I recently found some old project photos showing me wrapping up the first vertical plotter I built a few years ago. I thought damn! This was a nice project. So I want to share the story and my experiences I gained during this time with you guys.
So, right after I was asked to build a vertical plotter I was really excited. I looked forward to obtaining a solid knowledge about the topic and to create a nice and clean installation. The place of the installation was way bigger than I expected. Thus I had to figure out how to get things working.
Fortunately, the bracing of the window offered me possible fixing points for the plotter. I was able to take advantage of the horizontal brace from the window, which was at a height of almost 3 meters. The mounting itself has a recess that perfectly fits the thickness of the brace. To make sure the mounting stays in place, I added two security screws each. Snug as a bug in the rug!
With this approach for the mounting of the plotter, I started to figure out how the gondola should work. Other than other plotter gondolas, my gondola had to carry pretty heavy chalk pens. Here you can see the great diameter of the pen holder and the old connection mechanism between the gondola and the v-belts. Later on, I reworked this mechanism and applied it to another gondola. More later on.
To avoid climbing up the ladder all the time, I had to build a smaller version of the plotter first. This test setup was also used to observe the behavior of the gondola and to ensure it’s basic functionality. During some research work, I quickly came across a project called “Polargraph”. It’s open-source software that provides a wide range of functionality to control vertical plotters. Since I was fully concentrated on constructing and manufacturing the plotter itself, the Polargraph controller was a good choice for the software part of this project.
After a successful test run and a lot of calibration work, I was able to move on to the final installation. To achieve good and colorful chalk pen strokes, there had to be enough pressure between the gondolas pen and the surface. So, one thing to bear in mind to get enough pressure is, to find the right distance between the stepper motors pulley (little silver thing where the v-belt sits on) and the canvas your plotter is attached to. It’s a bit tricky, but essential if you want to achieve good results.
But, the most important thing I’ve learned during testing is, that the physical dimension of the plotter has to be the same as in the software. In other words, the calibration has to be PRECISE! Especially on such a big canvas, the smallest deviation makes a circle look like an oval or an egg.
For testing and calibration purposes I initially ran the plotter via USB. Later on, I switched to the Polargraphs’ queue sender and added a Raspberry Pi to my setup.
It included an Arduino Uno Rev3 with a motor shield, two stepper motors, a servo, a step-down buck converter, and a Raspberry Pi 3+. Since both stepper motors needed an operating voltage of 12V, I had to regulate the input voltage for the raspberry. In the end, all I had to do was to connect to the Raspberry via SSH and then start the queue sender script with my desired file.
Another thing I’ve learned later on is that these chalk pens run out of color quickly… So if I wanted to plot a big painting, I had to do it in several steps. After one step was finished, the gondola returned to its home position and allowed me to exchange the pen.
As I said before I wanted to show you the reworked mechanism of the gondola I tried on another setup I built. This mechanism allows the gondola to auto-align itself, no matter where the gondola is located on the canvas. It has its limits, but it is definitely an improvement over the first gondola I made.
During this project, I learned a lot and it also almost made me cry :D but the work was definitely worth it. I hope this story might help some of you guys out there that are looking forward to building your own Vertical Plotter.
Peace ✌
Links:
http://www.polargraph.co.uk/
https://github.com/euphy/polargraph/wiki
https://github.com/euphy/polargraph/wiki/Command-protocol
https://gist.github.com/euphy/75366a70346689190bb5
Setup:
Stepper Motor: https://tinyurl.com/y49x6kbu
Servo: https://tinyurl.com/y3g9r59b
Motor Shield: https://tinyurl.com/y58mmynv
Arduino Uno Rev3: https://tinyurl.com/y6qpqrao
Step down buck converter: https://tinyurl.com/y5jqjwqh
Raspberry Pi: https://tinyurl.com/y254t62w
