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Author Topic: My first attempts at laser engraving.  (Read 91518 times)

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Offline Tweakie.CNC

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Re: My first attempts at laser engraving.
« Reply #80 on: June 26, 2009, 02:47:17 AM »
I underline the points about the toxic fumes.
Good posting John.

btw. Have you tried cutting acrylic with a laser - what sort of surface finish do you get at the edges ?.

Tweakie.
PEACE
Re: My first attempts at laser engraving.
« Reply #81 on: June 26, 2009, 03:11:37 AM »
A CO2 laser at the right power / feed produces an optically clear polished finish.

All forms of mechanical cutting require flame polishing to replicate this.

Offline Chris.Botha

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Re: My first attempts at laser engraving.
« Reply #82 on: June 26, 2009, 05:30:35 AM »
my lasers arrived while i was away.. my supposed 150mw turned out to be a 100mw and it cant melt butter much less cut plastic. i think i have been had.

Offline Tweakie.CNC

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Re: My first attempts at laser engraving.
« Reply #83 on: June 26, 2009, 07:37:48 AM »
Just a word of consolation - my laser won't melt butter either.
However if somebody ever produced black butter the laser would surely cut it !.

Tweakie.

btw. These low power lasers have to be focussed to a dot the size of a pin point to have any affect on anything - do you have a good lens ?.
PEACE

Offline Chris.Botha

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Re: My first attempts at laser engraving.
« Reply #84 on: June 26, 2009, 07:41:42 AM »
i have a focusing lense in it and when i get it to pinpoint againts a surface its so bright it hurts my eyes.

i may be powering it incorrectly tho. the website say 5V ac so im usinga 5v AC @ 1000mah usb charger. possibly not enough power?

there is a secondary cable which no one, even the suplier is able to tell me anything about.

here are pics..

 

Offline Chris.Botha

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Re: My first attempts at laser engraving.
« Reply #85 on: June 26, 2009, 07:43:07 AM »
red and black are powerd by 5v AC by the way. blue and white i have no idea about?

[edit]

ok i got it burning. tried on black and blue surfaces and it started burning instantly..


« Last Edit: June 26, 2009, 07:59:47 AM by Chris.Botha »

Offline Tweakie.CNC

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Re: My first attempts at laser engraving.
« Reply #86 on: June 26, 2009, 08:53:11 AM »
Chris,

You need to be wearing protective goggles. Do not look at the reflected beam without them.
If you use a benchtop PSU then providing 2 to 3 volts to the laser control board the laser will emit a LED beam (without lasing) which is easy to focus. Then turn up the wick to 5 Volts. (a DC power source would be better).

Tweakie.
« Last Edit: June 26, 2009, 08:55:24 AM by Tweakie.CNC »
PEACE
Re: My first attempts at laser engraving.
« Reply #87 on: June 26, 2009, 09:47:21 AM »
Class 1


A class 1 laser is safe under all conditions of normal use. This means the maximum permissible exposure (MPE) cannot be exceeded. This class includes high-power lasers within an enclosure that prevents exposure to the radiation and that cannot be opened without shutting down the laser. For example, a continuous laser at 600 nm can emit up to 0.39 mW, but for shorter wavelengths, the maximum emission is lower because of the potential of those wavelengths to generate photochemical damage. The maximum emission is also related to the pulse duration in the case of pulsed lasers and the degree of spatial coherence.

Class 1M

A Class 1M laser is safe for all conditions of use except when passed through magnifying optics such as microscopes and telescopes. Class 1M lasers produce large-diameter beams, or beams that are divergent. The MPE for a Class 1M laser cannot normally be exceeded unless focusing or imaging optics are used to narrow the beam. If the beam is refocused, the hazard of Class 1M lasers may be increased and the product class may be changed. A laser can be classified as Class 1M if the total output power is below class 3B but the power that can pass through the pupil of the eye is within Class 1.

Class 2

A Class 2 laser is safe because the blink reflex will limit the exposure to no more than 0.25 seconds. It only applies to visible-light lasers (400–700 nm). Class-2 lasers are limited to 1 mW continuous wave, or more if the emission time is less than 0.25 seconds or if the light is not spatially coherent. Intentional suppression of the blink reflex could lead to eye injury. Many laser pointers are class 2.

Class 2M

A Class 2M laser is safe because of the blink reflex if not viewed through optical instruments. As with class 1M, this applies to laser beams with a large diameter or large divergence, for which the amount of light passing through the pupil cannot exceed the limits for class 2.

Class 3R

A Class 3R laser is considered safe if handled carefully, with restricted beam viewing. With a class 3R laser, the MPE can be exceeded, but with a low risk of injury. Visible continuous lasers in Class 3R are limited to 5 mW. For other wavelengths and for pulsed lasers, other limits apply.

Class 3B

A Class 3B laser is hazardous if the eye is exposed directly, but diffuse reflections such as from paper or other matte surfaces are not harmful. Continuous lasers in the wavelength range from 315 nm to far infrared are limited to 0.5 W. For pulsed lasers between 400 and 700 nm, the limit is 30 mJ. Other limits apply to other wavelengths and to ultrashort pulsed lasers. Protective eyewear is typically required where direct viewing of a class 3B laser beam may occur. Class-3B lasers must be equipped with a key switch and a safety interlock.

Class 4

Class 4 lasers include all lasers with beam power greater than class 3B. By definition, a class-4 laser can burn the skin, in addition to potentially devastating and permanent eye damage as a result of direct or diffuse beam viewing. These lasers may ignite combustible materials, and thus may represent a fire risk. Class 4 lasers must be equipped with a key switch and a safety interlock. Many industrial, scientific, military, and medical lasers are in this category.
Re: My first attempts at laser engraving.
« Reply #88 on: June 26, 2009, 10:02:04 AM »
Basically the above means that even the reflected and diffused beam from a 100mW laser is sufficient to cause irreparable, permanent, eye damage in less than 0.2 seconds.

Do not forget that at visible wavelengths, where the eye lens can focus the beam, a coherent beam entering the eye is focused to a point 100,000 times more powerful at the retina.

I know a man who has a permanent black spot covering about 25% of his field of vision in one eye, he described hearing a sort of "pop" inside his head as the beam caused boiling and cavitation inside his eye.

It was a 250mW "green" laser that did it.

Amongst other things he lost his truck drivers licence over it, one eyed jacks need not apply for a truck licence in the UK.

=====================

I have another mate who *KNOWS* lasers, he has a home built 80 watt CO2 laser, home built as he built everything, even the tube.

he dons a high end pair of very specific to the wavelength goggles, and then a modified welding mask with a thick slab of pilkington glass, before going anywhere near the power switch.

I laughed at him the first time I saw this, and he told me a story about some lab tech in the states in the mid eighties who had an "accident", the first thing the beam encountered was matey's protective goggles.

it burnt a hole in them.........

« Last Edit: June 26, 2009, 10:06:36 AM by GuyFawkes »

Offline Chris.Botha

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Re: My first attempts at laser engraving.
« Reply #89 on: June 26, 2009, 06:33:51 PM »
ok i get it. be carefull!

i will be carefull. i think this 100mw laser is no good tho. i found a 750mw blue one on ebay for 39 bucks with driver kit.

welding goggles it is then!