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February 19, 2020, 14:31:43 pm


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Author Topic: The Laser Project  (Read 5189 times)
dave benson
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« Reply #120 on: February 13, 2020, 01:11:39 am »

HI Guys

I've modified the Laser mount to suit the new Laser, it's thinner and longer than the other one.
I've test run it on the bench in the study and am impressed, the fit and finish of the circuit
boards is very good and the wiring to the laser is quite heavy compared to the others I have.

There’s a lot of photons coming out and I had a good time cutting in half pieces from
the packing box it came in, that is until the smoke alarm went off.  Roll Eyes
Lucky I didn't machine anything on the nozzle it turns out that the lens focus ring was 16 mm.

I set up a rectangular piece of black anodised Al to focus it with and oddly enough the best
focus was achieved with a distance (from the lens) to the block of 32 mm  they said the sweet spot
was 16 mm so I play with this further on the mill.

This is a shot of the block, the anodising is completely gone, the other holes for comparison are M3's.
I put he block at an slight angle as I was worried that the reflected light might damage the laser, I've
been told that you can get device that will prevent this (It'll pass the light through in one direction) and will look into it further when I get time.
So far I'm a happy camper.
Bubba I'm going to take your advice and get some better glasses as the reflected light
coming between the glasses frame and my cheeks  was a little worrying.

Dave


* Laser dot size.png (649.01 KB, 800x450 - viewed 12 times.)
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Bubba
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« Reply #121 on: February 13, 2020, 02:46:40 am »

Dave, I'm happy that you happy with the purchase. The googles that come with my laser were cheap green color googles, so I ordered new ones with higher safety rating, the color is very dark orange if you look thru them and appear dark brown in colour. Do you know what lens come with the laser? I need to look up the distances I use with my laser. The G2 lens (short focal length) is just about the 32mm you mentioned, but in my case is set from the laser body. By doing this way, I can change lens and use Mach3 auto zero with appropriate block height to set proper Z height in seconds..  By rereading your post and looking at your picture, the dot is to big. My old eyes are not helping but, I never couldn't measure the dot itself. Created a line by moving the table then measured it,  measure 0.009". So by lowering it to 16mm you may get there. Good Luck.   

On the attached picture the description says green color googles, witch is wrong. Wink


* Capture.JPG (44.23 KB, 723x254 - viewed 11 times.)
« Last Edit: February 13, 2020, 02:58:09 am by Bubba » Logged

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dave benson
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« Reply #122 on: February 13, 2020, 11:09:17 am »

Hi guys

Thanks for the Info Bubba.

I did a few preliminary tests with gasket paper and neoprene and a nozzle with
a 4 mm orifice.
I'm going to make another tomorrow with a 3.3 mm orifice and give this a go too.

The gasket paper (0.25 mm thick) cut very well at 300 mm\min to 600 mm\min at full power.
The faster you go the better the cut looked.
At 100 mm\m the wood supporting the gasket paper cut to a depth  of approx 1 mm. plywood

The neoprene on the other hand, to cut through required slowing down to 50 mm\min
and showed distinct signs of bubbling and cratering leaving a whitish substance on the cut surface.
On the last run the gasket could be easily pulled away from the parent material
but still had a ragged look under the microscope.

At this stage I think that I will re-run the tests at 200 mm\min this gives about half a mm
depth of cut, but cuts cut very cleanly like a knife and go round the periphery a few times.

Quote
 I never couldn't measure the dot itself. Created a line by moving the table then measured it,  measure 0.009"

I used some measuring software Bubba but I still think this is a bit arbitrary and will
write some Gcode tomorrow after making the nozzle and lay down some lines using
different feedrates and focus settings then measure the lines like you say and see how I go.

At 600 mm\m I can cut one turret worth of gaskets in 1 min 48 seconds which beats
the pants of the drag knife method.

Dave


* Gasket paper at 10x 300mm-m.png (324.63 KB, 466x373 - viewed 8 times.)

* Gasket paper at 10x 600mm-m.png (329.6 KB, 466x373 - viewed 9 times.)

* neophrene at 10x 50mm-m.png (354.98 KB, 466x373 - viewed 8 times.)

