SOFT HOMING

Topic's about PicSender
Forum rules
Be Kind to other's.
No Cussing or Swearing.
Don't post anything Illegal or Obscene.
Image attachment size limit is 500 KiB.
hooked
Posts: 42
Joined: Thu Jul 30, 2015 6:45 pm

SOFT HOMING

Postby hooked » Sun Dec 25, 2016 6:06 pm

Hi Guys,

Firstly Merry Christmas from Australia.

Now, I am using PicSender on my home made CNC router. It has no homing or limit switches which I know is fraught with danger.
That being said, I am looking at setting up so I can drive the machine to a corner and then set that as a "soft" home position.

So another words, trying to achieve both soft homing and limits.

This where I'm at:-

$130=700 (Xmax)
$131=500 (Ymax)
$132=75 (Zmax)
$20=1 (Soft Lmits)
$21=0 (Hard Lmits)
$22=1 (Homing)

This is what the procedure is at present.

Switch everything on.
$x Kill Alarm warning.
Jog machine to desired home position (Bottom LH corner)
Enter command G92 X0 Y0 Z0

Now when I jog in either X or Y direction the travel it allows one occurrence. If I try to jog again I get no machine movement or error in PicSender.

Am I going down the right path or is there another way to achieve the outcome I'm looking for?

THANKS in anticipation. :anyone)

Cheers

Daryl

User avatar
Picengravertoo
Full Access Moderator
Posts: 1092
Joined: Thu Dec 18, 2014 4:02 pm
Contact:

Re: SOFT HOMING

Postby Picengravertoo » Sun Dec 25, 2016 7:28 pm

Merry Christmas Daryl.

I don't have limit or homing switches on my Shapeoko 2. If you set $22=0, you don't have to $x kill the alarm. You then jog down to your lower left corner and zero the axis's where you wish, then close the com port, connect again and zero the axis's again. It will zero out the G54 and your soft limits should be from there, I believe. John can probably verify this as I'm not at my machine right now. I don't use the soft limits either.

Jeff

User avatar
Picengraver
Full Access Moderator
Posts: 338
Joined: Tue Dec 23, 2014 5:40 pm
Contact:

Re: SOFT HOMING

Postby Picengraver » Sun Dec 25, 2016 9:51 pm

Daryl,
I have never used soft limits, only hard limits, so I am not sure if the following from Grbl's developer, Sonny, is still valid or not. A lot has been changed in Grbl since he posted this.
************************************************************
" chamnit commented on Apr 29, 2013

@rverhag : Thanks for reporting on the soft limits. Haven't had too many people test it out and state how it works. First, it's never been tested on a mill on my end, as my machine is in storage while I've been remodeling my garage. So it will likely have oddities and bugs that I wasn't able to account for, mentally or by software testing.

Secondly, soft limits is designed to only work when homing is enabled and your machine is homed. When homed, the machine coordinates should only exist in the negative space, i.e. 0 to -max_travel for each axis. It shouldn't matter where you limit switches are. It should account for them. Then, soft limits will check for any move that is either positive or less than the -max_travel, before actually moving the machine. If it finds one, it'll alarm out. The machine should come to an immediate stop, if in cycle, or not move at all, but still retain system position.

If you don't have homing enabled or your machine isn't homed, soft limits will not work correctly. It'll just allow you to move in negative space. I probably need to create another level of system checks to automatically disable soft limits when homing is."
************************************************************
Try Jeff's suggestion and please let us know if it works.

John

EDIT:
This is the latest on Grbl's soft limits:
***********************************************************
"$20 - Soft limits, bool

Soft limits is a safety feature to help prevent your machine from traveling too far and beyond the limits of travel, crashing or breaking something expensive. It works by knowing the maximum travel limits for each axis and where Grbl is in machine coordinates. Whenever a new G-code motion is sent to Grbl, it checks whether or not you accidentally have exceeded your machine space. If you do, Grbl will issue an immediate feed hold wherever it is, shutdown the spindle and coolant, and then set the system alarm indicating the problem. Machine position will be retained afterwards, since it's not due to an immediate forced stop like hard limits.

NOTE: Soft limits requires homing to be enabled and accurate axis maximum travel settings, because Grbl needs to know where it is. $20=1 to enable, and $20=0 to disable."

https://github.com/grbl/grbl/wiki/Confi ... imits-bool
***********************************************************

hooked
Posts: 42
Joined: Thu Jul 30, 2015 6:45 pm

Re: SOFT HOMING

Postby hooked » Mon Dec 26, 2016 3:09 pm

THANKS Guys,

Your responses have given me something to further investigate

Cheers

Daryl


Return to “PicSender”

Who is online

Users browsing this forum: No registered users and 0 guests

cron