Can someone explain frequency.

[George McGinnis]

I have a epilog radius 30watt without air assist and have charring problems when cutting. I have read other posts about freq. Is this the same as rate?

[Frank Corker]

George, the manual for the Epilog is incredibly detailed and gives excellent recommendations for frequency settings. If you don't have a copy, go to the website and download it as a pdf file.

Charring problems are always an issue and air assist most certainly helps when cutting. You can sometimes reduce this by doing more than one cut at a faster speed, trying to cut too deep means that the laser is having to run slower, the beam is in contact too long and it burns.

Frequency is the pulses that the laser fires at, doing products such as acrylic requires the settings to be at 5000 pulses per inch, doing wood this figure is reduced to 100. If you were trying to cut wood at 5000, believe me when I say, charring would be the order of the day.

[Doug Griffith]

To see see frequency in action, try vectoring a piece of paper at a VERY low frequency and full speed. At close inspection, it will look perforated. You can see the space between the pulses. Be there when doing it because paper tends to catch fire. Especially since you don't have air assist.

To cut through something that does not fuse back together (ie. wood, not plastic), you want each pulse to overlap just enough to keep the cut going and be smooth. Any more will "re-burn" the previous pulse and increase char.

[Rodne Gold]

The problem you will face with 30w is the inability to use low frequency effectively. The reason is that there is not enough power to pierce some thick or difficult stuff completely with each pulse , and thus you space the pulses close so that the material is heated enough to vaporise , ie the previous pulses put enough heat in the material so it's easier for the next one to get to a localised temp to vaporise the material and thus pierce. this creates a huge HAZ (heat affected zone) and will result in some charring.
Bear in mind , a laser cuts by what's called treppaning , it drills a series of holes to cut.
You might do better off with a 2 pass job , each at low freq and full power , then the laser has 1/2 the work to do each pass and can then vaporise the material rather than burn and vaporise. Change your focus to 1/2 way into the material for a 2nd pass.
If stuff chars , normally you cant ever completely eliminate it , but you can make is far less messy etc.
Often using a thin cladding like tacky paper or masking tape helps a lot too.. it allows the top and bottom surfaces and edges to be clean and thus it looks a lot better.

[George McGinnis]

I don't a slide bar for freq. but the rate is there is this the same as freq.?
I have tried adjusting it and it doesn't seem to help much. I only have speed - power - rate on slide bars 1 - 100 for vector.

Thanks George

[Peck Sidara]

George,

Rate is essentially the same as frequency. On older model Epilog's, rate was adjustable from 1-100. newer equipment it's frequency from 10-5K.

Generally speaking, the lower the rate/frequency the less pulsing of the laser. You want to use a high rate/frequency when cutting acrylic, this gives you better edge quality as the pulses are overlapped. When cutting wood, you want to use a lower rate/frequency, this gives you less charring as the pulses are more spaced out.

You should see a difference in edge quality when adjusting your rate from 10 to 100%. 10% will likely give you preforations.

It's also possible that you're seeing the charring regardless of rate adjustment because you don't have air-assist, you're limited to 30Watts and you're trying to cut something thick.