An attempt to investigate pressure in the extrusion system
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Hi Ian, I was thinking the same thing about getting back on topic.
I sell 50w heaters and they get you up to temp quicker but the wattage whilst maintaining temperature is 8-9w and will be the same whether you use a 50,40,30 or 23w cartridge. It's getting the heat into the filament that is difficult. Circumferential heaters might do this better than larger heater blocks.
I'm sure a very long melt chamber would improve maximum volumetric throughput but would it decrease accuracy of extrusion? How differently does molten filament behave to solid? I don't know.
The Diamond 5 colour comes with an 80W heater for some strange reason (well I do know the reason but it's ill founded). It makes no difference to the melt rate and a 40Watt does the job just as well. It does get up to temperature really quickly but it's uncontrollable due to the large swings which even PID can't cope with.
As I've said before on numerous occasions, it's contact area between the heated surface and the filament that will help heat transfer. That and the time the filament is in contact with that hot surface. That's why mixing hot ends are so good for high speed printing (if you set the mixing ratio to 33% for each filament). Not only does a Diamond 3 colour have 3 melt chambers, but for any given print speed, each of the 3 filaments move through the chamber at 1/3 the speed giving much more time for the heat to penetrate from the surface through to the core.
One of these days, I'll see what speeds I can get up to with the 5 colour….........
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Circumferential heaters might do this better than larger heater blocks.
I just visualized a toroid shaped heater…that would be interesting and way more consistent than a lop-sided cylinder somewhere in the block. Aside from coiled induction heaters I haven't seen one suitable for our needs yet.
This is interesting if you haven't seen it yet: https://3dplatform.com/extruders/ note that some models use 6mm filament. I was thinking about this while thinking of the diamond sucking in 3 filaments at the same time. I am wondering how they deal with enough melting and throughput. I am assuming they run higher wattage heaters.
6mm filament is 4.5 times larger (surface area and volume) compared to 2.85mm filament. So there's 4.5x more to melt in the chamber.
See the mini hotend from deltaprintr, https://www.deltaprintr.com/product/mini-hotend/ I have one and it works great, a slightly larger heater would enable even better performance, as sudden changes in extrusion rate are not buffered by the smaller heat capacity of the heater block. But for any given set temperature I seem to heat filament to a higher temp than with an e3d style setup, this could be thermistor related sure but the circumferential heater as an idea has merit,
The other thing I think have got right is that their thermistor (which is very small) sits in a recess in the nozzle, so you measure and control nozzle temp, not heater block temp.
Love to see the 5 colour printing at max speed Ian.
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Ian, As always, I like the research you do to advance printing. Excellent work.
I hope this isn't too far off the subject,
So far my brief take on pressure advance (minimum user experience) is that it would be more accurate if it were applied by the slicing software instead of the controller board. The slicer software would be better suited to determine segment lengths and apply pressure advance as needed. Small round shapes would be recognized and adjustments made at the time of processing the gcode file.
Just my opinion,
Hi Tim,
Interestingly enough, you are not the first to come up with that. One of my blog followers (Rob Miller) just sent me this link https://mattshub.com/2017/10/02/linear-advance/
I swear I hadn't seen it before I did my tests. It's really spooky how they used the same test print method of parallel lines (nothing like the speeds I ran at though).
I don't necessarily agree with their assertion that the pressure is simply a factor of the "springiness" of the filament. Maybe it is but I'd have thought that the pressure would be pretty constant regardless of the print speed whereas with my tests, there seems to a clear link between speed and pressure. Or if it was just springiness, it would be linked to the length of the move perhaps? Maybe it's right but it's a dangerous assumption to make without some actual measurements IMO.
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Love to see the 5 colour printing at max speed Ian.
I might need to build a bigger printer. I'm not sure what the limit is for the 3 colour but with my bed size of 360mm, the best I could get with 500mm\s^2 acceleration is 424 mm\sec :). I guess I could up the acceleration and\or print across the diagonal…...........
Ref filament melting - How about do away with the heater and use a near infra red laser????
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Or induction, or various other methods. A resistor is cheap, simple and effective but we are talking extreme printing now.
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…......................but we are talking extreme printing now.
That's my kind of talk!…...........I like extreme.
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So thanks to all those who tried to help this old guy sort his blog out - especially bot. It seems all I had to do was put the URL on a new line! - DOH.
Anyway, video link is now embedded complete with fancy window and play button.
All I need to do now is chop it up into smaller bits and embed each clip at the appropriate point on the post. Might be a while before I get time to do that though.
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I watch the video and read the blog, yesterday night: very interesting!
As I think it would be interesting to have a closed-loop XYZ system (using encoders), it would be even more usefull to have a closed-loop pressure regulating system. But as you said, this would require to find a way to measure that pressure.
If you have an better idea what transducer could be used on your Diamond hotend, community might be able to help you getting one (either by financial help, or by providing one; some people may have access to such things)…
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Finding some way to measure and then use pressure values from within the hotend would be a massive move forwards in several ways, firstly we could eliminate blobs and strings provided that whatever extruder used has sufficient precision and power, and had been calibrated in some way to know when to lower extrusion force at the end of a line of infill, we could print potentially much faster whilst maintaining quality, we could eliminate the need for any type of extruder calibration, for any measured true nozzle size there would be an optimum value for pressure/mm extruded.
