Ask Hackaday: Auto Bed Leveling And High Temperature Force Sensitive Resistors

March 19, 2014 by Brian Benchoff 39 Comments

FSR

[Johann] over on the RepRap wiki has an ingenious solution for making sure a borosilicate glass bed is completely level before printing anything on his Kossel printer: take three force sensitive resistors, put them under the build platform, and wire them in parallel, and connect them to a thermistor input on an electronics board. The calibration is simply a bit of code in the Marlin firmware that touches the nozzle to the bed until the thermistor input maxes out. When it does, the firmware knows the print head has zeroed out and can calculate the precise position and tilt of the bed.

Great, huh? A solution to bed leveling that doesn’t require a Z-probe, uses minimal (and cheap) hardware, and can be retrofitted into just about any existing printer. There’s a problem, though: these force sensitive resistors are only good to 70° C, making the whole setup unusable for anything with a heated bed. Your challenge: figure out a way to use this trick with a heated bed.

The force sensitive resistors used – here’s a link provided by [Johann] – have a maximum operating temperature of 70° C, while the bed temperature when printing with ABS is around 130° C. The FSRs are sensitive to temperature, as well, making this a very interesting problem.

Anyone with any ideas is welcome to comment here, on the RepRap forums, the IRC, or anywhere else. One idea includes putting an FSR in the x carriage, but we’re thinking some sort of specialized heat sink underneath the bed and on top of the FSRs would be a better solution.

Video of the auto bed leveling trick in action below.

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3D Printers Can Only Make Trinkets — What About Kayaks?

March 19, 2014 by James Hobson 66 Comments

Wow. [Jim Smith] of Grass Roots Engineering has just put the finishing touches on his entirely 3D printed kayak. And it floats.

The individual parts were printed on [Jim’s] massive home-made 3D printer, which is loosely based off a RepRap — except that its maximum build volume is a whopping 403 x 403 x 322.7mm.

The kayak itself is made of 28 printed sections, and to hold it all together, he has installed brass threaded thermoplastic inserts, which then allow the pieces to be bolted together. Silicone caulking is applied before assembly to ensure a watertight seal.

It was originally based off of a Siskiwit Bay kayak by [Bryan Hansel] but [Jim] has heavily modified it to suit 3D printing. It was printed at a layer height of 0.65mm to reduce print time, which still ended up being over 1000 hours! He even optimized the design to improve performance based on his own height and weight.

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MRRF: 3D Bioprinting

March 18, 2014 by Brian Benchoff 4 Comments

There were a few keynotes at this year’s Midwest RepRap festival, and somewhat surprisingly most of the talks weren’t given by the people responsible for designing your favorite printer. One of the most interesting talks was given by [Jordan Miller], [Andy Ta], and [Steve Kelly] about the use of RepRap and other 3D printing technologies in biotechnology and tissue engineering. Yep, in 50 years when you need a vital organ printed, this is where it’ll come from.

[Jordan] got his start with tissue engineering and 3D printing with his work in printing three-dimensional sugar lattices that could be embedded in a culture medium and then dissolved. The holes left over from the sugar became the vasculature and capillaries that feed a cell culture. The astonishing success of his project and the maker culture prompted him and others to start the Advanced Manufacturing Research Institute to bring young makers into the scientific community. It’s a program hosted by Rice University and has seen an amazing amount of success in both research and getting makers into scientific pursuits.

One of these young makers is [Andy Ta]. An economics major, [Andy] first heard of the maker and RepRap community a few years ago and bought a MakerBot Cupcake. This was a terrible printer, but it did get him involved in the community, hosting build workshops, and looking into 3D printing build around DLP-cured UV resin. At AMRI, [Andy] started looking at the properties of UV-cured resin, figuring out the right type of light, resin, and exposure to create a cured resin with the right properties for printing cell colonies. You can check out [Andy]’s latest work on his webzone.

[Steve Kelly] has also done some work at AMRI, but instead of the usual RepRap or DLP projector-based printers, he did work with shooting cell cultures out of an ink jet print head. His initial experiments involved simply refilling an ink jet cartridge with a bacterial colony and discovering the cells actually survived the process of being heated and shot out of a nozzle at high speed. Most ink jets printers don’t actually lay out different colors on a precise grid, making it unusable for growing cell cultures. [Steve] solved this problem with an inkjet controller shield attached to a RepRap. All of [Steve]’s work is documented on his Github.

It’s all awesome work, and the beginnings of both bioengineering based on 3D printers, and an amazing example of what amateur scientists and professional makers can do when they put their heads together. Video link below.

