Différences

Ci-dessous, les différences entre deux révisions de la page.

--- machines:lasersaur:ajuster_lasersaur [2017/04/25 13:53] – créée mdupont
+++ machines:lasersaur:ajuster_lasersaur [2017/12/21 19:13] (Version actuelle) – modification externe 127.0.0.1
@@ Ligne 1: / Ligne 1: @@
 La phase de réglage est assez longue et fastidieuse. En attendant une traduction, voici les liens vers les explications en anglais sur le site de lasersaur:
 Page de réglage peu détaillée mais avec schémas: [[https://github.com/nortd/lasersaur/wiki/optics_setup]]
 Page plus détaillée du processus: [[https://github.com/nortd/lasersaur/wiki/Calibrating-mirrors-and-lenses]]
 Un montage pour aider au réglage des mirroirs avec un pointeur laser (pas testé): [[http://www.thingiverse.com/thing:639069]]
+Une explication d'une méthode de réglage:
+I'm a firm believer in NOT measuring the distance and assuming that's the
+right thing to do.  You've gotta adjust incrementally.
+One particular problem is that not all "75mm" lenses are really 75mm.
+Some of them are 3 inches - which is 76.2mm - but they aren't necessarily
+even that.  We're not keen on spending $300 for a lens from a 'reputable
+vendor' - when we can get them for $60 from some guy in Israel who sells
+them on eBay!  The cheaper lenses seem to have focusing ranges anywhere
+from maybe 72mm to 78mm depending on where they originally came from.
+I have the older focussing tubes where you rotate the lens tube to adjust
+the focus.  The Thor Labs parts have 40 turns per inch threads.  I put a
+white dot on the edge of the lens tube and count the number of rotations
+up or down to get the thing in perfect focus.
+So I measure off the 75mm "nominal" distance - and then cut a series of
+cm lines with the lens tube rotated in 2 turn increments (which is about
+.3mm) starting at 8 turns above the nominal distance and ending 8 turns
+below it.  This is kinda tedious...but we only have to do it when we swap
+out a lens.  We pick the best focussed line - and then try one turn above
+and one turn below that setting to get the very best.
+The final step is to rotate up in 1/4 turn increments...that's because
+lenses get gradually damaged - and very often, by rotating the damaged
+part somewhat out of the way of the beam (which is somewhat elliptical
+after all of those mirror bounces) - you can sometimes get better results.
+Also, focussing a millimeter or so higher than optimum gives the best
+compromise when our plywood is a little warped and won't lay perfectly
+flat on the bed.
+We just bought one of the newer lens tubes that Nordt sell where the
+entire tube slides up and down and you can't rotate it to get precision
+adjustments - I was rather disappointed with it - and we're currently
+debating whether to return it or to persevere with it.
+I suppose we could get similar repeatability & accuracy with a wedge slid
+under the tube, marked with it's thickness at various points...which is a
+tool that we could laser cut.  But I'm not convinced because the retaining
+ring below the lens can easily get turned around when you remove the upper
+retaining ring to get the lens out for cleaning...that would mess up the
+focus.  Since our lenses need cleaning every one or two days, that's an
+extra chore that we really don't need.