Laser Marking Techniques: Unlocking the Potential of Precision | MachineMFG

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Laser Marking Techniques: Unlocking the Potential of Precision

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I. Startup Procedure

Startup Procedure for Fiber Laser Marking Machine

1) Activate the main power air switch

2) Start the computer

3) Turn on the control power key

4) Activate the red light

5) Launch the software and import the marking design

Startup Procedure for Semiconductor Laser Marking Machine

1) Activate the main power air switch

2) Engage the emergency stop button

3) Turn on the control power key switch (water tank operation)

4) Wait for the water tank to start, then boot the computer

5) Turn on the Q-drive power supply

6) Engage the laser power switch, press START to indicate WORKING status, adjust current levels

7) Activate the galvanometer switch and the red light switch

8) Launch the software and import the marking design

Startup Sequence for CO2 Marking Machine

1) Turn on the main power air switch

2) Start the computer

3) Turn on the control power key

4) Activate the enable button

5) Launch the software and import the marking graphics

Note that the shutdown sequence for each machine is the reverse of the startup sequence.

II. Corrections for Software

1. Set the regional size

The regional size corresponds to the maximum actual marking range of the galvanometer. Enter the software parameters F3, and change the regional size in the parameter table based on the focal length of the flat field lens.

  • For f=100mm, the regional size is 60*60; for f=160mm, the regional size is 110*110;
  • for f=254mm, the regional size is 175*175; for f=330mm, the regional size is 220*220;
  • and for f=420mm, the regional size is 330*330.

2. Selection of the Galvanometer

Draw a rectangle within the workspace, observe the placement of the rectangle after the red light indicates. If it aligns with the direction in the diagram, then choose Galvanometer 1=X, indicating that the galvanometer output signal 1 from the control card is the x-axis of the coordinate system. If not, select Galvanometer 2=X.

3. Preliminary Dimensional Calibration

On the steel plate in focus, square lines equal to the region’s dimensions are marked, and their dimensions are measured.

If the actual marked dimensions are smaller than the design dimensions, increase the scalar parameter value; otherwise, decrease this parameter value.

When setting parameters, you can directly open the dialog box behind the scale, input the software set size and actual marked size, and the software will automatically perform proportion scaling.

4. Barrel Correction

Draw a square in the work area equal to the area size, turn on the red light indicator, and observe the convexity or concavity of the square.

If it is convex, increase the coefficient in the table; otherwise, decrease it. (Adjust the X and Y coefficients according to the specific deformation.)

Adjust the numerical value until the curve becomes a straight line. The adjustment range for this value is 0.875–1.125.

5. Trapezoidal Correction

During the square marking process, situations where opposite sides are parallel but lengths are unequal may occur, requiring changes to the trapezoid ratio parameters in the table.

With the horizontal direction as X, if the square is longer on the top and shorter on the bottom, increase its coefficient; otherwise, decrease it.

Sometimes, when the direction is unclear, you can first increase the ratio parameter somewhere, observe the red light indicator, and then determine the correct direction of change. The adjustment range for this value is 0.875–1.125.

6. Parallelogram Correction

During the marking process, a square may have equal side lengths but non-perpendicular angles, forming a parallelogram.

Use a right-angle ruler and high-precision caliper to measure, and change its ratio parameter until it becomes a right angle. (Test the diagonal length.) The adjustment range for this value is 0.875–1.125.

Dimension Calibration

Due to discrepancies between software-set dimensions and actual marked dimensions, it’s crucial to calibrate measurements to minimize errors.

This process involves marking a square on the steel plate at the focal point, then using high-precision calipers to measure the lengths of its sides and diagonals.

Should the marked dimensions differ from those indicated by the software, the scale parameters need adjustment. The method of adjustment mirrors the preliminary dimension calibration process.

III. Marking Parameters

Current:

The current configuration of the laser power supply directly affects the energy output of the laser. Greater energy allows for an increase in marking speed and light-sound frequency.

However, bolstering laser energy while keeping other parameters constant can lead to workpiece discoloration, blackening, or edge burring, which are not suitable for precise engraving requirements.

Frequency: 

This refers to the number of laser emissions per unit of time. Under the same current, a lower frequency results in higher peak power and greater laser energy output.

Lower frequency means each point is exposed for a longer time, which in turn deepens the engraving at each point, making it suitable for depth marking. Higher frequencies improve the continuity of lines and result in smoother, more even marking.

Speed: 

This refers to the distance covered by the laser per unit of time. Speed generally correlates with frequency; they must be well-matched to avoid discontinuous lines when the speed is too high or frequency too low.

Light-On Delay:

This is the delay time for the laser to start once the galvo scanner has located the beginning of the marking position. Properly increasing the delay can eliminate the matchstick-head effect, but a delay that’s too long can lead to a lack of continuity at the start. A typical setting is 50-100 milliseconds.

Light-Off Delay: 

This is the delay time for the laser to stop once the galvo scanner has located the end of the marking position. Increasing the delay appropriately can eliminate closure defects at the end of marking, but a delay that’s too long can result in a matchstick-head effect at the end point. A typical setting is 300 milliseconds.

End Delay: 

There is a period from when the light-off command is issued until the laser is fully shut off. If the delay is too short, there may be trailing points (the laser hasn’t shut off, but the machine moves to process another object). A typical setting is 300 milliseconds.

