Here’s a neat trick for your next 3D-printer build or retrofit: a Z-axis sensor using a DIY strain gauge made from SMD resistors. We’re betting it could have plenty of other applications, too.
Conventional load cells, at least the ones you can pick up cheaply from the usual sources or harvest from old kitchen or bathroom scales, are usually way too big to be used on the extruder of a 3D-printer. [IvDm] wanted to build a touch sensor for his Hybercube printer, so he built his own load cell to do it. It consists of four 1000 ohm SMD resistors in the big 2512 device size. He mounted them to an X-shaped PCB and wired them in the classic Wheatstone bridge configuration, with two resistors on one side of the board and two on the other.
The extruder mounts into a hole in the center of the board and floats on it. Through an HX711 load cell driver chip, the bridge senses the slight flex of the board when the extruder bottoms out on the bed, and an ATtiny85 pulls a limit switch input to ground. [IvDm] even did some repeatability testing with this sensor and it turned out to be surprisingly consistent. The first minute or so of the video below shows it in action on the Hypercube.
We found the use of SMD resistors as strain gauges pretty clever here, but there’s plenty to do with off-the-shelf load cells: measuring how much filament is left on a roll, checking the thrust of a model rocket engine, or even figuring out if you’re peeing correctly.
Continue reading “Quartet Of SMD Resistors Used To Sense Z-Axis Height”
Laser engraving and cutting has something in common with focusing the sun’s rays with a magnifying glass: good focus is critical to results. If materials of varying thicknesses are used, focus needs to be re-set every time the material changes, and manual focusing quickly becomes a chore. [Scorch Works] has a clever solution to avoid constant re-focusing that doesn’t involve sensors or motors of any sort. The result is a self-adjusting bed that compensates for material height changes, ensuring that the top surface of the material is always a fixed distance from the laser’s head.
The way [Scorch Works] has done this is to make two spring-loaded clamps from angle aluminum and a few pieces of hardware. When a sheet of material is placed into the machine, the edges get tucked underneath the aluminum “lips” while being pushed upward from beneath. By fixing the height of the top layer of angle aluminum, any sheet stock always ends up the same distance from the laser head regardless of the material’s thickness.
[Scorch Works] shows the assembly in action in the video embedded below, along with a few different ways to accommodate different materials and special cases, so be sure to check it out.
Continue reading “Spring-Loaded Bed For K40 Laser Acts As An Auto-Focus”
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.
Continue reading “Sonic 3D Printer Auto Bed Leveling Makes A Swoosh”
[Jeremie Francois] has been thinking about ways to improve tool height adjustment and bed leveling in his 3D printer for a long time. His dream was to never ever think about Z height again. A dream that’s shared by many. These days, a lot of 3D printers have a mechanism for auto leveling in the software of the 3D printer. This works pretty well, but for various mechanical reasons, it’s better to have the bed itself be level.
[Jeremie]’s approach is pretty clever. Since you can define any plane mathematically with three points, he has three Z-axis lead screws. This lets him tilt the bed at any angle he likes. Once he had the mechanics in place, he added some force sensitive resistors, an Arduino, and wrote an extension for the popular Marlin firmware. That’s when the problems started.
It turns out that solidly mounting the bed to the resistors transmitted way too many vibrations. The solution was a layer of neoprene rubber. The neoprene also acts as a cushion, so the nozzle won’t break the glass bed during the leveling procedure.
The video after the break is a bit wavy, due to YouTube’s terrible auto-stabilizing software, but if you watch closely, you can see the system at work.
Continue reading “Tribed 3D Printer Configuration Doesn’t Ever Need To Be Leveled”
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.
Continue reading “Semi-Automatic Bed Leveling Your 3D Printer”
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.
Continue reading “Bed Leveling With A Solenoid Actuator”
Lulzbot, or more specifically Aleph Objects, had a booth at Maker Faire this year, and unlike a lot of other 3D printer manufacturers they’re not afraid to show off what they currently have in development. The latest is code-named Begonia, although when it makes it to production it will probably be called the Lulzbot Mini. It’s a smaller version of their huge Taz 3D printer that trades build volume for a lower price.
The Lulzbot Mini will have a 6x6x6 inch build volume, heated bed, and all the other features you would expect in its larger counterpart. One interesting feature is automated nozzle cleaning and bed leveling. At the start of every print run, the nozzle runs over a small felt pad at the back of the build plate, touches off four metal washers at each corner, and recalculates the GCode for a level print. You can check out a demo of that in the video above.
Also in the works in the Lulzbot labs is a controller panel with an SD card, display, and (I think) a touch interface. Lulzbot didn’t have a demo of this, but rest assured, we’ll post something on that when it’s released. The last time we saw Lulzbot we heard of a 3D scanner project they’re working on that will turn any physical object into an .STL file, without having to mess about in Meshlab. Development on this project is stalled, but that is a very difficult problem. Can’t fault them for that.
Oh, the price for the unannounced Lulzbot Mini? Somewhere around $1300-1400.
Continue reading “Lulzbot & Lime Green Begonias”