Soft Limits - setup automatic or manual ???

If I remember correctly, in Mach3 I would enter a location for soft limits. However I don't see anywhere to enter such a value in Lcnc.

Are soft limits automatic in Lcnc. From the documentation I know that soft limits stop the axis BEFORE hitting the limit switches.

So does Lcnc automatically calculate exactly when to start decelerating the axis based on:

1) Limit switch position (entered in PNCCONF in my case)
2) Required distance before the limit switch to start deceleration, based on current velocity and accel/decel setting for the axis

And if the above is true, does Lcnc have a set distance before the limit switch that it stops the axis.

Or is there simply a setting somewhere where I tell Lcnc where the soft limit must stop the axis.

Hope all the above made sense.

Keith

Cheers Tommy,

so in the documentation I found this:

MIN_LIMIT = -1000 - The minimum limit (soft limit) for axis motion, in machine units. When this limit is exceeded, the controller aborts axis motion.

MAX_LIMIT = 1000 - The maximum limit (soft limit) for axis motion, in machine units. When this limit is exceeded, the controller aborts axis motion.

So just to clarify, my main question now is in the MAX_LIMIT case above, does the controller start to decelerate once it hits 1000 and therefore would actually stop some distance past the 1000 mark.
Or would the controller "look ahead" and decelerate so it stops at the 1000 mark.

Actually, I'm at the stage of connecting up my 7i96 on the kitchen table, with Estop, limit and home inputs, for testing. So I'll have to do a real world test on this with a ridiculously low accel/decel setting and see which is the case. My guess at this point is it will start to decelerate upon hitting the 1000 mark.

Keith

Yes It won't go past the soft limit.

It will decelerate before getting to that point and stop at the limit. Can confirm this worked fine at 500 ipm jog. Stopped on a dime..

Thanks guys,

also just confirmed it after giving my 7i96 board it's very first run on the kitchen bench. As you guys said it stops bang on the limit switch position that I entered in PNCCONF.

So it seems the limit switch position I entered in PNCCONF is also the soft limit position.

Based on this documentation:
linuxcnc.org/docs/html/config/ini-homing.html
and looking at the diagram/explanations in section 3, my guess is there are separate settings in the INI file for the limit switch position and the soft limit position, so that soft limits can be programmed to stop a small distance before the limit switch. If that's the case I'm surprised PNCCONF does not have somewhere to enter these separate values, it only asks for the limit switch position.

I see in my INI file there are entries for MIN_LIMIT and MAX_LIMIT in both [AXIS_X] and [JOINT_0]
Am I correct in saying MIN_LIMIT in one is for the limit switch position, and MIN_LIMIT in the other one is for the soft limit position ?

To try and answer my own question I made the MAX_LIMIT lower in [AXIS_X] than what MAX_LIMIT was in [JOINT_0] (got an error trying to do it the other way around, saying one was less than the other or something). However, this did not change where the soft limit stopped.
So at present I'm beginning to think the settings in PNCCONF are not at all for the limit switch positions but for the soft limit positions, and there are not any separate settings for actual limit switch positions.

Or have I got it all wrong LOL.

Keith

tommylight wrote:

Michael wrote:

It will decelerate before getting to that point and stop at the limit. Can confirm this worked fine at 500 ipm jog. Stopped on a dime..

Same here tested at 55 meters/minute.

500 is still numerically greater than 55 since imperial units are superior to the rest