The Z axis end atop the spindle has been replaced twice on our space’s X Carve due to the machine snapping the spring while homing.
Is this a common thing or is it something we need to fix in firmware?
Thanks and regards
You can use this procedure to determine why your Z axis switch is not working.
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If your switch isn’t the issue, also make sure you have your debounce set correctly, as well as home at slower speeds… The switches don’t actually stop the travel, they just signal GRBL that a switch as been tripped, then GRBL stops the motion. If you’re going at a high feed rate, you will crash your switches, if your switch debounce setting is too low, signal noise could cause you to also crash into them between innitial trigger, and the second trigger…
These are the settings on my 1000mm machine:
$24=50.000 (homing feed, mm/min) [How fast the machine moves to accurately position)
$25=250.000 (homing seek, mm/min) (How fast the machine moves before the first limit switch is hit)
$26=250 (homing debounce, msec) (How long between the time a switch is hit before starting movement again)
$27=1.000 (homing pull-off, mm)
Yes, this is a conservative set of numbers, but i no longer smash into my limit switches 
Excerpt from GRBL wiki:
$24 - Homing feed, mm/min
The homing cycle first searches for the limit switches at a higher
seek rate, and after it finds them, it moves at a slower feed rate to
home into the precise location of machine zero. Homing feed rate is that
slower feed rate. Set this to whatever rate value that provides
repeatable and precise machine zero locating.
$25 - Homing seek, mm/min
Homing seek rate is the homing cycle search rate, or the rate at
which it first tries to find the limit switches. Adjust to whatever rate
gets to the limit switches in a short enough time without crashing into
your limit switches if they come in too fast.
$26 - Homing debounce, ms
Whenever a switch triggers, some of them can have
electrical/mechanical noise that actually ‘bounce’ the signal high and
low for a few milliseconds before settling in. To solve this, you need
to debounce the signal, either by hardware with some kind of signal
conditioner or by software with a short delay to let the signal finish
bouncing. Grbl performs a short delay, only homing when locating machine
zero. Set this delay value to whatever your switch needs to get
repeatable homing. In most cases, 5-25 milliseconds is fine.
$27 - Homing pull-off, mm
To play nice with the hard limits feature, where homing can share the
same limit switches, the homing cycle will move off all of the limit
switches by this pull-off travel after it completes. In other words, it
helps to prevent accidental triggering of the hard limit after a homing
cycle.
Not all Grbl access programs will pass Grbl immediate commands to the Arduino. UGCS is one of the programs that does not send the immediate commands when you enter them in the “Command Tab”. You can use a terminal program like HyperTerminal or Putty to perform this function. Also, the Serial Monitor in the Arduino IDE will send the immediate commands.
Being a Newb… You have lost me… Badly! At the moment, I am using Easel. Where does one go in Easel to issue these commands. I cannot find it.
Failing that, since I have do the Arduino drivers installed, how do I get to this ‘Arduino IDE’?
Please forgive me, it feels like you are speaking, one programmer to another. I’m not trying to be dim, I do use computers, I just have no background with Arduino programing. I believe this to be a simple, but important test, but the instructions are much more convoluted and complex than I would have thought.
A little help at the beginning please.
If you’re using easel, you can go to Machine → Advanced → Machine Inspector Once there, you can directly issue commands to the machine using the Console Area
Perfect. I’ll give this a try when I get back to the shop.
On mine there is a threaded hole (M3 i think), to install a stop screw, keeps the z-carriage from crushing the switch. the screw was not provided but i had one that worked perfect, saved the switch several times already. My home switch works but when manually commanding it’s easy to get carried away!
wierd… i don’t have that in mine. It shouldn’t be too difficult to drill and tap an M3 hole there though.
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