How do I check my laser output power?
First of all, you will need to have access to a laser power meter. We make a nifty little hand held unit that will measure power up to 250 Watts, but there are a number of companies that build laser power meters.
On a marking system, there are several power measurements that will provide helpful data about the health of your marking components:
- - Power directly out of the laser – you will need to gain access to the beam between the laser and marking head. This usually means removing some sort of protective shield from the beam path.
- - Power out of the marking head (with lens attached) – this means that you MUST ensure that the head is powered up and that the mirrors are centered. Again, there may be some form of guarding that will have to be removed or defeated.
- - Power out of the marking head (with lens removed) – same as above, but the marking head lens is removed. This test is useful to see how much power is being absorbed by the lens.
In each case, you will be using the DigScope utility that is installed along with WinMark. YOU CANNOT GET AN ACCURATE POWER MEASUREMENT WHILE MARKING! The nature of marking is that the laser is being turned on and off throughout the mark, and a laser power meter will just give an average power reading, not the actual output power of the laser.
If you are using Synrad’s Power Wizard (PW) to measure the power, remember to follow this procedure:
- 1. Initialize the PW: press the ‘Reset/Power’ button for at least two seconds. Verify that the readout displays 0 +/- 0.3 W.
- 2. Let go of the ‘Reset/Power’ button and place the PW target in the beam.
- a. Do your best to keep all of the beam on the target, otherwise the accuracy of the power reading will be affected.
- b. If you are measuring the power of the beam coming out of the head with the lens attached, place the PW about ½ way between the lens and the focal plane. Measuring the power at the focused spot will eventually damage the PW target.
- 3. Hold the PW in the beam until the unit beeps.
- 4. Take as many measurements as needed, repeating steps 1-3. Be sure to allow the PW target to cool if taking multiple readings. DO NOT cool the target by immersing it in any type of fluid – doing so will damage the electronics within the PW.
To measure the laser power:
- 1. Verify that the marking head mirrors are centered: either fire a mark from WinMark, or press the test mark button.
- 2. Close WinMark.
- 3. Put something non-combustible (like a brick) in the beam path to block the beam, while leaving enough room to get the power measurement tool into the beam.
- 4. Open DigScope and verify that you can vary the laser power and turn the laser output on and off.
- 5. Set the laser power to zero, and turn the laser output off.
- 6. To measure the output of the laser:
- a. Remove whatever shrouding is in the way between the laser and the marking head.
- b. Turn the laser output on, and slowly bring the power slider up to 100%, verifying that nothing is catching on fire and no one nearby is getting tattooed.
- c. Place the power probe in the beam and take the power measurement.
- d. Turn the laser output off and remind yourself to start breathing again. Good.
- e. Take another two or three measurements, letting the probe cool down as needed between readings.
- f. Calculate the laser power as the average of the readings. If you find that one reading is WAY off from the others, try taking the same number of readings again. Quite often such an error is caused by a part of the beam missing the probe target, but you will want to verify that the laser power is not just fluctuating wildly.
- 7. And that’s it. Be sure to replace all the shrouding and guarding that you removed to perform the measurements.
Now that you’ve taken all of your measurements (well… the laser power measurements… we don’t need yours…) what does the data mean?
- - For the laser, you should see a power value at or above the power rating of the laser. That makes sense… if you are using a Firestar t60 laser, and measure 45W at full power, there is something wrong. Less than rated power could indicate a cooling problem or an issue within the laser or RF supply. Another item to check is to verify that the DC power going to the laser is not drooping under load – check the DC voltage while the laser is firing at 100% duty cycle.
- - For the power measurements through the head (without the lens), you should see no more than 5% power loss compared to the readings of the laser itself. If you are running an older SH or DH head, this maximum normal value can be up to 10 or 15%, because of the extra optics involved. More loss than this may indicate that the expander is dirty or damaged, the head is misaligned to the laser, or that the galvo mirrors are dirty or damaged.
- - For the power measurements through the marking head lens, you shouldn’t see more than 5% loss compared to the readings without the lens attached. More loss than this would indicate that the lens is dirty or damaged.
Clean the optics using the procedures and materials called out in the hardware documentation. DO NOT use glass cleaner, Isopropyl alcohol, or other industrial cleaners. Refer to the Technical Reference section under Maintenance.
Other than checking the laser cooling, cleaning the optics and correcting any marking head to laser misalignment, there isn’t much you can do in the field to correct damaged or problem components. If you get to this point and haven’t fixed the problem, give us a call at 425 349 3500.
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