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Comment by KeplerBoy | Hacker News Reader

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KeplerBoy·

How do 3 axis robots you can buy for 100$ (3D printers) have a static accuracy of 0.05mm?

It's not control theory, but mechanics and steppers.

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It’s the compromise between a gantry vs arm design

There are plenty of 3d printers without a complete gantry. The bambulab a1 mini or prusa mini to name just two.

Those two printers are also smaller and not as accurate at high speeds. The A1 Mini's slicer automatically places parts close to the Z axis in an attempt to reduce the issues and it uses input shaping, but given the printer can lift itself off the ground at default speeds that's not a perfect solution either.

There's a reason the larger and faster printers often use the CoreXY design instead.

Of course, there's always trade offs in (mechanical) design choices. But their static accuracy absolutely is that good, which is fascinating at that price point.

Yes but they're not robot arms so it's not as fascinating. The length of the arm amplifies error so if you made a "mechanics and steppers" arm with the same positional accuracy as a printer, the motors would have to be much more precise or if you geared them down, the backlash extremely low like an industrial robot arm.

Sure, there's no free lunch.

I'm curious what would be the best way to replicate an x/y (optionally z) system with 0.05mm or lower accuracy? Without sacrificing speed of course.

Depends on how much power you need (speed times force, acceleration and deceleration...) and how much stiffness you need (can't bend?).

Also depends on how much travel you need. It is easier to get 50 micron accuracy over a total length of 100 micron compared to a total length of 1 meter.

Making things lightweight is crucial, because otherwise inertia will make your toolhead deviate from the planned trajectory at any corner.

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