TTL Engineering Systems

Laser Cut Quality Guide

Optimize the cut quality for any material using the following steps:

  1.  Use the closest known settings to the material you are trying to cut.
  2. Verify that the lens and/or window is clean and in good condition.
  3. Verify that the nozzle is in good condition and is centered properly.
  4. Create a test part that has interior and exterior features.
  5. Adjust the focus either up or down until the best possible edge quality is visually achieved.
  6. Adjust the gas pressure up or down until the best possible edge quality is visually achieved.
  7. Begin by setting feed rate 10% below the recommended setting. Adjust the feed rate up in increments of 5% with each improving test part. When the cut begins to visually degrade, set the feedrate back to the previous setting achieving optimum edge quality .

Balance head levels and gas flow:

Cutting mild steel with a laser is a balance of how much material is heated up with the laser beam and how much assist gas flows through the cut. Heating up too small of an area or not having enough assist gas flow through the cut will result in the kerf (width of the cut) being too narrow.. Heating up too large of an area or having too much assist gas flow will result in the kerf being too wide.

Examine the cut

  • Look at striation marks
    • Top or bottom of cut
    • Leading or lagging
    • Oxidation
  • Cut angularity
  • Dross

Factory cut chart settings

The following show 12, 6 and 3.2 mm (1/2″, 1/4″ and 10ga) mild steel cut with oxygen on a 2kw fiber laser and examples of the same part cut with 1 variable changed to show how it affected the cut quality. The examples of the adjustments made will be similar for any CO2 or fiber laser cutting mild steel with O2.

Kerf too narrow

Kerf too narrow common characteristics visually result in a smooth cut edge on the top with a lack of oxidation on the bottom and/or heavy dross.

Kerf too wide

Kerf too wide common characteristics visually result in a rougher cut edge, more corner burning of the part, increased angularity on the cut edge and occasionally dross.

[Final installment in a series of three articles comparing metal-cutting lasers.]

In two previous articles we examined the differences in electrical costs and resonator operating costs between the various types of metal fabrication lasers.
We can recap the previous articles by looking at chart #1 below. It shows the operating cost over 8 years for a 4kW laser.

Chart 1
We can also see by chart #2 the actual differences of energy consumption for solid state lasers.

Chart 2
The differences in the operating cost are based on the maintenance and the efficiency of the style of laser being used. Chart #3 illustrates the different efficiencies for the various cutting lasers.

Chart 3
The final piece of the puzzle for laser processing is the cutting speed. Approximately 80% of the time while the program is running the laser is cutting, this is the majority of the processing time. The cutting capabilities of the laser is directly proportional to the beam quality and beam waste of the laser. Chart #4 illustrates the characteristics for the four cutting lasers.

Chart 4
Things to be aware of are the mode quality, beam waste, spot size, and depth of field. The depth of field generated by the laser will affect the cut quality and the thickness of the materials processed. The depth of field is the usable portion of the unfocused beam. This occurs on both sides if the beam waste (smallest spot size). As the focal position is shifted up and down to enhance cutting the operator must always keep the material within the depth of field or the material will stop cutting.

Nowadays 3D printing isn’t the only manufacturing technology found in the maker scene. Once strictly used by industrial manufacturers, laser engraving is increasingly adopted by small businesses, product designers, makers, and even hobbyists.

In some cases, a laser engraver might prove to be the most advantageous manufacturing technology for your specific application.

Here’s everything you need to know about laser engravers before pulling out your wallet.

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