# Cutting speed units

Is the number often quoted in inches per minute ?
If not, what are the units ?
I’ve searched, but can’t find the answer,

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Chicken tongues per shake of a lambs tail.

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Thanks. I expected it might be, but just needed it confirming.
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The are an obfuscated representation of speed that is slightly different depending if it is cutting or engraving. It isn’t any unit of distance over unit of time because there is an offset as well as a scale. That means 200 is not twice as fast as 100. 110 is twice as fast as 100 when cutting. 200 is more than 10 times as fast as 100.

Bonkers. How is that supposed to be user friendly?

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They recently changed it to be from in/min to made-up units. I’m not much of a fan, but then again I would have preferred mm/sec over in/min.

The current implementation is something like (in/min + 4)*2. It’s hidden somewhere in a spreadsheet linked on the forums.

I’m hoping they will add an advanced mode in the future that lets you specify your units for speed.

Other than the speed situation, I like what they’ve done with the power/dithering section. Really looking forward to trying it soonish. (Whenever mine arrives)

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Ok I was quite a bit off on the formula - it’s quite a bit more absurd. Here it is:

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It’s a bit more complicated than that:

cut = 100 + 400 * (ipm - 4) / 153
ipm = 4 + (cut - 100) * 153 / 400

engrave = 100 + 900 * (ipm - 4) / 331
ipm = 4 + (engrave - 100) * 331 / 900

The annoying thing for me is the software is metric underneath and the limits are round numbers in metric but was converted to IPM for the GUI and gave ugly limits. If they had just switched to mm/minute in the GUI they would have had nice round numbers that made sense. I.e twice as fast is double the number and both cut and engrave in the same units.

4 ipm was actually 100mm/min, 157 was 4000mm/min. 335 was 8500mm/min.

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Our posts crossed.

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At least the proton packs did not explode creating a black hole…

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I’m really, really sorry I asked.
John

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do we know if this is actual ?

See the article, below, where Glowforge attached a spreadsheet full of calculations.

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are the orginal units in inches or arbitrary ?

I’m unsure. I believe they’re inches. No way for me to empirically test that, though (no Glowforge).

I don’t think that’s the secret sauce because its linier

and from what I have seen the slow down is exponential

this is based on the formula

So all that formula does, is take the first set of A and B as old min/max, and the second row of A and B as the new min/max, and makes a linear conversion between them. So 4 goes to 100 and 157 to 500. The first set is presumably the min/max limits in IPM that are “reasonable” for cut/engrave, and that is mapped to a 100-500 or 1000 scale. The engrave max speed is approximately 2x as fast as the cut speed limit, although not exactly, so that’s probably why they doubled the scale.

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Yeah I understand how it works, I just think it’s unnecessary and makes converting between other things that much more painful.

Not really sure if they wanted to make a nice big round number, or were trying to hide the fact max speed on a Glowforge is a lot slower. Could be both…

Either way, neither of those are really doing a service to the user. I’m hoping in future versions they will allow you to choose the units it displays.

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do we know what the actual speed is for max ?

1000 in fake units
335 in/min raster engrave
157 in/min vector cut/score

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Do we know the curve its easy to put 100-1000 on 0-157 linier but I swear the difference from 150 to 100 is ten times slower then 200 to 150