The probe is actually pretty darn close to 0.59 exactly so I’ll leave it as is for now.
I was reading a previous post of yours and & started looking at the G90 again on my VCarve files. I see now why it is important. Is there an automatic way to make VCarve add this or does it have to be done manually?
Error: Does not compute. lol… I’ll have to dig into that after this issue is fixed.
The ?? makes sense now too and can help confirm that it is a soft limit issue.
Other responses:
-Yes, I have seen the Error 9 when I try to make any movements in the alarm state or try to reprobe.
-I typically clear the alarm by homing, but the $x is a good bit to know as well.
Shortly after meaning I see 2 ok’s in the Console, however the Z axis never moves at all when it is past it’s limit. To me, this rules out any issue with the probe thickness or distance from the bit.
Also, I changed out my Z axis pulley set screws with metric hex head screw and I have those torqued down pretty good (with blue loctite of course, thanks @PhilJohnson) .
I got curious and started doing different tests with varying $132. Below are my results.
$132 = 100
Max Z probe success (mm): -21
$132 = 110
MZPS: -31
$132 = 120
MZPS: -41
$132 = 140
MZPS: -61
$132 = 150
MZPS: -71
The formula is MZPS = -($132 - 80)
So, now it seems like to get my Max Z travel of ~82mm, which I measured earlier, I would have to set $132 = 160. I was too scared to test at this condition since it was so low. This is also why a valve of $132=80 was not allowing me to probe from anywhere but from the home position.
I read through the other Grbl Constants and I don’t see anything about a Z offset or any type of scaling… I feel like I am now confident that my machine will run consistently with $132 = 160, but the WHY is killing me!
It just hit me…I’d be willing to bet that it’s the max probe distance value in Easel. It’s sets to 3.1 inches. That is about 79 mm. 21 + 79 = 100. That has to be it, right? If you change that to 1.6 inches, you should see the lowest Z go to -42 mm. And with soft limits enabled, GRBL will plan the motion and it will calculate it to potentially violate the soft limit so it does nothing, just like a motion command. Now it all is making sense.
Inventables is assuming two things with their Easel probing defaults:
The user may start Z probing immediately after homing so the Z would be all the way at the top.
Most users aren’t enabling soft limits and if they are, they will modify the probing values to avoid this.
I tried the 1.6 Max Probe Distance and I can see that the Z value for the Probe G code command change but I checked my Constants line by line and there is no change (New: http://i.imgur.com/XjDcVS5.jpg / Old: http://i.imgur.com/kQhB8Hm.jpg)
I repeated the test from before:
$132 = 80
Max Z probe success (mm): -39
$132 = 90
MZPS: -49
$132 = 100
MZPS: -59
$132 = 110
MZPS: -69
The formula is now MZPS = -($132-41) or a difference of +39mm from before just with the Max Z Probe change from 3.1 to 1.6.
You were exactly right, Justin. I typically never probe from the home position and I just enabled the soft limits after crashing my machine. This is interesting and I may have to try to take it all in again tomorrow after some sleep, but I couldn’t let it linger over night.
Couldn’t stop thinking about it but it makes sense now.
The order of operations was:
Crash machine
Turn on soft limits with $132 = 80.
Cut 1 of the 3 cut carve used a long bit and I was able to Z probe my 0.75" stock because it was close to home position when starting the probe sequence.
Cut 2 used a shorter V bit that I was trying to probe from a lower Z position. Ive never really thought about it, but I usually jog the bit within an inch or so from the Z probe before starting the probe sequence.
Ill have to think a little more on why the max probe distance affected that, but Im happy its fixed. Thanks to all who chipped in.
So, at the most basic level, a probing command is a normal movement command that moves the Z down a specified distance slowly and stops when the circuit is closed (bit hits the puck). The circuit can be closed after a short distance or it could be closed at the very last mm of travel, GRBL has to plan for the worst case and move the entire specified max distance (79mm default in Easel).
When soft limits are enabled, all movement commands are checked to see if they violate the soft limit (the whole point of soft limits). So with Easel defaults, the probing command is set to 79 mm. You’ve got a max travel of 80mm. If you’re anywhere but at -1mm (the default position after homing), the command will exceed the max travel so it alarms. So if you’re at -10 mm, the probing routine could take you to -89 and 89 > 80 so therefore alarm and don’t move.
@JustinBusby it’s all starting to come together now. So that is why they us a relative G91 command for the probe so it will start from any position and go down the specified distance. It is interesting why Inventables would default to moving the entire length of the Z axis and keep soft limits off. I guess they figure too many noobs like me will get confused by the alarms.
@PhilJohnson I think I’m confusing you with my poorly named acronym, MZPS. Basically, im trying to show the lowest position I can start the Z probe and not have it trigger the soft limits.
I am using negative work space and in my second test, I had my max Z probe distance set to 1.6 in or 40.6 mm. With a $132 = 80, the lowest I was able to start my Z probe was at Z = -39 since 39 + 40.6 = 79.6. Anything lower than Z = -39 (-39.4 technically) would trip the soft limits.
By default, easel suggests a max Z probe depth of 3.1in or 79mm which is why I couldnt start the probe anywhere but from the home position at Z=-1 (with $132=80).
I agree, positive workspace makes much more sense and I will have to look into that more soon.
I think I will set my $132 = -82 (previously measured) and keep my max probe distance at 1.6 in (40.6 mm). To me, these settings will satisfy not letting the Z carriage fall off the rails and will allow me to start the probe from -1 to -41.
Is this making sense, or have I built up too much confidence in 2 days after not even knowing what a machine constant was?
@PhilJohnson ah, right. I confused the Z positions and the $132 setting when I typed that.
I crashed my machine going up during carve set up jogging before I had soft limits turned on. Will the soft limits prevent the jogging from going outside the limits as well? I’m guessing so and will test when I get home.
