Puzzling extruder speed problem
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Hmm, that's certainly something to consider. I'm going to go off in the corner and play with a calculator for a while.
I've used .8mm nozzles for all of this. heck, the reliable speed is slower with this volcano/duet/titan-direct setup with a .8 nozzle than with my v6/smoothieware combo when I had a .8 mm nozzle. I saw clear symptoms of melt-rate problems with v6/smoothieboard/direct drive bowden with a .8mm nozzle there, the motor would audibly skip if I went too fast. Nothing like that here, no symptoms other than measurable underextrusion. wouldn't I see some evidence of slippage, grinding, or a more normal indication of loss of steps if that were the case? I can get those symptoms to show if I go reaaally fast, like 2000mm/min, I start getting extruder motor clicking and skipping.
e3d's support contact doesn't seem to think I'm hitting anywhere near the melt rate limits.
Maybe it's finally time for me to convert to volumetric extrusion
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Well, you can calculate the melt rate easily enough. I guess one way if you are just extruding filament in air would be to take the area of the filament multiply it by the length to get the volume and divide that by the time. If you are printing, use the area of the nozzle x the layer height x the print speed. Multiply the results by any extrusion factor if you are using anything other than 1.0.
However, it does seem that there must be something else amiss if the volcano is no better than a standard V6 with the same nozzle size. Have you measured the nozzle to make sure it is actually the size that it says? Any sign of a partial blockage anywhere?
Have you tried running M122 and looking at the diagnostics? That might tell you if you are getting missed steps.
How about motor itself? What is it's rated current and what are you driving it at. For info, I have three Titans feeding a Diamond hot end and use these motors with no problems. http://uk.omc-stepperonline.com/nema-17-bipolar-step-motor-29v-07a-18ncm255ozin-17hs100704s-p-260.html. They are rated at 0.7 Amps so I run them at 600mA.
Just some other random thoughts
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ok, so working from the speed that I just start seeing an issue at,
915mm of 1.75mm filament (that's how long my stupid measuring stick is, double checked with another tape measure) extruded over 91.5 seconds is 17.5mm/sec cubed but 15mm/sec cubed is fine. Interesting.
yeah I've checked for obstructions and even have gone as far as completely replacing my entire feed path including the nozzle with genuine e3d stuff. No change.
I keep forgetting about M122, I'm going to go look at that.
I've got a 1.3A 40 oz-in motor running at 1.3A but I question the quality. Came in one of those cheap printer kits. I'll replace it with something well known before I start chasing too many more things.
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I get a different answer (but I'm a 63 year old who has forgotten much of the maths I learned). Area = Pi x Radius ^2. Radius of 1.75mm filament is 0.875mm That squared is 0.765625 x 3.142 (Pi) =1.20559375 mm^2. That x length of 915mm is 2,201.11828125 mm^3. That divided by 91.5 seconds is 24.0559375 mm^3/sec. From what I have read, a volcano can do 20-30 mm^3 /sec so it looks about right to me.
One other thought. I've hardly ever used ABS (the fumes trigger my cluster headaches) but is it harder to extrude than PLA? I'm assuming it is, as the melting point is higher. The point being that you might get a higher melt rate with PLA.
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Have you tried different brands of ABS, some flow much better than others. 40mm^3/sec requires some flowy polymers.
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What heater cartridge are you using? Maybe it's not 40w and can't keep up with the flow rate? I have a cloned volcano and with 0.8mm nozzles I can't go faster than 35mm/s, it just stops melting if I go any faster. As such for a large object it's not really faster as a 0.4mm nozzle running at 80-100mm/s would be as fast. However the large object with coarse layers is very strong, one is a lookout from paw patrol that my son has dropped an amount of times that would have destroyed an object printed with a 0.4mm nozzle. So I don't see volcano as a way to go faster, rather a way to print big things with big nozzles which are stronger.
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I get a different answer (but I'm a 63 year old who has forgotten much of the maths I learned). Area = Pi x Radius ^2. Radius of 1.75mm filament is 0.875mm That squared is 0.765625 x 3.142 (Pi) =1.20559375 mm^2. That x length of 915mm is 2,201.11828125 mm^3. That divided by 91.5 seconds is 24.0559375 mm^3/sec. From what I have read, a volcano can do 20-30 mm^3 /sec so it looks about right to me.
One other thought. I've hardly ever used ABS (the fumes trigger my cluster headaches) but is it harder to extrude than PLA? I'm assuming it is, as the melting point is higher. The point being that you might get a higher melt rate with PLA.
yup, looks good to me. I tried to take a shortcut and got a wrong number. I underestimated just how much plastic that was flowing. I guess what needs adjusting is my perspective! I can't find anywhere if Reprapfirmware supports volumetric extrusion, do you know? I might be able to get this whole thing automated for me. It would be nice to be able to define a maximum volumetric rate, and no matter which nozzle size I put in there, it'll handle the speed for me.
I've been printing almost exclusively ABS for 2 years, I find PLA to be less tolerant on everything except shrinkage (abs is far more tolerant for retraction length settings, multiple retractions over the same length of filament, and a relatively wide glass transition temp, doesn't require as much if any forced cooling for small slow details, etc). I've discovered that some brands are super stinky and make lots of fumes, and some brands make pretty much none. I'll try a roll of PLA I've got kicking around, that might prove this out.
