Frequency

[Dave Lock]

Hi all,

I have had my laser for some time now and produced many pieces with successful results and without any real quality issues that I couldn't deal with by playing with speed and power settings.
I have however started to cut some 1/8" ply more regularly which results in a bit of charring, so I thought I would investigate the implications of changing the frequency setting.
The frequency setting on my chinese laser thus far has always been set at 20,000. It is labelled as PWM.

I often see posts here where a frequency is mentioned in your settings, and it seems that 5000 I regulary mentioned as the max on an Epilogue.

Am I comparing the same setting here? and why would the frequency on a Chinese machine be so different?

Over the next couple of days I am going to try some different settings. Could anyone advise the pro's and con's of making frequency changes.

As mentioned I don't have any specific problem that I am aware of but it would be nice to know how I could make changes of frequency work for me.

Advice/comments appreciated.

Dave.

[Chris J Drew]

pro: Lower frequency means less heat buildup in the cut, so less charring.
con: Vertical lines on the cut edge may become more pronounced.

With plywood it's often the adhesive between the ply which gives you issues, rather than the wood itself.

[Dan Hintz]

And don't let numbers fool you... the max ppi on my ULS is 100. It's somewhat obvious this is meant as 100% of whatever the max frequency or pulse width is (which the user doesn't necessarily know or care about), but certainly has no immediate connection to the 5,000 or 20,000 listed earlier (which is the maximum pulse frequency, 20kHz, of the Chinese unit). The point is, understand the generalities of how to work with the materials (such as lowering ppi for plywoods) rather than the specifics, and you'll find working with any machine much easier.

[Stuart Orrell]

Hi Dave,

I too have wondered about this when cutting 3mm Baltic birch laser ply. I tried adjusting my frequency with many different settings but didn't see any visible difference on the cut. So I'm not sure if this is is a variable on the Chinese machines. (Mine is a LS6040 and I too use lasercut 5.1).

I seem to remember that in the settings, there is a number called pulse unit (from manual: "distance the laser head moves when the control system output a pulse") Mine is set at 0.007943125. I'm assuming that this is mm per pulse = 0.00031272 in per pulse which then = 3000 ppi.

I can't remember now but I may have tried changing this too. I may have not though in case it did something unexpected. Memory loss.......

I did end up not changing anything and got my best results but making a few passes at a lower power. This still left a bit of a brown finish but much better than my previous atttempts with a single pass to cut through.
I think most of the charing is from the glue between the plys. The wood itself wasn't bas at all.

Good luck with your trials. If you find anything, please let me know.

Regards!

[Scott Shepherd]

And don't let numbers fool you... the max ppi on my ULS is 100.

It is? I thought it was 1,000. It says PPI and it goes to 1000. I know there is a big different in running something at 100 PPI and 1000PPI.

Please explain in terms a 3rd grader can understand :)

[Dan Hintz]

Sorry sorry sorry... I was thinking in terms of 100% power in increments of 0.1. The point I was trying to make is still valid, just ignore my stupidity :o

[Scott Shepherd]

:::marking this day on calendar:::::

August 12, 2009. Dan was wrong on a technical issue.

Got it :)

Whew, that's like a Solar Eclipse :)

[Brian Robison]

FYI, I try to vary my htz dependent on the speed as well as materials.

[Dan Hintz]

:::marking this day on calendar:::::

August 12, 2009. Dan was wrong on a technical issue.

Got it :)

Whew, that's like a Solar Eclipse :)
Well, there was the Perseid meteor shower last night... :D

[Bill Cunningham]

Well, there was the Perseid meteor shower last night... :D

Ehyup!! and it's on for the next several days.. This may not be your week for techy stuff :D