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 Accuracy between layers
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By: Anonymous: Jeremy () on Thursday, February 10 2011 @ 10:29 AM PST (Read 2267 times)  
Anonymous: Jeremy

I've been playing with the Egg-bot for the last couple weeks and I think I have narrowed down my frustration with it's accuracy (or lack thereof).

When plotting multiple layers, the second or third layer almost always will be "off". It isn't a specific direction, it sees random. At first I thought the issue was occurring when I was switching out the pens, and that perhaps I was mounting the second or third pen a small degree off from the first. However, I've since plotted multiple layers and DIDN'T change the pen in between and it still skewed the registration a centimeter or two from where it should have been. This makes the layers overlap in incorrect ways and the egg ends up in my "to be cooked" bin.

Any thoughts on this? I wouldn't think it could be sloppiness in the hardware as the pen is lifted and dropped many times on a particular layer and always matches up fine. The only offset occurs when it finishes a layer and starts a new one.

I can attached a picture later if my description didn't make sense.


By: Windell (offline) on Thursday, February 10 2011 @ 11:11 AM PST  

If your Eggbot is set up properly, you should be able to plot the exact same layer over and again, and see very good overlap. So, this doesn't sound like a layer-related issue at all, but is rather a matter of setting up the Eggbot correctly to plot the first layer without losing registration.

Please carefully read through our documentation about setting up the Eggbot and improving your plot precision:

With a little patience, you should be able to identify the cause of the registration loss. Most commonly, this is due to poor centering of the egg-motor interface, so that the egg "cams out" while it turns, or due to slipping at that interface, so that the egg does not turn as much as the motor.

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By: Anonymous: Jeremy () on Thursday, February 10 2011 @ 12:07 PM PST  
Anonymous: Jeremy

Thanks Windell, I'll re-read the doc and see if I missed anything.

Btw, I wasn't implying poor build quality, I've seen enough pictures to know others are having great success with it. I'm sure the issue is in my setup somewhere, I'm just hoping to get some help pinpointing it. I'll focus on the egg-motor interface and see if I can find it.

I'll try some very simple layers tonight, single circle within a circle kind of stuff, to see if I can rule out it being associated with multiple layers. That's just been the only time I've seen it manifest itself. I'll also try repeating the same layer to see if it still skews.

By: dnewman (offline) on Thursday, February 10 2011 @ 12:42 PM PST  

BTW, to see the amount of mechanical slippage, draw a 3200 pixel long, horizontal line and then plot it. If the ends meet, that's excellent. If they fall short, that will be caused by mechanical slippage, the egg precessing, or some other problem. By making adjustments and redrawing the line (at different latitudes), you can see if your adjustments are to good effect or not.

Be warned that Inkscape will sometimes include the line's stroke width in the length it shows for a line. For instance, if you place the following SVG in a file,

<path fill="none" stroke="black" stroke-width="1" d="M 0,400 L 3200,400"/>

and then open that file in Inkscape, then Inkscape will in some tools report the line's length (extent) as 3202 pixels.


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