M3 Endstop Woes

[myfingersarecold]

So i finally built my enclosure for my M3 and set it all up, however I am having issues with the X endstop. If i enable hard limits, it wont make it through the homing cycle successfully, and won't allow me to jog because it seems to think its hit a hard limit. I have the endstop connected correctly on both sides, on the board side, with red to the left, and the connectors on the 2 pins that the capacitor is connected to, being NO & GND. Do i have a bad endstop? If i turn hard limits off, the first time i run a homing cycle it fails. If i run it again the Y & Z axes home, and then it slams into the X axis. I have some endstops kicking around from my 3d printer, but i havent tested those yet.


EDIT*** Removing the X Endstop fixes the issue. so i can only assume if i replace it i should be all good. 

[myfingersarecold]

So i resolved this. I designed and 3d printed an enstop holder, using an endstop i had kicking around. it contacts the wheel, and i dont think i lost any build volume

[Bruce]

Once you have the X axis limit switch fixed. You can also turn hard limits off. They have to be setup correctly to work and it doesn't really get you much by using them.

[myfingersarecold]

Jun 10, 2020 2:49:41 GMT Bruce said:

Once you have the X axis limit switch fixed. You can also turn hard limits off. They have to be setup correctly to work and it doesn't really get you much by using them.

i like the idea of having them just in case. soft limits accomplish the same thing i guess.

[Bruce]

Here is the info on both the soft and hard limits:

$20 - Soft limits, boolean
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.

$21 - Hard limits, boolean
Hard limit work basically the same as soft limits, but use physical switches instead. Basically you wire up some switches (mechanical, magnetic, or optical) near the end of travel of each axes, or where ever you feel that there might be trouble if your program moves too far to where it shouldn't. When the switch triggers, it will immediately halt all motion, shutdown the coolant and spindle (if connected), and go into alarm mode, which forces you to check your machine and reset everything.

To use hard limits with Grbl, the limit pins are held high with an internal pull-up resistor, so all you have to do is wire in a normally-open switch with the pin and ground and enable hard limits with $21=1. (Disable with $21=0.) We strongly advise taking electric interference prevention measures. If you want a limit for both ends of travel of one axes, just wire in two switches in parallel with the pin and ground, so if either one of them trips, it triggers the hard limit.

Keep in mind, that a hard limit event is considered to be critical event, where steppers immediately stop and will have likely have lost steps. Grbl doesn't have any feedback on position, so it can't guarantee it has any idea where it is. So, if a hard limit is triggered, Grbl will go into an infinite loop ALARM mode, giving you a chance to check your machine and forcing you to reset Grbl. Remember it's a purely a safety feature.

[myfingersarecold]

yeah I've encountered issues with soft limits when setting my work zero to close to the physical limitations of the m3 which is nice.

I also installed an e-stop switch for the router and hooked it into the CNC shield as well. Very happy with it.