Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Lulzbot TAZ retractable Z-probe auto bed level compensation with G29 Mod

by 1013, published

Lulzbot TAZ retractable Z-probe auto bed level compensation with G29 Mod by 1013 Jul 14, 2013
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This mod makes manually leveling the build bed a thing of the past.This is for Advanced users only, Firmware and hardware modification is required and likely will affect any warranty on the machine. This also reduces your X printable area by about 8mm, at the max X position.

video's of the prototype in action:
deployment: http://youtu.be/tMdS1dXkoAc
printing with Z motion http://youtu.be/c8dM1KpBXJ8

Inspired by this: https://www.matterhackers.com/news/automatic-printer-calibration-update

The Z-probe is a micro-switch wired up in parallel with the existing Z min switch and attached to a cam operated toggle. The probe is deployed when the X-carriage goes to the max X position, and retraced when the carriage goes to X0. This allows for automatic bed probing before each print.

NOTE: this is designed to work with TAZ's that have my stiffened X motor and bearing mounts. http://www.thingiverse.com/thing:107553 It can work with standard TAZ parts but may require a custom 8mm spacer on the lower X smooth rod since the probe is activated by pushing against these parts.
It is also recommended and probably necessary to remove the Z-backlash that is in the standard TAZ by following the instructions in this mod: http://www.thingiverse.com/thing:117950

Lulzbot TAZ specific configuration.h file:
G-code for probe deployment and bed probing:


be sure to do the anti-Z backlash mod first, and the stiffened X mounts (though this one may be optional, with an 8mm spacer on each side). links are in the sources or description

For best results, replace all 10mm linear bearings on the TAZ with LM10UU ball bearings.

accessories required:
-(3-4) M3 washers
-(1) M3x16mm bolt, longer should also work
-(2) M3x12mm bolts
-(3) M3 insert nuts and inserting tool(short, mcmaster carr)
-3mm drill or reamer
-(1) roller tipped micro switch (radioshack 275-0017 or other electronics store)

To Do:
-Print all parts. ABS recommended. support material is not needed
-trim and/or file the bearing holder and activator so that the base of the bearing holder is flat, and the activator slides easilly in the slot.
-install 2 insert nuts in the toggle, and one in the bearing holder where the toggle mounts. It should be below the surface in the bearing holder, and not sticking out either side of the toggle.
-drill or ream the holes in the micro switch to 3mm (depending on the switch, this may not be necessary)
-Install the micro switch with the 2 12mm screws as shown in the pictures.
-Install the bearing in the bearing holder
-temporarily install the activator in the bearing holder
-temporarily install the toggle as shown int he pictures with the 16mm screw and washers. 2 or 3 washers should go in between the toggle and bearing holder and one on the outside of the toggle for the bolt to push on.
-test the operation of the toggle. it should take some force but not too much. be carefull, and adjust the toggle axis bolt tension or trim and file the parts until the move freely.
-remove the toggle and activator
-install the bearing block on the X-carriage, re-using the mounting screws from the original part.
-slide in the activator
-attach the toggle
-wire up the micro switch
-replace the Firmware
-calibrate the probe. see here for help: https://www.matterhackers.com/news/automatic-printer-calibration-update
-add the G-code to do the bed probing before each print
-remove the 4 springs from the bed corner mounts and never re-level your bed again.

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Very nice job!!
The link for firmware on instructions don't work is it any possibility you can provide working link? :)

This is great, any chance anyone has some working G-Code for a Lulzbot TAZ 4? I've searched and got it almost right, however it deploys fine, probes 4 corners (my preference), retracts the probe, and then tries to print an inch over the bed (basically the height of the probe to the bed). I'm sure I'm missing some type of temporary Z-probe offset function. Would be great to see what others have out there working. I'll post mine once I have a working example to share or if someone wants to see what I have PM me and I'll send it over. I don't want to add to the confusion by posting G-Code that's not work 100% here. I have combed through the G-code reprap wiki and found some great stuff there, however I am new to 3D printing and not sure what I'm missing. Any advise would be awesome. Thanks!

heres what id do...
G28 XY
G1 Z30; Rapid movement Putting z position somewhere above the bed and objects on bed if any
G1 X205 ; The 205 is max x position that deploys probe ...change it to whatever your probe needs to be at in x axis to deploy
G28 Z; Home z (the bed center is All axis zero in this case so the carriage moves to center bed in xy before probing z home)
G29; probe bed after homing axiis
M500; save g29 probe settings to eeprom
G1 Z30; raise z to Safe area above bed again
G1 X5; Far enough to retract probe but NOT far enough to bump endstop because you may end up losing all probe findings from previous G29 depending on firmware setup ect.
then run the rest of your startup code and be sure to change it if it conflicts with the probing code above ...and dont forget---> verify that the gcode looks right. load it up in cura or whatever software you have that allows you to view layer output first before you click print and save alot of headaches and time.
I actually use a rack type system to deploy my probe and this is how i do it. I wish i understood marlin functions better so i could change g29/g28 coding to include the deployment and retraction of the probe before/after g29 or g28 when it is called upon, then i could flash it to firmware permanently and do away with the startup gcode.
Anybody out there got any idea how i can change g28/28 code to include the probe deploy/stow in marlin?? thanks in advance

anyway neotype33... i hope this helps

I also have a Taz 4 and have made these parts. Please post your G-Code when you have it working. Thanks!!

Great project. I've made all the parts, but can't get to the firmware code. I get a 404 error. Can you repost, or direct me to the source? Thank you

On Matterhackers we are told about an all software bed leveling method.
Is this hardware one still relevant or should I explore this software only solution ?

I ve just printed the x stiffened mods. I wonder if I should print pieces for this retractable probe :-).

I love this! Well done.

I wish my printer had this mechanism on it. We would love to work with you to get MatterControl working with this setup probe. Do you have a branch of the firmware that makes it move to the side rather than the up motion?

i have not modified the firmware (besides the config file). The moving to the side to deploy and retract the probe is all done in a custom G-code that is run at the beginning of each print. and this is of course slightly custom to each machine. If you could setup a G-code script to run as a "probe bed" command, instead of a simple "home-Z" command...that would work. Maybe an option to run a G-code program in place of the home-Z command.