Tuesday, 26 April 2016

Better hardware, same problems

Dremeled the large gear nut trap enough to get the hobbed bits centered properly

The large gear is mounted slanted enough to move 1.8 mm in and out of the small gear. That brings it awfully close to the bottom of the small gear. I should probably fix that before doing much extrusion.

Some power measurements since I found a power meter:

Idle - 17 W
Heating hotend - 60 W
Keeping hotend hot @185 - 32W
Extruding w/o filament @185 - 32W

Heh - extruder gear ran the wrong way. This is not a pultrusion machine, thankyouverymuch. Switched wires to opposite order and marked black on the flat cable.

50 mm extrusion request extruded 38 mm filament. Time to adjust the firmware. And once more to remember to use floating point. But even with that not enough filament got extruded, in fact even less, and I could see it moving slower and slower. Stripping again? Why does it strip so easily?

Aaand tried to pull out the filament while it was still at about 120, which got it stuck. FML.

Edit: Possible explanation could be that I can't get the material out of the nozzle as fast as I put it in. The extra material melts and starts squeezing back up, increasing back-pressure, especially as it cools down further up. Eventually the back-pressure is enough to cause stripping.

This should then be solvable either by turning down extrusion speed or possibly by increasing the temperature. I can also attempt to check this by finding out the feed rate and seeing if the extrusion rate is (2.85/0.5)^2 times that. 32 times. Seems fast. Could measure by filming.

Thursday, 21 April 2016

My smallest fan

Brief update: Replaced one of the screws for the extruder mount with a shorter one so it can get out of the way of the hotend fan. Boy, this is tight design. All things wire up nicely and run, the new hotend heats quickly and cools off slowly. Unfortunately, and I should have checked this before, the hobbed part of the hobbed bolt is not where it should be, due to the nut not being far enough into the gear. Melting was not good enough. I will have to dremel.

The fan on the hotend is small but noisy. Handy, though, that it could be wired to the P connector on the breakout board. Hopefully it'll keep the filament from melting too high up.

Update: An overexposed view of the molten mess that is the nut trap of the large gear. There is a fairly obvious extra layer that should be gotten rid of, though I'm not sure it'll be enough. We'll see.

Tuesday, 19 April 2016

Putting it back together, again

With a new pair of gears from Thomas, I put the extruder back together again. It took a fair amount of sanding and Dremelling to get the bits to fit, but eventually they did. The screws holding the hotend are rather bent, and not able to reach the holes on the other side:

Getting the extruder onto the X carriage was also quite fiddly, worse than before because this extruder mount is lower and so there's less space below the motor. Not sure why it's so important to have it be as low as at all possible. Once this works, I may just redesign it to be a bit higher and print a replacement. See that little space under the motor? I got a washer and nut in there to meet up with a bolt. Not simple.

At the same time, I've moved from my previous Linux laptop (which, alas, was driving me nuts in a number of ways) to a Mac (which merely confuses my Ctrl/Alt muscle memory). I made a copy of my home directory with all the Arduino stuff, but it wasn't quite enough to get the Arduino program to accept the Sanguino board just yet. Grrr.

Wednesday, 6 April 2016

I appear to be cursed

My colleague @Thomas Riedl very kindly printed a new Wade's Extruder main part for me, being careful to get the support off nicely. It required a bit of drilling, sanding, and dremelling to get all the parts in, but at least it looks solid.

Alas, the weird version of Wade's I had was not only narrower in the hotend mount, but also taller, so the large gear doesn't fit, it hits the X carriage in a place where I can't just cut a hole.

Fortunately, I had also ordered a Greg's Hinged Extruder, a molded rather than printed version, just in case Thomas ran into problems. It has a strange rubbery top to it, which I a bit later found out was is because they have pre-inserted and closed off the two hex nuts:

So I remount the motor on that, only to find that the gears are not compatible and I could not get the small gear off the motor rod. I suppose I could get a new motor and finally have nothing left of the original extruder. But the old large gear does work, so I can use that instead! After mounting that and the idler, getting the hotend fixed was difficult. Due to extra lee-way, the left-hand screw would actually move the hotend down on its side when far enough in, making the hotend slant:

I'm pretty sure that's a bad idea. But that's not all, once I got everything together, I found that the extruder mount was right-handed instead of left-handed. See how it sits over the edge of the X-carriage with space left on the left:

After disassembling it, I found the mounting screw had actually dug into the hotend:

My best option now seems to be to have Thomas print a new large gear - looks like I need a 37 tooth 5mm pitch gear, though it's possible a 39 tooth one would work, which is nice because that's the normal one with Wade's.