Forum

Welcome Guest 

Show/Hide Header

Welcome Guest, posting in this forum requires registration.





Pages: [1]
Author Topic: machine drawing smaller than drawing area
joeypes07
Newbie
Posts: 3
Permalink
Post machine drawing smaller than drawing area
on: February 14, 2019, 21:28
Quote

Hi! First post here. i recently built a polar-graph machine out of an Arduino uno, an adafruit motor-shield v1 clone, and two old stepper motors from my Anet a8.

I set everything up corectly, and am running the controller from source with processing. The problem is that, although the machine is printing, the images are slightly distorted when printing vectors (narrow on bottom) and when i do move to point, to the edge of the page in the controller, it doesn't go to the edge of the page in real life.

This is not a measuring issue as i have checked probably 10 times. Im thinking the problem is that i do not know the steps per rev, and step multiplier settings for my motors. I've been trying to find it online, but without much luck. I have been trying different combinations of these, and did all my small squeezed prints with 200 steps per rev, and step multiplier:1. the main problem is that i do not exactly understand these settings.

I believe the model of the motors im using is: 42shdc3025-24b

Any help would be appreciated. Thanks!

sandy
Administrator
Posts: 1402
Permalink
sandy
Post Re: machine drawing smaller than drawing area
on: February 14, 2019, 21:56
Quote

Hello! Good work on your build. If you're using the standard polargraph_server_a1 firmware, then your machine will be using an interleaved step style which effectively doubles the number of steps on your motor.

const int stepType = INTERLEAVE;

https://github.com/euphy/polargraph_server_a1/blob/master/configuration.ino#L17

Your motors have 200 steps per rev motors, so you need to set your stepsPerRev in your controller to 400. Step multiplier is 1, that bits right.

If this is set wrong though, then your drawing will be half the size of what you expect, and you didn't mention the overall size being wrong, rather than just a bit distorted. I'm confused about that.

You've checked your size lots of times, have you checked your mmPerRev distance? So that's the length of cord that wraps around the driving sprocket.

If that's all done right, then the last thing that is usually wrong is the home point.

Narrow bottom

The drawing tapers as the pen moves down the page, and has a concave bottom row.

Usually: The pen is actually slightly higher up the page than the machine thinks it is / The strings are slightly shorter than the machine thinks they are.

Maybe your home point is physically higher than you have told the controller, or the pen was actually higher than the home point when it was calibrated.

Less commonly: Bad specification. The pen is in the right place, but the machine is physically narrower than it thinks it is.

So the machine thinks the distance to the home point is 800mm (for instance), but it's actually only 750mm.

Solution: Measure, fix, re-upload machine spec!

Do a bit of diagnosis by doing set home then physically moving the pen 10mm down, and see if that makes the distortion better or worse. Select an area in the controller and do Draw outline selected to quickly sketch out a rectangle for testing.

https://github.com/euphy/polargraph/wiki/Distorted-drawings

joeypes07
Newbie
Posts: 3
Permalink
Post Re: machine drawing smaller than drawing area
on: February 22, 2019, 21:36
Quote

Hello! Thank you for the quick response, and sorry for this late reply. Im just about to set my steps per rev to 400, i've usually done it at 200. Ill let you know how it goes. Could i perhaps try other stepping styles other than interleave? And so far the problem has been a small and distorted drawing. I have taken a look at that "Distorted drawings" page and have tried messing with the height of the home point without much luck. I'm just about to fire up my machine. Once i do i will thoroughly check over all my settings and report back.

Thanks again!

p.s. I have checked mm per rev, but will be double checking now

joeypes07
Newbie
Posts: 3
Permalink
Post Re: machine drawing smaller than drawing area
on: February 26, 2019, 20:34
Quote

Update: I changed the settings to what i said i would and it is now printing beautifully! thank you so much for your help. I absolutely love this project.

sandy
Administrator
Posts: 1402
Permalink
sandy
Post Re: machine drawing smaller than drawing area
on: February 26, 2019, 21:24
Quote

Oh that's great! Glad you got to the bottom of it - good luck drawing!

sn

Pages: [1]
Mingle Forum by cartpauj
Version: 1.0.34 ; Page loaded in: 0.066 seconds.