Today I mistakenly enetered a MDI command - G0 G54 x0 y0 z1 - the machine moved to the commanded postion, which for z was past a soft limit. I have Z zero at the machine zero.  Machine Z zero is a microswitch. Of course I mistakenly set Z to a positive vs negative number, which drove the z axis UP AND past the soft limit. Why is this? I assumed soft limits would protect against this mistake. I also moved to G54, then moved my Z well below the soft limit by jogging. Then used the MDI command - G0 G54 X0 Y0 Z.2 - it again moved past the soft limit. I couldn't manually jog any higher, but could jog outside (lower) the soft limit. When below the soft limit I can't manually jog past it.

The machine is a three axis router, Mach 3 control, Pokeys57 machine controller board.

Any ideas why the setup ignores the softlimit when using the MDI command

Hi,
Soft Limits only works and makes any sense if the machine is Homed or Referenced.

Soft Limits are really like a description of the machines boundaries. For example the North boundary is 15m from 'here', the South boundary is 5m from 'here',
the East boundary is 10m from 'here' and the West boundary is 7.5m form 'here'. That only makes sense if you know where 'here' is in that description.

That is what Homing or Referencing does in Mach. It drives the machine location defined by Home switches, and that location is the 'here'. Then you can Enable
Soft Limits and if the machine receives a command that would exceed those boundaries it just ignores the command.

When I first started my machine had neither Home or Limit switches. Eventually I put three Home switches on it. Thereafter I was able to use Soft Limits with good effect.
I had three crashes in seven years after fitting the Home switches with that little machine, but was crashing about three times a month prior to. Fitting Home switches
and developing a rigorous Homing procedure was easily the single best improvement I ever made. I always meant to get around to fitting Limit switches...but after seven
years still had not done so. My new machine is much MUCH bigger, way faster and vastly more powerful, and it has nine switches, three Homes, and six Limits, all on their own
dedicated input to my BoB/ESS combination. In the two years I've been using it I've never hit a limit switch as Soft Limits have always saved the day.

Craig

Hi,
Soft Limits only works and makes any sense if the machine is Homed or Referenced.

Soft Limits are really like a description of the machines boundaries. For example the North boundary is 15m from 'here', the South boundary is 5m from 'here',
the East boundary is 10m from 'here' and the West boundary is 7.5m form 'here'. That only makes sense if you know where 'here' is in that description.

That is what Homing or Referencing does in Mach. It drives the machine location defined by Home switches, and that location is the 'here'. Then you can Enable
Soft Limits and if the machine receives a command that would exceed those boundaries it just ignores the command.

When I first started my machine had neither Home or Limit switches. Eventually I put three Home switches on it. Thereafter I was able to use Soft Limits with good effect.
I had three crashes in seven years after fitting the Home switches with that little machine, but was crashing about three times a month prior to. Fitting Home switches
and developing a rigorous Homing procedure was easily the single best improvement I ever made. I always meant to get around to fitting Limit switches...but after seven
years still had not done so. My new machine is much MUCH bigger, way faster and vastly more powerful, and it has nine switches, three Homes, and six Limits, all on their own
dedicated input to my BoB/ESS combination. In the two years I've been using it I've never hit a limit switch as Soft Limits have always saved the day.

Craig

I have home switches, the machine is homed everytime I start it up, soft limits are on and active, yet if I input a MDI command past Z0 it ignores the softlimit.  Everytime! 

Hi,
its been nine maybe ten years sine I used Mach3 but that 's not what I recall, and certainly in Mach4 if a command, be it MDI, jog or Gcode job exceeds
Soft Limits it will be ignored.

Craig

I have confirmed MDI commands can drive the gantry past the soft limits in all access.  When jogging it stops at soft limits though.  When past a soft limit I can jog back to the safe side but can't jog deeper into the 'no go' zone.  Why do MDI commands entered into Mach ignore the soft limits.  Normal G-code is limited, jogging is limited, but MDI command line blows right past any soft limit.

Hi,

Why do MDI commands entered into Mach ignore the soft limits.  Normal G-code is limited, jogging is limited, but MDI command line blows right past any soft limit.

I don't know. I don't recall Mach3 doing that, but its possible either I never encountered it or I've forgotten it.

I have just confirmed on my machine that with the Soft Limits enabled Mach4 just ignores my MDI command if that command would violate the limits and
just does nothing with this error message 'Error, X axis commanded over Soft Limit'

I've been using Mach4 for eight years, its light years ahead, you should consider it. All development on Mach3 ceased eight years ago, whatever bugs its got, like this one,
it will always have.

Craig