The [Sort of] Revival of the V-Plotter
This week we decided to take the dust off of an old project to be able to get a V-plotter that has been sitting around the lab to work better. I will give a spoiler off the top - it did not work well...
And the culprit of this failure is twofold - One, the tuning of the device is a little off I believe, and that is because the steppers are somewhat small for the design. And two, this thing:
The [slipping] chain holder
How did we get here?
Initially we had a v-plotter in the lab that we had been working on a while back. Though not perfect it managed to get some images out but most of our documentation was lost. A V-plotter is a simple device in concept but difficult in execution. It has two motors that will pull chains and those two chains, when in tension, will move a gondola with a pen on it to create shapes.
The math of it eludes me a little but it essentially involves altering the radius of two overlapping circles to move an object to any point in 2D space. Here is a rough description of what it is and our device itself:
And here is an image of our plotter
The chain makes really cool shadows but that is neither here nor there. Just a fun fact.
How did we make this? [Tutorials]
Making anything new requires some learning involved and we did the same thing, we followed a tutorial from Youtube. If you search on instructables there are MANY designed V-Plotters on the website.
In our case we used this video here:
They were even so kind as to link a github that had information on how to upload all the programs needed.
Step One: Build it
We had most of the device built at this point and just needed to add a few weight holders for the sake of balance. So we found these on thingiverse and made it work. If you do not like the design we used hint: it does need work and we will discuss that later then you can make your own or search the plethora of designs that exist online!
With this weight added the machine was theoretically going to work well.
Step Two: Flash the Arduino Uno
Here there were a few steps that needed to get done to make the device work. First was flashing the server for a program called polargraph that has not been supported since 2017 onto the Arduino. To do this you can easily find the program in the Github above.
There is just one issue: The program does not compile in versions of Arduino past 1.8.5
Step Two point One: Revert Arduino to 1.8.5 or before
In my case Arduino 1.6 is the one that worked but luckily doing this is simple. You just have to google the IDE version you wanted and then you can go back to that edition.
This Website holds all of the versions of this that all you do is download the installer, compile and upload to the board
Step Three: Install and run Processing
In the same GitHub Folder you can install and use a program called processing. This will convert images and control the actual device. Installing is straight forward and if you follow steps in the tutorial video you can go ahead and have that program running. Here you have to set te size of your board and your paper to be able to start drawing. This has to all be done in mm. If done correctly the image ends up looking like this:
Here everything was connected but I managed to press go. Once I pressed go, nothing happened...
Debugging
With the device not even working, we needed to see why that was happening. In this case, several things were tried.
Changing the Arduino and shield and reuploading everything
Disconnecting and changing steppers. Then reconnecting the steppers.
In the end, reconnecting the steppers is what did it. They were connected wrong. It is possible the boards were part of the problem but I cannot fully be certain because once the boards were chaning things reuploaded much more smoothly.
Stepper Test 1
Stepper Test 1.5
Stepper Test 2
Gantry Move Test
Conclusions
At this point in time this device works nominally. But it keeps slipping and some work needs to be done to it.
- Change the chain controls - Less Slippage
- Re do the controls using timing belts
- Change the steppers or stepper mounts for less slippage