RigTig
commented
7 years ago Matthias, there is a design (work-in-progress) using motors at the supports (see https://hackaday.io/project/13420-rigtigs-big-3d-printer) and it has been done several times before too. And the steppers are really light too. BUT, cabling is a pain especially when you want to adapt or move the support nodes. In fact, I started with cables to each node and found it far too awkward to set up each time, so I am now trying to use a local wifi network. Besides, using long cables for high-current purposes is a poor design choice, made worse when you consider the effects from rapid off-on cycles (slower ramping speeds and power losses).
You said that you are:
allowing for much higher accuracy, resolution, acceleration and speeds
but what accuracy, resolution, acceleration and speeds do you need when working at much greater scale than a desktop 3D printer. I've decided that for a 10 metre length of printing, a 2mm resolution is very acceptable (0.02%). And the speed needs to match the material being 'extruded'; note that clay can be pumped only so fast anyway. Assuming that accuracy refers to reproducibility, then the variation caused by the material is probably much higher than the effector location anyway. Anyway, this rant is really about choosing a desired outcome based on practicality rather than just pushing limits for the sake of pushing them. If you or others are so keen on another branch, then just create a fork and go for it.
Tobben, I reckon you have achieved something quite amazing. Your whole printer fits into a bucket or backpack for transport and yet can print very large objects upon installation. Once I have finished this iteration of my own 3D printer, I am going to have a go at putting all the motors on the effector (as you have successfully done). I wish I had thought of it myself, since communicating with the remotely positioned motors has been the core of the issues with my approach. At least I have learnt a lot in the process of getting this far.
tobbelobb
twikis
Tesla3DTore
Hi Tobben!
Thank you very much for this amazing work, I just ordered the Vitamins for the printer and I'm going to print out the parts very soon.
Here's a thing: a few interested people and me are wondering why you haven't/aren't moving the movement steppers to the mounting points, in order to save weight on the printing head? This would save 600-750g (of course depending on the steppers used) on the print head, allowing for much higher accuracy, resolution, acceleration and speeds. The two simplest ways for doing this I can see are:
I understand that this will make the whole printer less compact and split it up in multiple parts, thereby making it less of a beauty, but I do think it's worth it when thinking about the speeds that could be archieved. Which is on the other hand making it much more attractive to everyone. How about a second brach for "enthusiasts"?
Alternatively you could of course gear down the motors for smaller stepper motors, as the rpm limit of steppers isn't even closely reached (unfortunately I don't have the skills to design this myself, otherwise I would).
Another thing we have come across: We've been thinking that much smaller motors may be sufficient for the D-Lines and extruder, thereby saving another few valuable grams. Could you provide any numbers regarding neccessary N/cm? Maybe by trying out how low you can go on current on the motors?
Greetings!
Matthias
PS. We've created a facebook group for the Hangprinter, you can find it here: https://www.facebook.com/groups/176856636157837