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Laser power vs. real laser efficiency.

Laser power vs. real laser efficiency.

When you plan to use a laser for a laser cutting or laser engraving it is quite obvious that more powerful laser – the better but even that might not be suitable to make your dreams come true.
So here is a case – more powerful does not simply mean more efficient.

For example if you want to cut transparent acrylic with 445 nm it is simply not possible with any laser power – the reason is simply – this wavelength goes through the material and does not interact with it.

Let me explain what matters when you do laser cutting or laser engraving.

  • Laser power.
  • Laser wavelength.
  • CW / impulsive mode.

However it is not all. It is relevant to the laser but what about the material.

It matters what material you are going to cut and what properties it has besides its shape and thickness.

There are some properties of material that should be taken into account:

  • Color.
  • Density.
  • Heat capacity and thermal conductivity.
  • Absorption level for particular wavelength.
  • Burning / melting temperature.
  • Sensitivity to oxidation.

So when you plan to engrave or cut you need to understand how there properties will effect engraving or cutting process.

Let me explain in details.
Color – if you use a laser in visible light spectrum then the darker the material the better it will be engraved of cut. The reason is simple – let light will be reflected from the material and more power will arrive to the engraved spot. Also if it is transparent – then the laser will not simply interact with the material at all – it will go through.

Density – very important property – for example if you are going to cut PVC or PLA it will be cut much easies comparing to hard wood. More densed material is – more power you need to cut it through.

Heat capacity and thermal conductivity – for example if you want to engrave on wood or plywood it will be done much easier comparing engraving on metal surfaces. For example, silver, copper and gold are very good thermal conductors and that is why more power is required to engrave in these types of metals.

Absorption level for particular wavelength – it is very necessary to know that some materials absorb some wavelength much better. For example, aluminum is more sensitive to 800 nm wavelength. It means that due to structure of the atom and molecules more energy can be absorbed in different wavelength.
material wabvelength Absorption

Burning / melting temperature – very simply property. More melting temperature you have more power you need to melt the material. For example burning temperature of aluminum is about 650 C while aluminum oxide (Al2O3) is more than 1000 C which makes engraving an aluminum plates more complicated process since you need to burn Aluminum oxide first before engraving on aluminum.

Sensitivity to oxidation – engraving is a process of an oxidation of the material in open air. It means that for example engraving on gold is simply not possible since the gold does not interact (oxidized) on air at all. That makes this process impossible in chemical point of view.

Hope that this info will help most laser makers in their endeavors.