Frequently Asked Questions

Q: What is Hangprinter?
A: A cable driven RepRap 3d printer.

Q: What is the Hangprinter Project?
A: The Hangprinter Project develops and spreads the unique motion system.

Q: What can a Hangprinter do?
A: It can use existing structures, like walls and ceilings, as its frame. Framelessness makes Hangprinter relatively a cheap, and relatively small/compact. It also enables very large prints.

Q: What's the goal and purpose with Hangprinter?
A: The Hangprinter Project wants to design and spread a robot that makes its owners free and independent. More in this blog post.

Some design goals I've stuck to for the last three years are outlined in this blog post.

An explanation of the connection with democracy is outlined in this blog post.

Other formulations of my personal motivation for working with RepRap are found in my thesis work. See this blog post and this blog post.

Q: How do I get one?
A: Currently, the only option is to source and build oneself. The documentation contains some guidance, but you'll probably need ask questions in the project's channels.

Q: What does it cost?
A: Parts for a v4 is estimated to cost around $1500.

Q: Will kits be available?
A: No plans for kit supplying are currently known.

Q: Should I build v3 or v4?
A: I (tobben) recommend the v4. It is a more practical and useable machine overall.

Q: How can I contribute?
A: See the contribute page.

Q: What license is the project under?
A: Hangprinter (the repo) is under GPLv2, line-collision-detector is GPLv3, hp-mark is GPLv3, auto-calibration-simulation is MIT, ODrivefirmware is MIT, RepRapFirmware is GPLv3, and most of is MIT, except the docs, which is GPLv2. That is not the full picture, it gets more complicated if you look closely at the repos.

With that said, I made Hangprinter so people could use it and build businesses around it. If any of the licenses above are problematic for your business or project, try contacting me (tobben) in person and let's discuss it.

Q: How large can it print?
A: It depends. Check out this blog post for more details.

Q: What materials can it print?
A: Hangprinter is compatible with most tool heads on the market. This includes thermoplastics, but also ceramics and paste tool heads.

Q: What's the precision?
A: The proper answer is very complex, so I'll skip it here. You should expect similar print surface quality as you get from other 3d printers.

Q: What's the accuracy?
A: The proper answer requires direct measurement on each machine, and it will be different in different parts of the build volume. A computer vision system called hp-mark has been developed. It wants to bring good accuracy measurements, as well as other good things, to every Hangprinter.

Q: Can you put a 3d scanner on it?
A: Probably yes. I haven't tried because I don't now of practical ways to use Hangprinter as a 3d scanner. My main concern is about lines touching the unknown object.

Q: What are Hangprinter's strengths?

Q: What are the known limitations?
A: None. Ok, just kidding.

Needless to say, I'm constantly working on, and prioritizing between, the various weak spots of the Project.

Q: How is the project funded?
A: Ca 10% via donations. The rest via my (tobben's) private money.

Q: Why is this not patented?
A: Hangprinter is designed to be self-replicating, and to be flexible. As much as I want to make money and to privatize my ideas, the current patent system would limit users too much. As everyone else in open source hardware, I'm looking for alternative ways forwards.

Q: How do you slice for Hangprinter?
A: Similar to other 3d printers. Default slicing settings are not yet developed. Export stl and check for line collisions before you slice.

Q: How can I contact you?
A: See the resources page. Personal and private contact details are hard to find on purpose. I enjoy being hard to find.

Q: What is the Project's history?
A: See the about page. For a deeper dive, check out the dev blog archives.

Q: Does the print head rotate?
A: In general, no. See "tilt problem" above, for one exception.

Q: How are rotations avoided?
A: By keepings pairs/triples of lines parallel and equally long. See this Youtube video for a visual explanation.

Q: How should I configure RepRapFirmware for Hangprinter v4?
A: Check out the example config.g in the repo. It should be somewhere under firmware/RepRapFirmware/Duet3 or similar.

Q: How do I find correct bulidup factor (M666 Q-parameter)?
A: The buildup factor determines how much firmware should try to compensate for line buildup on the spools. Theoretical, but a bit naive buildup factor calculation (assumes cylindrical, straight line):

Buildup factor is equal to (line_cross_section_area)/(height * pi):
((0.5/2) * (0.5/2) * pi)/(8.0 * pi) = 0.0078 mm
In practice, you might want a bit more or a bit less than the naive theoretical calculation gives you. I don't have a good procedure to fine tune it though, and it doesn't make too big of a difference. I'm planning and hoping that auto-calibration-simulation-for-hangprinter becomes the default way to do anchor calibration. It will spit out the buildup factor, and hopefully the user shouldn't need to know what it is or how it was calculated.

Q: Should I use steppers or BLDC motors?
A: Short answer: The default for HP4 is BLDCs. As of August 2021, they ones I'm using is expected to show up in the odriverobotics web shop very soon.

Longer answer: Four really beefy steppers with SmartStepper would do as good a job as the four BLDCs at a slightly lower price tag, for a small and light Hangprinter. The Hangprinter application lies right between the sweet spot for steppers and the sweet spot for BLDC application. The bigger and heavier your Hangprinter is, the more BLDC starts to make sense.

I often hear the importance of travel speed being plaid down. Personally, after some long prints, and tens of kilometres of travel moves, I'm willing to pay for fast travels. It shortens print time, but also improves print quality a lot, since it limits ooze problems.

Q: I want to manually calibrate my anchor locations. How do I do that?
A: Just a warning: it's hard to get right. After releasing the HP3, got so many questions about this that I decided to develop auto calibration as fast as possible. Auto calibration now works far better than I've ever managed to hand calibrate.

But back to the question: Check out this discussion. Also see these comments and timestamps of a live streamed HP3 calibration.