Wednesday, 1 November 2017

Scary prints

For Halloween, I'm printing various things downloaded from Thingiverse. Mainly spiders:


These print flat, but you can always heat the legs (or other parts) to pose them. They print really easily with my black flexible PLA, though getting them off the bed has been a smidgen tricky. So now, since I need more spiders, I'm doing prints at increasing Z offset, and once I see what offset is the highest they can still hold on to, I'll go back and do my calibration routine. At 1.1mm Z offset, they printed somewhat tightly on the bed. At 1.2mm there was some filament visible on the bottom, which is fine. At 1.3mm the legs started coming apart from lack of bed adhesion. Calibration (the day after) had only a bit of resistance at 1.1mm, not the full stoppage I usually go for.

Attempting next to print a large box, I ran into dimensional trouble - my print surface wasn't quite big enough for the full size I wanted. Testing the size, I ran the fan into the clips holding on the glass on the bed. I was able to improve this a bit by having the clips clip onto the cardboard insulation under the bed, making them flatter. But even so, I cannot currently print larger than 17x20 cm. I could possibly squeeze out about 1/2 - 1 cm by adjusting the Y direction a bit, it prints a bit towards the back. However, the point is moot, since when starting a reduced-size print, it turned out it would have taken multiple days to print, and I don't want that running in my bed room. Also, the bed isn't quite flat out at the edges - I had it calibrated a bit low, and the middle parts got too low, leading to stripping. On the upside, it made for a pretty feather-like structure:


Fixing the strippedness showed two interesting things: 

Firstly, the pulled filament was rather dark. This could be carbon build-up over being heated to full temperature for several minutes, but more likely it's a bit of the flexible PLA left over. A couple of minutes of heating shouldn't do this much carbon buildup.


Second, the stripped material on the hobbed bolt is fairly loose, which is different from the grey material on my first bolt. I'm not sure if it's the bolt design or the PLA, but in either case it's possible to just brush away the filament rather than having to take out the bolt and pry it out with a needle. I should possibly invest in a small stiff brush for the purpose.

The hobbed bolt after simply brushing it with a standard small pain brush
After cleaning, and with measuring Z height only to where the paper starts having a bit of traction (1.7mm), I ended up with a nigh-perfect test cube (#69). It's curious that it moved up so far - maybe each time I pull the filament out I pull the Z axis bolts a little further into their sockets. If the sockets aren't perfect near the top, it may take some pulling to get them all the way in.

Saturday, 28 October 2017

New fan, new prints

The hotend fan had been slowly dying, first making a lot of noise while starting, later not starting unless prodded, and finally not starting at all. Given the temperatures I print at, this hasn't been fatal, but might have contributed to my issues lately. I got a new fan, and this time tested which way it blew before mounting - turns out it needs to be mounted sticker-side in:


The new fan came with a short cable and a looong extender. Because I'm lazy, I just wound up the extender rather than shortening and soldering it:


I've also been poking a bit at getting the probe in. First I need to have a voltage splitter so the 12V output can go into a 5V GPIO. But when I do a standard splitter,  the total drop over the splitter is only 8V. Odd.

Together with our friend Mr. Carson I've also been designing a thing to assist air flow from radiators. For that purpose, I designed a corner air indraw piece, the first printing of which failed horribly, as did my attempt at photographing it with my phone:

Failed print (photographed with Nexus 5X)
Same failed print (photographed with Canon 60D + EF-S 50mm + flash)
Trying to get a new print ready for this, I was again struck by how poorly Slic3r generates support structures - they have mostly been useless for me, sticking really badly to the print or being too thin to stick to the bed. I saw MatterControl mentioned as being better, so I downloaded it. It does have most of the settings I need (Z offset being important), but ho-boy is it slow at generating layers! Slic3r does in less than 10 seconds what MatterControl took about 10 minutes to slice. It adds a lot - a lot! - more support material, as in a total filament usage of 161g to Slic3r's 60g. Most of the interior is filled with support, getting that out would be a lot of work

Saturday, 21 October 2017

Remote viewing

Rather long pause since what happened the last post, for no particular reason.

I decided that I should make use of that old Logitech webcam that +Carl-Eric Menzel kindly donated. It's a Logitech QuickCam Pro 9000 according to lsusb, and that appears to be supported. Of course, the setup pages for webcams on Raspbian go "no configuration needed!" following by two parameters, and doesn't mention the need to install ffmpeg which is not part of the normal installion. After poking around a bit, I found this page with a rather long instruction on how to install it.  There's also this answer saying to use libav instead. Neither of which work very well. The `motion` program does better, but failed utterly at rotating.

