On 12/10/24 09:24, Viesturs Lācis wrote:
pirmd., 2024. g. 9. dec., plkst. 12:29 — lietotājs Robert Schöftner
(<r...@unfoo.net>) rakstīja:
It's really none of my business but that laser-tube "installation"
really looks scary. Are you going to run those tubes in that enclosure?
How do you maintain alignment with this kind of non-rigidity?
I welcome any questions or suggestions or criticisms on that approach
of laser tube mounting because I do not have experience with lasers. I
tried to search the web for any existing examples of mounting laser
tube on a moving stage of the machine and found only one case. The
fact that basically nobody is doing it this way makes me think that
there are reasons which I am unaware of. So I am open to any input - I
see it as a potential to save me some headache later. Client had the
idea to build it this way so now I am trying to implement it. The
bonus of this arrangement is the short path of laser beam from tube to
lens with only one mirror that does not move relative to laser tube.
That is why I think that maintaining alignment should not be that hard
(customer initially wanted to mount the tube vertically right above
the head and lens but I talked him out of that).
That box will be bolted to those aluminium supports. They might flex a
little in Y direction which is parallel to laser beam so that should
not affect anything (and if it does - that is easy to fix with a
diagonal element). I am not sure about the laser tube inside the box.
Encapsulating it in foam seemed the only way to fix it in place
without introducing any additional stresses. IMHO mounting it with
clamps and bolts will put a stress on it and it will crack. Those 4
pieces hold together only at the ends where the laser beam is turned
around and then with 2 plates near ends (it can be seen in the picture
with more close-up view) where it is put on few spots of epoxy or
something similar (and I am convinced that it will not stick to the
glass really strong) and then in that closer look picture there can be
seen short pieces of small diameter glass tube in the gaps between
those main elements - they also do not seem to be melted together
really much so might break off easily. I asked chinese manufacturer
for instructions how to lift and handle that thing - they only showed
how to connect cooling water and power supply. My whole impression is
that grabbing and slightly lfiting that thing by one corner will break
it. That is why I do not even want to attempt taking it ouf of that
box but rather try to come up with a way to fix in the place as it is.
Taking off those side panels would be easy but I I still have no idea
how to proceed from there.
I have zero experience to reference, but my concern with this stems from
potential leakage since the tube is a CO2, meaning infrared. The human
eye can't see it but can be blinded by it. A few watts of leakage from a
dusty mirror might warm the wooden crate up enough to start a fire, not
to mention the possibility of eye damage from any leakage that escapes
by reflection off the target.
Most of the smaller laser engravers being sold to 3d printer people have
colored plastic skirts to surround the target area to preclude such
leakage even if its only a 1 or 2 watt laser. At 600 watts it seems
like a huge problem if not well contained. They make translators which
could be used for leakage detection by making it visible, much like the
leakage papers for testing kitchen microwaves.
So be careful, Leonardo.
Some swiss school made a linuxcnc fork that has a jerk limited TP, but
it's not easy to integrate that with stock linuxcnc, the code structure
is dissolved in acid, digested, and then reconstituted in a new
directory structure/build system/everything. And the TP mainly consists
of some MATLAB-generated C-Code
If you want to look yourself, I recently found prunt3d.com which uses
"pythagorean hodographs" to round corners and generate jerk-limited
trajectories. But it is written in (of all languages) ada!, and the
preprint i found of the paper it is based on is somewhat hard to read.
The published paper is locked behind a paywall.
Besides my cnc machinetool activites I also work for technical
university so I have access to published papers and articles. If you
can provide me with authors or paper name or DOI number I am pretty
sure I can get it.
Viesturs
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Cheers, Gene Heskett, CET.
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