A paper-making machine, reduced to create a 10mm strip of paper pulp, rolls around and around and around to build up a three-dimension object. This is the extruder part: water and pulp goes in, water and air is sucked out, and the paper pulp layer is rolled onto the surface. This is a true myminifactory; it's mine (and shared with you), it's mini (or even micro) and it is certainly a factory (it makes paper).
This design has NOT BEEN TESTED. It is published partly to ensure I do not lose the files (as I did with an earlier iteration), and partly because there is a competition that has a mechanical category. Paper-making machines can be huge (workers can use bicycles to ride from one end to the other); this machine is about 72mm tall and about 32 x 21 mm cross-section.
For our paper extruder, the suspension of paper fibres comes in through a tube (3mm ID) into the central hole, through a 2mm nozzle and onto the sieve, which is a wheel with a mesh 'tread'. As the extruder moves forward, the wheel presses the paper pulp onto the surface, where the pulp sticks (hopefully). We do not want the water to just flow over where we have just rolled out a thin layer of paper pulp, so we use active suction on the inside of the rolling sieve to remove the water from the inside of the wheel, and it drags a lot of air as well. At the top, there are four tubes to ensure plenty of flow of air and water out of the extruder head.
The designed operation of the rolling sieve wheel is like a caster wheel, so that the wheel skids a bit going around corners, but still continues to roll along in the direction of movement; but it must have a turning axis about the vertical. This means that there has to be a 'fixed' part at the top for all the tubes, and part that rotates about the vertical axis whilst still allowing for flow of suspension of paper fibres in, and the flows of water and air out. The wheel has to freely roll based on contact with the surface under it, and allow suction from inside.
This is definitely the smallest paper-making machine ever (try using your favourite search engine to find a desktop-sized working model of Foudrinier machine)
Besides, I had to figure out the suction mechanism: finally used a 12V bilge pump with a venturi on flow line. The flow line from the pulp tank also needs a solenoid to control the flow. And I haven't got the GCODE interpreter done yet, either.
To make paper, you start with a suspension of paper fibres in water at something like 4gm/l to 12gm/l. The suspension of paper fibres is run out onto a sieve to catch the fibres on top and let the water fall through, often with some help using suction. In a paper mill, the whole process is continuous, usually based on the Foudrinier machine, and proceeds through a large number of rollers. In hand-making of paper, the wet sheet of pulp is carefully taken off the sieve (called a mold) onto a fabric base (traditionally felt), squeezed to remove excess moisture, then each felt with its sheet of paper is hung up to air dry.
Paper pulp is sometimes called paperclay, or even paper mache. However, paper mache can also be just sheets of paper glued together, often over a supporting frame of wire or wood.
The cheapest and easiest way for hand paper-making is to start with waste paper. Of course, what you put in does have a significant effect of what you produce and there are many sources of suitable fibre.
Paper mache has been used to make furniture (in France about 1850s, I think).
Paper shrinks about 15-25% from wet pulp to final product (and you thought ABS was bad). Allow for shrinkage in the design of objects to print.
Even a single sheet thickness of paper pulp can take several days to air dry, so a thick object needs lots of time to build so it can dry enough not to rot on the inside. Anyone got an idea for a paper dryer and a mechanism to follow along behind the extruder?
Does anyone else use paper in a 3D printer?
MCOR have a range of printers that work with a stack of paper, cutting each sheet for that layer (see mcortechnologies.com). And they can apply colour as they go. They are the only ones I know of using paper, and I know of no-one else actually 3D printing with paper pulp. Any updates or corrections are more than welcome.
Why am I bothering with this at all?
I have been working on making a 3D printer that can print room-sized or house-sized objects (see hackaday.io/project/13420-rigtigs-big-3d-printer). I avoided materials like concrete and clay because, well, what do you do with a failed print? Besides concrete is too heavy for any normal suspended flooring to support when you get to 1 to 2 metres across (and I didn't fancy trying to explain to the car owners in the parking underneath that the several tonnes of concrete was just my 3D printing experiment that fell through the floor, and I didn't think the building owner would like it much either). I wanted something that could be recycled easily, was not too heavy, was cheap (like free) and yet be made quite large. In a presentation at a makers' place several years ago, one audience member said he could provide 10 tonnes of waste paper to me every week, delivery in metro area free (but I did respectfully decline his generous offer). I am still using what comes through my letterbox!!
More to do
I am slowly doing things to move the greater project forward. However, if you want to have a go yourself, please let me know if you need any clarifications. And everyone, including me, will love to see how you go. Please share. This project is for everyone (well, at least those who are crazy enough to tackle a whole new 3D printing material).