Monday, 20 February 2017

Three, count them, three different extruder mounts

[Note: This post is not in chronological order]

After my previous failures, I decided it was time to get this mount right. So let's try no less than three ways to get a good mount!

Way #1: After drilling out the filament hole with a 4mm drill, use a heated metal stick to smoothen the inner surface. Would have been easier if I had had an exact match. This might make my self-printed mount smooth enough that it doesn't drag the filament, but I doubt it - it might simply be too wide by now, so there's room for the filament to bend a bit and cause extra friction. Giving this a try, I noticed that the extruder heat setting was 200C, not 220C as I usually use. Weird. So I delve in a little more, and find that it's been using some default settings rather than the ones I changed - the changed ones were still correctly changed, just ignored. Computers! Slic3r's config system is still the most horribly overcomplicated and confusing one I've seen (outside of the BIOS/Xorg/Window Manager stack which is mysterious beyond belief).

Changing the settings to think my filament is not 1.75mm but 2.85 - which it is - made a print that smacks of over-extrusion:

Cube #57: Look at that oozing!
Cutting the extrusion multiplier to .75 reduced the overextrusion a bit:

Cube #58: Somewhat oozy
And getting down to .5 brought me to a very nice piece, quite acceptable:

Cube #59: Ooze-b-gone! Nice and straight, maybe a tad extra on the corner here.
So it's entirely possible that that was the problem, together with some early clogging and dragging. That's what I get for switching extruder mount and computer and firmware version and Arduino app version and Pronterface version and Slic3r version at the same time. Don't do that.

Way #2: Order a print online. I went to and had a print made using ABS (technically PCABS, which is a Polycarbonate/ABS blend, but I just wanted the heat resistance and solidity of any kind of ABS). This got done by Kinamico's Hub on a Zortrax M200, much more expensive than mine, for €17 + €12 (!) shipping (international shipping, even from not that far away, adds up, alas). The service was really good, calling me back quickly after uploading and asking pertinent questions. Getting it took a while, though, partly because I delayed answering some of the questions, partly probably because the security conference in Munich caused chaos. I got it one working day late (unlike an Amazon package which got delayed by three working days. So much for Prime). But what a beauty! Smooth, solid, and all the holes totally on the spot.

New extruder, with various nuts and bolts fitting perfectly.
Look at that built-in support piece neatly not touching the side of the hole.
If I get any trouble with my now-working extruder mount, I will switch immediately to this one. Until then I'll just cuddle up with this little beauty when going to sleep at night:)

If you want to order from 3DHubs, you can follow this link to give both me and yourself a $10 printing credit:

Way #3: Here's the interesting variation. The black mount I got from +Thomas Riedl  worked quite well as long as the mount was secure, but the mounting mechanism with two cross screws just didn't work well (hinc illae irae). Inspired by +nop head's mount that uses three bolts from the bottom and washers to keep the E3D in place, I decided to see if I could convert this piece. Actually adding three such bolts would have been infeasible, so instead I got a 1mm thick strip of steel and cut it to shape using my trusty Dremel. Getting the outer shape and bolt holts in was easy:

Slightly trickier was figuring out where to drill the filament hole, until I remembered the trick of using a nail to mark through a hole. Bang! A precise marking that's also a good start for the drill.

Dot never, ever marks the spot

So I'll drill a slot from one side wide enough for the neck of the E3D (gotta love having a proper diagram), and the two bolts holding on the motor will also clamp the plate to hold the hotend. The only remaining part is having a 16mm stop-gap piece above the hotend because this mount design is deep:

Check out that deeposity

That I could actually cut out of wood, it shouldn't get very hot up there. Or I can use washers. But given my success with approaches #1 and #2, I'm disinclined to further pursue this venue until conditions require it.

Since I have pinged +nop head anyway, I will direct his attention to my note at the bottom of my previous post about the nut traps for the idler screws not keeping the screw from getting turned further and digging into the extruder motor.

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