Sonic 3D Printer Auto Bed Leveling Makes A Swoosh

3D Printering: the final frontier. These are the voyages of another 3D printer hack. Its mission: to explore strange new ways of leveling a print bed.

So far, we’ve had servo probes, Allen key probes, Z-sled probes, inductive and capacitive contactless switches, just to name a few. All of them allow a 3D printer to probe its print bed, calculate a correction plane or mesh, and compensate for its own inherent, time variant, inaccuracies.

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Rethinking Automated Bed Leveling For 3D Printers

Automatic bed leveling is the next killer feature that will be found on all commercial filament printers. It’s a problem that has been solved a few dozen times already; there are just so many ways you can go about it. The Printrbot uses an inductive sensor to determine the position of the metal bed in relation to the nozzle. The Lulzbot Mini touches the nozzle itself to four contacts on the corner of the bed. There are even a few projects that will mechanically level the bed with the help of a system of cams and springs. It’s a difficult problem, and none of these solutions are perfect. [mjrice] has been thinking about the problem, and he hit upon a solution that is simple, elegant, and can be replicated on a 3D printer. It’s the RepRap solution to 3D printing, and it looks cool, to boot.

Instead of using the nozzle as a contact, getting an inductive sensor, or fabricating a baroque system of gears and cams, [mjrice] is doing this the old-fashioned way: a simple microswitch, the same type of switch you would find on the limit switches of any RepRap. Having a switch at the same Z position as a nozzle is an iffy idea, so [mjrice] made this switch retract into the extruder during printing, without using any motors, servos, or other electromechanical contrivances.

The key to this setup is a simple spring and a rack gear. When this rack gear is hit from the left side, it moves an arm and places the switch down on the bed. Hit the rack from the right side, and the switch folds up into the extruder. Combine this with a bit of G-code at the beginning of the print, and the switch will move down, figure out the actual height of the bed, and flip up out of the way. Beautiful, elegant, and the algorithms for bed leveling are already in most major printer firmwares.

You can check out the video of the mechanism below. It’s a great little device, and since it’s on a RepRap first, it’s not going to show up in a proprietary 3D printer next.

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Semi-Automatic Bed Leveling Your 3D Printer

Two of the most important prerequisites for successful 3D printing is making sure the bed is level and correctly setting the Z=0 height. Getting both of these right almost guarantees great adhesion since the first print layer is not only at the right distance from the build platform but also at a consistent distance for the entire bottom surface of the part.

Manual bed leveling is tedious, requiring the user to move the print nozzle to different points around the build platform, adjust some screws and make sure the nozzle is a piece-of-paper’s thickness higher than the platform. If you want to get complicated, there is an automatic option that probes the build platform and makes height corrections in the software. The probes come in several flavors, two common methods being a deployed mechanical switch (usually mounted to a servo) or force sensors under the build platform that sense when the nozzle touches the build platform. This method also requires some fancy firmware finesse to get working correctly.

[Jonas] posted a video showing the semi-automatic bed leveling capability of his printer. The build platform is held a bit high by springs that surround each of the 3 screws that support the bed assembly. The nozzle is moved directly over one of the 3 screws and then moved down until it noticeably presses on the build platform, compressing the support spring. A thumb wheel is then tightened at that location, locking the bed in place. The same process is performed for the other 2 support points. The result is a perfectly level build surface. Check the video out after the break to see just how quick this procedure is!

We’ve seen a somewhat similar concept that uses a clever gimbal and lock system under the bed.

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Bed Leveling With A Solenoid Actuator

Ah, the woes of printer bed leveling. Unless you have a fancy 3D printer, bed leveling is a tedious task. [Rupin] got tired of messing around with his printer, so he decided to make his very own bed leveling sensor.

The goal was to create a Z-axis probe that works as both an auto-leveling sensor and as an end stop. He originally was trying to design something using a servo motor probe, but ended up chucking the idea since the motor was noisy and calibration was difficult.

He’s since switched over to use a solenoid actuator with an optoisolator to determine the position. The actuator extends an M3 screw which will touch the bed — as the position is adjusted, it is possible to adjust the bed using software for a perfectly level bed, every time.

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