* neophrene at 300 mm-m.png (336.09 KB, 466x373 - viewed 10 times.)
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Bubba
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« Reply #123 on: February 13, 2020, 13:27:12 pm »

I used some measuring software Bubba
[/quote]

Hi Dave, what kind of measuring software did you used? Never heard of such a thing.. As to neoprene cut, I think it would require lots of as pressure coming from the nozzle. Overall I like the looks of of those cuts.
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EddyCurrent
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« Reply #124 on: February 13, 2020, 18:18:51 pm »

Dave, the main thing is it's working, just needs fine tuned now.
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Bubba
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« Reply #125 on: February 13, 2020, 20:21:31 pm »

Dave, the main thing is it's working, just needs fine tuned now.

Yep!
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dave benson
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« Reply #126 on: February 14, 2020, 00:27:39 am »

HI Guys

Bubba the software is called BitRule, I've had this for many years now and am sure there would be
newer and better ones.

Quote
As to neoprene cut, I think it would require lots of as pressure coming from the nozzle

Yes I think so too, I also think that making a fixture to raise the material to be cut of the table
will allow the air somewhere to escape.

I have a small spindle head mounted compressor and at the moment I'm running it
at its slowest speed and have fitted, on the end of the flexible hose (The one's used for coolant) a
removable tip with a 0.8 mm hole which gives me a reasonable amount of pressure and volume
for cutting down to 6 mm deep in 1018 steel.

I know I have a micro filter/regulator combo somewhere and will try to fit that as I think some filtering
would be required so as not to dirty up the lens.

In some of the video's I watched that Eddy pointed to (Russell) made a few nozzles up with
different diameter holes as small as possible but big enough to pass the laser beam.

I'm off to the shed to make another one too, I don't know if I can it may be a bit too fiddly but will try
to make one with a removable plug that goes into the bottom and make a few different sizes.

I'm well aware that if the hole is too small and the tip is machined from Al then the reflected light
will damage the laser so will make the tips out of UHMWPE.

I've also noticed while watching a few Youtube videos that some people have put
a fairly hefty radius on the bottom of the exit hole which I'm thinking would detract from
the Laminar flow and will try to clean up the edge of the hole without putting much of
a radius on it if any.

Quote
Dave, the main thing is it's working, just needs fine tuned now.

Yes Eddy I must say  it's been enjoyable so far, being spindle mounted makes it easy to swap out
and I've found a blow molded case from a long dead router to keep it in when not in use.

After watching the laser cutting the gaskets out, I've realized that I can make some optimizations
for Gcode size and have already optimized for movements between objects to be cut and will
do this once the hardware is finished.

Dave
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Bubba
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« Reply #127 on: February 14, 2020, 01:35:03 am »

Yes I think so too, I also think that making a fixture to raise the material to be cut of the table
will allow the air somewhere to escape.
***************
 Dave, that's why I'm glad I got hold of damaged (leaking coolant) truck radiator, and it works like a charm.
Thanks for the software info, I will check it out. Are you using Mach3 and CB to run the laser? I wonder what Eddy will use with his laser as well. I think I read this somewhere that it comes with it's own software.

The air for my laser is provided by 60 Gal compressor, it has inline pressure regulator with water separator. I'm not worrying about the lens being dirty because how the nozzle is made. The two mating parts machined to very close fit so the air is forced out of the nozzle end only. But, I'm guessing here and been wrong before. Wink Cheesy Grin Grin
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dave benson
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« Reply #128 on: February 14, 2020, 12:55:44 pm »

HI Bubba

Quote
Dave, that's why I'm glad I got hold of damaged (leaking coolant) truck radiator, and it works like a charm.

That's a great idea Bubba, somewhere here I have a oil inter-cooler from a auto transmission about 12 mm
thick by 300 mm long  and 150 mm wide just the right size for my table.
If I can't find it I'll purchase some SS expanded mesh, I've seen some with quite small diamonds perhaps
25 mm long and 12 mm wide by only 3 mm deep.

Here are some more testing shots.

I noticed that after doing some of the text that it was still burning a bit and so stopped the mill and
regenerated the file with 800 mm\m feedrate and dropped the power to 40 percent.
A job on the todo list is to make some laser friendly fonts.
The holding tabs worked well.
At this speed and having exact stop on the mills movements were slightly jerky not to bad but noticeable.

Dave


* Gasket paper 800mm-m 39 percent power.png (724.75 KB, 800x450 - viewed 12 times.)