I'm still puzzled as to why I dont see any clues to this anywhere other than in the measuring or underperforming infill. On all of my other machines, when underextrusion has occurred for a chemical, thermal, or mechanical reason, there's evidence. Filament grinding, motor stalling, tubes popping out of PTC connectors, etc…
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What heater cartridge are you using? Maybe it's not 40w and can't keep up with the flow rate? I have a cloned volcano and with 0.8mm nozzles I can't go faster than 35mm/s, it just stops melting if I go any faster. As such for a large object it's not really faster as a 0.4mm nozzle running at 80-100mm/s would be as fast. However the large object with coarse layers is very strong, one is a lookout from paw patrol that my son has dropped an amount of times that would have destroyed an object printed with a 0.4mm nozzle. So I don't see volcano as a way to go faster, rather a way to print big things with big nozzles which are stronger.
I don't see more than 1C variation out of the temp graph during the minute and a half test, I don't think it's a temp drop. I've experienced a temp drop trying to use a .8mm nozzle on a standard v6 block and saw that in the graphs.
strength is certainly extreme. I may just have to adjust my expectations to be in line with your view.
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Have you tried different brands of ABS, some flow much better than others. 40mm^3/sec requires some flowy polymers.
yup. almost identical. small variation though. I was quoting 40mm/sec linearly, not volumetrically (which, now that I do the volumetric math, is worse). Sill, you'd think E3d would have told me about melt rate limits of that combo when I emailed in. They appeared just as puzzled.
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Probably one of their first tier techs that was unfamiliar.
Note that you're doing 1000mm of sustained extrusion, not everyond does that as it isn't a fair test - rarely does a print not pause the extruder for corners/travel in a 1000mm extrusion.
Best case scenario, Volcano can do about 40mm^3/sec. That's super flowy polymer, extra high temperature, 1.2mm nozzle. More typical is around 10-20mm^3/sec. At 600mm/sec you're doing ~13 mm^3/sec and only seeing ~2% slip. I would be surprised if that 2400mm/min wasn't slipping. Where'd you see that quoted?
50-100mm (5-10%) of underextrusion is not shocking at high flowrates, E3D has documented this and presented it previously (a couple years back, can't find it now). Just asked Sanjay for the data, will post here once I get it.
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I'm still puzzled as to why I dont see any clues to this anywhere other than in the measuring or underperforming infill. On all of my other machines, when underextrusion has occurred for a chemical, thermal, or mechanical reason, there's evidence. Filament grinding, motor stalling, tubes popping out of PTC connectors, etc...Do all of your other machines use Titan extruders?
I'm currently doing some research into maximum melt rates using a Titan extruders and a Diamond hot end under printing conditions, and finding it very difficult to determine exactly when I've hit the limit. I was expecting to suddenly find clear evidence of drastic under extrusion, similar to the signs you mention, but in reality all I'm getting is a rough finish and ripples on the surface at a certain speed, which get worse as I increase the speed. It seems the Titan is doing too good a job of forcing the filament through "under duress".
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I'm still puzzled as to why I dont see any clues to this anywhere other than in the measuring or underperforming infill. On all of my other machines, when underextrusion has occurred for a chemical, thermal, or mechanical reason, there's evidence. Filament grinding, motor stalling, tubes popping out of PTC connectors, etc...Do all of your other machines use Titan extruders?
I'm currently doing some research into maximum melt rates using a Titan extruders and a Diamond hot end under printing conditions, and finding it very difficult to determine exactly when I've hit the limit. I was expecting to suddenly find clear evidence of drastic under extrusion, similar to the signs you mention, but in reality all I'm getting is a rough finish and ripples on the surface at a certain speed, which get worse as I increase the speed. It seems the Titan is doing too good a job of forcing the filament through "under duress".
nope, my other machines use a 3dator style extruder (fixed tension rather than spring loaded). My first indication that I hit any kind of limit was infill not able to run a complete line across the interior of the part (rectilinear infill).
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nope, my other machines use a 3dator style extruder (fixed tension rather than spring loaded). My first indication that I hit any kind of limit was infill not able to run a complete line across the interior of the part (rectilinear infill).
Then I would suggest that the Titan extruder is the reason why you are not seeing under extrusion manifesting itself in the same way as your other printers. I'm having exactly the same issues with the tests I am doing on my Diamond hot end with Titan extruders. I'm trying to ascertain the maximum melt rate by pushing the print speed higher and higher. I'll be doing a write up on my blog with accompanying videos when I've finished so I don't want to say too much until I've finished all my testing. However, I can say that I am finding that there is no clear black and white distinction as to when I've reached the limit of how fast the filament can be melted. Rather it seems to be a gradual "thinning" of the filament bead as I continue to push the speed up. Eventually, there will be distinct ripples in the surface but I don't get much in the way of "clicking" and no sign at all of any grinding of the filament. These damned Titans just push and push. It's actually quite annoying for what I'm trying to do.
