Glowforge precision and accuracy (measured)

techniques

#1

Hello everyone,

I was wondering what is the precision and accuracy of the Glowforge. I found a value of 0.025 mm but it is sometimes called accuracy and some time positioning precision…
Also, Has someone (a lucky one) measured this two parameters on an existing machine?


#3

They’ve said it’s accurate down to 0.001" (or, as you put it, 0.025mm) many, many times. That’s probably not a realistic number. IIRC, ~20" Mitutoyo calipers don’t even claim to be accurate down to a thousandth.

Really, with laser cutting, trying to get down to a thousandth is silly. The cut will frequently have a taper to it, and the taper alone can destroy any hopes of getting anything truly accurate to 0.001".

I think they’re talking about what I might call “positional accuracy” but is more correctly called “resolution”. (palmercr and I have argued about this terminology, and now that it’s probably at least a year later I’m finally willing to admit that he was right).

I’d say you’re probably doing pretty good if your cuts come out within 0.2mm (~0.008") from one side of the bed to the other, but I don’t have a Glowforge yet so this is only speculation.

I can’t recall anyone doing any extensive accuracy tests… or anyone even measuring anything larger than a few inches in length. Of course, many people on this forum could care less about “real” numbers and are content with whatever the marketing wankateers* have told them.

*credit to AvE


#4

The resolution is actually 0.01875mm, hence 1355LPI instead of 1000LPI.


#5

Do you have a particular use case? From what I’ve experienced I suspect you’d need some high grade measurement tools.


#6

When / if I get a machine I will test the accuracy in a kerf independent way. I don’t have tools that will measure something the size of the bed though. Since it only cuts wood and plastic thermal expansion and expansion due to moisture absorption will swamp .0001" over bed sized distances. Even the metal rails of the GF will change more than that with temperature swings.


#7

This resolution is the theoretical one. it doesn’t include the mechanical system effect on the positioning.
I want to benchmark the GF with other existing machine. The kerf is related to the optical system and can be tested separately.
To measure precision on the machine, a dial indicator mount on the machine can be used. An indicator with a 0.01 mm accuracy costs about 50 €. For accuracy, multiple measurements will help to get the Gaussian plot and calculate the accuracy.


#8

Yes I have dial indicators, precision calipers, a micrometer with 1um resolution and lots of hole gauges. Just need a GF to put it through its paces and compare it to the marketing.


#9

I was thinking about what material it would be best to test the glowforge with and had decided acrylic since it has to be more consistant that anything else offered.


#10

Thanks! hopefully you’ll get it before me and I’ll have more info for taking my decision on this machine. I’ve started to benchmark the GF with other lasercutter and the precision/accuracy is one important parameter. The kerf is also something to take in account for each material but if the mechanical structure is not accurate, a very tiny laser beam won’t help…