kaledly

Thanks again for the tips gr5, I really appreciate you taking the time to help. I'm out of time to experiment today, but I'll take a look at it again next week (the printers are work machines) and see if I can make any progress.

Thanks for the tips. The printers both have 2-3k hours on them, but I've performed maintenance on both hot ends recently (<100 hours ago) by installing new E3D nozzles and TFM couplers instead of the older PTFE style ones. I didn't replace the Bowden tube itself, but I did trim it down a 1/4-1/2" on each end and re-bevel the edges. I have a new Bowden tube from UM on hand so I can try installing that and seeing if it makes a difference. On your list, the only thing I think I have an issue with is the isolator spring pressure. I've got a 1-2mm gap between the isolator nut and the bottom side of the coupler. I'm not sure I understand the reasoning behind minimizing this gap. The only way I can see to reduce this gap is to unthread the Olsson block a bit to reduce the gap, but if I do that, wouldn't I run into an issue with molten filament leaking between the isolator nut and the block?

Thanks for the advice gr5. I did some more testing on one of my machines yesterday. I basically performed a modified melt flow index type test to find out how much material the extruder was able to push through the nozzle before it started to kick back and skip steps. TLDR, with a 0.4mm nozzle I'm only able to push about 2-3 mm^3/s through my machine before seeing issues. My test protocol was as follows: Machine Setup: UM2 Extended Stock black extruder Olsson Block w/ 0.4mm E3D nozzle Test temperature range 190-260'C in 10'C increments. ~4m long free piece of filament removed from the spool. Machine heated to 240C when new filament was loaded and 60mm of filament was extruded to clear residue from previous test. Pronterface was used to send extrusion commands and control machine temp. Testing: 1. Heat machine to test temperature and wait 1 min for equilibrium. 2. Extrude 20 mm of filament at specified rate (starting at 10mm/s). If extruder clicks reduce extrusion speed by 5 mm/s and retest. If extruder does not click, increase extrusion speed by 5 mm/s and retest. On to the results! A couple of interesting points: I had one old role of Gizomodorks black PLA that had really high results compared to all other spools of PLA I tested, so I reset the machine and verified the numbers, which were repeatable. Interestingly, this role old/brittle and was saturated with water to the point where it visibly steamed while coming out of the nozzle. I may try and stick in the oven to dry it and retest to see if the higher flow rates are due to moisture content. The Matterhackers PETG showing signs of under extrusion when printing walls is what kicked off this whole thing and it actually had really good maximum flow results compared to any of the PLA samples I tested. I saw under extrusion on inside perimeters at 60 mm/s print speed which only equates to about 5 mm^3/s of required flow, and the required flow value is less than half of what my test result showed at 245C. Based on that metric it looks like under extrusion starts to show up way earlier than when the extruder will kick back due to excess feed pressure. My data appears to be consistent with gr5's recommended print speeds for PLA (actually they may even be optimistic in my case). So, it looks like I need to upgrade the extruder on my machines and significantly lower my expectations regarding print speeds.

Hi all, this is my first post and it's a long one. I'm relatively new to working with UM machines and I've got two of them at work that I'm having some extrusion issues with. Both machines are UM2e's with Olson Blocks installed and 0.4mm E3D nozzles. Basically, I'm seeing a lot of gaps between lines in the infill and between perimeters which is an obvious sign of under extrusion. If I try and print at what I would consider normal temperatures for PLA (190-210C) the extruder will click and you can tell that it's obviously missing steps. With PLA, I have to crank the temperature up to 225-235C to stop the extruder from skipping at which point print quality goes down hill. Similarly, with PETG I have to print between 245-255C, which is also quite hot compared to normal. I've rebuilt the hotend on both machines with new nozzles, PTFE couplers and bowden tubes and I've not seen any improvement in extrusion quality. The only thing that seems to work are unreasonably high temperatures or really low speeds. Looking at the volumetric flow numbers, I'm well within range of what I've read the machine should be able to do, so I'm a bit stumped as to why I can't achieve good flow. Nozzle temperature varies by a few degrees during printing (+/- 2C from target), but what I'm seeing in the microscopy pics below is that heat transfer just isn't sufficient to provide consistent extrusion. See below for some PETG test prints that I did for an example of the issue. Left, Cura defaults for 0.2mm layer height. Middle, Cura defualts, but slowed inner perimeters to 30 mm/s to match outer perimeter Right, Cura defaults, but all speeds set to 20 mm/s Left side print from top photo - Matterhackers black PETG - Cura defaults for 0.2mm layer height, 0.4mm line width, 30mm/s outer walls and top infill, 60 mm/s for inner walls. Note the gaps between perimeters and top infill lines. Top infill and outside perimeters printed at 30 mm/s have a volumetric flow of 2.4 mm^3/s, inner perimeters are double that at 4.8mm/s. Both should be within range of what a UM2 can do from what I've read (10 mm^3/s max, <5 mm^3/s preferred). Middle print from top photo - Matterhackers black PETG - Cura defaults for 0.2mm layer height, 0.4mm line width. Inner walls slowed to 30 mm/s. Volumetric flow rate of 2.4 mm^3/s Right side print from top photo - Matterhackers black PETG - Cura defaults for 0.2mm layer height, 0.4mm line width. All speeds set to 20 mm/s. Volumetric flow rate of 1.6 mm^3/s I think both machines are running the stock 25W heater cartridge. I have the 35W versions on hand and can install, but since I'm not seeing a temperature drop while printing faster (30-60 mms/) I don't think that's going to change anything since the lower wattage units seem to be able to keep up with power demand. The only other thing I can think of to fix the issue is upgrading the extruder to supply more feed pressure to get a more consistent extrusion, but I don't really want to drop $400 on the UM2+ upgrade kit to find out that that doesn't work either. Any ideas to fix this, or do I just have to print at super slow speeds with these machines?