Why am I having to run with an extrusion multiplier of 60%?
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It's starting to sound like a slicer problem of some kind - if the extruder is putting out just what it was asked to, then the slicer must be asking for too much plastic, surely?
Nothing wrong with that logic. However, when I slice a 1cm x 1cm x 1cm cube, with 100% infill and no skirt or brim, then check the gcode file, slic3r reports the volume to be 1cm^3 and that it will take 417.8 mm of filament to produce the object. If you do the maths, using 1.75 mm dia filament you get (1.75/2)^2xPi x 417.8 = 1000mm^3 (or 1cm^3). So on that basis, the slicer is asking for exactly the right amount of filament (and I now know that the printer will deliver exactly what it is asked to deliver).
When I print the object, it has the appearance of being printed with too high an extrusion rate and if I print it with 80% of the correct amount of filament, it has the appearance of being printed with the correct amount of filament. Note that I am now using the expression "appearance of" rather than stating that it is over extruded. I think there is a distinction somewhere between the two - but I'm not sure yet what that distinction is.
Ian
Not that this is driving me crazy but I have to go - there is a little man wearing a white lab coat knocking on the door….....
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Have you tried a different filament?
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I wonder if your printer is not printing in the correct x/y scale? Have you verified this? If your 10x10 cube with the correct volume of plastic is trying to take up 9.5x9.5 area, it would be squishy. Maybe incorrect Z scaling, too?
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@bot:
I wonder if your printer is not printing in the correct x/y scale? Have you verified this? If your 10x10 cube with the correct volume of plastic is trying to take up 9.5x9.5 area, it would be squishy. Maybe incorrect Z scaling, too?
Hi bot
As per one of the above answers, cubes are a little undersized when extruding at 80% (about 0.2 to 0.3 mm) and a little over sized when extruding at 100% (again, about 0.2 to 0.3 mm). That's regardless of the size of the object so on a 10mm cube its +/- 2 to 3 % but on a 100mm it's +/- 0.2 to 0.3% depending on the extrusion amount I use. Given that it can be under or over, I'm reasonably certain that the steps/mm in X Y and Z are correct.
Ian -
Have you tried a different filament?
I only have PLA - that's all I've ever used to date. I get the same result with "solid" Black and White and translucent Red, Yellow, and Clear, so 5 different reels but all PLA. They were from 3 different sources and bought at different dates about 4 months between the earliest and newest. I keep the filament in evacuated plastic bags with silica gel in the bag - the colour changing stuff that tells me when it's becoming saturated (and it's not).
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Latest (and probably final) update. Firstly here is a link to a picture of the issue.
https://drive.google.com/file/d/0B_MwtHtQR_ZvbkJoN0l1Y3FUYTQ/view?usp=sharing
It's exactly the same part, the only difference is that the one in the foreground was printed using an extrusion factor of 1.00 and the (better) one in the background was printed using an extrusion factor of 0.80. When the printer puts down the first layer, with extrusion factor of 1.00, the edge of the extruded filament is "rippled" - as if there is too much filament with nowhere to go, but with an extrusion factor of 0.80 it's a nice smooth "tube" of filament. When the vertical sides are being printed, these large blobs appear using 1.00 and I get stringing as if there is too little or no retraction, but there is no sign of any of this using a 0.80 (80%) extrusion factor. It's almost as if there is a build up of pressure at the nozzle tip caused by too much filament trying to be forced out through too small a gap and then suddenly is just "explodes" and releases the pressure but causes the blob. It looks like it can happen at any point, either on the perimeters or in the solid infill.
My thoughts at this moment in time are that it has to be over extrusion and that there is nothing else weird happening that is being masked buy under extruding. There also seems to be quite a bit of discussion on the "interweb" with many users of slic3r version 1.2.9 having the same problem. Some have said that rolling back to an earlier version fixes it. I know that if I slice a 1cm^3 in slic3r it generates exactly to correct amount of filament to fill that space. Maybe that's the problem. As someone has said, because of the way the filament is laid down, it's not "cube" shape so there will be gaps between individual threads at some points. So, it should take less filament to fill a given space to account for these gaps (but 20% or more seems an awful lot).
I've looked at other slicers but don't want to pay money in case that's not the problem. Other free ones don't have the features I need (like support for firmware retraction and multi colour parts for example). So, much as it pains me, in the interest of saving what little sanity I have remaining, I'm going to give up and just run with slic3r and a low extrusion factor, or maybe try an earlier version.
(Unless of course, someone comes up with a better idea…........).
Ian -
You tried this? https://www.raise3d.com/pages/ideamaker
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You tried this? https://www.raise3d.com/pages/ideamaker
Thanks for the thought - had a quick look- seems to be specific to their machines - apart from anything else, it only support 2 extruders and I have 3.
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Hi Ian
Try Cura to see if its the slicer, even if it does not suit all your other needs.
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Hi Tony,
I'm convinced it's slicer (slic3r) related. Got Cura but it doesn't do firmware retraction (at least I can't find it). So even if it worked in other respects, I'd be printing with effectively no retraction and the prints would still be awful. At least with slic3r and setting extrusion factor of 80% in the filament section, I can get decent quality prints. I've enquired of S3D as to whether they have plans to support firmware retraction -waiting for a reply. AFAIK, slic3r is the only one that does multi part (multi colour) objects and firmware retraction.
