Is laser math?

[Angus Hines]

Relative ????

Meaning if I do one job at 80/spd and 8/pwr.....will I get the same effect at 100/spd and 10/pwr

Or do I need to do the trial and error thing in order to get the job up to 100%spd?

[Scott Shepherd]

I believe the answer is no. I recall reading in some manuals that one is relative, one is not. Seems like speed was relative, power was not, but I could be mistaken. It's been some time ago when I read that.

[Joe Pelonio]

Scott's right, the math doesn't work, plus the frequency and resolution get mixed in to throw it off even more. Lot's of trial and error and keeping careful records of what works for next time, using the manufacturer suggested settings as a starting place.

[Gary Hair]

I am sure there is a way to set up a linear progression of the power/speed ratio but that is beyond me. It's definately not something where you go up a certain percentage on both to get the same result, I wish it were that easy. What I have found for most things I engrave is that I'll start with 100% power and reduce speed until I get the result I desire. Some substrates, like paper, are just the opposite - start at 100% speed and increase power to get to the result I desire - unless vectoring, then I start at 10% speed and 1% power and only increase power.

Gary

[Shane Turner]

The main reason this wont work is the nature of the materials you're engraving. The materials will behave differently if the laser is on them in a short powerful burst or a longer weaker one. The total power may add up the same but the effect will be different.

[Angus Hines]

Thanks guys for clarifying that.....

[Rodne Gold]

We always use the fastest speed possible , the GCC machines perform as well at 100% speed as any other. My prime objective in any lasering is to reduce cycle times while maintaining acceptable quality. I often reduce the cycle time of an object 1/2 of what it originally was by using various strategies.

[Craig Hogarth]

I am sure there is a way to set up a linear progression of the power/speed ratio

I compare it to cooking a turkey. Increasing temperature doesn't speed it up, it only ruins dinner.

[David Hirschfield]

I set up a type of template which graphs speed vs power, one for cutting and one for engraving. Each has a graph for the typical materials I use and the thickness when cutting. Look like rectangular protractors 4" x 9" with a line drawn out from the origin plotting power vs speed. The lines drawn are a sort of average of the points I plotted based on actual values. I did it to determine maximum speeds and at which point my 60W is too weak.

But, the data I used is derived from actual results from my table and my material suppliers. These will drift as my mechanics, laser and PS age. Each brand of acrylic will vary.

The caveat is that one has to realize that these are rules of thumb, more like start points. And usually I will run a sample starting from the template and adjust from that. I'm a visual person so it helps to have a visual representation of the levels required for all my materials in one glance.

While making it, I wondered if there was some sort of "grey card" we could use on a laser like one uses in photography to set exposure as light varies.

Theoretically, it could be software that allows you to enter a response curve from each machine for the materials you use to cut and engrave. If you are familiar with photo RAW conversion software, it allows you to enter variables because each copy of the same model camera is different, even from the same production line.

The response curve can be based the depth cut at particular power/speed settings entered into the software. It would be simple to then have a universal factor that can be changed to account for deterioration in power over time.

One would then choose the material/thickness to cut/engrave(depth) and the particular machine and the settings will be there. This could apply to marking as well.

[Darren Null]

We always use the fastest speed possible , the GCC machines perform as well at 100% speed as any other. My prime objective in any lasering is to reduce cycle times while maintaining acceptable quality. I often reduce the cycle time of an object 1/2 of what it originally was by using various strategies.
Would you consider starting a new thread highlighting some of these strategies? Being down at the 10W end, it would be of intense interest to me in particular, but it'd be useful for anyone with an engraver I should think?

[George Elston]

Another fly in the ointment, especially with low power lasers is convergence. I recently was trying to cut some 1/2" hard wood, I knew I could cut 5/16" with two passes, so I figured I could cut 1/2" with three or four. No Go. Problem was convergence, (see image) when I lowered the laser to get the additional depth all I did was etch (burn) the area adjacent to the cut line, and not get any additional depth. In checking the depth of field for the lens I found that what I was doing was tunneling the beam and effectively cutting my power by 3/4, (area reduces geometrically by pi as diameter reduces). So, you can't always figure that if you can cut half way through in one pass, you can get all the way through in two.

[Garry McKinney]

Hi Angus,

See if I can help. When we purchased our ext I talked to a tech who told me the simple reason it isn't.

Although the power works in liner progression, the speed doesn't. The movement of the machine is not on a liner scale, which makes it impossible to do a direct liner progression.

Garry

[Gary Hair]

Hi Angus,

See if I can help. When we purchased our ext I talked to a tech who told me the simple reason it isn't.

Although the power works in liner progression, the speed doesn't. The movement of the machine is not on a liner scale, which makes it impossible to do a direct liner progression.

Garry

Garry,
That's close, but not exactly true. The speed of the machine is linear. If you set 100% speed, you get 100%, it you set 50% you get half of the 100% speed. The caveat is that speed takes a bit for the laser to reach so on a small piece you may never truly hit what you have set. There is a ramp-up and ramp-down time on any laser and the higher the speed the longer that time will be. One way they make up for that is by moving the head past the actual area to be lasered. That's why you get 3" of movement even though you are only engraving 1/2" of area. Even though the speed is adjustable in a linear fashion, the results may not be linear.

Gary

[Garry McKinney]

Gary,
Thanks. a much better description of what is taking place.
Garry

[Bob Davis]

Hi Gary,
Isn't it the case that the ramp allows the laser to actually be at the correct speed for all of its travel over the engraving area?
That is; accelerate/reach correct speed/maintain speed/ decelerate/ stop/ repeat.