Corner Delay: 

This is the delay time between each segment during marking. A delay that’s too long can cause over-marking at the corners, while a delay that’s too short can round off the corners. A typical setting is 100 milliseconds.

Defocusing: 

In general, positive defocusing refers to the focal point being below the work surface, while negative defocusing refers to it being above. The degree of defocusing depends on the material being marked and the desired effect.

IV. Prototyping

Generally, before prototyping, the processing surface of the sample must be at the focal point, where the beam diameter is smallest and the energy is highest.

When finding the focal point, you can first lower the current and reduce the photoelectric frequency, making the laser emit continuous light, and adjust the position of the workbench to the brightest point of the light, which is the focal point.

Before prototyping, it is best to use a material similar to the sample material for initial testing. After achieving the desired effect, apply it to the sample. If this is not possible, test the effect by using small letters on the sample.

For speed selection: during the processing, if rapid machining or assembly line processing is required, adjust parameters such as speed and fill density first to ensure completion within a customer-satisfactory time frame.

Then, adjust parameters such as current and frequency, assuming you have achieved the desired sample effect.

For frequency selection: generally, first draw a small square and use different frequency bands, observe which frequency band yields the best result, and then fine-tune within this frequency band.

If depth is required, low-speed, low-frequency, high-power marking should be used. However, during depth marking, the depth is not always deeper with slower speed, because there is more accumulation when the speed is too slow.

The laser’s energy is not enough to completely vaporize it, causing the deposits to pile up on the surface of the workpiece, preventing the laser from penetrating. This does not only prevent deep marking but can also roughen the workpiece surface, wasting laser processing time.

For defocusing selection: generally, marking only needs to be done at the focal point. However, for deeper markings (0.1mm or more), positive defocusing should be used. For materials such as stainless steel that need to be marked black or colored, negative defocusing is needed.

After marking a deep sample, check first if there are any burrs. If burrs are present, the power is too high, and it can be appropriately reduced. Or, after a few high-power markings, use high-frequency, low-power rapid sweeps to reduce burrs.

If the sample needs to be filled, test it on a metal nameplate before marking to check if the fill effect is good. Adjust the line spacing and whether outline is required based on different needs. When filling a deep mark, you can also adjust the margin to reduce burrs.

If stripes appear in the fill pattern, it is due to irregular internal point arrangement and unstable energy, generally it can be improved by changing the filling method to unidirectional filling, the arrangement of the points will be relatively more orderly.

During the defocusing marking process, inconsistencies between the color of the edge and the color of the inside fill can occur. This is because the size of the light spot after defocusing tends to be larger than the set margin, causing the edges to glow. To avoid this, do not enable the outline during filling.

When marking precision samples, a pinhole light barrier can be added to the optical path. The barrier filters out uneven areas, improving the quality of the light spot, though laser energy will decrease correspondingly.

When making a master sample, position the marking pattern in the center of the work area. Secure the sample, aligning the red light indicator with the edge of the sample face. Adjust the workbench to move the red light to the specified marking position to prevent the text or graphic from being offset.

V. Safety precautions:

Lasers are high-brightness, high-power, high-energy beams. Do not directly touch the laser source, which is class 4 in output power. Do not look directly at the laser or the marked sample.

When marking highly reflective materials, use safety glasses (different glasses for different laser wavelengths) to prevent harm to the eyes and skin and avoid medical accidents.

Exposure to a CO2 laser beam can cause skin burns. Staff operating this equipment must remember not to extend their hands into the laser’s range.

The water tank of the semiconductor marking machine needs to be changed and cleaned regularly. In hot summer weather, set the water tank temperature higher (around 26-28 degrees Celsius) to prevent condensation on the water pipe due to a large temperature difference, affecting the light output.

The lenses of the marking machine need to be cleaned regularly. Dust on the lens can block the laser and cause lens burns. Use 99% purity alcohol and a damp soft cloth or a special lens cloth to clean the focusing lens.

When marking high-reflective materials like copper and aluminum, do not place the processing pattern in the center of the work area to avoid reflected lasers burning the lens.

For semiconductor marking machines, when changing the current size, adjust slowly to prevent the voltage from not responding in time, and the power value during marking does not reach the expected value.

Do not reverse the positive and negative poles of the laser power supply. During the transport of the semiconductor laser, short-circuit the positive and negative poles to prevent static electricity from puncturing the module.

Turn off the power when replacing electrical components to avoid puncturing electronic components (such as galvanometers or marking cards) through live plugging and unplugging.

After the galvanometer power supply is connected, test the voltage to avoid mismatch or reverse polarity that could burn the galvanometer.

VI. Setting of the Chiller:

Hold down the SET button on the water tank for 5 seconds, and it will automatically switch to the temperature setting. You can adjust the temperature using the up and down keys.

Generally, in high summer temperatures, the water tank temperature should be adjusted to within 5 degrees of room temperature to prevent surface condensation from affecting light output due to a large temperature difference inside and outside the water pipe.

However, in winter, when the temperature is low and the air is dry, the water pipe is not easy to condense, so the temperature only needs to be set around 20 degrees Celsius.

After setting the temperature, continue to press the SET button, and the system will automatically switch to the temperature difference setting.

Adjust its value using the up and down keys. Generally, the temperature difference is set between 2 and 5 degrees.

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