E steps are calibrated. When I was calibrating my printer I got a flow of 79.56% I had tried printing at that flow and at 100%. I was able to get a print out where I could watch the printing in the trouble areas and the first layer on top of the infill was very thin and stringy and the layers afterwards looked like they struggled to correct for it. Not sure what settings would effect that though, maybe connected to my meh overhangs and bridges.
So your flow is set to 100% (and NOT 79.56%) and you are getting all that under-extrusion? That should not be happening at 100% flow.
Have you taken the hot end apart? The bowden tube needs to be right up against the back end of the nozzle. If there is a gap there then retractions can (and will) pull material into the gap and cause a partial plug. It isn't enough to cause "missed steps" on the extruder but it can certainly be bad enough to cause under-extrusion.
The bowden tube itself is a "consumable". As the X moves back and forth the tube will rotate in the fitting on top of the hot end. As it rotates the little blades in the fitting chew up the outside of the tube and although it can't pull out, it can back away from the nozzle. That is why every once in a while (call it 30 hours of printing) the bowden will need to be removed from the hot end and have 5 or 6mm cut off with a nice square cut. The nozzle also needs to be removed (heat the hot end before trying to remove it) and a proper sized wire (you can probably find a 1.7mm metal coat hanger that is just right) needs to be pushed down the hot end to push out any plug of plastic that might be in there. Then you can put the nozzle back into the warmed up hot end and leave the nozzle about 1/2 turn from tight. Then push the bowden back in to seat it on the nozzle, and finally carefully tighten the nozzle to make a seal with the bottom of the bowden tube.
In regards to Flow:
Calculating flow is really easy. When the volume of any extrusion is exactly equal to the amount of filament required for that volume then flow is 100%. To say it another way - when [Volume Out] = [Volume In] then the Flow is 100%. Setting it at some number a lot less than 100% will definitely cause under-extrusion.
My filament measures exactly 1.72mm diameter and that is what I have input into Cura for my custom PLA. My Layer Height is .2mm and my line width is .4mm. Given those numbers, if I have an extrusion that happens to be exactly 29.04mm long then that extrusion needs exactly 1.00mm of filament. Not 0.7956mm.
Edited by GregValiant
Good to know about the maintenance, I knew parts would need servicing/replacement but wasn't sure of the timeframes for that. That and I haven't quite built up the confidence to do maintenance on it yet, though I suspect the something extruder needs lubrication as I sometimes hear a squeak. Will also try another print at 100% in case I missed a setting in between tests. I am clearly still very much in the "I have no idea what I'm doing phase" 😄
I picked up a microscope at a garage sale. When I first started printing I was having problems and I was running around different websites reading and trying to figure out what I was doing and I was chasing my tail. Then I thought about the microscope sitting on a shelf and collecting dust. Ah Ha! Then I could see what the heck was going on.
The chances of coming across a $3 microscope aren't good but a decent magnifying glass can be a good tool to inspect a print with. When you look at a flat surface and it has ridges then it's over-extruding. If you can see gaps between the extrusions so you can see the layer below then it's under-extruding. Vertical walls are pretty useless for troubleshooting because they look decent at a wide range of flows. They will show speed and acceleration problems better.
Here is my newest version of a calibration shape. I was playing with ironing. This was at my standard settings (75mm/sec, 35 for outer walls, .2, .4, and flow was 100%. Yes, it says Bite Me on the side. (It's my calibration cube and I can make it look however I want.) This from my Ender 3 Pro (8 bit mainboard and Micro-Swiss hot end).
I don't think it's just the slopes. It's hard to tell with white filament but it looks like the under-extrusion is pretty consistent all over.
Have you calibrated the E-steps? If so then you have all the flow rates in Cura set to 100%?
(If you say "No" and it's because you used a single/double wall calibration cube then I will not be happy.)
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