Why Not Always use Full Speed?

feeds_speeds

#1

Question for those of you out there that have been forging for longer.

When I engrave/raster on Proofgrade Medium Cherry, the built in settings are 500 zooms and 41 pews.
I’ve been wondering to myself why I shouldn’t up the zooms to 1000 considering that engraves/rasters already take forever. All I would have to do is figure out how many pews work well with 1000 zooms.
So far as I can tell, anywhere between 60 and 75 pews work great for 1000 zooms in Proofgrade Medium Cherry.
Any reason I would prefer the pre-built settings instead?

Love to know everyone’s thoughts.

Jason


#2

You can’t always get the same amount of contrast in engraves when you use higher speed/power versus lower speed/power.

Higher speed might remove the same amount of material, but it doesn’t bake the wood as much.


#3

This stuff is more art and less science so please experiment with your scrap. Often there is more than one sweet spot.
Also, Ref @takitus post above.


#4

Hi Jason,

I’m sure others are more experienced than me, so please take my findings as hearsay.

There are two ways to cut through material. The first way uses more power. The second way uses a slower speed – so the laser lingers over the area for a longer time.

So 500/41 may be the same as 1000/75 on that material. (Slower with less power is the same as faster with more power.)

So why use lower power? The laser is like a lightbulb. The longer it runs at full power, the shorter the lifespan. So if you can get away with less power then it will last a lot longer. (I don’t think the tradeoff is linear; if you can reduce the power by half then you increase the life by more than double.)

The other thing to remember is the quality of the line. This shows up with some material more than others. Basically, fast cutting results in rougher cuts. Show cutting results in smoother cuts. You’ll see this on really curvy edges. This is kind of like the LPI setting with engraving: at 225 LPI, you might see raster lines. 340-600LPI typically has no visible rastering. (And bigger LPI means more overlap in the laser strikes. So on thin material, like paper, you can often cut using engrave with a slower speed and high LPI.)

Edit: I stand corrected. Lower power doesn’t lower life.


#5

I’ve been thinking about this also in terms of the ramp up and ramp down on the change in direction. It’s not linear here either. I thought the other day I set up to print a design and had it on 1000 and 65% power. I noted the time of the engrave, kept same dpi and then just changed the speed to 500. The print isn’t 1/2 as long. Maybe I was misreading everything.


#6

@dan says here that running the tube at higher power doesn’t reduce its life.

I had this same question earlier today as I was engraving some acrylic. The Proofgrade setting seemed unnecessarily slow. There must be a reason for it, I’m assuming it some way it improves the quality (maybe less vibration leading to more accuracy?) Anyway, upping it to 1000 still did the job for me so why not save time.


#7

Totally agree with this, if you get the quality you find acceptable for a use case go faster.


#8

That’s because they have full power governed below the threshold of tube damage. Their best effort to protect us from ourselves. :sunglasses: Lasers for the masses!


#9

I did find when running some small detail engraves on acrylic that I could get better/more details with a lower speed and lower power than a higher speed and higher power. I think that has to do with just how “instant” the laser can be triggered.


#10

You’re correct, it’s not linear. But you’re not correct in thinking it’s going to more than double by cutting power by half.

The way CO2 lasers work, cutting a non-100% power setting by half will likely have an almost unmeasurable effect on tube life.

The lifespan curve of a CO2 is almost flat from 0 to 95 to 98% rated power. At power levels about 98% and above the lifespan curve falls off a cliff - it’s not just exponential, it’s approaching logarithmic. That’s why many lasers have a governor setting available to limit the top power so no one inadvertently burns the tube out by using 100% power - you can tell it 100% in your project settings but that’s gonna be 95% or whatever the limit is set to. The operator won’t ever know.

So there’s no tube lifespan benefit from running it under 95% of it’s rated power. Since GF says running at full power doesn’t affect the lifespan, it suggests that contrary to some industry practice, they’re under-rating their tubes. The 40W Basic may really have a 45W tube and the 45W Pro may have a 50W tube. That way 100 or Full pew pews is less than 100% power.

Oh and remember that power and speed settings on the GF are non-linear because there’s an offset built in (their conversion spreadsheet has the calculation).


#11

Related question for you guys, how do you tell what the proofgrade settings are?
On mine it just shows that it is going to do it “automagically”


#12

If you click on Manual settings after you have selected a Proofgrade option the correct settings are loaded into the slots. You can adjust them by a little without needing to know what the starter settings are.


#13

Sweeet! Thank you!


#14

Just wanted to come in and say there’s a really big difference in the amount of charring/local heating depending on how long the laser dwells on a particular spot aka how fast it goes. That’s one of the reasons that people do multipass for cutting some materials. But sometimes you want the char for color or for uniformity of melting.

It’s also possible that at full speed you don’t get quite as much horizontal detail in engraves, because the laser has a maximum rate of turning on and off (and the material does not heat to burning/vaporization instantly)


#15

Another factor to consider is that the margins (allowable work area) are dependent on the engrave speed. It takes longer to slow down at 1000 them out does at 500.


#16

My testing order for speed now is as follows:
•1 - can I do this as a score instead (sooooooo much faster for stuff like text)
•2 - test the PPI - get as low a setting as possible (I have noticed the Proofgrade sets at 400+. for MY art I have noticed no Dif in quality but huge speed jump by setting this at 175-300 tops - depending on the complexity of the artwork)
•3 - start with speed/power at full
•4 - reduce power until desired results
•5 - fine tune with speed reductions

As many have stated and demonstrated there is not a direct correlation in % between [1-FULL] on the sliders - so it is best to use a swatch test to dial in the setting. I also test my artwork on scrap before committing to a final setting.


#17

The current engrave settings are designed to give you a super high quality finish. By moving more slowly, the laser turns on and off more often per inch, so you can get better horizontal precision. Similarly, more lines per inch makes it darker, but gives you better vertical precision. We do have some work in the hopper to give you more options; right now, we err on the side of “looks really really good (but is pretty slow)”.