Hey, guys!

I just switched to GRBL on my C3D Mini board and its much, much better so far.

One thing that I haven’t fully fund any clear info is Z bed homing. I am able to move my Z bed up and down without problems, but when I try to home it, Laserweb gives me a a very long error box that the command is not supported by the firmware. Is there a different GRBL firmware that works with a Z end stop? I got mine from https://github.com/cprezzi/grbl-LPC/releases. Also, while I’m here, I had a similar question about Lightburn, I had a trial version and it was pretty good, but it would update laser head coordinates when it feels like it, even when I clicked the “update coordinates” button and I couldn’t find a way to home my Z bed even back when I was running Smoothie firmware. I’d like to start using Lightburn software, because it works much smoother than laserweb, but homing Z is a vital part of my operations. Any suggestions?

By the way, I’m running Windows 7 64 bit

images/7b05e3550cfdffe7a0945b2b1c19260e.jpeg

“Bklyn Ghost”



Jim Fong May 21, 2018 13:52

Custom version of grbl-lpc for xyz homing. Smoothieware needs a minor configuration change in the config.txt to support z homing. Check the docs on howto.

Download and rename to firmware.bin. Copy to sdcard and flash the c3dmini

You may have to change the grbl configuration for z homing direction. It would depend on where your limit switch is located. Grbl1.1 docs will explain under Homing and Limit switches

dropbox.com - firmware grbl-lpc c3dmini 4axis with XYZ homing.bin


Jim Fong May 21, 2018 16:45

Link

dropbox.com - firmware grbl-lpc c3dmini 4axis with XYZ homing.bin


Bklyn Ghost May 21, 2018 17:06

+Jim Fong Thank you so much for the link, I flashed this firmware and the error is gone. I’ve configured the directions and Z actually moves when I send a homing command, but it completely ignores the limit switch. My switch is mounted to the top of the bed, I know I’m missing something in my settings.

$$

$0=10

$1=255

$2=0

$3=3

$4=0

$5=1

$6=0

$10=0

$11=0.010

$12=0.002

$13=0

$20=0

$21=0

$22=1

$23=5

$24=70.000

$25=100.000

$26=250

$27=1.000

$30=1000

$31=0

$32=1

$33=5000.000

$34=0.000

$35=1.000

$36=100.000

$100=160.000

$101=160.000

$102=3200.000

$103=160.000

$110=24000.000

$111=24000.000

$112=60.000

$113=24000.000

$120=2500.000

$121=2500.000

$122=2500.000

$123=2500.000

$130=300.000

$131=200.000

$132=50.000

$133=100.000

$140=0.600

$141=0.600

$142=0.000

$143=0.000


Jim Fong May 21, 2018 17:22

Check to see if the z limit is connected right and if grbl sees it. Type ? In the console will show the state of the switches

The default grbl-lpc endstop limit switches is high so it will show

Pn:PXYZA when typing in ? Status

The respective endstop will disappear from the status when activated low


Bklyn Ghost May 21, 2018 18:16

+Jim Fong Just checked it with PuTTY, when no switches are engaged, I’m getting Pn : PZA, When I press the switch on Z table, it returns Pn : PZ, does that mean that GRBL thinks that my Z switch is A? The X and Y show up when pressed.


Jim Fong May 21, 2018 18:29

+Bklyn Ghost looks like your z limit is plugged into the A limit connector. Change it.


Bklyn Ghost May 21, 2018 20:08

+Jim Fong My board didn’t have limit switch pins for A, but I moved the switch from Zmin to Zmax and now it recognizes everything, but now I’m having a trouble because the XY switches are stock K40 ones and the Z came with my C3d board. It appears that XY are Normally open and the Z is normally closed, or vice versa. When I change the value of $5, The homing sequence recognizes the Z switch when pressed and proceeds to look for XY, but it thinks that the switches are already pressed. Is there a way to reverse the pins just for the Z switch?


Jim Fong May 21, 2018 20:16

Change $5=5 and see what happens

Oh ya no A limit. I’m at work and don’t have the board in front of me. Going by memory.


Bklyn Ghost May 21, 2018 20:37

+Jim Fong I tried doing that, unfortunately it only accepts 0 and 1. Would I have to modify config.h file? I found this page github.com - grbl with advanced settings which seems like exactly what I would need (lines 198-204) But How do I even get to config.h? I don’t remember seing that file on the SD card after flashing grbl for the first time.


Jim Fong May 21, 2018 20:46

That’s right it’s all or none. You can’t mask $5

The other way is to see if the actual z switch has a normal open connection that you can hook up instead.

I would have to look at the source code later to see if it can be modified to work for you.

Any modifications to the config.h would need a re-compile of the source code.


Bklyn Ghost May 21, 2018 22:37

Yeah, I started digging deeper about modifying the source code and the whole process looks like it would be way beyond my capabilities. I do miss the simplicity of Smoothie in terms of configuring it, but it was not stable enough for rasters for some reason and I’ve wasted a lot of material/time with it. I don’t have any other switches laying around to replace the current ones. I hope you can come up with something, if not I guess I would have to replace the switches with three identical ones.


Jim Fong May 21, 2018 23:12

+Bklyn Ghost if it is a mechanical switch. see if it has 3 terminals on it. The third one will be the normally open connection.

If not, it would be easiest to just change the one Z switch to normally open. Don’t mess with the X and Y limit switches.


Jim Fong May 21, 2018 23:20

What problems did you have with smoothieware anyway?


Bklyn Ghost May 21, 2018 23:42

It is one of those red PCB makerbot switches with 4 wires. Looking at the board it has NC and NO printed underneath the connectors, I wonder if I could possibly switch the wires on it, or desolder it from the board and use just that. I don’t want to mess with the switch pins unless I am absolutely sure, because from what I’ve read if connected wrong, it could fry the board. That means I would have to wait for a new board and they are on backorder currently and I use the machine for my business.

Smoothie did well with vector cuts, but rastering was problematic. The X would shift during engraving, I’ve tried re-generating the G-code, using different file formats, taping the workpiece down to the table, checked the belt tension, cable, different computer etc. It would work fine for a while and then bam, shifts left right in the middle of the job. I wasn’t using too high of a speed, I don’t think somewhere within 250mm/s. The movement was very jerky as well, Grbl is so much smoother, quieter and faster.


Jim Fong May 21, 2018 23:53

+Bklyn Ghost of you can, just move the wire that is connected to the NC terminal to the NO terminal.


Bklyn Ghost May 22, 2018 01:03

+Jim Fong That did the trick!

Turns out the XY endstops were wired as NC and the Z switch is NO. I soldered the wires on the XY switches to NO and voila, she’s homing. Now I have to configure homing speeds and all, but that’s easy.

Jim, thank you so much for all of your help. Your time and advice are highly appreciated.


Joe Alexander May 22, 2018 14:12

it might be worth trying smoothie again with the sd card sharing disabled, some have have had luck with smoother engraving and less stuttering this way. theres a line in the config file named disablemsd that needs enabling, will disable the ability to access the sd card through the usb cable.


Jim Fong May 22, 2018 18:10

+Joe Alexander you still need a special version of the firmware found here to use the disablemsd config switch or the one I compiled which permanently disables the sdcard access.

forum.smoothieware.org - Troubleshooting - Smoothie Project


Jim Fong May 22, 2018 18:13

My version of the disablemsd

plus.google.com - Apologize for the long post but need explaining…. I’ve always had random h…


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