Freq what is it and what does it do

[Bert Kemp]

I see this term Freq 500 or 700 ect ect used in setting for Epis and trotec's a lot
what does it do?
Is there something similar on a Chinese machine?

[Kev Williams]

"Epis" comes up zilch on google-?

On a Trotec, assuming an RF laser, "Freq" most likely is a 'new' term used in place of DPI/dots per inch. I've always been a bit perturbed at the industry names for, literally, the spacing between where a laser beam fires. In the X axis, an RF laser truly fires in dots-per-inch spacing, and the spacing is exact regardless of running speed. However, in the Y axis, the spacing is not in dots-per-inch, but engraved lines-per-inch. Yet rarely if ever have I ever heard Y axis laser spacing referred to as 'lines per inch', it's always DPI or PPI (pulses per inch, same thing), or 'GAP' as Chinese software (mine anyway) calls it..

Fiber lasers, depending on their power and controllers, typcially fire between 30kHz and 80kHz. But whereas C02 laser fires X amount of times per a given space, regardless of engraving speed, a fiber laser fires X amount of times PER SECOND, regardless of engraving speed. This means that while a fiber does essentially fire 'dots per inch', the dots per inch changes with engraving speed. I've spoken to many on this board who believe that the lower the frequency the more deep engraving power you have. But that's not always true. For instance, engraving at 1000mm/second at 30kHz is exactly the same as engraving at 2000mm/second at 60kHz, because the actual fired dots per inch is equal in both cases. However, because a fiber fires so quickly, the on-time of the laser increases with slower speeds, which in effect closes the gap between the actual fired 'dots'. And then there's the lesser power density applied to the work at 2000mm/sec vs 1000mm/sec... So deep engraving involves tweaking power, frequency and speed ratios to attain the best burn. When the laser is showering sparks like crazy, you've hit a sweet spot for quick deep engraving :) (usually :D )

[Bert Kemp]

Ok Thanks Kev I get this. That Freq or "DPI" will have an effect on engraving but I don't see were it would make a difference in cutting. I'm referring to the "can I cut 1/4" Baltic Birch with a 30 watt laser" thread. Where the OP changed his Freq to cut different thickness's of BB.
When cutting doesn't the laser fire continuously ?

[Bruce Volden]

I found this, kinda clears things up??
https://www.engraversnetwork.com/support/universal-lasers/laser-how-tos/dpi-vs-ppi-laser/

[Bert Kemp]

So dpi is scan gap on a Chinese and PPI is controlled by the laser on a Chinese machine. I knew scan gap but PPI is the Freq on Trotec and epis?
Guess it doesn't really matter if theres no way to adjust it on my machines , never really gave it much thought as when I say cut it cuts LOL and I can adjust the scan gap for engraving. To tell the truth I don't think I ever changed the scan gap as I have always be happy with the engravings.:)

[Steve Utick]

I see this term Freq 500 or 700 ect ect used in setting for Epis and trotec's a lot
what does it do?
Is there something similar on a Chinese machine?

There is no equivalent on the glass tube Chinese machines. It's the frequency of pulses the laser fires when you are vector cutting. From the Epilog manual:

Frequency: The number of laser pulses that the laser fires per inch of travel. The frequency is set in the dashboard and can be adjusted from 1 to 100. A lower frequency number will have the effect of less heat because fewer pulses are being used to cut the material. Lower frequency rates are helpful for products like wood, where charring is evident at higher frequencies. High frequencies are useful on materials like acrylic where a large amount of heat is desirable to melt or flame polish the edges.

[Mike Null]

With Trotec the terminology is Hertz for frequency. You might, for example, use your lowest Hz setting to perforate paper instead of cutting it.

For engraving the Trotec has 6 dpi settings beginning at 125 and topping at 1000. I do a lot of work at 333 which provides an excellent image; particularly on plastic.