Z-Probe and Z-Homing

Hi,

i´m in the process of building my own Printer, has by now roughly 30x22x8 cm Print Area (Z-Axis will be raised afterwards, if everything works well). It consists mainly of reusing Parts of my Easythreed-Printers (Board, mainly two Z-Axis Shafts with and interconnected X-Axis, each has its own Motor). It uses a Glass bed of an old Flatbed Scanner. The Y-Axis and the stabilizing frame is self-built.

What i´d like to have is some sort of Auto leveling by using a Z-Probe. So i´ve constructed somewhat like a manually deployed Z-Probe with magnets holding the lever in either position and a Switch on one End (see picture), much like the Allen Key solution. G29 seems to need homing of the X/Y/Z-Axis before performing auto leveling, but i´d like to use the deployable switch as both for homing -and- performing auto leveling in a grid with the same switch, so that i wouldn´t need a second (currently unavailable) Connector on the board for the Probe switch and save the original Z-Axis-Home Switch, because i think that the usual homing by using the fixed Z-Axis-Endstop-Switch is unnecessary with this construction, as long as this Probe is deployed. Is this combination/configuration possible to do in Marlin (or any way to override the need for homing when performing G29)?

Kind regards
Stef

Edited 6 time(s). Last edit at 02/04/2023 11:52PM by stef123.

Looks like you want to enable USE_PROBE_FOR_Z_HOMING.

Yesss :-) Works like a charm :-)

With one restiction - if i define PAUSE_BEFORE_DEPLOY_STOW and Marlin sends a pause message for manual deployment, i can resume with M108, but when it tells me to stow the probe, i can´t resume with M108. So i have to deactivate the pause.option. Currently i have no keys or display attached (its too early in the construction process).

Edited 3 time(s). Last edit at 02/05/2023 12:36AM by stef123.

"Works like a charm" - well, sort of. That Belt-Driven Z-Axis-Construction is not the way to go at all. Why: Both Z-Axles utilize 24BYJ28-Steppers with 1:64 Ratio and they have unfortunaly a lot of clearance
between two positions when the toothbelt-gear is moved by hand (approx up to 1/3 tooth out of a total of 14 teeth @ 8.2 mm diameter). So one of the Z-axles could "slip behind" the other one if they don´t push/pull
at exactly the same time, resulting in different heights at the X-Axis. I measured up to 1.2 mm difference with variations each time the Z-Axle moves up/down. The Steppers also do not like Steps with 0.1/0.2mm at all in that configuration- they react too late (or "sum up" the steps and go for 1mm at once); so auto leveling would be pointless.

Additionally the tension between the X-Axis-Rods makes it even worse when the Z-distance raises or lowers. The needed precision in terms of the same X-distance throughout the entire Z-axis cannot be reached in this way.
Maybe interconnecting both Axis on top by using another rod would do the Trick, but that has to be precise as well

One XZ-Axis alone doesn´t do it either, because the Z-construction, which holds it in place, is too wobbly ex works. The X-Axis can be easily bent down or up - this was to main reason why i tried to use two Axles. So the thing to go for Z would be unfortunaly the standard configuration with theaded rods.

Edited 4 time(s). Last edit at 02/06/2023 10:15PM by stef123.