In the end, I turned off the streaming video and set it to do a picture a second. Rotation is still broken - it tries to use ffmpeg for that, it seems, despite there being many better ways to rotate a jpg. I also had to set up a cron job to remove all the snapshots once a minute, lest the poor little 'Pi be full of jpgs. Even so, to avoid wearing out my SD card, I move the snapshot dir to a tmpfs (temporarily hosing the system due to a typo).

The webcam is mounted sideways because it's taped onto the shelving system next to the printer. It turns out to be surprisingly difficult to rotate the picture. ffmpeg can rotate video, but installing that is a large task. jpegtran can rotate a picture, but the web server keeps serving up the unrotated version. Bother, but not a huge deal.

I'm printing with a new blue filament, which is mostly behaving nicely. The oddest thing is when I printed some more of the glass markers, the side of them came out all blobby:


And then they started seemingly stripping, but in an odd way:


This may have to do with the filament being on a new spool and jumping over the side, then getting pulled tight and adding extra resistance. As long as I keep the filament from doing that, it's fine.

But now it's doing pretty well - the fan on the e3d is being a little problematic, though, I may need to replace it. I redid the floaters from before with a flat bottom to make them stick properly (Slic3r's rafts are awful, just like their supports):


And, of course, since this is a new filament, there's a Boaty McBenchface. The bottom is a little funny, because I was doing the image capture as well as using a browser on the 'Pi, which was too much for it. So the print would just stop momentarily as OctoPi couldn't get to the processor. I'm calling it carbuncles. For some odd reason, the brow of the ship is flattened, which none of the other ships show. The usual suspects are also there, like the gaps in the front deck and the hanging in the windows. plus there is a bit extra wobbliness around the windows. The bottom was nice and readable, though. So this filament just behaves a little different.


Sunday, 10 September 2017

What can you say about gluestick-covered aluminium beds?

The new bed takes forever to warm up. Even after about 8 minutes it was not too warm to touch. Using hairspray on this did not lead to adhesion.

Increase bed temperature to 100C, didn't help much - the bed did get appreciably warm, but the test cube still had two corners lifted:


Trying now with an UHU stic [sic] on warm bed. That stuck like crazy  - in fact the cube stuck so much I scratched the bed badly trying to get it off. In the end I put the plate in the freezer, after which I could get the cube off. But taking the bed to the freezer after each print is a bother and waste of energy.

With the chilled bed, I tried with hairspray and gluestick both. No sticking with either. However, that does indicate that with a temperature in between cold and hot, gluestick should work.

Tried with setting the bed temp to 30C for a while, until it was lukewarm. That gave a removable but still properly cornered piece.

Unfortunately, the bed starts off colder than this, otherwise it would have been nice to be able to not do any bed heating at all.

I'll probably get a glass plate, as it has a wider range of good adherence using hairspray, but I'll keep the aluminium for things that have small footprints. For instance, this replacement floater from one of my plant box:

[floater]

To try something flatter, here are some mounts for the tomato rail. They were a bit difficult to get off, they stuck enough to bend a bit.


The need for glue stick is annoying and hard to get right. There's not a lot of leeway between too stuck and curled corners. So I went to the local glazier and got a new piece.

The new bolt had different enough dimensions that I ended up flipping the big gear and just use tension to keep it in, rather than having a nut on the outside in the nut trap. This is probably why it stripped fairly quickly. It stripped with a lot more powdered filament than the old bolt. Now I'm using the nut with fastening screw on the far side and a nylock on the near side. Would have been nice if the bolt itself had flats at the end for fastening nuts.


Finally just found the right place for a nut and epoxied it on.

-- Vacation break --

With the now well-hardened nut on the bolt, it's easy to put the whole thing together right, and extrusion looks good. It did another of the really slow Z moves, I still don't understand why that happens. When homing, it went at full tilt.

Z offset 0.6. Printing simple cube without any hairspray, because this glass plate seems extra smooth, and I want to see if the idea that the adhesion is better at high smoothness has any merit. Not really, the corners are still turned up a bit.



