Saturday, 29 April 2017

Bolt the Thirde

In the mail today, a package from the UK - not subjected to import tax just yet - containing my third hobbed bolt, this one from E3D, so goes well together with my hotend. I expect them to make good stuff, and having it made out of steel rather than brass ought to keep it going a bit longer.

The design is a lot simpler than the Hyena from

Just plain grooves, nothing particularly fancy. If they prove dissatisfactory, I might go for that place that sells a hardened steel Hyena.

First simple extrude test took 80mm filament when asked to extrude 50mm. But oh! Did it do it beautifully:

Nice and precise extrusion
This matches nicely with the fudge factor of 50/78 I had put in Marlin. Removing that, and the extrusion of 50mm extracts... 94mm? Let's try that again. Yes, quite accurately that much. Ah, but I was looking at the wrong copy of the Marlin sources. Why do we even have that lever? The right one had 41/50 correction factor. Changing that to 50/96 clearly slows down extrusion, and brings us to - extruding 2x50mm for extra accuracy - as close to perfect as I'm able to measure.

Time for, of course, a calibration cube! Today's Z offset is 0.5mm at an indoor temperature of 20C, outdoor humitidy of 96%,  and pressure of 1008hPa. Clearly I need to hook up my little Grove humidity sensor so I can get a usable humidity reading. According to that, I have 25% humidity and 22C. Now I should set that up so that I can just have it running at all times and store the results - for science! Or something.

The cube came out really nice, fewer gaps at the top than usual and nice even walls. I'm liking the bolt so far.

Had to do another Benchy, of course, building up the fleet. This one was even nicer, the writing on the bottom partly legible, fewer gaps in the foredeck, though still some unevenness around the middle of the side.

The first thing to get printed has to be the further Settlers of Catan pieces, this time the Egyptians. It's a new day, calibration is still at 0.5mm Z offset at 25% humidity and 20C. Curiously, when I connected Octoprint (since I think I have the gcode ready there), it centered the X and Y axes reeeally slowly. Looks like the G0 comment uses the wrong speed. But eventually it came up and I was right indeed.
Pyramids and sphinxes and sand-covered roads, oh my

The problem I have with Octoprint is that it has no way to adjust Z offset, so I have to have the GCode contain the Z offset, which is not handy. Getting my prober up and running would be better, unfortunately the prober mount design I found doesn't work with Sturdy Mendel90.

Before delving into modifying a prober STL, I took a look at doing a simple adapter for the dog basket mount I have on my bike. Required a bent tube module, which was easy to find. Also requires a proper way to slice, so I installed the Slic3r plugin. Wasn't too difficult, but for some reason the STL file uploaded doesn't allow slicing - the icon is disabled. No obvious error messages, but Octoprint has started to behave oddly, loading very slowly and sometimes not connecting. Re-uploading the STL after having installed the Slic3r module and enabled it didn't help. The other computers can't run Pronterface without a printer attached enough to actually slice.

Friday, 14 April 2017

I grow weary of this bolt

After +Tim Hatch's suggestion started making more and more sense, I re-soldered the Z and E microstepper jumpers. After that, it's time to recalibrate - I might have thrown all the microstepping off.

First with current settings, extruding 50mm at 220C, 25mm/min, 16 microsteps, fudge factor 50/90. Extruded roughly 5mm.

Removing fudge factor, extruding 50mm. No movement of filament. Seriously? Stripped again? Taking it apart and doing a cold pull. Bolt doesn't look stripped.

Extruding 5 mm looked fine. Extruding 50mm extruded 41mm. Applying that as fudge factor.

Extruding 100mm extruded ... nothing. Once again forgot to make the fudge factor a float.

Extruding 100mm again got 42.1 mm. This is freaking random. The gears move correctly, but little comes out.

Maybe the hobbed bolt is worn down? Sounds unlikely, since it's supposedly high quality, and I haven't used it that much, but let's have a look:
When newly purchased

Current state

They actually do look worn - the thin parts that come in pairs are clearly worn at the ends, less clearly in the center, but still worn down enough to be below the bigger flat pieces. That would explain lack of traction without actual stripping.

This bolt was the Hyena 2.0 from It lasted a bit over a year of intermittent use, and that was even the chrome-plated supposedly more durable kind. Dis-a-pointed! What's the best hobbed bolt these days? There's the Concentric from Airwolf3d, but I read that it's so wide and shallow that the filament tends to wander. Then there's the Hobb-Goblin from E3D, which is at least stainless steel, but the grooves look shallow. Various forum comments sound good, though.

There's a fairly comprehensive test on Instructables - not including the Hyena, alas. But they give pretty good grades to the Hobb-Goblin, so I'll get that. Only the RobotDigg were better, but the ones tested were different from the Wade's-compatible ones, and I don't see what material they're made from.