Machine Design

The assigment page
The goal of this week was to actuate and automate our machine build last week.
Group page

Last week David, Dima and me designed, mill and assemble an analogic karaoke machine. There's it is:

Like you can see in the video, we had to make some tweaks to have fluid movements.
So this week I worked with David friday to have the basics movements. Later in the week, Dima manage to improve the code.
When David was coding and trying the code, I improved axis movements, made first text and timing.

Some improvements
David printed a new belt holder, the first one was touching the carriage and the mechanism sometimes stuck because of that.
I've installed it on the machine:

After installing the belt, we saw that it was impossible to strech it in a good way. It was because one of the holders was floppy.
I reinforced it by drilling 2 holes in the machine and bend the stand with a collar:

Now the belt is tense.

The carriage with the pointing hand (I cut a new one pointing in the right direction btw) didn't stay in place. I model and cut a 3mm mdf rod to maintain the hand against the paper.

Install an end switch on the machine
We forgot to plan an end switch for the timing axis. So with a drill I managed to make a hole on the machine to stuck it.
End switch dimensions: 20x10x6mm

I put the end switch and screw some nuts on the carriage's threaded rods to improve the contact.

First timing settings
David succed to get the stepper motors working. So now time to calibrate it.
I had to find how many centimeters the carriage will travel during one revolution. So I took the carriage, mark a starting point, we launch one revolution, mark the stopping point.
During one revolution, the carriage travels 4cm. There's 200 steps per revolution so now it's pretty easy to calculate how many steps you need for each time.

D = Distance to travel
S = Number of steps

S = (200xD)/4

We decided to use Frère Jacques as a test song because it's simple 4/4 beat song. I designed a A4 sheet with the first verses:

Frère Jacques
Frère Jacques
Frère Jacques
Frère Jacques

I use a monospace open-source font, Déjà Vu Sans Mono, to simplify timing calculation.

So there's 3cm between each line. So we have to move the paper down using 150 steps (200x3/4).
And for the timing I mesured 4,4cm between each. So 220 steps.

We've installed the paper and make the homing pointing the first word in the first line:

David code this and here's the first result:

We can see all the problems who will be resolve later but most important thing: the motor isn't fast enought when is coming back !
We found a funny solution: each 2 lines, the words are displayed in reverse. Like this, the carriage didn't have to coming back.

Here's the first final result (with homing):