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2-axis "duh-moment"

A project log for CD/DVD mechanisms and cartesian thinggie[s?]

DVD-laser-etcher, dremmel-router, possibly a 3D printer? Who knows!

esot.ericesot.eric 06/08/2016 at 08:520 Comments

I'mma keep working on this, pictures/explanation to come later...

But let's just say I had a major "duh" moment... And I think the results will be quite a bit easier for most 2-axis systems.

It wasn't an *easy* duh-moment... In fact, it was the result of many iterations of over-engineering-reduction. And, by "reduction" I mean... extra-engineering to accommodate flaws in said-over-engineering to the point that it got completely unwieldy and eventually that "duh-moment" *finally* struck...

No, not even then, actually... In fact, if I gotta get my facts straight, the "duh-moment" was the result of something entirely different, *after* all that over-engineering got in the way, then was "reduced" (which, again, means that it was actually even more over-engineered, until it was too much to bare... But Even Then, I didn't see the obvious duh-moment... until giving up on that and beginning to deal with an entirely different aspect deserving of "duh" as well.).

So, actually... *TWO* "duh-moments".

I'll tell of the latter...


The latter being: The laser-output of the DVD-sled, once the focussing-lens is removed, appears *mostly* collimated... It's not perfect... It comes out of the under/stationary-lens as a circle about 1/4in-1/2in wide... And when it hits the ceiling it's something more like 2in... So, kinda collimated, but not perfect. That guy, I fed into a regular-ol' lens with a reasonable-enough focal length (about 2in), which meant that I had about 2 inches between the laser-sled and the work-surface... Which seemed like a lot a while back, but turns out is not that much space to work within (making adjustments of the work-surface, etc...). Additionally, it means that the beam widens somewhat dramatically with only a few mm of distance-change...

OK, so... I had the thing set-up with a "shield" surrounding it, so it wouldn't blind people... And then I had the brilliant idea to try out different lenses... maybe I'd find one with a more reasonable focal-length (yahknow, maybe 6-8in?). That'd give more space to work within, as well as making the focus less-susceptible to minor error due to, say, the two axes not being perfectly parallel...

Right, so I removed the lens I hot-glued in a while back... And I turned the thing on its side (as opposed to facing down onto the table, as it was designed to be run) so I could do focussing-experiments...

And turned it on (with LOW POWER, BE CAREFUL WITH YOUR ONE-REMAINING EYE!), and started to play around with different lenses...

And only after playing around with a new lens for quite some time--and not able to get it to focus on the "shield"--did I realize... wait a minute... What the Heck am I looking at...? That's not a 1/2in beam hitting that shield (when the lens is removed)... It's a friggin' dot. It's, in fact, a highly-focussed dot... shining on some arbitrarily-placed cardboard a good 10-12in away.

The Friggin' "poorly-collimated" beam doesn't splay outward from the friggin' lens--1/4in at the bottom and 2in at the ceiling--it has a friggin' focal distance about 12in away.

Which, frankly, is downright perfect.

(Hey, yahknow, there's HaD-FAILs... but no HaD-DUHs? Hmmm...)

So, we don't need an additional lens, at all, *and* the other "duh-moment" came from this exact procedure/experience, as well, but I'mma save that for later...


Oh, and another "duh-moment"... I couldn't find a tapered-head bolt long enough for my needs... So...

One of these...

Combined with one of these...

(not my images)

... actually works *way better* than I'd've ever expected.

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