Simultaneous hard limits and soft limits?

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Ernesto2
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Joined: Sun May 06, 2018 7:17 am

Simultaneous hard limits and soft limits?

Post by Ernesto2 » Sat Jun 09, 2018 8:17 pm

I'm asking this because I tried it and got erratic errors. It could very well have been operator error though.

Is it possible to have hard limits and soft limits turned on in grbl at the same time?

When my machine hits hard z limits, which uses a mechanical NO switch that switches between the shield 5v ground and the z limit input, and when the floating head anti collision sensors that trigger relays that connect 5v ground supplied from the shield to the ABRT input are triggered, I have to reset the rpi and grbl to get the machine to move again. The unlock, reset, and $X commands in bCNC/grbl do nothing until I shut down and power cycle everything. Other functions such as changing tabs on bCNC work fine. It just won't reset.

I think all of the wiring and hardware is fine because I cut metal with it for four hours straight and it only randomly stopped cutting twice, with no error, which is easy to deal with. The z limit and anti collision triggers that are causing the lockup I'm taking about here were due to bad g-code and a slight misadjustment on the floating head.

Is it possible/recommended to set soft limits and set those limits just slightly inside the hard limit coordinates?

Should a z limit hit lock everything up? I've restarted bcnc, can connect and disconnect, but the alarm won't reset even if I physically move the z axis off the switch. I haven't tried to repeat the possible issue with the x and y limits yet.

Also, which control input pin in the protoneer board is supposed to cause the same action as clicking the Stop button in bCNC? I need to use whatever input stops machine motion and turns off the spindle/torch. ABRT seems to make an entire system reset necessary, which means reopening bCNC, reloading the code, etc, and RST seems to lose the work coordinate zero, which makes restarting in the middle of a failed cut a pain. I may have this backwards but nothing seems to just stop motion and stop the spindle like hitting the stop button does.. Will verify Tuesday.

Bertus Kruger
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Re: Simultaneous hard limits and soft limits?

Post by Bertus Kruger » Tue Jun 26, 2018 8:11 pm

Ernesto2 wrote:
Sat Jun 09, 2018 8:17 pm
Is it possible to have hard limits and soft limits turned on in grbl at the same time?
Yes... I would suggest making the soft limits smaller than the actual hard limits.

Bertus Kruger
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Re: Simultaneous hard limits and soft limits?

Post by Bertus Kruger » Tue Jun 26, 2018 8:34 pm

Ernesto2 wrote:
Sat Jun 09, 2018 8:17 pm
Is it possible/recommended to set soft limits and set those limits just slightly inside the hard limit coordinates?
More details on softlimits...
https://github.com/gnea/grbl/wiki/Grbl- ... ts-boolean

Ernesto2 wrote:
Sat Jun 09, 2018 8:17 pm
Also, which control input pin in the protoneer board is supposed to cause the same action as clicking the Stop button in bCNC? I need to use whatever input stops machine motion and turns off the spindle/torch. ABRT seems to make an entire system reset necessary, which means reopening bCNC, reloading the code, etc, and RST seems to lose the work coordinate zero, which makes restarting in the middle of a failed cut a pain. I may have this backwards but nothing seems to just stop motion and stop the spindle like hitting the stop button does.. Will verify Tuesday.
I don't know of a way to stop it like bCNC...

Hold is an option but it will not sync with bCNC

Ernesto2
Posts: 46
Joined: Sun May 06, 2018 7:17 am

Re: Simultaneous hard limits and soft limits?

Post by Ernesto2 » Mon Jul 02, 2018 4:52 pm

I'm having to run the machine with all limits off to get it to run reliably for now. Still fighting EMI.... I think.... :roll: It looks like I'm going to have to rewire the limits for NC, go ahead and install my limit optoisolator board, and order some ferrite rings for the cables between the opto board and the protoneer.


I also have a lot to learn as far as optimum feed rate and plasma machine settings go. I spent hours trying to figure out why the torch height controller wasn't working right and it turned out that because the feed rate was just slightly too low or the amperage was too high, the material was blowing out so fast that the torch couldn't maintain a constant voltage.

It was also triggering the collision sensors here and there because the torch would run into its own kerf, again, due to incorrect feed/amperage/thc/decel settings. GRBL definitely doesn't seem ideal for plasma cutting with it's default corner deceleration settings. Slowing way down at corners for milling is a good thing but it makes it super tricky to tune a standalone thc. I'm sure there are settings that I can play with for this so that's another thing I need to research. I'm so researched out... I'm probably going to be a cnc/arduino guru by the time I get this thing running reliably though, so that's a good thing in the long run. :D


Thanks again for the input!

Ernesto2
Posts: 46
Joined: Sun May 06, 2018 7:17 am

Re: Simultaneous hard limits and soft limits?

Post by Ernesto2 » Mon Jul 02, 2018 6:05 pm

I just ordered one of these:
https://www.amazon.com/HiLetgo-Analyzer ... B077LSG5P2

You won't be hearing any more out of me about erratic alarms until I solve it. ;)

KENSTV
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Re: Simultaneous hard limits and soft limits?

Post by KENSTV » Thu Jul 12, 2018 4:51 pm

Are you using laser grbl ? I think it optimizes the settings in grbl for laser cutting
On the emi try grounding the torch tip back to the common ground on the cutter case, I read where it cut the emi but with a side effect of more consumption of consumables, the tip changes polarity after initial arc if your using a pilot arc type cutter, I can link to the discussion if you need
the ferrite torids will help some but its best to distance the plasma cutter as much as possible from the raspberry, the trigger wire to start the plasma needs to be run thru an optoisolator-which is what they do on commercial cnc plasma cutters, also double filtering on the ac input side of the plasma power supply is employed as well as caps on all the ports to the micro--this would be all the end stop, reset etc. pins

Ernesto2
Posts: 46
Joined: Sun May 06, 2018 7:17 am

Re: Simultaneous hard limits and soft limits?

Post by Ernesto2 » Mon Nov 26, 2018 9:33 pm

I never tried laser grbl but tried everything else that you suggested and got to the point where both systems just randomly stop responding for no apparent reason. I was hoping that a water table would help with the EMI thing on the plasma table but when my router system started doing it too, we had to cut our losses, give up and order a commercially made machine.

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