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Greg Holt
02-08-2012, 6:28 PM
I have built myself a laser. 60w RECI 900 x 500

On the Laserbits site they have a table with suggested speed and power settings for different materials. I am sure the laser manufacturers provide a similar guide with their machines.

Now I do understand that these suggested settings are a guide and each machine needs to find its own sweet spot. However to me they look like a good place to start from.

Speeds and feeds are generally talked of as, for example, speed 60 power 100.

Power as a percentage is straight forward. We know what power the laser is. Or at least fairly closely.

However speed as a percentage is not so clear, to me at least.

Percentage of what? Does this not vary with machine? So how fast is 100% ?

Thanks for any guidance,

Greg

George M. Perzel
02-08-2012, 6:38 PM
Hi Greg;
You are indeed correct-speed should be specified in mm/sec or inch/sec or % for machine that has max speed of X ips. However, even that is not really accurate as I have found that telling the machine to ruin at 100% does not always guarantee that speed-depends on the design and what is being ebgraved or cut-especially true for vector cutting.
George
Laserarts

Gary Hair
02-08-2012, 9:09 PM
However, even that is not really accurate as I have found that telling the machine to ruin at 100% does not always guarantee that speed-depends on the design and what is being ebgraved or cut-especially true for vector cutting.

And then you have to throw in the differences between vector speed and raster speed - my GCC is 80ips in raster and 40 in vector. And to continue with what you said - I have found many cases where a slower speed will actually run a job faster because the ramp up and down is shorter with the slower speed.

Glen Monaghan
02-08-2012, 10:49 PM
I have found that telling the machine to ruin at 100% does not always guarantee that speed


I've noticed the same thing... When I tell the machine to ruin a job at 100%, it frequently does it much quicker, like at 80%, 30%, etc. Actually, I prefer it ruin it before the percentage I specified because that way I don't waste so much time on it... ;^)

-Glen

Dan Hintz
02-09-2012, 7:02 AM
Greg,

This has been discussed before, and in the end there's no clear consensus other than "That's how it was done when i got here, that's how I'll continue to do it." Who knows how much longer that attitude will last with some many new machines coming to market, but it's no different than reading a foreign map... you just need to understand the key (legend).

While not ideal, the 30S/60P type nomenclature does tell you a lot. The typical Western machines (ULS, Epilog, etc.) all pretty much raster at around 75ips. So, 30% of 75ips is akin to saying "I raster at 23ips". If your machine is capable of only 40ips (like many Chinese machines), you need to use "58S". The faster Trotecs run at 140ips, so basically halving the value to 15S should get you close.

This all assumes you are basing this on the same power laser. So what if their setting was 100S/30P, but they have a 60W and you have a 30W? At 100S, laser power can be pretty linear, so roughly doubling their power setting is a good starting point.

In the end, you should always pay more attention to what the substrate is telling you during the run than what someone else's setting is leading you to believe.

john banks
02-09-2012, 8:08 AM
Interesting thread Greg, I've come across the same trying to compare my 100W RECI with Chinese steppers (really to make sure it is working to expectation, results look good and with the right material are fast enough), so far I've found the following:

Engraving hardwood:
800mm/s 90% power - nice
400mm/s 90% power - nicer/darker/deeper

Cutting hardwood 4mm thick:
30mm/s 90% power - nice
25mm/s 90% power - nicer, pieces fell out rather than being pushed out

Cutting very small <1mm holes in 3mm hardwood:
100mm/s 90% power - cutting <1mm holes didn't seem speed sensitive, it must reduce the speed to change direction so fast.

Cutting MDF 9mm thick:
3mm/s 70% power - this overpowered the back side in places, reduced the power because I could not have 3.5mm/s and it didn't always cut through at 4mm/s 90% power

Cutting 2mm white acrylic (no idea what sort) bath panel (don't have any other acrylic yet), very large (through front and rear slots) so variable focus:
4mm/s 90% power - nice
3mm/s 90% power - cut through even out of focus but sometimes overpowered material

I was surprised how fast the 4mm hardwood cut, how slow the 9mm MDF cut, and especially surprised about the acrylic and how slow it needed to be, but it is a bath panel.

I suppose we could have the same info about power, but usually people state the power of the machine so it is easier to work out.

Dan Hintz
02-09-2012, 8:29 AM
Note: Vectoring speed is not comparable to rastering speed. Most (all?) machines severely limit the max speed for vectoring, most (all?) do some trickery on curves that slows things down even more (and evidently rarely works optimally... why is beyond me as it's not complicated code to design, and I've done it myself), and 100% vector speed is rarely an advertised spec (most reps don't know it, and getting it out of tech support is often an exercise in futility).

