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Author Topic: Trouble with alignment
abscindo
Newbie
Posts: 6
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abscindo
Post Trouble with alignment
on: May 18, 2017, 19:37
Quote

Awesome project by the way I've had a blast working on it. I'm closing in on my first successful run but I seem to be having difficulty getting it into alignment. with every new line it starts it shift over and up and I don't seem to be able to make any changes that can mitigate it.

Any help here would be really great.

# *** Polargraph properties file ***
#Thu May 18 14:16:52 EDT 2017
controller.pixel.samplearea=30
controller.pictureframe.position.y=182
controller.pictureframe.position.x=256
controller.testPenWidth.startSize=0.5
controller.machine.colour=969696
machine.motors.mmPerRev=110.0
controller.window.width=1242
controller.frame.colour=C80000
controller.image.position.y=175
controller.image.position.x=248
machine.motors.accel=400
controller.image.height=300
controller.machine.serialport=0
controller.window.height=598
controller.maxSegmentLength=2
controller.geomerative.polygonizerLength=1
machine.penlift.up=180
machine.penlift.down=90
controller.page.position.y=150
controller.vector.scaling=100
controller.page.position.x=196
controller.pictureframe.width=431
machine.step.multiplier=1
controller.grid.size=25.0
controller.testPenWidth.endSize=2
controller.pictureframe.height=284
controller.page.colour=DCDCDC
controller.testPenWidth.incrementSize=0.5
controller.image.width=450
machine.motors.stepsPerRev=400.5
machine.pen.size=0.8
controller.page.width=554
controller.pixel.mask.color=00FF00
controller.machine.baudrate=57600
controller.vector.minLineLength=2
machine.width=946
controller.geomerative.polygonizer=1
controller.page.height=355
controller.vector.position.y=0
controller.background.colour=646464
controller.image.filename=H\:\\Project\\nicolas_vector_by_deto15.png
controller.vector.position.x=0
controller.homepoint.y=150
controller.guide.colour=FFFFFF
machine.motors.maxSpeed=500
controller.homepoint.x=473
controller.density.preview.style=3
controller.pixel.scaling=1
controller.densitypreview.colour=000000
machine.height=688

I am using the AFMSv2 if that matters

I'll try and upload a video of its misadventures to give you a better idea of what is going on.
Image
Image

abscindo
Newbie
Posts: 6
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abscindo
Post Re: Trouble with alignment
on: May 18, 2017, 19:42
Quote

As Promised.

abscindo
Newbie
Posts: 6
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abscindo
Post Re: Trouble with alignment
on: May 18, 2017, 21:38
Quote

This is what my machine believes a square looks like... comical and frustrating...
Image

sandy
Administrator
Posts: 1224
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sandy
Post Re: Trouble with alignment
on: May 19, 2017, 22:06
Quote

Yep that ain't no square, I agree!

The motors don't have enough torque to pull the pen around at that top section. This is the main problem with both Adafruit shields - you have to match the power supply to the motors to get the best out of it, because you can't adjust the power or torque afterwards.

The video of the outline of the rectangle shows the pen moving to the start position, dropping steps on the way. Couple of ways to solve this, or improve it!

1) Reduce the weight on the gondola
2) Try your home point further down, and try your sample square smaller. If that works, then you might just want to reduce your drawable area. There's more torque required at the top and it's more unbalanced at the edges, so try drawings right in the middle (at or around, or below the point where the two cords are at 90 degree angles)
3) Different power supply - match it to your motors

Do you know what kind of motors and PSU you're using right now?

sn

abscindo
Newbie
Posts: 6
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abscindo
Post Re: Trouble with alignment
on: May 21, 2017, 19:11
Quote

Great, thank you Sandy this gives me a good place to start I was stumped. To be honest when it came to the power I'm a bit clueless...
I'm using these Adafruit Steppers:
https://www.amazon.ca/gp/product/B00EYIFW70/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

and I'm using this PS:
https://www.amazon.ca/gp/product/B01BQUS8MY/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

Am I under powering this thing? I worry about it bursting into flames if I get the power wrong.

abscindo
Newbie
Posts: 6
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abscindo
Post Re: Trouble with alignment
on: May 23, 2017, 15:38
Quote

Can I use a 12V DC 1000mA PSU without burning my machine to the ground?

abscindo
Newbie
Posts: 6
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abscindo
Post Re: Trouble with alignment
on: May 23, 2017, 21:26
Quote

Just tested with the 12V DC 1A PSU to no avail. The result was exactly the same as the previous runs. Back to being stumped.

On the bright side it didn't burst into flames... mind you it was only running for a few minutes for the test.

Edit: I also reduced the gondola weight significantly as well as the counter balance weights.

Thought: The bead spacing and sprocket spacing don't line up well... could this cause these kinds of indescrepencies?

sandy
Administrator
Posts: 1224
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sandy
Post Re: Trouble with alignment
on: May 23, 2017, 22:12
Quote

Ok, here's my working out with 34 ohm motors (https://cdn-shop.adafruit.com/product-files/324/C140-A+datasheet.jpg)

With a 9 volt supply, you're doing something like:

Voltage / resistance = current
9 / 34 = 0.26

Each motor will draw 0.26A, which is 0.52A. Look at me, doing sums! It's Ohm's Law.

The motorshield can supply 1.2A per motor (https://learn.adafruit.com/adafruit-motor-shield-v2-for-arduino/overview), but with 12V, it won't ever draw more than 0.35A, and that'll require a PSU that can supply 0.7A (two motors).

So aye, running it with the 12v supply will be fine - it's what the motors are rated for.

You could get more torque by upping the voltage again, though the drivers will only go up to 13.5v so you don't have much headroom. That'll get more current going through the motors (13.5v / 34 ohms = 0.4A). They'll get a bit hotter - probably not worth the hassle of tracking down a higher voltage supply.

sn

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