metal ecthing setup

A little writeup on some experiments with metal etching:

[www.reprap.org]

-Matt

You did wax-resist etching to make the metal compliant joint? Wow. I just figured that you had hand-carved each segment as a stand-in for punching it out with a steel tool. That's.... fascinating. How well does the aluminium compliant structure work in comparison to the acrylic or paper?

Yep, the compliant mechanism project started out as a proof-of-principle for the etching work. The point of looking at compliant mechanisms, in the big picture, is that they might be produced using some crude low-tech method (like wax-resist etching). The idea is: how do we build a precision motion stage without using precision components to begin with? Compliant mechanisms are of course just one possible avenue, with their own advantages and drawbacks.

But anyway, to answer your question: The aluminum structure did not work very well. It is much too stiff and has a very low deflection. The max (theoretical) deflection is only +/- 0.017 inch (0.44 mm). An aluminum structure could in theory work quite well, but the aspect ratio (length / thickness) of the flexural members would have to be much greater than it was in the original test structure.

The cardboard structure is too flexible. It is a bit stiffer than a Slinky, but pretty useless as a linear positioning stage. Also the cardboard de-laminates after a few cycles.

The plastic version is sort of a happy medium. The flexural members are flexible enough to allow a high deflection, yet stiff enough to keep off-axis bending under control. Importantly, the spacing between flexural elements is increased in the plastic version, which increases off-axis stiffness while leaving "on-axis" stiffness relatively unchanged. However, the plastic version is still way too floppy for use in a real application.

With enough optimization and experimentation, I think a compliant mechanism could work "for real", say as part of a printer's z-axis. But given the other options that are out there right now I am not sure if it would be worth the effort.

... for flexure structures (and others too) i used etched or lasercutted 0.1mm thick steel-foil or milled POM-sheets with 0.5mm or 1mm thickness - the 0.1mm thick steel is slightly stiffer than the 0.5mm thick POM, but the POM is more reliable ...

For etching metal i'm thinking coating the surface with a black finish and 'engrave' the structures to etch with my 5Watt-diodelaserheads - this should be the easiest way and an 'engraving' tray of 0.1mm width is accurate enough for most practical uses (the actual finest cut is 0.02mm with my fiberlaser, but could be optimized until 0.005mm)

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Cool! This guy [www.youtube.com] uses black paint as an etch-resist for cutting steel. If the wavelength of your laser is IR, you may also be able to use an aerosol "clear coat" since many clear polymers are actually black in IR wavelengths... At any rate I really like the idea of combining laser and etching to allow cutting of metals.

... my 5Watt-diodes hawe 975nm and the fiberlaser 1070nm, so any black/dark colour will work, but i don't know if the aerosol "clear coat" will work - most clear polymers i used, weren't burned away by the diodelasers ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]