Reflective Metals Laser Cutting

Have you ever wondered how the sparkling gold ring you wear may have been engraved? Highly reflective metals pose a risk to operators using lasers to process these metals. Reflective metals are mirror-polished aluminium, copper, bronze, brass, and stainless steel. These metals are primarily used in a diverse range of industries.

It can maintain the cut quality if the fabrication is done with an appropriate laser cutter and prudence. It can also influence the metal thickness and, most significantly, destroy the laser lens.

Several techniques and metal laser cutters ensure the cut precision of reflective metals. What are these techniques? Let us explain in detail.

Why Cutting Reflective Metal Can Be Challenging?

Reflective metals are difficult to cut because their infrared light is capable of low absorption. Yet, solid brass and copper are efficient reflectors of heat radiation.

Pure copper, for instance, reflects over 95% of heat radiation(IR radiation) in its stable form(1 m wavelength). When using a laser to cut, the surface causes the beam to bounce back up the nozzle, possibly destroying the lens and inflicting additional damage to the bellows and optics.

Reflective metals lose reflectivity as they heat up. However, these metals better absorb the laser energy in melted form.

Common issue With Cutting Reflective Metals

When the laser, optics, and cutting process are optimised, a laser beam quickly melts the surface of reflecting materials—allowing it to interact with the more absorbent molten metal and commence an efficient, steady cutting process.

A poor laser/optical setup or non-optimal process settings might result in excessive laser dwell time with the solid metal and hence an excessive amount of back-reflected light. Too much reflection, in turn, leads to inefficiencies in the cutting process and probable optical damage.

The critical stage in cutting reflective metal is the onset of the process, notably the piercing phase, when the laser contacts solid metal. After the cut, the laser beam predominantly interacts with the molten material.

Can You Cut Reflective Metals With A Laser?

Yes, You certainly can. These metals can be laser cut despite the risks of reflected beams and damaged laser devices.

Most current laser-cutting equipment comes with a self-protection system. In the event of a laser beam reflection, this device shuts down the laser cutter, preventing the lens from being destroyed.

The entire system is based on the principle of radiation measurement. However, technological advancement has resulted in the development of laser cutters that are resistant to such situations, and these are fiber lasers.

Fiber Laser Technology

Fiber lasers are the most recent advancement in laser cutting technology. Fiber lasers use optic cables rather than mirrors and gases. They have become the most cost-effective and quickest technique for cutting thin sheets of reflective materials.

The reflective quality of reflective metals without using mirrors and fragile lenses poses little risk of injuring the cutting equipment, making it both faster and safer to set up.

With this in mind, it’s simple to see why fiber laser technology is quickly becoming a preferred way of cutting reflective metals.

Essential Factors To Consider While Fiber Laser Cutting Copper And Brass

1. Cup Speed

Reduce the highest feed rate the process can support by around 10 – 15%. It will reduce the chance of the cut extinguishing, causing significant amounts of beam energy to be applied to a material in its most reflecting state.

Begin at a slower rate than you are confident the procedure can sustain. Allow enough rest time to ensure the piercing hole is entirely through before repositioning the beam to begin the cut.

2. Gas Cutting

To improve process dependability, high-pressure oxygen (100-300 psi depending on thickness) is commonly utilised as the cutting gas for piercing and cutting copper. When oxygen is used, the surface development of copper oxide diminishes reflectivity. Nitrogen-cutting gas works well for brass.

3. Focus Position

Place the focus position as close to the upper surface as the cut quality allows for piercing and cutting. This increases the quantity of surface material that interacts with the beam at the start of the procedure, optimising the beam’s power density and resulting in faster melting.

Waterjet Cutting

Fiber Laser technology is incredible, but it has limitations. What are the constraints? Fiber lasers are most effective on thin sheets of up to 5mm thickness. If the sheet thickness exceeds 5mm, the cut roughness may result, and the cutting speed may suffer significantly. Even conventional CO2 laser technology can only treat aluminium up to a thickness of 10mm. Because waterjet cutting can treat materials with thicknesses of up to 230mm, it becomes a more realistic option.

Limitations Of C02 Metal Laser Cutter While Cutting Reflective Metals

The emission wavelength of fiber lasers is roughly 1.07 m, which is less than CO2 options. That’s why its laser light is more easily absorbed, and the shorter wavelength can be engrossed into a point 1/10th the diameter of a CO2 beam.

Hence, metal penetration becomes easy since the power density is increased. This comes handy while cutting metals like brass and copper. Cutting such metals has been difficult with CO2 or near-IR lasers with low peak power.

Recommended Cutting Techniques For Reflective Materials Of Various Thicknesses

 

The table contains a list of all reflective metals and cutting guidelines.

Metal Thickness Recommended Cutting Technique
Aluminum Up to 10

10-15

More than 15

Fiber laser

C02 Laser

Waterjet cutting

Brass Up to 10

10-15

More than 15

Fiber laser

C02 Laser

Waterjet cutting

Copper Up to 10

10-15

More than 15

C02 laser

Waterjet Cutting

Fiber Laser Cutting

Bronze Up to 10

10-15

More than 15

C02 laser

Waterjet Cutting

Fiber Laser Cutting

Titanium Up to 8

More than 8

 

Fiber Laser Cutting

Waterjet Cutting

Silver Up to 5

More than 5

Fiber Laser Cutting

Waterjet Cutting

Gold Up to 5

More than 5

Fiber Laser Cutting

Waterjet Cutting

 

The above chart shows  Fiber Metal laser cutting machine is currently highly effective at cutting reflective metals. When compared to other metal cutting procedures, the results of a fiber laser cutter are incredibly exact.

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