4 ms·

It's my understanding that higher quality plotters/3d printers/mills' accuracy and precision come from higher quality motors (e.g. stepper motors instead of ser

It's my understanding that higher quality plotters/3d printers/mills' accuracy and precision come from higher quality motors (e.g. stepper motors instead of servos). Will it be possible to someday just put cameras on the plotter which watch the current print and self-correct as needed? That's basically what our eyes do when we write/sculpt/carve. Will cheap motors + cameras + software eventually meet or exceed the quality of expensive high precision motors/controllers?

tpmx 7y ago
https://en.wikipedia.org/wiki/Visual_servoing https://en.wikipedia.org/wiki/Visual_servoing seems related.
deleted 7y ago
[deleted]
yakz 7y ago
Rigidity is a major factor--if you inspect one you'll notice that high speed and high repeatability machines (e.g. a 6-axis +/- 0.020mm repeatability manipulator) are made from rigid (often high-mass) components with robust joints.
- diafygi 7y ago
  I see. I wonder if my hypothesis is still valid, even given lower quality rigidity. Human arms aren't made of big heavy metal rods, yet we can still draw beautifully. Couldn't cameras and software compensate for cheap unstable draw arms?
roland35 7y ago
I can see this helping with low-force motion such as a pen-plotter but I think with things like 3-d cutting there just isn't a replacement for rigidity and high-power motors that can maintain a consistent cutting feed rate for a quality finish.
hortense 7y ago
You can improve the precision by using visual feedback, but there are movements that are impossible to do if you don't have precise enough motors.
mrandish 7y ago
That's in interesting thought but instead of a camera what if it used an optical mouse sensor? Even cheap ones in $5 mice can do hiDPI now and track on most surfaces. Maybe it could slide on the paper next to the pen with a fixed offset telling the software exactly how far the pen has moved.
- squilliam 7y ago
  Optical sensors will drift over short timescales so you will never have a repeatable "zero" point. it would probably work for small organic shapes but anything more geometric would not turn out well.
dekhn 7y ago
precision and accuracy don't come from motors. Mostly it comes from rigidity and squareness of the assembly, the smoothness of the rods, the quality of the bearings. The steppers I work with are not really accurate or precise, mainly they just average out errors as long as you're doing roughly the same number of moves in each direction. Interestingly, servos mean different things. The servos used here are cheap crap (but work well enough) but in the Real World, servos are actually more like steppers that have feedback based on absolute or relative positioning. I am also intriguided by the "can cameras be used for realtime feedback" but I don't think they have enough resolution to determine accurate sub-mm movements.
rwmurrayVT 7y ago
There are similar techniques used to self-correct 3D printing. You can actually license a system from NASA.[0] [0]https://technology.nasa.gov/patent/MFS-TOPS-70 https://technology.nasa.gov/patent/MFS-TOPS-70
MrsPeaches 7y ago
> (e.g. stepper motors instead of servos) Servos are more accurate than steppers. See: https://en.wikipedia.org/wiki/Servomotor#Servomotors_vs._stepper_motors https://en.wikipedia.org/wiki/Servomotor#Servomotors_vs._ste...
GistNoesis 7y ago
Something like the "Shaper Origin" ? but it's still not cheap
samwillis 7y ago
Replace large "cheaper servos" with a human and a self correcting small servos and you sot of have this: https://www.shapertools.com https://www.shapertools.com Its very cool...
sandos 7y ago
I believe cheap servos are inherently very discrete due to noise in the "potentiometers" used: it will not be possible to do precise positioning no matter how exact your timing pulses are. But thats just a guess. If its a noisy potetiometer/wiper but monotonic it should be possible to correct in software. If its non-monotonic and has reverses gradient it will be much harder or impossible I guess.

tpmx 7y ago

https://en.wikipedia.org/wiki/Visual_servoing https://en.wikipedia.org/wiki/Visual_servoing seems related.

deleted 7y ago

[deleted]

yakz 7y ago

Rigidity is a major factor--if you inspect one you'll notice that high speed and high repeatability machines (e.g. a 6-axis +/- 0.020mm repeatability manipulator) are made from rigid (often high-mass) components with robust joints.

diafygi 7y ago
I see. I wonder if my hypothesis is still valid, even given lower quality rigidity. Human arms aren't made of big heavy metal rods, yet we can still draw beautifully. Couldn't cameras and software compensate for cheap unstable draw arms?

roland35 7y ago

I can see this helping with low-force motion such as a pen-plotter but I think with things like 3-d cutting there just isn't a replacement for rigidity and high-power motors that can maintain a consistent cutting feed rate for a quality finish.

hortense 7y ago

You can improve the precision by using visual feedback, but there are movements that are impossible to do if you don't have precise enough motors.

mrandish 7y ago

That's in interesting thought but instead of a camera what if it used an optical mouse sensor? Even cheap ones in $5 mice can do hiDPI now and track on most surfaces. Maybe it could slide on the paper next to the pen with a fixed offset telling the software exactly how far the pen has moved.

squilliam 7y ago
Optical sensors will drift over short timescales so you will never have a repeatable "zero" point. it would probably work for small organic shapes but anything more geometric would not turn out well.

dekhn 7y ago

precision and accuracy don't come from motors. Mostly it comes from rigidity and squareness of the assembly, the smoothness of the rods, the quality of the bearings. The steppers I work with are not really accurate or precise, mainly they just average out errors as long as you're doing roughly the same number of moves in each direction. Interestingly, servos mean different things. The servos used here are cheap crap (but work well enough) but in the Real World, servos are actually more like steppers that have feedback based on absolute or relative positioning. I am also intriguided by the "can cameras be used for realtime feedback" but I don't think they have enough resolution to determine accurate sub-mm movements.

rwmurrayVT 7y ago

There are similar techniques used to self-correct 3D printing. You can actually license a system from NASA.[0] [0]https://technology.nasa.gov/patent/MFS-TOPS-70 https://technology.nasa.gov/patent/MFS-TOPS-70

MrsPeaches 7y ago

> (e.g. stepper motors instead of servos) Servos are more accurate than steppers. See: https://en.wikipedia.org/wiki/Servomotor#Servomotors_vs._stepper_motors https://en.wikipedia.org/wiki/Servomotor#Servomotors_vs._ste...

GistNoesis 7y ago

Something like the "Shaper Origin" ? but it's still not cheap

samwillis 7y ago

Replace large "cheaper servos" with a human and a self correcting small servos and you sot of have this: https://www.shapertools.com https://www.shapertools.com Its very cool...

sandos 7y ago

I believe cheap servos are inherently very discrete due to noise in the "potentiometers" used: it will not be possible to do precise positioning no matter how exact your timing pulses are. But thats just a guess. If its a noisy potetiometer/wiper but monotonic it should be possible to correct in software. If its non-monotonic and has reverses gradient it will be much harder or impossible I guess.