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MRRF: Repables, The Nonprofit 3D Object Repository

March 17, 2014 by Brian Benchoff 40 Comments

Repables

There’s a problem with online repositories of 3D printable objects: The largest repo, Thingiverse, is generally looked down upon by the 3D printing community. Thingiverse, owned by Makerbot, has seen protests, and calls for a an alternative repository. A few people have stepped up to provide a better Thingiverse, but these alternatives are either connected to specific 3D printer manufacturers like Ultimaker’s YouMagine, or have done some shady things with open source licenses; Defense Distributed’s DEFCAD, for example.

Repables, launched at the Midwest RepRap Festival this last weekend, hopes to change that. They are the only repository of printable objects and design files out there that’s backed by its own nonprofit LLC. It’s free for anyone to upload their parts and share, without the baggage that comes with an ‘official [company name] .STL repo’.

Just about everything can be hosted on Repables – .STL files for printable objects, .DXF files for laser cutter files, and even PCB files and Gerbers for circuit boards. Now, .STL files are able to be rendered in the browser, with support for viewing other formats coming soon.

It’s a really great idea that solves the problem of printer manufactures building their own hosting sites and the segmentation that ensues. It’s also headed up by a Hackaday alumnus, [Gerrit Coetzee]. We’re everywhere, it seems.

MRRF: Stuff From Lulzbot

March 17, 2014 by Brian Benchoff 8 Comments

A lot of the big names in 3D printers were at the Midwest RepRap festival showing off their wares, and one of the biggest was Lulzbot with their fabulous Taz 3 printer. This year, they were showing off a new filament, a new extruder, and tipping us off to a very cool project they’re working on.

The new products Lulzbot is carrying are Ninjaflex filament and the extruder to go with it. Ninjaflex is the stretchiest filament we’ve ever seen, with the feel of a slightly hard silicone rubber. Straight off the spool, the filament will stretch to a little less than twice its original length, and in solid, printed form its a hard yet squishy material that would be perfect for remote control tank treads, toys, and 3D printed resin molds. With all the abuse the sample parts received over the weekend, we’re going to call Ninjaflex effectively indestructible, so long as you don’t try to pull the layers apart.

Also from Lulzbot is word on the new 3D scanner they’re working on. The hardware isn’t finalized yet, but the future device will use a webcam, laser, and turntable to scan an object and turn it directly into an .STL file. Yes, that means there won’t be any point clouds or messing about with Meshlab. Lulzperson [Aeva] is working on the software that subtracts an object from its background and turns it into voxels. The scanner will be low-cost and open source, meaning no matter what the volume of the scanner will be, someone will eventually build a person-sized 3D scanner with the same software.

Videos of [Aeva] below showing off the new stuff and talking about the scanner.

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MRRF: ARM-Based CNC Controllers

March 17, 2014 by Brian Benchoff 23 Comments

8-bit microcontrollers are the standard for RepRap electronics, but eventually something better must come along. There has been a great deal of progress with ARM-based solutions, and of course a few of these made a showing at the Midwest RepRap Festival.

First up is [Mark Cooper], creator of Smoothieboard, the ultimate RepRap and CNC controller. It’s an ARM Cortex-M3 microcontroller with Ethernet, SD card, and up to five stepper drivers. It had a Kickstarter late last year and has just finished shipping all the rewards to the backers. In our video interview, [Mark] goes over the functions of Smoothieboard and tells us about some upcoming projects: the upcoming Smoothiepanel will feature a graphic LCD, SD card, rotary encoder and buttons, all controlled over USB by the Smoothieboard.

Next up is [Charles] with a whole bunch of CNC capes for the Beaglebone. By far the most impressive board was a huge I/O expander, motor driver, and everything controller for a Beaglebone featuring – get this – three parallel port interfaces. This was a one-off board costing thousands of dollars, but [Charles] did show off a few smaller and more practical boards for Beaglebone CNC control. Here’s a link to [Charles]’ capes.

Videos below.

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MRRF: 3D Printed Resin Molds

March 16, 2014 by Brian Benchoff 26 Comments

Visiting the Midwest RepRap Festival, you will, of course, find a ton of 3D printed baubles and trinkets. A slightly more interesting find at this year’s MRRF was a lot of resin cast parts from [Mark VanDiepenbos]. He’s the guy behind the RotoMAAK, a spinny, ‘this was in the movie Contact‘-like device designed for spin casting with resins. At the festival, he’s showing off his latest project, 3D printed resin molds.

With the right mold, anyone with 2-part resins can replicate dozens of identical parts in an hour. The only problem is you need a mold to cast the parts. You could print a plastic part and make a silicone mold to cast your part. The much more clever solution would be to print the mold directly and fill it with resin.

[Mark] printed the two-part rabbit mold seen above out of ABS, filled it with urethane resin, and chucked it into his RotoMAAK spin casting machine. Six minutes later the part popped right out, and the mold was ready to make another rabbit.

Video below.

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