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Author Topic: Drawing issue when using Servo (pen lift/drop)
cawer
Newbie
Posts: 9
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Carlos Werberich
Post Drawing issue when using Servo (pen lift/drop)
on: March 9, 2015, 10:16
Quote

Hello guys!
I'm using a servo motor in order to lift and drop the gondola (phisically it's very similar to Sandy's design) but I'm getting the effect as attached image. The place where the pen starts a vector line dropping, for example, should be the same where it lifts when finishing the segment, but there is a little gap. I mean, first pen is dropped and starts the segment and, at end, ben is being lift a little earlier, before reaches the segment.
Any idea or suggestion?
Thanks!

Image
Visualbyte
Beginner
Posts: 33
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Post Re: Drawing issue when using Servo (pen lift/drop)
on: March 9, 2015, 11:24
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As a starting point try adding a little more weight to the gondola,

cawer
Newbie
Posts: 9
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Carlos Werberich
Post Re: Drawing issue when using Servo (pen lift/drop)
on: March 9, 2015, 11:47
Quote

Thanks for reply, Visualbyte.
I'll try to add more weight to the gonola. In fact, my gondola is almost weightless since there is only the bearings, pen and servo. Didn't think that more weight was required but it might make sense in this case.
My servo is a 9G SG90. Regarding the orientation, the pen starts drawing each segment from left -> right (anti-clockwise).
Thanks and will reply with the results!
sandy
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Posts: 1317
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sandy
Post Re: Drawing issue when using Servo (pen lift/drop)
on: March 9, 2015, 12:12
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Visualbyte's advice is good - a little extra weight can help pull the pen tip more tautly into line with the gondola. So I think this is probably as simple as the pen tip dragging a little behind the direction of movement. This is normal, and with a good taut "hang" and a firmly perpendicular pen, it can be reduced, maybe so much you'll not notice it, but it'll never really go away. As long as there's friction between the surface and the gondola.

The direction that the pen lift servo swings in from can also move the pen too, during the lift. If it is horizontal (so it swings in from the side), it can pull the pen at the same time as lifting, or dropping. Did the outer-most shape join up naturally, or is that a manual fix? It looks like there was an overlap.

sn
dickholmer
Beginner
Posts: 39
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Post Re: Drawing issue when using Servo (pen lift/drop)
on: March 9, 2015, 12:15
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hi,
how would the picture look like if you completely disconnect the servo? would the two ends fit to each other? maybe something with the calibaration (machine width and home point) is not 100% correct?
thomas
sandy
Administrator
Posts: 1317
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sandy
Post Re: Drawing issue when using Servo (pen lift/drop)
on: March 9, 2015, 12:19
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Don't think this has anything to do with calibration. But disabling the lift might be a good way to tell if your issue is mainly pen tip drag, or is mainly the action of the lift moving the tip during the lift or the drop.

sn
cawer
Newbie
Posts: 9
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Carlos Werberich
Post Re: Drawing issue when using Servo (pen lift/drop)
on: March 9, 2015, 14:10
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Great, thanks for all these tips.
I'll try disabling the servo and see how it works.
I'm pretty sure that it's just a detail to fix it. Almost there! 🙂
cawer
Newbie
Posts: 9
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Carlos Werberich
Post Re: Drawing issue when using Servo (pen lift/drop)
on: March 13, 2015, 11:03
Quote

I'm replacing my whole machine with much better and stronger stepper motors and a new gondola (and plus an arduino mega). So, new updates soon.
Thanks.
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