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Daid

Printing at more then 0.2mm layers is just wrong?

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I've printed the same part twice, once at 0.28mm layers and once at 0.2mm layers. And the results are much better then what I expected.

See for yourself:

http://daid.eu/~daid/IMG_20111027_195618.jpeg

The top print is at 0.28mm layers, the bottom is 0.20mm layers. Note that they are both printed at 205C, and in the same print time, the top was at 60mm/s and the bottom at 80mm/sec (ok, that's slightly slower)

The top of the first one is ruined, but that had nothing to do with the settings. But seeing the differences I think 0.2mm should be your absolute maximum layer height. Larger layers don't give more speed (which is limited by the amount of material you can push to the extruder at that point)

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0.20 is almost 50% better Z resolution than 0.28!

I think you've still got some fill issues - get those calipers! - but once you get that dialed in, try experimenting with smaller thread widths, too.

 

Larger layers don't give more speed (which is limited by the amount of material you can push to the extruder at that point)

At the same extruder speed, the time difference between 2 copies of the same object is (mostly) the difference in the sum of non-extruding (aka: travel) moves. If you're printing an object that doesn't have many travel moves, you don't really save time by going to a thicker layer height. If you're printing an object that does have a lot of travel moves, you can save a lot of time by going low-res.

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It's not just 50% better resolution (or 33% better, depending on how you calculate), the layers are sticking to one another a lot better making a cleaner and stronger part.

These where still printed at the wrong 2.98 setting, I also printed one at 2.89, which has better fills but still shows gaps. I set it at 2.85 for the next try, but I haven't got around printing yet.

If I want tinner lines I need to reduce the W/T ratio? I find that setting a bit awkward, not sure what it represents, so I'm using the hint that W/T needs to be 0.4/layerheight, which is 2.0 in my case now.

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If I want tinner lines I need to reduce the W/T ratio? I find that setting a bit awkward, not sure what it represents, so I'm using the hint that W/T needs to be 0.4/layerheight, which is 2.0 in my case now.

W/T is thread width divided by thread height.. If the term "aspect ratio" is one you know, it's basically the same thing.

if w/t = 1.0, threads are as tall as they are wide

if w/t = 1.5, threads are 50% wider than they are tall (1x tall, 1.5x wide)

if w/t = 2.0, threads are twice as wide as they are tall (1x tall, 2x wide)

In general, W/T less than 1.0 doesn't make sense - it's hard to make the nozzle put down a thread that is thinner (in x/y) than it is tall.

So, anyway, "thinner threads" is a little tricky because w/t is a ratio. A w/t = 1.5 on a 0.3mm layer height makes threads that are 0.45mm wide. A w/t = 1.5 on a .2mm layer height makes threads that are 0.3mm wide.

Usually, I pick what thread width I want then figure out the w/t based on the layer height. If I want threads that are 0.4mm wide, I divide that by the layer height and that tells me w/t. So.. for 0.4mm wide threads with 0.1mm layers, it's w/t = 4.0; for 0.4mm wide threads with 0.2mm layers, it's w/t = 2.0.

I haven't tested how thin you can go with the stock ultimaker 0.4mm nozzle but I suspect (against reason) that it's about 0.3mm. Not sure what the upper limit is but I'd guess around 0.7mm.

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It's worth noting that changing your W/T doesn't specifically change your actual thread width, it just tells the machine what to "expect" as the thread width, and then it creates lines closer or farther apart based on that expectation. Printing at .2mm I find a W/T of about 1.3 is as far as I can push it down. I get better cleaner (more transparent) prints with lower W/T but sometimes run into problems with skipping and too much filament being pushed together in the layers. For now I'm using 1.4 but once I have stronger motors I am planning on pushing back down to 1.3. :D

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It's worth noting that changing your W/T doesn't specifically change your actual thread width, it just tells the machine what to "expect" as the thread width

It's tells skeinforge how far to space the threads, not the machine.

There used to really be 2 schools of thought on how to configure skeinforge. One said that you should pick your feed and flow rates (x/y speed and extruder speed) and do a test print of a single-walled object. You'd then measure that object and do a little math vs the layer height and that would tell you the w/t to input into skeinforge.

The other (which I favor very much) is that YOU decide what layer height, feed rate, and thread width YOU want then do some math vs the filament diameter and some machine info (filament gear diameter, etc) to calculate the correct flow rate.

Both ways actually work but I've never been a fan of the 1st one. The 2nd way even got built into SF started at version 40. No more measuring wall widths or doing dozens of calibration prints. w00t.

 

Printing at .2mm I find a W/T of about 1.3 is as far as I can push it down

That's threads which are 0.26mm wide, which is (unexpectedly) really good for a 0.40mm nozzle..

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It's tells skeinforge how far to space the threads, not the machine.

Yes, of course :D

 

There used to really be 2 schools of thought on how to configure skeinforge. One said that you should pick your feed and flow rates (x/y speed and extruder speed) and do a test print of a single-walled object. You'd then measure that object and do a little math vs the layer height and that would tell you the w/t to input into skeinforge.

The other (which I favor very much) is that YOU decide what layer height, feed rate, and thread width YOU want then do some math vs the filament diameter and some machine info (filament gear diameter, etc) to calculate the correct flow rate.

Both ways actually work but I've never been a fan of the 1st one. The 2nd way even got built into SF started at version 40. No more measuring wall widths or doing dozens of calibration prints. w00t.

I have been very happy with how skeinforge calculates flow with version 40+, for the most part I simply leave flow and feed the same and it all seems to work out. I have had some good results increasing the flow by about 10% over the feed, but again my steppers sometimes have a hard time with all the excess plastic and I am slightly obsessed with getting completely solid filled layers.

 

That's threads which are 0.26mm wide, which is (unexpectedly) really good for a 0.40mm nozzle..

Yes but, as I was trying to say, I don't think this actually means my threads are that narrow. It just means skeinforge is going to try and put another thread that close to the last one, because it thinks the threads are that narrow, (because that's what I told it). Actually I'm pretty sure my threads are quite a bit wider, but I'm pressing them together intentionally to get maximum infill.

Also I still print at 240, I didn't like the results with lower temperatures and transparent PLA.

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I do remember, back when Rob Giseburt & I were just starting out messing with calculating flow rate, that things tended to get blobbier as the thread width decreased.. I never got the math right for handling this but think it was due to how threads are shaped.

Most of these calculations assume the thread is rectangular but it's more like a rectangle with rounded edges. With wide threads, the majority is rectangular so it works pretty closely if you do a sinple width * height to calculate cross section area but as the width decreases, that math (in theory... IIRC) becomes less correct as the majority becomes rounded.

So, anyway, yeah. As you drop w/t and (probably) especially drop it below the nozzle size, threads become more blobby unless you do things to prevent it. There's no setting in SF to deal with this - you just have to change the Filament Packing Density or the feed:flow ratio or something when you know you've gotten down into the weird zone. It'd be nice if somebody came up with the correct forumula to deal with this but I don't think anybody has.

 

Yes but, as I was trying to say, I don't think this actually means my threads are that narrow

Well... That sorta depends how you define it - I think it's arguable that they actually are that width but aren't formed correctly.

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