Software limit on Z axis travel in Easel?

Fixed :slight_smile:

Been reading about Soft Limits. I have set mine and have been experimenting with their use with my X-Controller. When I exceed the limit the system correctly locks things down. I can close and open the port but the violation still exist so the alarm/lock down is again set. I realize I need to move the carriage to correct the error BUT the motors are locked (as per my settings). The only way I see to manually move and correct is to completely shut down the X-Controller. Is this correct?

Also, the only way I see the Z soft limit is useful is by setting it to the travel of my shortest bit which is about 16.3 mm but that seems of minimal value when I normally run longer bits. Is it normal procedure to reset the value with each bit change?

After you open the COM port, if you have homing enabled you should see something like this:
[‘$H’|‘$X’ to unlock]

You clear that lock by doing a homing sequence ($H) to re-establish machine zero. If you don’t use homing you can use $X to unlock the system, but then machine zero is located where the spindle was when you did the port open.

The soft limit on Z is marginally useful. I just set mine so that the carriage will not come off the rail.

You could set a new soft limit on Z for each bit change, but that gets old quickly.

Got It! Not sure what I was doing wrong when testing but it seemed the work position was not being reset when I closed the port and when I re-opened it the fault value was still showing and it engaged the alarm. At that point UGCS was faulted and all buttons and controls greyed out so no input was possible. BUT now I went back and tried again (there was a reboot involved) and everything works as you described.

Also, I had read that if soft limits are used that homing is needed. I assumed this meant that if you didn’t home the limits wouldn’t work because of the inaccurate machine home position. But I believe my assumption was incorrect. It appears that if you don’t home Easel won’t carve. If I am running the process correctly it lets you go through the initial steps of the carve process but when you actually hit the final “carve” button nothing happens - just sits there.

If this is incorrect please correct me. I am adding this to the thread so when other newbies like myself are looking for info about soft limits it will better clarify the process.

Homing is required to use soft limits.

Depends on whether or not homing is enabled. If not, then Easel will carve without homing (pretty sure of this - I don’t use Easel).

To use soft limits ($20=1) you have to have homing enabled in grbl ($22=1). If you turn homing off ($22=0) then soft limits are also turned off ($20=0). You can have homing enabled without using soft limits ($20=0).

Try to distinguish the difference between Home Position, Machine Position, and Work Position and it will make things easier for you. Also, be careful to use the correct term and not mix up references so that your statements are clear.

Home Position is the position where the homing switches are tripped. Grbl has a built in pull-off ($27=1.000 mm default) of 1 mm so that the homing switches can also double as limit switches.

When you home your machine then grbl sets Machine Zero at the Home Position. If you don’t home your machine then grbl sets the Machine Zero at the location of the spindle when grbl is powered up. These are the only two methods to set Machine Zero.

Work Zero is the position that you set when you jog the machine to the starting point on your material and manually (or if you have touch probe system - semi-automatically) set the zero position.

Once established Machine Zero does not change unless you disconnect from grbl and reconnect (with homing off), or home your machine (with homing on).

Work Position is relative to Machine Position.

Some G-code commands work with Machine co-ordinates, and others work with Work co-ordinates.

Appreciate the help. I have a lot to learn but very much enjoying the process.

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