machine off the limits.
But, in practice, once homed the machine should not be able to get to the limits. And with a stepper machine you might well be able to just disable the drives and push the machine off the limits.
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