* Gasket paper 800mm-m 39 percent power 1.png (728.71 KB, 800x450 - viewed 13 times.)
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Bubba
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« Reply #129 on: February 14, 2020, 13:33:08 pm »

That looks good Dave, do you need the holding tabs?

Best..
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dave benson
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« Reply #130 on: February 15, 2020, 00:32:42 am »

Yeah I'm afraid so Bubba, here is a shot of a failed attempt.
I definitely need to raise the material of the mill table and give somewhere for the air to escape.

These to pieces did have holding tabs 0.25 wide and I had set the mop sequence so that the holes
were cut first and then the outside of the shapes were done, and what happened was that  as the
first hole was cut the air was able to get in between the paper and the backing piece of wood and
this lifted the paper of the wood maybe a mm to two and the air pressure broke the holding tabs.

The piece on the left is where all but one the holding tabs broke allowing it to move, the one on
the right all of the holding tabs broke (I couldn't find it anywhere)  and later found it wedged
underneath the paper between the backing plate  in the far corner and so it did not get cut at all.

And for the next successful attempt I increased the holding tab width to 0.5 mm and changed
the order of the cut.
So far I've determined that 600 mm\m and 40 percent power is the sweet spot for this particular
gasket material.
I found the micro reg\water trap but don't have any olives to suit the hose and will have to get
some more.
I'm just going to use the water trap and not the regulator.

Quote
Are you using Mach3 and CB to run the laser?

Yes because I'm going to use CB and for vectors (the gaskets) I completely rewrote the code
It makes smaller files than the original CB file and optimises all of the moves between the shapes
to be cut.
It uses the M11\M10 pair and you set the feed rate and spindle speed (PWM) from the mop.

some of the others I wrote can do all of the methods raster\vector variable everything as well
as scaling but because of this they can not be optimised as well as a single fit for purpose file generator.

All the other methods now have there own separate .exe and PP.

I know this converter is good as I've run it on the machine many times now, and will in the future
do some more testing of the others as I get time.

Dave


* Gasket paper one of the failed attemps.png (775.14 KB, 800x450 - viewed 7 times.)
« Last Edit: February 15, 2020, 00:35:29 am by dave benson » Logged
Bubba
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« Reply #131 on: February 15, 2020, 01:08:33 am »

Dave,
I understand now, using air. While back when I cut sample gasket for you to see, I did not use air at all. Cut the cardboard in two passes @ 100% power at little higher feedrate. Try it, see what you get  Grin   
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EddyCurrent
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« Reply #132 on: February 15, 2020, 12:57:30 pm »

When cutting thin stock I believe using air assist causes problems. I have fitted a pressure reducing valve and a flow valve to allow full control of the air, also a solenoid valve to cut it off completely.

To raise the material I am using "metal spike 20mm", search for that on ebay.
They can be fastened to the bed or left loose to place where required, a bag of 50 is quite cheap. I might make some wider plastic bases for better stability.


* spikes.jpg (65.6 KB, 794x619 - viewed 8 times.)
« Last Edit: February 15, 2020, 12:59:06 pm by EddyCurrent » Logged

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Bubba
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« Reply #133 on: February 15, 2020, 20:18:16 pm »

To raise the material I am using "metal spike 20mm", search for that on ebay.
*******************
Eddy, that should work well.
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dave benson
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« Reply #134 on: February 16, 2020, 02:12:09 am »

Good Idea Eddy.
Who would have thought the punk rock era would have given us anything useful! Grin

What I mean with using the air is that I have turned down the flow control valve
in the hope of at least having a small positive pressure in the nozzle enough  to
keep the lens clean (this may be an unfounded concern) but not enough to disturb
the paper, but with this unit I have installed as you turn down the flow it hits a certain
point then shuts off completely but this is still too high a flow rate when its on.

It's just from the salvaged parts bin and not specified for the job at hand it may well
be that it is working correctly but it's operation range is to high for what I need.

This morning I have  found a very old all brass\bronze manual control valve and
that can be turned down to almost nothing so will give this a try.

I have no evidence to want this slight positive pressure in the nozzle at all
times just a gut feeling after seeing how much smoke is generated and how close
the laser head is to it.

What I'm afraid off is that some smoke particles will settle on the lens and then get
baked on by the laser
edit: Sheesh you think I could spell particles by now.
Dave
« Last Edit: February 16, 2020, 02:17:21 am by dave benson » Logged
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