[Arm-netbook] $150 taobao knock-off 3d printer doing 200mm/sec

[Luke Kenneth Casson Leighton]

https://www.youtube.com/watch?v=3IGQ_8K3tGI

this is a quick video of the horribly cheap and cheerful taobao $150
plus $40 shipping 3d printer making a HELL of a racket, successfully
PRINTING at 200 mm / sec.  acceleration settings have been turned up
to... enormous: 4000 mm / sec^2 for X and Y, and 9000 mm / sec^2 for
the extruder.

in previous tests i was running at 2000 mm / sec^2 and at 120 mm / sec
print speeds there was clear signs of "bulging" along the 0.7mm wide
screen bezel, where at the last moment the print head would slow down
*but extrusion clearly didn't*, and instead of a nice line you get
this "teardrop" effect.  by putting the acceleration so insanely high
that artifact *DISAPPEARS*.

now, due to the bone-rattling speed the frame is clearly vibrating
around, which results in this "wave" pattern as the printhead goes
through this massive 180 reversal, *but*, i am amazed to find that the
"wave" pattern stabilises after around 4mm and is not hugely
noticeable anyway.

it's basically outperforming the mendel90 for quality, yet still
matching it for speed.  i'm... absolutely astounded.  still to
consider is putting in some acrylic / MDF / hardboard surrounds that
would stiffen up the frame.

l.

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crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68