A UniCoFil vase

Back in August, I did some more prints with the UniCoFil filament after replacing the heatbreak. It's possible that replacement wasn't necessary, but I will never know. Even after that, the stripping continued, though possibly not as often or as much. After printing out a failed hexagon vase that simply came apart at a layer that had stripped, I changed the filament settings to a) have a 1.0 extrusion multiplier, and b) extrude at 230°C. That eliminated the stripping, and I was able to print this nice small vase:

Just goes to show that each filament has its own best settings. 

Prints That Go Boom in the Afternoon

More work on the temperature tower, since I want to calibrate that for PLA as well. Also, I should probably calibrate it separately for separate nozzles sizes. Anyway, feeling too lazy to change all the numbers in Bob long if-clause, I change it to this:

; For Fast_Informative_Temperature_Tower, 10 levels at 8mm

M104 S{230 - (4 * int((layer_z / 8)))}

While this doesn't show the exact temperatures at each level, it is a lot more concise and easy to adapt to other temperature combinations.

Printing the temperature tower with the 0.25mm nozzle takes a lot longer than with the 0.8mm, but it actually looks nice, and doesn't wobble eerily when printing the top. This minimal tower is rather unstable.

The PLA tower with 0.25mm nozzle is simply... perfect. At all temperatures from 230 to 190, no stringing, no change in the quality. I had to go into the gcode and double-check the output from above to convince myself that it was doing the right thing. 

No, it's not twisted, that's just the perspective.

A PETG tower with the 0.25mm nozzle (Z offset -1.05) and temperatures from 250 down to 210 gave me an entirely new experience: An exploding print. I was sitting next to the printer when I head this sound of plastic bouncing around, and this is what I saw:

Look in the background, there's where the parts landed.

The pieces collected. A part of the foremost pieces has also fractured off, but stayed put.

At too low a temperature, the print simply fractured - probably from the stress of being pulled back and forth. It's really difficult to see the stringing, but I think 230 is about the right temperature. Unless I am missing a chunk, it broke off while printing the 224°C layer. So my previous test with the 0.8mm nozzle giving the best result at 220°C doesn't work well here.

I'm surprised that this would happen with PETG, it's supposed to be less brittle that PLA.

Temperature Towers and other tweaks

As mentioned in the last post, I did some temperature towers (using Bob's sneaky gcode) and found better settings for PETG. The standard towers are a little too detailed to work well with the 0.8mm nozzle, but I tried anyway. Here are the Fast Informative Temperature Tower, at 4 different retraction rate settings (default 1.4, 2.0, 2.5, and 3.0):

String galore, but less so at about 220°C and 3mm retraction. I don't think I want to retract more than that, I see several sources saying it can lead to hot plastic getting too far up towards the PTFE tube.

My 0.4mm nozzle was pretty full of PLA. I didn't want to scratch it using any kind of metal tool, instead I heated it up in a candle flame to get the PLA soft enough to run out. I would have preferred a butane lighter, but ours was out of fuel. The PLA didn't run out on its own, but I was able to attach a piece of filament and 

For PETG, I'm using the steel powder bed, as the smooth one just doesn't let go of the print, and for the 0.8mm nozzle with 0.4mm layer height, I have calibrated it to a Z level of 1.150. The layer height does make a difference for that. 

I'm using the stealth mode more. It is really a lot quieter (average 46dB instead of 52, measured with a phone app, the phone lying right in front of the printer) and only minimally slower, but it turns off crash detection, which I definitely want to have on when starting a print and leaving. When I'm watching the print, it's not so bad.

Step up the reactor power three more triangles!

Took apart the hotend after failing to do an atomic while it was put together. Saw some black stuff on the second pull. These pulls are more difficult than I'm used to, I guess the tolerances are smaller.

Several pulls later. It still takes a lot of pressure to get filament through, even at 200 C. At 210, it goes smoothly (and slightly smokingly at first!), but soon becomes tougher and eventually it becomes almost impossible to press anything through. The pulls come out clean, though.

Could I be feeding filament too fast? I would rather not turn down the speed, but it could be a start, then up the speed to as much as it can handle.

Could there be a gap between the nozzle and the heat break? Then filament would squeeze in there once it softens enough and gets under enough pressure, and that would create extra drag.

I also need to fix the gears before they eat each other. Dremeled the hole some more, and rotated the nut, now it

Weird. I set up to do a 5cm test extrusion at 25% speed. When I first hit extrude, it ran crazy fast for a few seconds (while actually extruding), second try was indeed at very low speed.

Doing a second test, I notice the filament comes out at an angle before falling down nicely. I seem to remember that being a sign of clogging.

Second test @25% speed, 200C (properly measured) was spot on in length, good.

Third test, same settings, the filament doesn't fall in the same nice circle, but more randomly. Length is 4 mm short.

Pro tip: After doing test extrusion, check for random pieces of filament around the moving parts.

Fourth test @25% speed fell 2mm short. Chalking this up to random variation or poor measurement.

First test @50% speed (50mm/min). Extrusion is now straight and the filament falls in a nigh-perfect circle. 4 mm too short.

Second @50%, accidentally 10cm. Fell 9.5 mm short.

Added a piece of soft foam at the filament intake to get dust off.

Third test @50%, fell 4mm short. I'm starting to see a pattern here.

At 75%, fell 4mm short. Good.

There's definitely drooling going on at 200C.

At 100% speed, fell first 8 then 10 mm short. Not so good.

Back at 75% speed, first 6 mm short, then 5mm, then 6, then 5.

Some posts indicate that the e3d is not the best for PLA, because it has a relatively small heating area, so you need to raise the temperature or lower the speed. That matches what I have seen. I guess I will print at 200 or 210.

Recalibrates ro 204.5. Look, I gained half a millimeter of printing height due to much engineering effort on the e3d team's part.

Putting the new fan duct on. For reference: Red goes on the left of the two bent fan pins,  right goes on the loose wire from the ribbon cable. Gcode to start/stop fan is M106 S127/M107.

The current assembly (not cabled to avoid touching the bed yet). If you look carefully, you'll see the hotend mounting screws sitting at an angle and not all the way in.

Aaand... it's totally misaligned. There is no way this fan will work, it goes over a centimeter below the nozzle. A better design would lay the fan flat like the original, but just have a wider opening for the hotend.

Update: Looks like this design might work: http://www.thingiverse.com/thing:631311