Cutting Laser Frequency?

[MC Design]

I was messing around last night (as i do and usually end up in trouble) and started to experiment with the laser frequency.

Has anyone tried adjusting this? Is it a bad idea? I see alot of Epilog users always talking about frequency changes?

[endcan]

Hi we have played with frequency change it doesnt seem to make a massive difference ... if we reduce to 500 it seems to be a little less smokey but remember how to reset it....

[Matrix]

I've also been playing with that setting.
We got hold of some PETG to test out as a more impact resistant alternative to acrylic, and I found some stuff on the net advising that lowering the frequency would help that material to cut better. Turned out the PETG wasn't too clever - lots of discolouring at the cut edges, though less so with the lower frequency.
The way I have seen it described is like this...

The laser is never continuously on when cutting - all cuts consist of very closedly spaced individual 'holes', one from each pulse of the laser.
Changing the frequency, then, is rather like altering the resolution of a photo when you use a regular ink-jet printer - a lower frequency will produce slightly more 'ragged' edges due to the pulses being spaced further apart. How much this shows on your workpiece will depend a lot on the material you are using, and the speed of the cutting head, of course.
The trade-off is that fewer pulses mean less heat pumped into the workpiece, and the laser tube is turned on for less time (so, in theory, may last longer and require less cooling).

But that's just the theory - I have yet to do any properly controlled experiments to prove it in practice with the kind of machines that we are using. I do intend to do this though, as our machine is very heavily used (6-7hours a day cutting 5mm ABS and acrylic) - and we do often have problems with heat warping smaller ABS parts that I'd like to minimise.
I'll report back if I get any promising results (or not!).

Steve.

[Spooky]

All checked,

I've just asked Chris and he said HPC have done quite a bit of experimenting with Frequency changes and haven't noticed too much in the way of either benefits or drawbacks so really didn't have much of a position on it being a good idea or not. Chris did mention that as it is unknown if it will affect tube life and should you decide to play with frequency settings then the responsibility will rest with the end user for the outcome.

For me personally the only adage that springs to mind is "The light that burns twice as bright burns half as long" but I have no evidence anecdotal or otherwise to say one way or the other.Logic would suggest more pulses will make a smoother edge but I'm sure there are limits before reliability is affected.

Sorry for delaying the thread but I'm sure you will understand that settings being changed other than basic ones can sometimes cause problems hence need to be run past Chris to ensure nothing is posted here that can damage peoples machines.

best wishes

Dave

[SimonMallas]

Hi,
How's the messing, I mean research? Done a bit of research on frequency but nothing really noticable or beneficial. The only thing it seemed to help with was cutting / kiss cutting delicate materials. Other than that, if the material is burning then speed it up, if youve max out on speed then look at turning down the frequency.
Twice as bright half as long, is right, you can cut things on less power for longer or more power cuts for not as long. In theory it talks up well, but in practise means nothing really.....
Cheers Simon

[Matrix]

Hi there,
Firstly, thanks Dave, for checking with Chris and reporting back - in retrospect, it was probably rather daft of me to assume that LaserCut would only allow 'safe' settings to be used.

The results of a little 'messing' so far agree pretty well with what Simon just said - very little noticable difference except for the most delicate of materials.
Apart from my earlier remarks regarding the PETG (which was not a useful material anyway) - cutting paper/labels for enclosure marking is the only place, I've noticed any benefit. We're cutting some pretty small, irregular shaped holes, and found that cutting too fast results in mis-shapen cuts (presumably the result of the 'stepped' nature of the control motors and backlash creating a bit of 'wobble'). As we are already using minimal laser power, reducing the frequency has allowed cutting at a slightly slower speed without too much heat being pumped into the paper (so it seems at least) - and the holes come out much neater.

On a related note - if I reduce our 6090PRO output power below about 15-20%, it seems that the laser does not fire at all - I'm assuming that like, say, a flourescent tube, a minimum 'energy' is required to initialise lasing, and this is perfectly normal (no problems at all with the laser under all other conditions). Anyone else have any thoughts on that? (sorry if a little off-topic).

[SimonMallas]

Hi matrix,
Ya spooky is right the tube does need some power to fire up, it tends to be around the 10% mark.
Dave are you saying that you've got 30% more cut speed by changing the frequency to ?? on what material??
Cheer Simon

[Spooky]

I'll mail you direct about it Si

[SimonMallas]

Hi Dave,
May have a Drop of spare time in the morrow. Fancy fiddling with your frequencies : ) lol any chance for the settings?
Cheer Simon

[Spooky]

Sounds good Si

I missed Chris's call today as I was driving and me phone was on silent

If I give you a yell at work about 12 to 1 ish?

best wishes

Dave