Mike Troncalli
02-09-2012, 9:24 AM
Even as a "noob" I have run into the samequestions. I had a project to raster a 6 x 6 piece of material. Total time wasabout 3 min. at 100% speed. I reduced the speed to 50% and it only added about.30 sec. to the overall run. :confused: I have been running a CNC for about 5 years so Ido have some experience with computer controlled engraving / cutting devices.
I am running a Full Spectrum 40w which is basicly a chinese laser that has been retrofitted with their controller boards and software, but I wonder if I should attempt to move over to Mach3 as my controller. I'm not sure if I could get a faster speed that way or if I am just waisting my time.

While I have tried to use reference charts on new materials that I am unfamiliarwith I have realized even after only 3 months on a laser that experience is thebest teacher and that you do develop a good idea of what your machine can andcannot do.

Ernie Balch
02-09-2012, 9:34 AM
LaserBits offers an online course in laser use but don't mention Chinese lasers at all. All their power and speed values are only mentioned for Systems like Epilog and Universal but even these will change with time as the laser tube ages, mirrors get dirty etc. Since they didn't have any answers I decided to run some experiments to optimize the quality.

As mentioned above the different raster speeds really make comparisons difficult. I am making a series of boxes with known numbers of square inches and timing the system to find the optimum way of laying out engraving jobs. Which is faster to engrave stacking jobs in a vertical orientation or spreading them horizontally across the table? How much time difference is there in adjusting the speed and gap offset. Bi-directional looks better at low speeds rather than high, what happens to throughput if I go to single direction at 2X the speed?

It would be neat to have a standard vector cutting file that people could run and time their system. This could allow members to accurately compare systems and come up with a percentage multiplier for system comparisons.

Richard Rumancik
02-09-2012, 10:18 AM
Greg, much as I'd like to tell you that "speed and feed" is all very scientific, I am afraid to tell you that in the laser-engraver world it isn't at all. Although you can do back of the envelope calculations like Dan proposes, the bottom line is that the Power and Speed settings are really only valid for the machine that they were derived on. Maybe two brand-new machines would behave similarly within 10 or 15% or each other but it's downhill after that, when crossing models, actual substrates, laser tube age, lenses, and on and on.

There is a sophisticated feedback system with these lasers it is called the operator. You have to get a feel for what the ballpark will be and iterate from there. I always cringe when people ask for settings info. For rastering, start at 100% speed and guess at the power based on experience. Then iterate from there. For vector cutting, you will probably set the power to 100% and guess at the probable speed based on past experience. Then adjust.

If a one-shot project there is not a lot of value in dialing in the exact parameters. (Perhaps my speed was a bit slower than needed to cut effectively, and I could have saved a couple minutes on the job, but it would have taken me 15 minutes to optimize. Not a good tradeoff.)

For bigger projects it pays to optimize. If cutting a lot of 3mm acrylic then find out the speed at which it won't cut, then slow down some percentage.

Since you built your own machine, you won't be able to use any tabulated values at all. The speed scale on your machine will be an arbitrary scale, just like it is on Epilog, Universal, GCC, Trotec etc.

Greg, you say power is straightforward. I wish. We don't actually know what our laser power is, even with a new machine. That is because most people don't have a power meter. And with tube aging and with added attenuation due to optics, we may know within +/-20%. Which is not very accurate. (We really want to know delivered watts, not laser-tube watts.)


. . . However speed as a percentage is not so clear, to me at least. Percentage of what? Does this not vary with machine? So how fast is 100% ? . . .

Yes, it varies widely by machine. To answer this for the GCC Many machines are speed-rated based on the maximum RASTER speed obtainable. Operating speed is a % of this. The maximum speed will probably only occur on full-wide raster scans. So on narrow raster images you will not achieve maximum speed. But there are lots of fudge factors and compensations built in to the drivers to make the relationship pretty much useless. For example, my GCC won't vector faster than 30% speed. Sure, I can SET it for 40%, but it will still vector at 30%.


. . . While I have tried to use reference charts on new materials that I am unfamiliar with I have realized even after only 3 months on a laser that experience is the best teacher and that you do develop a good idea of what your machine can and cannot do. . .

After 3 months Mike has it figured out. Some of us just wish that it was more scientific and try to use charts and math to make sense of it but with the current laser-engraver technology it is an exercise in futility.

Greg, start your own chart. This will be the only one that will be useful to you.