Monday, 16 May 2016

Yet more tests, yet more filament clogging.

Thomas Riedl is accepting of printing me yet another piece, so now I want to make sure the fan design I found fits properly.

The mount atop the fan is 14 mm high, and will sit roughly top-aligned with the top of the X carriage (perhaps a little higher). The fan itself is 15 mm high. The nozzle is at 55 mm down from the top of the X carriage. The bottom of the heatsink fan is 40mm down. This leaves me with 25mm from duct fan to nozzle, 15mm from heatsink fan. That should fit the 25mm version of this:

Installed and set up Slic3r again, setting PLA temperature to 210, bed to 190x200 (no way to mark X as going leftwards), adding Y home at end, leaving the rest at defaults (0.4mm layer height, 3 perimeters and infill). First print was actually quite nice, even without fan and with the temperature for some reason staying at 180C. There is one little gap on one side, and the top (like before) is not very tight.

[Cube #35]

Next I reduced the Y size to 190 to avoid drooling over the each while heating up, actually 180 would be better. Also reduced layer size to 0.3 mm, and now it actually went up to 200C. The front side has a slight waviness to it when seen in the right light. The gappiness on the top decreased, but there is a bit more droop into the infill holes.

[Cube #36]

Reduced Y size to 180 and layer thickness to 0.2mm. Quite nice, actually.

[Cube #37]

With these nice results, I went on to doing a slightly larger design, but less than 13 minutes in it had stopped extruding. I pulled it, and sure enough there were stripping marks.

One post suggested that tangling in the filament spool could be a problem, and indeed I had some. I unwound a fair amount of filament and put it back in a more orderly fashion.

I cleaned the hobbed bolt, reassembled with slightly higher tension, and extruded a bit. It quickly started stripping again, and the extruded filament changed between curling up beneath the nozzle, coming out straight, and coming out at an angle. Sounds like clogging to me. Again:(

From this post, a nice overview of problems that can give these symptoms (though for a slightly different system):

  • Nozzle is contaminated with dirt or dust. Can be solved with a careful cleaning or replacing the nozzle. [Should get the tools for a proper cleaning.]
  • Filament is too large and jamming in the front end. Measure the filament diameter with a digital caliper and make sure it's not larger than 1.80mm [3mm for me]. Feel along the filament for any bumps. Try a different roll of filament. [All my measurements have been fine.]
  • Filament has dust on the outside which is clogging the nozzle. Pass the filament through a sponge just before it goes into the feed mechanism to wipe off dust (also, give the nozzle a good cleaning). [I have recently added the sponge]
  • Filament is contaminated with foreign material in the plastic itself. This rarely happens but has been known to be an occasional problem. Get a different roll of filament and clean your nozzle. [I believe igo3d is a reasonable quality, so this is unlikely but not impossible.]
  • Too much back-force on the filament path. Check for binding by pulling filament by hand, it should pull smoothly. If it binds or catches at all, this is a manufacturing defect and should be covered by warranty. [Different machine issue]
  • Excessive heat buildup in the cool side of the extruder is causing filament to soften in the feed gear. This happens most often with PLA, but If your hot end isn't put together properly (heatsink missing or out of place, fan not working right, etc.) it could happen with ABS, too. If you're an expert user you can easily take apart and reassemble your extruder, but as a novice you probably don't want to do this. This is a manufacturing defect and would be covered under warranty. [Shouldn't be a problem with the heatsink fan]
  • Not enough clamping force between the feed gear and the bearing to properly grip the filament. If this component is out of spec it could cause filament to strip rather than feed; this would be a manufacturing defect and covered under warranty. [Just how much should the idler be tightened?]

My filament is actually 3mm, not 2.85 as seems to be the more common variety. While I have a spare spool, it's a rubbery filament, and thus hard to measure accurately. The order calls it 3mm, and I seem to have to apply some pressure to make it measure as 2.85. I don't think I want to add the complications of soft filament until I have normal filament working.

I think I need to do a nozzle cleaning again. Sigh.

Friday, 6 May 2016

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: