What's a good extrusion width to use for .4mm layer height?

Hey guys, I've been using my Prusa Mendel V1.0 for the past couple of months or so, but I still am running into issues with the width of the first layer, what is a good width to use for .4mm layer height? Also, is there a good rule of thumb as for the relationship between layer height on extrusion width? Thanks in advance!

I've heard the general rule of thumb is not to use a layer height more than 60% of your nozzle diameter. That's not really an adjustable parameter though, it's a matter of how physically large your nozzle is. With my .5mm nozzle I can print up to .3mm layers, though I find that .25 produces better results for me.

Thanks for the info, I also have a .5mm nozzle as well but I've been printing at .4 mm layer height, so I adjusted my settings and my current print is looking a lot more consistent, thanks!

// I've heard the general rule of thumb is not to use a layer height more than 60% of your nozzle diameter.

This seems logical, however my in theory then my .35 nozzle should not use a layer height of more than .21 but I regularly print at .25 (not a major difference but still a difference) and it works fine that way.

Maybe on my next prints I will try .21 instead and compare to see if there is any real difference.

tmorris9 Wrote:
-------------------------------------------------------
> // I've heard the general rule of thumb is not to
> use a layer height more than 60% of your nozzle
> diameter.
>
> This seems logical, however my in theory then my
> .35 nozzle should not use a layer height of more
> than .21 but I regularly print at .25 (not a major
> difference but still a difference) and it works
> fine that way.
>
> Maybe on my next prints I will try .21 instead and
> compare to see if there is any real difference.

This ratio has to do with the printed path width not the actual nozzle diameter and if you are using something like slic3r and have it set to auto (0) for the width than it will be printing a path far far wider than the nozzle diameter. I personally think Slic3r tries to print to wide for any given nozzle diameter when set to auto. I feel J-heads should be set to print the same width as the hotend is sold as, 0.5 for 0.5mm nozzle. For other hotends you want it set to 0.05mm wider than the rated size. This is when you need to worry about the height no more than 60% of the width.

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The limits are W/T > 1.5 or too weak layer adhesion.

W * T < PI D^2 / 4 - plastic must be stretched, so the cross section must be smaller than free air extrusion diameter D. That depends on the die swell, so is different for different plastics. With ABS I can use layer heights close to the nozzle width.

As T gets smaller W has to be closer to the nozzle width because the opportunity for the plastic to spread is less.

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The rules below 1 mm nozzle size are different then that for above.

Below 1mm nozzle sizes should never exceed .5 mm. 50% is okay for layer height, but remember, taller layer height means more buldging = less accurate parts.

Above 1mm nozzle should be more like 30% of nozzle diameter = layer height. I'm not sure why, this is just my observation.

Until today I'd followed Richrap's advice that Slic3r's automatic width calculation was fine to use. I'd been meaning to test some different ratio's to see what effect they had but had never got around to it. Slic3r calculated a 0.58mm width for my 0.4 mm J-Head with a 0.21mm layer height. Moving to a 0.4mm width (1.905 ratio) had a much bigger impact than I had imagined, especially on items like gears where the teeth are being printed so much more cleanly (they weren't bad before after I sorted my cooling but it's still a huge improvement) - definitely a parameter that's well worth playing with!

FWIW, the reprap calculator suggests you keep the ratio above 2 or parts are easier to break.

I have a 0.5mm nozzle and had been using a 0.3mm layer height (which I hated) and using the skeinforge ratio defaults of 1.5 and 1.8 (one's for perimeter and one's for infill - I forget which is which) and I was adjusting the feed and flow rates to correct issues. Based on this thread, I did some research and lately have been following Triffid Hunter's calibration suggestions. I now use a layer height of 0.2 and a W/T ratio of 2.5 (giving me a extrusion width of 0.5) and I set the feed and flow rates to be equal. I have been very happy with the results. It takes a bit longer to print things, but I think I am getting greater quality.