Ian
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Ahh fair enough, I don't use firmware retraction, never found the need at least in a single extruder setup.
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I have it in mind to support auto firmware retraction as Marlin does, i.e. identify retraction/un-retraction gcodes and use the firmware retraction parameters for them. But there is the possibility of mis-interpreting moves. So firmware retraction support in S3D would be better.
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Just looking through the online documentation, it doesn't look like S3D can support 3 extruders either. Dual extruders but not 3 (unless someone can advise me otherwise).
Slic3r actually gives you the choice of 4 extruders (tools) to choose from if you define the printer as having 3 extruders. I guess the authors were aware that with a mixing hot end you can have any number of combinations. Shame it's giving me this problem because otherwise, it does everything I need (but at least I've found a workaround). -
Looking at my S3D Install it appears that it CAN support upto 6 Tools (Don't ask how you configure it) but you can select from tool 0 to tool 5.
Doug
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About the 2 cubes, with the weird 1st layer print patterns.
It looks to me as if the bed isn't level. On the brim it looks as if the layer thickness in the foreground is better than in the background. The foreground looks squished while in the back it looks put down loosely on top.
That could account for the strange patterns in the first layer.Will not help you with the extrusion issues, tho.
Lykle
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I'm not sure I understand - why can't you use software retraction? More generally, why should anyone prefer firmware retraction over software retraction?
Regardless, it might be interesting to print some experiments with Cura even if they have no retraction; maybe even some slic3r experiments without retraction to compare. The point is, is slic3r doing something wonky? (The bug in slic3r 1.2.9 is supposed to occur only when filling tiny gaps, which get overfilled.)
It can't hurt to check dimensional calibration on your printer. By this I mean the dimensions used by the motion system; extrusion problems will mess with any dimension by a fraction of an extrusion width, so you want to print the biggest part you can accurately measure. I also found it helpful to print both "outside" and "inside" dimensions to measure, so that they would be affected by extrusion wonkiness in opposite ways. I designed a part that should show what I mean: http://www.thingiverse.com/thing:1688991 (last object) That's for a (small) delta; on a Cartesian you'd make it rectangular. And to decrease the volume by 80% you'd only need to scale the axes by 93% each, so it wouldn't take all that much dimensional inaccuracy.
I should say, though, that I can print cubes sliced with slic3r 1.2.9 and get perfectly-reasonable-looking output with steps/mm calibrated to reality, filament diameter set to the measured 1.72 mm, and an extrusion multiplier of 1.0. So if there's some weird slicer bug, I don't see why it hits you alone.
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About the 2 cubes, with the weird 1st layer print patterns.
It looks to me as if the bed isn't level. On the brim it looks as if the layer thickness in the foreground is better than in the background. The foreground looks squished while in the back it looks put down loosely on top.
That could account for the strange patterns in the first layer.Will not help you with the extrusion issues, tho.
Lykle
Hi Lykle.
Agree with that. Sorry, I mean to report back but got overtaken by other events. Bed had moved by 0.05mm. Not apparent when extruding normally but when the extruder was seriously under extruding that 0.05 makes a noticeable difference to the first layer.
Ian
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@ peridot.
Firmware retraction is needed for mixing hot ends such as the diamond which I use. More accurately, it is necessary to retract all filaments simultaneously when they share the same nozzle. DC42s implementation of G10/G11 allows that to happen. If one only retracts one of the filaments, then all that happens is that filament is drawn from one of the other inputs, rather than from the nozzle tip.
Edit. As for your other suggestions (thanks for taking the time though), I'm fully aware that it could be, and most probably is, something specific to my machine. Obviously, when I first noticed the issue, that's the route I was taking (for several weeks). I've checked the dimensional accuracy numerous times as well as orthogonal accuracy and just about everything else I can think of. Speed, acceleration, jerk, temperature, (fast, slow, hot, cooler) - none of these make any significant difference. Fast speed is maybe slightly better than slow but not much in it. It was only after doing weeks of these sort of checks that I stumbled upon the fact that I could remedy the issue by lowering the extrusion amount.
I don't know if you saw this in one of my earlier posts https://drive.google.com/file/d/0B_MwtHtQR_ZvbkJoN0l1Y3FUYTQ/view?usp=sharing. The only difference between the two prints is that the one with the blobs and strings and lines in the layers was printed with an extrusion factor of 1.00 and the other at 0.80. It beats me….......
Ian
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It's also handy because you can make adjustments to your retraction on the fly rather than having to make changes in the slicer and start over. This is very helpful when getting your retraction settings dialed in for a particular filament or when trying new extruders and hot ends.
@ peridot.
Firmware retraction is needed for mixing hot ends such as the diamond which I use. More accurately, it is necessary to retract all filaments simultaneously when they share the same nozzle. DC42s implementation of G10/G11 allows that to happen. If one only retracts one of the filaments, then all that happens is that filament is drawn from one of the other inputs, rather than from the nozzle tip.
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I get the idea of tweaking the retraction while the print is running but the simultaneous retraction can be achieved by sending something like G1 E-1
-1 unfortunately slicers don't appear to support these constructs.As slicers can be configured to setup the correct firmware retraction based on the type of filament used in the start gcode, so it's all good.
