Some handy websites with information
Smok is a graffiti artist. We asked him some questions about graffiti. We found him because Lee's father knows him.
A graffomat is a machine that also prints graffiti on a wall. We are going to make something along the lines like that in a different way. You can see the graffomat in the picture.
Thingiverse is a website where you can download community created 3D printable objects. This can help makers allot when doing a project.
Our design
We used a 2 meter aluminium extrusion as the base of our graffiti printer. We are going to use 2 wooden plates to create legs to hold up the aluminium extrusion. We have multiple 3D- printed pieces that can be slid on and locked in place on the extrusion to perform tasks like, connecting the legs and the extrusion or holding the timing belt.
As you can see on the photo to the right of this text, we used a stepper motor to control a timing belt, connected to a piece we can slide over the extrusion. On top of that slider there sits another stepper motor. This stepper motor we use to spool a reel which pulls the graffiti can up and down.
To power all our motors and servo we have a 12-Volt lead acid battery. We need a stable and clean 12-Volt signal out of the battery, this is achieved by the buck boost converter. As the brain of our graffiti printer we use an arduino with a CNC-shield on top. The CNC-shield is used to easily connect stepper drivers. Those are in turn used to more easily connect and control the stepper motors. On the CNC-shield there are 2 stepper drivers . We also have a little DC-fan to cool the stepper drivers.
Troubleshooting
We first started our IP with trying to automatically control the spray can, this is where our love hate relationship with all the troubleshooting started. At first we just mounted a cheap, very low power servo above the can. This didn’t work at all. Then we designed some kind of curve to press the can, this worked even less. Afterwards we started to design a mechanism which used an electromagnet to press on the can. However, to be honest we didn't think this would work and the current drawn would be immense. Luckily, we had a meeting with an inventor who already made a graffiti printer. He gave us valuable insight as to our overall design and how we could improve it. But, most importantly, he gave us his 3D printable files he used to create a mechanism which can press the can’s top with enough force to spray graffiti.
So with that fixed, we could work on our IP until another issue got in the way. This time it was our spray can holder that wasn’t designed right. We designed our spray can holder to be a container with an open top connected to the spool using fishing wires at the most bottom plate, which was a bit larger, to accommodate the holes for the wire. We put a lot of effort in getting the container laser cut. It was made of very clean plastic acrylic. Although, the issue we ran into was that because of the fact that the connection points were so low, the spray can tipped over very easily. This happened so often during our testing that the container came to an unfortunate end. It hit the ground for the final time and a piece broke loose. We had to design a completely new container, this time two wooden planks held together by 200mm long screw thread. The fishing wire is this time connected to the top plate. This is much more stable.
Afterwards our next issue was that the fishing wire rolled up unevenly on the spool due to differences in the angle of the wire going to the spool, we easily fixed this by making a 3d printed conductor to make sure all fishing wires roll up onto the spool evenly.
Now comes the worst part of our troubleshooting, We had to take the IP apart and put it back together for the open school day. This caused the fishing wire to be completely tangled in a sort of modern day Gordian knot. Like Alexander the Great had done before us, we also resorted to cutting through the knot to fix our problem. We had to reconnect the fishing wire to our spray can container afterwards. Nevertheless, to add insult to injury during this whole ordeal, the fishing wire disconnected multiple times from the spool.
The problem which we are trying to fix right now is that our motor that rolls, is acting up. It seems to be going side to side instead of in one direction half of the time; the other half it’s working fine until the spool starts slipping and the spray can comes crashing down. We are currently redesigning the spool to fix the slipping. We hope that also explains the rocking back and forward. In spite of that, it can also be a wire connected wrong or even worse, a faulty stepper driver or Arduino.
Video pitch
Underneath this text you can find our video pitch that explains a little more about our IP.
Credits:
Gemaakt met een afbeelding van Roberto - "spray paint cans for graffiti painters"