Going with the Flow

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Re: Going with the Flow

Postby nuggetz » 02 Nov 2017, 15:56

Polymax PLA
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Re: Going with the Flow

Postby nuggetz » 02 Nov 2017, 15:57

Polymax PLA from this month's makerbox.
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Re: Going with the Flow

Postby mhackney » 02 Nov 2017, 16:00

That seems like a very low flow rate for PLA. With a V6 you should be able to do 8mm^3/s easily.
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Re: Going with the Flow

Postby hacker » 03 Nov 2017, 05:09

mhackney wrote:That seems like a very low flow rate for PLA. With a V6 you should be able to do 8mm^3/s easily.


Interesting, I seem to be able to get around 4-5 mm^3/s with PLA, bowden ~500mm, titan extruder. It's not like it can't extrude faster, but I get some ugly finish during flow test:

IMG_1684.jpg

IMG_1683.jpg


This is 10 to 0.5 (I think), PLA glow in the dark (I had a tiny bit better results with a plain PLA, but have no picture), 200ºC, 40% fan, I think. I'm thinking if this is maybe a problem with layer time in fact and not the flow?

And what would be your expected flow rate with ABS?
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Re: Going with the Flow

Postby mhackney » 03 Nov 2017, 07:58

ABS is going to be similar to PLA. My ABS typically is in the range of 9mm^3/s. But I try never to push to that end point. If I need to print something that fast or at that flow rate, I'll use a printer with a Volcano on it.

I agree, the photos look more like a layer time/cooling issue. You want to see the rip line. Calibrating flow rate is all about determining the upper flow rate limit that can be safely used. If you go faster than this limit, the extruder can not keep up - meaning that it can not melt filament fast enough to flow. This looks like filament starvation and ultimately your hot end will plug.
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Re: Going with the Flow

Postby nuggetz » 03 Nov 2017, 08:56

mhackney wrote:That seems like a very low flow rate for PLA. With a V6 you should be able to do 8mm^3/s easily.


Perhaps this PLA could benefit from higher temps as its very strong. But I was running it at 230. I know temp calibration is first in the list but if I could use more temp here, is it ok to bump things up? I suppose I'm blindly following the wizards without any deviation from the docs.
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Re: Going with the Flow

Postby mhackney » 03 Nov 2017, 10:46

It may just be the fillers they use in that PLA. I'd do the temperature wizard on it just to be sure.
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Re: Going with the Flow

Postby hacker » 03 Nov 2017, 10:52

mhackney wrote:ABS is going to be similar to PLA. My ABS typically is in the range of 9mm^3/s. But I try never to push to that end point. If I need to print something that fast or at that flow rate, I'll use a printer with a Volcano on it.

I agree, the photos look more like a layer time/cooling issue. You want to see the rip line. Calibrating flow rate is all about determining the upper flow rate limit that can be safely used. If you go faster than this limit, the extruder can not keep up - meaning that it can not melt filament fast enough to flow. This looks like filament starvation and ultimately your hot end will plug.


Thanks. With ABS I go even lower than that, although cooling time should be less of an issue with ABS. Problem is, I don't remember now what was the reason why I have lower ABS rate ;-)

I should probably try the flow that shows nice seam (the first picture in my post shows that it's no more than 10mm that give me ugly seam), not overall finish. Unfortunately we have no layer time wizard.

And yes, I used to have Volcano, which was faster, but no miracles (well I did use it with 0.4 nozzle, so I didn't expect much from the bigger melt area). I put v6 back when I started to experiment with switching materials lately — https://www.thingiverse.com/thing:2618510 — to avoid purging too much.

Anyway, thanks again, I've just opened a new spool of PLA and will try tuning with adjusted criteria now. Temperature test from 230 to 180 gives nearly no difference from top to bottom :)
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Re: Going with the Flow

Postby nuggetz » 03 Nov 2017, 15:46

So, I think I've gotten my flow wizard under control and have moved onto Preload. Started from scratch trying to dial in Colorfabb NGEN. Temps using the wizard put me at 255 degrees. Flow Wizard gave me a max of about 3.8 mm^3/s. Moved onto Preload Wizard and tried running the "drip" test. Had to run this a couple of times. Job runs and extrudes 50mm and then beeps. I pull the filament off the nozzle and let it ooze. Problem is it curls back up onto the nozzle. Tried a few times until it didn't do that and got a straight line coming out of the nozzle. Length was 134mm and the average thickness of the ooze was about .44mm. However, plugging in these values computed a preload of 13.5. Since I really don't understand the ins and outs of what's actually going on I let that populate the Preload in my material style and then went for the Preload test. I set the range between 0 and 2x the computed Preload which is ~26. Unfortunatly the print didn't complete and came away from the bed. Not sure if the wacky amounts of extrusion caused my nozzle to catch the print. It got about 3/4 of the way and the print looks like ass. Mid print would have been the 13.5 us mark that I calculated from the Visco wizard. There are no parts on the print that actually look good except for maybe the first few layers :-)

Here's what the Preoad part looks like:
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WIN_20171103_15_45_30_Pro.jpg
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Re: Going with the Flow

Postby mhackney » 03 Nov 2017, 16:17

So far so good. Keep in mind the "ooze" test is REALLY crude. Don't sweat it, just try to estimate to the nearest 5mm and you will be fine.

I don't know NGEN but your print actually tells you something. This filament needs a preload down near the bottom of that range most likely. Now you can do an "expanded" preload test by setting the Z=0 to 0 and the top to whatever the wizard calculated in this run you did - measured about 5mm up or so just to give a good range. Rerun the wizard and now you will have a more precise range to choose from.
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