My 3D printed paper folding machine may be the first of its kind. The machine can fold A5 size paper. Theoretically, however, you could scale the system and thus fold larger sheets.
In everyday life, we deal with folded paper on a regular basis, without often thinking about how exactly these folds are created. The idea to design and build a 3D-printed paper folding machine came to me when I reduced an A0 sheet to A3 size using a conventional paper folding machine. After opening the machine, I quickly realized how the functionality could be realized.
3D printing should work without any problems. I always design my parts so that they are printable without a support structure. I have printed the parts from PLA. PLA is perfect for technical parts because of its high strength.
The parts were printed with my self-designed and built 3D printer. This I have built a few years ago. Despite its rustic design, it has served very well for many years.
For large components I like to use acrylic glass in my constructions. Acrylic glass can be cut, drilled, filed and generally processed very well. Threads with a high strength can be cut cleanly. The outer contour of the acrylic glass I cut with a scroll saw. It is important to always put a drop of cutting oil on the saw blade. Otherwise it becomes hot and melts with the acrylic glass.
To drill the holes accurately, I glue the paper template to the acrylic using spray adhesive. Before drilling, I use a center punch to punch the holes. This helps to prevent the drill from slipping during the drilling process and thus achieve more precise results.
The folding rollers consist of 32mm PVC pipes with plugs attached to both ends. A 6mm aluminum shaft is inserted through these plugs, which I fixed with super glue. To ensure a clean paper feed, I took measures to increase the friction on the rollers. For this I used homemade rubber rings from an old bicycle tire. This allows for optimal paper guidance during the folding process.
The components shown in the pictures, which I call „buckle“, fulfill the function of the paper guide. The combination of the two buckle with the aluminum rods creates a shaft along which the paper is guided. The insertion plate consists of a 0.2mm thick metal sheet, which was fixed by means of glue. This sheet has the task to guide the paper into the correct shaft. Later you will see what I mean by this.
How to separate the sheets?
The core function of the folding machine is to separate the sheets, for which a feed roller and a friction pad are used. The separation support includes two friction pads, consisting of 3 mm thick rubber. At the top of the paper stack are the feed rollers, which come from an old printer. The paper stack rests on a push plate, which is pushed upwards by spring force to press the paper stack against the feed rollers.
The procedure is as follows: The top sheet is pressed against the feed rollers, which move clockwise. This causes the top sheet to be pulled off, since the friction between the feedrollers and the sheet is greater than between the paper underneath and the sheet to be pulled off. The lower sheets, all but the top sheet, are held in place by the lower friction pads, as again the friction to the pad is greater than between the individual papers.
Although this method of paper separation is not the most reliable, it stands out constructively for its simplicity, as only a few parts are required.
How does the paper folding work?
Now, when the paper has been separated, it enters the first pair of folding rollers. This conveys the paper against the upper buckle. At the rounding of the buckle, the paper is deflected downward. It then hits the 0.2 mm plate and is deflected upwards. Now it moves into the upper chute and hits a stop. This results in a fold on the second roll, which is arranged horizontally. This fold is then clamped by the horizontal second roller pair and conveyed further. The previously created fold collides with the rounding of the lower buckle and is deflected again. The paper now moves into the lower chute and also bumps against a stop there again. The second fold is now created between the vertically arranged third pair of rollers. The paper is then conveyed out of the machine.
The video shows this process more clearly.
The machine is driven by two motors – a smaller motor for separating the sheets and a larger geared motor for the folding rollers. The two motors are controlled by an Arduino in conjunction with an L293D Motorshield, which allows the rotational speeds of the motors to be precisely controlled.
The Arduino code is designed to be quite simple. The folding rollers move continuously at a constant speed. The singulation rollers are controlled by switching them on and off in time. In this respect, it would be useful to include a sensor that monitors when the sheet has been completely captured by the folding rollers before the separation rollers are deactivated.