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General Mach Discussion / Re: Limiting 5th axis rotation, new setup
« on: September 15, 2018, 10:21:45 PM »
Hi,
my preference would be something like the attached.
Note that the home switches are independent of all limit switches. In an industrial machine if any of the limits switches activates the machine
de-powers, not just stop, but kills the electrical supply.
Thus when you home the machine, if you combined a home and a limit switch, then the machine would stop. Mach can handle this by ignoring limits
when the machine is homing. That means when homing the machine is in a potentially dangerous state, it could accidentally exceed it limits and Mach
would not shut down. For large equipment this would be contrary to safety law in many countries.
Note that in industrial machines each limit switch would have its own input as well, it would allow the controller to permit the operator jog the machine
in the direction that brings the machine back into bounds and disable th jog direction that makes it worse. This would require even more inputs and wiring
for which very few hobbyists bother.
While I recommend the advantages of having separate and multiple inputs for limit and home switches you may, and probably are, constrained
by the number of inputs on your controller or BoB. If you have only two inputs to spare then your previous diagram will work but Mach will not know
which limit switch has just operated, just that one has. Likewise should any of the home switches operate while Mach is expecting the Y axis home
switch to meet its pre-programmed homing order Mach will interpret it as Y Home, when it was in actual fact an false activation of the B axis home switch
say. Consequently the Y axis would be mis-referenced and a crash is now likely.
my preference would be something like the attached.
Note that the home switches are independent of all limit switches. In an industrial machine if any of the limits switches activates the machine
de-powers, not just stop, but kills the electrical supply.
Thus when you home the machine, if you combined a home and a limit switch, then the machine would stop. Mach can handle this by ignoring limits
when the machine is homing. That means when homing the machine is in a potentially dangerous state, it could accidentally exceed it limits and Mach
would not shut down. For large equipment this would be contrary to safety law in many countries.
Note that in industrial machines each limit switch would have its own input as well, it would allow the controller to permit the operator jog the machine
in the direction that brings the machine back into bounds and disable th jog direction that makes it worse. This would require even more inputs and wiring
for which very few hobbyists bother.
While I recommend the advantages of having separate and multiple inputs for limit and home switches you may, and probably are, constrained
by the number of inputs on your controller or BoB. If you have only two inputs to spare then your previous diagram will work but Mach will not know
which limit switch has just operated, just that one has. Likewise should any of the home switches operate while Mach is expecting the Y axis home
switch to meet its pre-programmed homing order Mach will interpret it as Y Home, when it was in actual fact an false activation of the B axis home switch
say. Consequently the Y axis would be mis-referenced and a crash is now likely.