Have you ever noticed that a smaller object may cut better than a larger object?

Beyond the Manual
#1

While working on some chipboard settings last night, I got some results that absolutely did not make sense to me: cut settings that worked fine for a small object failed to cut through on a large cut. (This is in BTM because I have to discuss non-PG settings.)

Here’s the test object, 0.050" black chipboard. This shape is about 5.5" x 8.5". Ignore the engrave tests on the material, this is about cutting.

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By cutting test 0.5" circles I figured out that this stuff cut nicely at Speed 500, Power 100. Then I let 'er rip on the larger piece, the 5.5" x 8.5" journal cover in the photo, including the small holes for comb binding.

Well, all the binding holes cut through. Those small pieces dropped free. The long outer cut did not cut through. It wasn’t even close.

The material was dead flat, I did enter the material height correctly, and as this occurred repeatably on a large piece, I do not think that the red ranging dot missed the material on every run.

You might think that it’s the “corner effect,” we know more power gets put down in corners… but a half-inch circle also cut cleanly at 500/100. No corners!

Tonight I plan to cut concentric shapes to see if I can quantify this result.

This isn’t expected, right?

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#2

It’s possible that your material is denser in some sections than others. I’ve had that happen with other materials.

But I’ve never tried chipboard.

I would be surprised if larger shapes is the cause of this.

#3

It takes time for the head to come up to speed from the start of a line. So more energy is dumped into the material, and it cuts through. Curves have the same issue. This effect is most noticeable in corners, where you might see the pin-hole effect. A few people have commented on the small cut effect before. I’m surprised more people haven’t commented, but I guess most just work around it.

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#4

True, but in this test piece that line of small holes all cut through, and the long cut right next door did not.

I guess it must come down to that. I had just never seen such a stark example before.

This is a case where some of that ol’ Glowforge magic would be appreciated… Seems like they could compensate for lower speeds during acceleration by lowering power. Though that would bring a new set of problems, I guess.

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#5

Chipboard, in my experience, is very consistent.

I’d say this is likely a result of the Head not coming up to max speed for the small object. When you cut a larger object, it is hitting max speed and thus not delivering the same amount of energy.

Not sure what you are cutting overall, but in my testing, I would pull out 6 inch lines from the puzzle and test from there - so that I was testing with the same conditions I would be cutting in.

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#6

I run into this cutting card stock all the time. I almost always separate out different bits of any given job into their own operations for this reason.

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#7

To add to this, I suspect testing with a circle might also not be hitting top speed. @jamesdhatch put together a template to test different speeds - I believe he picked 1/2" squares to make sure the head was up to speed: Cut Calibration Template. So far I’ve had very consistent results using the first setting to cut through (and sometimes a touch slower if I think the material is potentially inconsistent).

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#8

Thanks guys, I guess it is just something to live with!