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Author Topic: Machine/page size not matching with actual machine
saarah
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Posts: 3
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Post Machine/page size not matching with actual machine
on: April 9, 2015, 04:47
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Hello! I'm building the polargraph for the first time, using the instructables tutorial. I have everything working...but the page size in the controller seems to not match up with the actual page! My machine is 665mm wide, 888mm tall, and the page size is 457mm wide, 610mm tall (I'm using 18 x 24 in paper). These are the values I used in the controller, but when the machine runs, it seems like they're not matching up. For example, if I "move pen to point" to the end of the page, the gondola only moves about halfway down the page. I've tried changing the weights (I thought they might be affecting how the chain was moving), and changing the speed/acceleration, and I'm not sure what's wrong!

I'm using these motors and have modified the steps/rev to 400 (instead of 800): https://www.creatroninc.com/product/bipolar-stepper-motor-32ozin-200-stepsrev/

Any help would be much appreciated!! 🙂
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hashampers-
and
Beginner
Posts: 28
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Post Re: Machine/page size not matching with actual machine
on: April 9, 2015, 18:31
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A useful trick I learnt is to 'draw outline' of what you think is your drawing area is, then you can see where your machine deviates. IE is it deviating for one axis only, or are both skewed equally? Is it squashed or distorted ( too much friction / unequal counterweights)

I would say that the counterweights shouldn't make as much difference as:
-getting your steps per revolution and step interpolation right,
- making sure your motors are provided with sufficient power. (What voltage are your motors being driven at?)
Also make sure you always upload changes to the machine when changing the machine spec. Often, if you change fundamental measurements like mm per rev or steps per rev it will throw everything else out, requiring a resync. That and setting the home point every time kept me intrigued for a bit!

Good luck!
hashampers-
and
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Post Re: Machine/page size not matching with actual machine
on: April 9, 2015, 19:00
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I can just see from the picture that the machine size is stated as <something> by 1867mm. It looks like the measurements were altered when you changed some of the fundamental machine measurements (steps/mm). Reset all the measurements, save as a new config, then upload to the machine.

Draw outline of framed area and then recheck!

sandy
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Posts: 1317
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sandy
Post Re: Machine/page size not matching with actual machine
on: April 9, 2015, 19:13
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Hashampersand's summary and recommendation is exactly right. I hadn't spotted the 1867 in the top there.

Changing the steps per rev, or the mm per rev does throw the controller app into confusion. For those settings, I always modify the default.properties.txt file directly, and then re-open the controller, rather than use the controls in the app. You might find that saving your settings, closing the app down and re-opening it will illuminate what's really going on.

And yes, then a "upload machine spec".

sn
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Post Re: Machine/page size not matching with actual machine
on: April 11, 2015, 19:22
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Thank you for such a quick response! I have been saving, restarting the controller, and uploading the machine specs, but I didn't notice the machine size changing. Also, I am using a 12V power supply.
I will try what you have suggested and let you know how it goes!
sandy
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sandy
Post Re: Machine/page size not matching with actual machine
on: April 11, 2015, 21:30
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Am I right that you're using an adafruit motorshield with an UNO? Which firmware are you using, and did you compile from source code or use a precompiled hex?
saarah
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Posts: 3
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Post Re: Machine/page size not matching with actual machine
on: April 15, 2015, 05:57
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Yes, I am using the adafruit motorshield v2 with an arduino uno. I'm using the latest polargraph firmware, version 1.10.6, and I have been using the source code, as the application versions kept crashing on me.

I tried editing the settings file directly, and while it did fix the dimensions within the controller, the machine still isn't aligned to it properly (I did upload to machine).

The first image shows the settings, where the machine is the right size, the second shows what I wanted to draw, and the third shows what it looks like when the machine draws it. The top part is skewed because the chain slipped a bit, but as you can see, the size is completely off!

I'm not sure what I'm doing wrong. This is my first big Arduino project, so I may have missed something really basic. Thanks for your help!
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sandy
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sandy
Post Re: Machine/page size not matching with actual machine
on: April 16, 2015, 23:06
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Sorry I didn't reply earlier. Aha, motorshield v2 is a slightly different beast than the v1, so takes different settings.

In short, v2 (AFMS2) uses 16 microsteps in between each real motor step, and it's not really safe to stop on these steps. The adafruit v1 (AFMS1) has a kind of interleaved half step in between each real motor step, and it IS safe to stop on these steps, and it grants a "free" extra half step, so doubles the number of steps per rev.

For AFMS1:
stepsPerRev = motor steps * 2 (because of the safe half steps)
stepMultiplier = 1 (the internal resolution is identical to the external resolution)

for AFMS2:
stepsPerRev = motor steps
stepMultiplier = 16 (the internal resolution is 16 times higher than the external resolution).

So maybe you need to half your steps per rev, and change your step multiplier.
saarah
Newbie
Posts: 3
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Post Re: Machine/page size not matching with actual machine
on: April 17, 2015, 14:43
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Yes, that worked perfectly!! Thank you so much 🙂
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