Machine homes at the usual speed. Focuses at the usual speed.
…but when it starts moving toward the cut position, it’s moving veeeeerrrrrry slooowwwwly.
Like, maybe an inch every thirty seconds.
The motors, belt, etc. are all clearly capable of moving at full speed, but when it goes to reach position, it’s suddenly crawling along?
…err, any ideas?
My 1st answer to all issues is turn it off and back on. My 2nd answer is to check the settings. 3rd answer is change browsers.
Once it gets to the proper position does it cut/score/engrave at the usual speed?
Truth be told I haven’t been willing to sit there that long, but once I get back to the house I’ll give it a try because that’s a good idea!
…also weirdly, one of the tests I ran this morning was to do something on Proofgrade – once I set that as the material (it wasn’t actually Proofgrade), the laser ran at full speed to the cutting location.
OK, I’ve just done the test suggested above (I made a small engrave/cut test target, placed it in the far upper left so I wouldn’t have to wait so long)
…and the laser head still creeps slowly toward the cut area, then cuts/engraves at the appropriate speed, and then goes back to the home position at normal speed.
??
So the motors are, as before, clearly working. Proofgrade settings cause the head to move at normal speed at all times. ANY manual setting causes the head to creep slowly toward the target area, then everything proceeds normally.
Multiple reboots, different browsers, different files.
Proofgrade settings are just manual settings that you don’t key in. If you type in settings nearly identical to the Proofgrade setting does it creep?
Intriguingly enough, no!
Using PG medium acrylic numbers (SD engrave 545 speed, 70 power, 270LPI, 1x) (Cut 171 speed, Full power) the head behaves normally.
Using my numbers for this material (Chemcast 1/8” white), engrave 120/25/75LPI and cut at 150/98 (I like this because it doesn’t cut the backside masking), the head creeps.
Even weirder, if I slightly change the PG numbers (eg: drop the speed to 540 for engrave and 170 for the cut), the head behaves normally.
If I drop the numbers further (cut the speeds down to 165 for engrave and 100 for cut), the head creeps into position again.
…so it seems like perhaps the GF is using one of the speed settings I give it for initial positioning? And then it goes back to the “correct” speed when going to Home?
I have never seen an engrave speed for acrylic that slow - engraving at 120, but cutting at 150?
This behavior remains a mystery. I would keep experimenting to try to understand the factor that makes this happen. Does it matter if the entire file is cut/score?
That’s a good idea; I’ll try making up some test files & investigate further.
…regarding the speeds, yeah, I generally have always preferred to keep my laser power low (hoping it’ll extend the lifespan; I’m still on my original Kickstarter model) at the expense of therefore having to move slowly. It helps that it’s just me dinking around with things, so I generally don’t much care if it takes longer (except, as in this case, where moving to the target location takes as much time as the operation itself!)
At the very least, it’ll extend the amount of time before you notice any power loss in your tube. It’s full power where I could tell I wasn’t getting “full power” any more on my first Glowforge. At lower power settings it still worked fine. I could also continue to cut 1/8" materials pretty reliably, but 1/4" became impossible in one pass.
That’s not working the way you think. You’re actually decreasing to lifespan of your tube relative to the number of projects made because it’s taking longer to cut and the tube is aging while getting less productive use. CO2 lasers tubes do not have a linear relationship between power levels and lifespan. If we ignore the impact of age (CO2 glass tubes are very slightly permeable so just sitting on a shelf never being used will ultimately result in it being unable to fire. This is usually a long time, but it is measurable, especially in cheap tubes.); laser tube lifespan is not appreciably impacted by power levels until the power hits something in the high 90s percentagewise of the rated power. Many lasers allow a governor to be set in the control software so that calling for 100% power will only yield a true power level of 90% for instance. So your 100W laser at 100% power might only generate 90W.
Laser tubes can also be overdriven so your 100W tube could be pushed to say 120W. If course this drastically reduces lifespan because the power to lifespan curve is exponential at levels over 98% or so. Cheap tubes will use the overdriven tube output as the advertised output even though running it at that power level will drastically reduce the life of the tube.
Quality tubes are generally marketed using the true design output or even slightly lower so there’s a cushion in the event the user overdrives the tube. GF controls the power and won’t let you overdrive the tube. Further, GF de-rates their tubes so 100% power is less than the design capability of the tube.
The GF’s tube used to be something in the range of 50W & not the 45W or 40W they advertised. Dan posted back in the early days that there is no tube life degradation caused by running the tube at Full power (GF power units are not %ages as is commonly used in other lasers). So Full power (which is more than 100) is something less than the design power of the tube and possibly less than the de-rated advertised power.
It’s hard to tell exactly what the buffer they built in is because typical laser power meters are hard to use inside a GF. But it’s safe to assume it’s a fairly robust cushion because they used to routinely tweak the power settings for people who reported unsuccessful cuts using PG settings (I don’t know if they’re still doing that).
So it would not be imprudent to start using Full power and higher speeds 
For the benefit of future searchers, this turns out to be expected behavior, added back when they were fiddling with precision, acceleration/deceleration etc.
Since I had a long hiatus, I didn’t notice the changes – the last time I used the laser it was before the new behavior, and then the next time was after the new behavior, so I assumed a funky error, complicated by the fact that I do engraves before cuts, so any file with an engrave in it appeared to work at the same speed as “before”.
My solution, for files which only contain cuts going at low speeds (there are a couple of materials where I tuned my settings to only lightly scorch the back masking while also giving me a nice edge, thereby cutting my weeding time in half), is to create a dummy operation and put it first in the queue – basically, a 1mm spot that I’ve set to max speed, power 1, low LPI. The laser sees this, zooms into position, lightly warms a tiny spot of masking, and then proceeds with the actual work.
Probably not recommended if you’re concerned about positioning accuracy, which I’m not (have like literally 2 metric tons of material in my garage, so waste is irrelevant).
Thanks for adding to the collective knowledge base!
This topic was automatically closed after 30 days. New replies are no longer allowed.