Laser Cutter Notes

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There is a serious risk of getting blind when working with lasers. Always wear appropriate laser goggles!
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Laser Cutter

Release status: unknown

Beamy.jpg
Description
turnkey or DIY laser-cutter toolheads
License
Author
Contributors
Based-on
Categories
CAD Models
External Link


RepRap Research/Writeups

See the Laser Cutter Working Group@forum.reprap for discussion.

Background

See Laser_Cutter/Background

Cost Estimate

- comercial 'naked' diodelaser with 8Watt@975nm and 0.1mm atached glass fibre: ~230 Euros (in quantities above 5 pcs).

- turnkey-system with 10Watts@975nm, a visible red pilot-laser and jack for the glass fibre: ~1000 Euros (in quantities above 5 pcs).

Components

Laser Light Sources

- Different laserdiodes:

1 watt pigtail diode laser with optical head (focus ~50 microns):

1Watt Diode-laser with focussing head all laserdiodes

- IR-diodes internal assembly:

opened 5Watt-, 9Watt- and 25Watt-diodelasers

Internal Assembly 5Watt- and 9Watt-Diodelasers Internal Assembly 25Watt-Diodelaser


- Complete modules:

5 watt pigtail diode laser with 4xLM317-driver atached and lighting on a beam-indicator without optics:

5Watt-Diodelaser with 4xLM317-driver


complete 5 watt pigtail diode laser-module with 4x or 5x LM317-driver, MOSFET, microcontroller, armored tube and an optic head - prototype on the left, V2 on the right:

5Watt-Prototype1 5Watt-Prototype1


- Applications:

'real blue' 445nm-diode with 1Ampere current and roughly 1Watt output power. - left = focussed beam, middle = burning without filter, right = UV-filterplate:

445nm von Vorne kl.jpg 445nm - 1Watt ohne Filter.jpg 445nm - 1Watt mit Filter.jpg

1. Laser-source:

- CO2-lasertube ... sealed (RF) or 'naked' glass-tube

- diode-laser ... best with atached glass fibre (=pigtailed)

- ...

beam-feeding optics

2. beam-feeding optics:

- CO2: - mirrors

- diode-lasers: - glass fibre and/or lenses and mirrors

- ...

focussing optics

3. focussing optics:

- CO2: - Germanium- or ZnSe-lens for CO2-laser ... concave mirror is possible too

- diode-lasers: - 'normal' optical lenses

- ...


3.1. Embedding a Pilotlaser as guide or beam-indicator:

Pilot-Laser

power source and output-power control

Main article: Bright Light Circuit

4. power-source:

- CO2: - mostly monolithic PS, good when below 40 Volts for RF-CO2-lasers, 'naked' and DIY-CO2-tubes need above 1000 Volts

- diode-lasers: - constant-current-driver (e.g. more LM317 in parallel)

LM317 parallel

- a 5xLM317-driver with switching MOSFET:

5xLM317

- modified driver with 2xLM317 with 1Ampere each and 3xLM338 with 2, 2, and 2.6 Ampere for free combinations from 1 to 8.6 Amps:

5xLM317

- ...


5. output-power controller:

- CO2: - embedded in RF-CO2-lasers - mostly TTL-input capable of switching the laser output with some ten kHz

- diode-lasers: - current-modulation and/or PWM-switching for diode-lasers until some kHz

- diode-lasers: - AOM (AcoustoOpticalModulator) switching until some hundred kHz

- ...


6. controlling the output-power:

- generating geometrically defined pulses from the XY-clocks of the CNC-controller:

XY-pulsegenerator

- calculating the needed power relative to moving speed of the laser focus

- ...

air jet

While not strictly necessary, many laser cutters have a blow a jet of air at the point being cut. Is it better to use (a) relatively cool room-temperature air, or (b) hot air?


Usage

CO2-laser cutting acrylic:

CO2-cutting encoder-disc


Diode-laser:

- cutting:

VDX-RepLas2.jpg Hase celtic.jpg

- brazing / hard soldering:

hard soldered gold-paste


Multi-Diode-Laserhead:

- similar to an inkjet-printer, where many nozzles ar aligned in an array to print many dot-lines synchrone, you can align multiple diode-lasers in an array to process parallel lines simultanuous.

With falling prices of laserdiodes it should be possible to build a head with 8 hating/burning spots in a line with a distance of 5mm (diameter of typical small collimator-lenses) between them (or less, when arranging in a zigzag-array) in a DIY-range below 1000 Euros.

With a software separating the processing data for the single lasers you can speedup the time per sheet along with the count of lasers ...

Capacity/Specifications

Requirements

Power
Nitrogen tank or clean dry compressed air.

Cutting speed

The primary factors affecting cutting speed v are laser beam power P, the material being cut and its thickness h. The dependence of v on P and h is approximately proportional, i.e. severance energy P/hv is approximately constant for a fixed material and cutting process. Severance energy can be thought of as the laser beam energy needed to make a cut of 1 mm2 area (i.e. 1 mm cut length × 1 mm thickness). Note that 1 Watt power is 1 Joule of energy per second, so a 36 W laser should cut 3 mm acrylic sheet (P/hv=1.2 J/mm2) at the speed of about v = P/h / (P/hv) = (36 W) / (3 mm) / (1.2 J/mm2)=10 mm/sec.

Severance energies (10.6μm CO2 laser) from [1], p. 159
Material Typical severance

energy (J/mm2)

Min-max severance

energies (J/mm2)

Cardboard 0.5 0.2–1.7
Acrylic sheet 1.2 1–3
Plyboard 31 20–65

Health and Safety

Laser-goggles are essential when working with lasers!

This laser-goggles have blocking ranges of 700-1100nm (for diode-lasers and NdYAG) and 10600nm (for CO2-lasers)

Laser-goggles


Fumes and vapours are extremely toxic and carcinogenic!

You can absorb the toxic vapours by exhausting the fuming area through a charcoalabsorber - e.g. the disc-shaped filters often used in deep fat fryers, or filtering units for soldering ...

Common laser-fume absorbers are really big parts but much more capable than absorbers for soldering vapours:

Laserrauchabsorber.jpg


When using inert (and other) gases in an enclosed room you have to test for leakage or monitor the oxygen-concentration in the room.

Similar projects

There are some similar projects to create an Open Source laser cutter, some of them already shipping devices:

External links

  • Steen, Mazumder. Laser Material Processing, 4th ed, Springer-Verlag, 2010.
  • Retrieved from "https://reprap.org/mediawiki/index.php?title=Laser_Cutter_Notes&oldid=104373"