Author Topic: Laser focus ?  (Read 1039 times)

moritz

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Laser focus ?
« on: November 10, 2017, 11:52:50 PM »
maybe a stupid question but where is the most power from the Laser beam if the laser is nearest the material or if it is far away ?
i replaced the laser holder and i wonder if there is a difference for the focus of the beam ...

treinbert

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Re: Laser focus ?
« Reply #1 on: November 11, 2017, 01:14:59 AM »
I have a feeling the distance is not the question. The focus is more important. As long as the laser is fully focussed, the power is there concentrated. The size of the final spot can differ from laser to laser and in my case a 3500 mW laser is less effective than my previous 2500 mW laser, as the spot of the 3500 mW laser is bigger and therefor less concentrated.

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Zax

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Re: Laser focus ?
« Reply #2 on: November 11, 2017, 03:47:47 AM »
As treinbert explained, distance is not very important but you must focus (concentrate) the energy to the smallest spot possible for cutting. When engraving I leave it slightly de-focused as it blends the lines for a better looking result.

moritz

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Re: Laser focus ?
« Reply #3 on: November 11, 2017, 05:18:50 AM »
so buying a 3.5 Watt Laser makes no big difference because the spot is bigger ? ....how about the 40 Watt CO2 Laser they go for 400 Bucks but are they safe enough ?


pedwards2932

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Re: Laser focus ?
« Reply #4 on: November 11, 2017, 05:24:35 AM »
I am assuming since you are in the Cutting category you want to cut  What I have found to work the best for focus because I have a hard time determining the best focus by judging the thickness of the line.  I take index cards and stack them up till they are the exact thickness of the material I am cutting.  Then I try to focus to get the smallest  laser dot.  Then I burn a line and start dialing in a little at a time burning a line and after burning a few lines I look to see which line burns thru the most cards, I usually find one line that burns thru more than 2 cards and that is the best focus.  This has worked great for me...I mainly cut balsa but it worked for plywood as well  I have the 2.5 watt laser.

Stonemull

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Re: Laser focus ?
« Reply #5 on: November 11, 2017, 06:42:38 AM »
A lot depends on the lens itself, I believe the standard 3 element lens on the 2.5W is designed to give modt power at between 1 and 2 inches from the material, you will find it tricky to burn a foot away obviously and there is an optimum distance that the innermost lens elements need to be to the laser diode. At some distances you start to get reflections off the interior walls or the element is not large enough to collect all the emitted light.
To test out the beam set it to a low power and aim at a piece if paper a few feet away and check the shape, this shape is the same as it is at the focus point a lot closer to the laser, however you dannot view that..
 The laser emits a line of a sort, for burning you want to see that line shape on the paper .. moving the lens in and out but moving the paper also to retain the same spot size (say 10mm) will show when the beam is best, then note the distance the focal point is from the front of the lens. That is what you want to use. Mine appears better at 2 inches than 1 inch.
I posted some USB microscope pictures somewhere .. I think early on in the pcb etching thread in projects as this was why I was trying to obtain best focus.

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moritz

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Re: Laser focus ?
« Reply #6 on: November 13, 2017, 02:36:17 AM »
yes i am in the need of cutting leather up to 3mm, mostly the burning line comes out to strong and the leather is melted on the cut before i am passed true.....i have added a aquarium Pump to blow air with a fine noozle ..wil give a try to set this fine as possible maybe with Printer Noozles....

Also i have noticed that some time if i engrave on leather and my laser is standing still for a moment without getting off my leather has a hole so i assume the power must be enough for cutting it...

what about a better lens is there an option to pump the 2.5watt laser ?
and do i have better cuts if i switch to an TTL Laser with PWM `?


Kindly Moritz


ROSS

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Re: Laser focus ?
« Reply #7 on: November 13, 2017, 02:48:31 AM »
So what speed and power rating are you using?  What experience have you using lasers?
If you are not familiar with laser cutting then.....>>>>Read this

Benbox Laser Machines/CO2 Lasers/3D Printers General Category Cutting leather cutting (OPEN)

Read  on this forum about cutting different materials.  You will get an idea of a starting figure(s)........
« Last Edit: November 13, 2017, 05:12:54 AM by ROSS »
.
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moritz

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Re: Laser focus ?
« Reply #8 on: November 13, 2017, 05:47:55 AM »
i am working now for a while with my Laser mostly engraving and lasering my Logos...leather is a problem beacause every leather is different also the color the thickness the absorbing .,..so my question was in general to have some ideas from professionals in here..i will give a try to learn as much as possible anf i apreciate the help....

what i also was thinking was to switch on one the cheaper CO2 ...


Kindly Moritz

moritz

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Re: Laser focus ?
« Reply #9 on: November 13, 2017, 05:49:00 AM »
i forgot i run at 200 to 500 speed and the beam on 80 % to not overburn the lens...

ggallant571

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Re: Laser focus ?
« Reply #10 on: December 06, 2017, 02:45:06 PM »
Set your acceleration very high for leather. Also might want to try laser mode with the 1.1 grbl.
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