Attaching Limit Switches Q

[martinbatts]

I have a homebrew CNC I'm building, and have limit switches that lack a good place to screw into the plates that the rails and screws attach.
So.. I'm thinking of gluing them to the screw support.
I'd rather not, but I am super limited. As it is, I only have ~ 6" Z Axis travel, and if I screwed into the plate, I'd lose another 1" of travel which I really don't want. If anyone agrees with gluing, what glue?
I could attach a pic of the Z Axis sub-assemble if that helps.

Also a related Q. I have this attached bench testing style to the CNC12. All works great (thanks Martys CNC, Franco, and this forum!)
I see from YouTube etc that most have only an origin limit switch, not one on both ends. And then use the Wizard to limit the max + limit.
But it appears that every time I turn off the CNC12, it doesn't remember where it is. And I surmise there is no CMOS memory on the Beagle Bone board, etc.
So.. don't I "NEED" a limit switch on both ends?

Thanks in advance
"

[Nigelo]

Q2
No, the software travel limits are calculated from the Home position and therefore only operational after Homing.

[Sword]

You could try some 3M mounting tape. I used it on a benchtop Techno Isel to mount some 3D printed holders and targets, and it's working well.

[martinbatts]

Q2
No, the software travel limits are calculated from the Home position and therefore only operational after Homing.

Thanks, but forgive me for not understanding completely. Is 'Homing' something you have to do every time you turn on the machine?
i.e. if the spindle isn't homed, and you turn the machine off, then when you turn it on, do you have to manually 'Home' it, for the calculated travel limit to be effective?
(in which case, I'd prefer the safety of switches on both ends)

thanks

[tblough]

The axis need to be homed everytime the machine is started or e-stopped.

[kb58]

... Is 'Homing' something you have to do every time you turn on the machine?
i.e. if the spindle isn't homed, and you turn the machine off, then when you turn it on, do you have to manually 'Home' it, for the calculated travel limit to be effective?
(in which case, I'd prefer the safety of switches on both ends)

Yes. When powered up, the controller has no idea where it is. It doesn't save the last location in memory before power is shut off, and even if it did, there's the of physically moving the axes with power off and the controller wouldn't be aware.

So yes, Every time it's powered up it must be home to re-synchronize the controller to where everything is. When the Home routine is run after power up, the controller drives all axes toward home, never the other direction, so having switches at the far ends has no effect on homing.

[tblough]

Others have said that soft limits work fine, and they do... IF everything is working correctly. If you loose steps, then it's possible to run past the limits because they are no longer valid. If you have the inputs for it, I recommend limit switches at both ends of travel on all axis.