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How thick IS a piece of paper?

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This is sort of a metaphysical question, but how thick IS a piece of paper?

I get a bit annoyed at 3D printer instructions that tell you to set the extruder height by using an undefined piece of paper as a feeler gauge, because the thickness of a piece of paper varies from .002" (.05mm) to .006" (.15mm).

I've had some prints that didn't adhere, and some that were knocked over in mid-print, and I'm pretty sure that the extruder height is the critical factor.

So I want to use a steel feeler gauge for reproducibility and durability: which steel leaf do I use?

Just how exactly much height should one set for the the extruder-to-plate gap, expressed in international measurement units, rather than in pieces of arbitrary paper?


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Thanks - I'm an old car guy - still got a set of feeler gauges for "spark plugs".

.004" (.1mm) is what I had come to by trial and error.

I'd bet that if you measured 100 brands of "standard" printer paper, the median thickness would be close to .075mm, and with quite a spread of values. Paper manufacture isn't that closely controlled a process.


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If you are an old car guy and have a dial indicator, there is a dial indictor holder that allows you to place the indicator into the head.

I'm thinking of going that route because even with a feeler gauge, I just can't get the feeling right. Sometimes the feeler is tight or lose or feels the same. And any pressure on the bed can allow the feeler to go under the head and add in compressible blue tape and I find it very inconsistent.


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Hmmm that is a good point. Problem is, so does the downward pressure of the feeler gauge so it is hard to know the "feel" unlike say a spark plug that is rigid at both points.

the feel is different is you are even slightly pressing down on the feeler. I've even seen the gap change from the weight of the hex driver that came with the UM1 kit.

I guess if comes down to consistency. If you know that 10.7 cm under the pressure of the gauge works for the front and 10.5 for the back then at least you can repeat prints without fussing around with the first layer or two.

Are there any gauges with a very light spring pressure?


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I know this is an old article, but using a feeler gauge is a very good idea, as it is a high precision measuring device.

But to achieve success you need to know how to use it. It should not be used a tool to determine the grip or resistance of the hotend pushing on it. A feeler gauge is a smooth metal tool that will not exert much or any resistance under pressure.

The correct way to use it is to measure if the tool "fit or don't fit" in a gap. Thus, you need to slide the tool under the hotend, if it "slides under" it means the gap is either accurate or to big. So you adjust the gap slightly smaller, and try again, until it does not slide under anymore. Then you back out as little as you can, and test again, and repeat this until the feeler gauge slides under.

Now to ensure you have to backed the hotend out more than your tolerance you need to select a slightly larger feeler gauge (if your tolerance is 5% and your gap is 100 microns, you need to select a 105 microns gauge) then if that does not "slide under" it means you have not overshot your tolerance, if it does, it means you did and you need to try and make a finer adjustment.

Pro tip: To help you make small adjustments, use one hand to compress the spring that pushes against your adjustment screw. Then you can easily adjust your screw and then let go with the other hand to let the plate return to the adjusted level.

PS. A feeler gauge is a cheap tool. Just buy it from any motoring supplies shop.

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I do the leveling (UM2 non-plus) the "gr5-way". First adjust the nozzle until the plain white laser A4 printing paper has a bit of resistance, but not too much. Yes, it is very subjective and not standard indeed. But at least you can get about the same calibration on all three spots.

Then print a test model with a lot of skirt lines. And manually adjust the three leveling screws to get the most even distribution. Because sometimes when the corner is perfect, an area halfway is not, and is 0.05mm or less off. It is not much, but it is visible in the first layer when using low layer heights (0.1mm or 0.2mm). So the easiest way to level this out is is visually.

Edit: just realised that I hadn't answered your original question. A piece of plain white paper is 0.11mm here. This is standard "80 gram" A4 laserprinter paper. I measured it on about 20 papers of different brands and batches, which were laying around here, mostly printed (thus having been through the printer's heater and rollers).

Measured with good quality professional digital Mitutoyo calipers with 0.01 mm resolution. Thus theoretically the result could be between 0.10 and 0.12mm, but since the calipers were zerod well, and since the final size was displayed very stable (no blinking last digit), and since it are small values close to the zero-point calibration, we can safely assume the value is between 0.105 and 0.115mm, thus averaged and rounded to 0.11mm. This was for all papers I tried.

Thicker, better quality paper, like for company letters, is 0.12 to 0.13mm. This might be "100 gram" paper, but not sure.

Things could of course be different in other parts of the world.

Edited by Guest
Added paper thickness

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