It is recommended to experiment a bit with focus distance and line spacing, it is fun and gives a lot of insight/experience.
In my example, there are 2 black boxes, consisting of 10mm lines. One box has 100 lines, the other consists of only 50 lines. But at the same time as I halve the number of lines, I have “defocused” 2mm. This gives roughly a twice as wide line or better said focus point on the material.
That is precisely what you can also see clearly in @Kuth answer.
The “effect” also brings a halving of the process time. A defocus together with e.g. cross-hatch can also be used in some cases, I use it mostly for decorative effects.
Try it a little, it can be done with all machines.
Interesting, variation of life span of both CO2 and diode variants is complex. Dynamic voltage and current regulation that keeps laser in its safe operating area, enough cooling is next. Backflash from media surface hits laser causing heat stress shortening life span. CO2 water cooled can safely run 80-95% power, diode lasers over 30 optical watts, generally are air cooled with no voltage, current or thermal management. Running over 70% in high power mode significantly degrades laser useful lifetime. Generally when laser degrades below 80% of it’s original output it’s not viable. CO2 lasers have other gasses required to keep it stable. Helium is one of those, and it eventually leaks out seals in sealed lasers, lasers that have continuous gas flow are rechargeable. Many CO2 tubes can be recovered with refill of gas if starting filament is intact. As far as focus, defocusing can be done either direction. Depending on desired effect and material. With wood a mix of bees wax and carnuba wax rubbed on before lasing leaves minimal ash, and nice Carmel tone.
This is not entirely correct. Normal standard CO2 tubes have a non-linear power distribution / output over their nominal operating range. This means that a CO2 tube will have the maximum power effect, somewhere between 50 to 100% of the respective specified in mA. The tubes I have tested had their maximum power at approximately 65-75% of their rated power, all additional energy added did not increase the tube’s efficiency / power any more. Since energy cannot disappear without a trace, the additional energy added will most likely be converted to heat. Therefore, I consider it very relevant to achieve the longest life of your tube, to know its power characteristic. That is to say, a 60 Watt rated tube with its specified maximum operating power at 23mA, will normally be significantly below that, here with my current tube this value is between 16 and 17 mA. I am convinced that sticking to your tube’s real max output will have a life-extending effect on the tube.
It should be noted that I do not have a laser power meter, but only measured the laser’s physical effect/impact in acrylic, which gives an excellent realistic picture of your power curve.
Hey there! After testing this I just had a few more questions - I would assume that based off of this test, from left to right would be negative focus to focus?
Maybe I am just over complicating things - But would it also benefit to run a material test before or after a focus test so that I know what speed/power I need to use? Or once I find my focal points would it be universal?
In my head, having this test in front of me, I would probably run a job with this at either notch 3 or 4. This being at 200spd/9.7pwr with a 0.040 interval (which Im sure I could increase with spd/pwr.)
Please let me know your thoughts - even if they have to be elementary lol
I thought 4 or 5 due to the engraved texture of the surface and how does that bright edge around the squares look to your eye in terms of quality finish?
First, sorry for my late reply.
From my point of view, negative focus can be interpreted as cutting focus, carving focus, or even focus below the face of the material.
Theoretically, yes.
Perhaps you are being meticulous.
From my experience, the results obtained in material testing are not always reflected in the final product. This is because the test is usually conducted on a very small area, and the heat generated in this small area sometimes produces different results than in larger areas. To better understand, while in a small area the laser passes several times over the same zone (spaced by the DPI or LPI (Dots per Inch or Lines per Inch) value), not giving the material time to cool down, in a larger area when the laser passes over the same zone again, the material has already cooled, resulting in a different tone than in the test. However, this behavior varies greatly between materials.
Some people are so meticulous that they run multiple tests with different settings to find the ideal one. And in my opinion, that’s testing materials specifically for a given job.
I didn’t quite understand that, but only because I have difficulty translating correctly.
Basically, this issue has to do with the fact that you can increase the durability of the laser by decreasing the operating time.
I’ll give as an example my laser diode which has a focal spot of 0.08 at 20mm. If I lower it to 18 or 19mm, my focal spot will become 0.1 or 0.2. With that, I can increase the LPI value (Otherwise, the lines will overlap (burning twice where they overlap, affecting the final result), which will at least reduce the number of passes (per inch) = fewer passes, less time the laser is operating. And eventually reduce the laser power if you don’t want the laser to penetrate the material so deeply. (Less power = lower laser demand)
I hope I have been able to clarify things in some way.
I understand the material test could have different results as between the last time we spoke and now I had stumbled upon that! I have some IP issues going on at the moment so I got side tracked. But its all slowly making more sense to me. I want to get to a point to where when I get a job ticket I can just quickly dial things in and get the job out without wasting material. Plus, it would be nice for the jobs to be put out at a quality that I can be proud of.
I will get there! Just missing small pieces of the puzzle
Me too, but after all this time I still make a lot of mistakes and ruin material.
Anyway, for that, it will be necessary to take notes and save all the settings that really matter. If you are looking for diversity and quality, in my opinion, you will need the equivalent of a database! But yes, it starts with having a comprehensive knowledge of the combination of materials, power, speeds, etc.
As a rule, higher speeds are prone to a greater probability of defects.
but I think the effect is very clear)
