by Yun-Han Lin
I have always wanted to build a more advanced Pintograph since the last model in June.
Read our last article on Pintograph: https://vmaker.tw/archives/36818
Find out more in the video: https://youtu.be/DpHBdhuYsPU
In my former project, I used the geared five bar mechanism that features bar movements using gear-links, while every bar and linkage function independently. Now, I want to try a more mechanical approach for my artifacts.
Once there is a blueprint in my head, I decide to replace the original gears with parts of that can function independently, and I will need to fit in 2 sets of five-bar linkages. At the same time, I decide to enlarge the design by 4 times into a 50*50cm model, so that I could demonstrate it at 2019 Maker Faire Taipei!
Structure: 3mm medium-density fiberboards (MDF) & 3D-printed parts.
Motor: As the model is to be enlarged, I need a motor with higher precision, such as a NEMA 17 stepper motor, also because there is more information of it on the Internet that I can refer to.
Control panel: I am still new to putting together electrical appliances, so I adopt an Arduino CNC Shield V3+ Uno driver as the control over 3 sets of motors, which is more user-friendly.
Power: An external 12V power supply
Strengthening structure: If you wish to enlarge a piece of laser-cut part, a wooden material will appear rather fragile and therefore not a good choice. The simplest way to strengthen the structure is to stack up the MDFs to a thickness of 6mm.
Replacing drawing paper: The biggest problem with the previous design was that replacing drawing paper was not easy. Therefore, I decide to stick a sheet of plastic on the bottom plate using 3M spray adhesive, which should make it easier for users to replace the drawing paper.
Controlling friction: Friction is also one challenging when it comes to woodwork. In addition to leaving more spaces between parts, I place a few steel ball omni wheels under the bottom plate, so that friction during movements can be reduced due to the decreased contact area.
Fixing the linkage arms: Another challenge I face in the previous design is the length adjustment and assembly of the linkage arms. Because of this, I try with magnets (which usually works well in all kinds of handicrafts) to fix the shaft at the center of the plate.
Takeaways during the process
A4988 stepper motor driver: The A4988 stepper motor driver features adjustable current control for users to fix the voltage within a certain range, but it takes some time for beginners to get used to it. To prevent overheating, I set the reference voltage between only 0.4~1V. However, due to this constraint, the motor was not able to run at its full power.
Magnet: Holds the parts together and is also easy to replace. A good choice for modular works.
Positioning pin: The more laser-cut pieces I work on, the more I find positioning pins useful. In particular, they are really handy when I try to align the two parts with a fixture, as they can hold the pieces together evenly without an inch apart.