Tuesday, 13 June 2017

A new bed

I rather obviously need to get a new bed to replace the broken glass. I started looking at places that will do aluminium sheets and quickly found metal-fachhandel.de, which has lots of options. Particularly confusing is the choice between "gefräst" (milled), "gewalzt" (rolled), "gegossen" (cast), and "hochfest" (high strength). There also seems to be some difference in exact composition, between AlMg4,5Mn, AlZnMgCu1,5, and AlMg3. I guess milled and cast are rougher than rolled

I looked at a few posts around the subject, and found the choice of aluminium over glass is not as simple as I hoped for. Longer discussion here.

Pros:

  • Can use the distance sensor on the whole plate
  • Heats up faster
  • Doesn't break if you foolishly drop the print head from really high
  • Can do away with the clamps
Cons:
  • Possibly warps (though some special mounting trick might fix that)
  • Could get scratched if the hotend runs into it
  • Could generally scratch over time, leading to prints that are hard to get off
Trying with an alu bed for a while cannot be that bad, though, I can always change it if I want the glass advantage. Ordered a 5mm sheet from Stahljunge GmbH / Team Heavymetal (heavymetal-aluminium.de) Tuesday, it arrived today - that's pretty fast! And nicely packaged, as well:

Before doing a test print, I wanted a shot of the tip of the hotend, to see if it had taken damage. This is the kind of shot where my DSLR shines, though holding it right was a challenge.


I think that might be a piece of glass up there, I should extrude carefully at first. But other than that, I think it doesn't look too different from a fresh one (modulo scratches).

Calibrating by hand shows that, of course, the new bed is a lot higher, about 4.8mm current Z offset. I tried to update the firmware to use a more appropriate Z height, but for some reason it couldn't upload it. Annoying, but no deal-breaker, I'll just start my calibration cycle with G0 Z6 instead of G0 Z2. Once I've figured out how to hook up the proximity sensor, it'll be a moot point anyway.

Trying to push the apparent piece of glass out by extruding a bit didn't work. I managed to break off the remaining piece of filament trying to push, so now I'll have to take apart the extruder to get that out. It's also possible that my attempt at doing a cold pull with too little filament to pull on caused fusing of melted filament to some part of the extruder.

In the end, I had to take the whole extruder setup apart and do a cold pull together with some needle poking on the standalone (or rather hangalone) hotend. After putting it together again, I calibrated to 5.2mm Z offset, had to change the initial GCode to not go to Z5 while heating. The bed doesn't heat through very fast, even at print start it's lukewarm to the fingers.

I'm trying at first without any hair spray and a relatively high Z offset. It's not sticking at all. Tried with hair spray, still no good. Lowered by 0.1, still no good (but the hairspray was old). Tried with hair spray added after the bed got heated, it at least sticks a bit, but the print ended up with lifted corners despite the filament being clearly squeezed tightly:



Saturday, 27 May 2017

Oops

My most recent print died partway through when the red filament tangled itself:



Ok, that's somewhat annoying. I'm not sure if it came this way or if taking the filament in and out of the extruder has caused this. I should look at ways to prevent this from happening, in any case

Fixing it is easy - just snip the filament and untangle it. *Snip* *Swoosh* *Clang* Oh, wait, the filament was the only thing holding up the X axis and extruder, and it just fell down onto the bed, with predictably disastrous consequences:

It's at least a pretty pattern

This might be my chance to switch out for an aluminium bed. That should also make it easy to mount it using the corner bolts instead of clips. Still, whoops.

Wednesday, 24 May 2017

Lots of printing, now also with PETG

With proper X axis tension, the printer is happily printing. I left it run for hours while we were away for the Street Food Festival, and it was still running merrily when we came back.

This particular print was designed this morning to match our balcony bench's feet, so it can stand up more straight on the slanted balcony. I didn't incorporate the angle of the bench's feed, so it might not work well in the long run, but it works for now, and I don't want to do another print of that length without good reason.

I suspect the reason for the Z offset changes has less to do with the frame expanding and more with just the holders getting push a tiny bit up every print, more if the print warps. The offset is always increasing and then gets reset when I fiddle with it. If it was the temperature/humidity/pressure, it would be going more up and down. So I should try gently bonking down the two Z axis mounts to check if that keeps the calibration.

After my failure with the AA battery dispenser extension, I filed a bug against Slic3r - originally for failing to slice right, but it turned out the model was just broken. I changed the bug to suggest doing a better error message - "auto-repaired" sounds like it actually works, "attempted repaired" would be better. The discussion around this pointed me at netfabb.com/service, which offers repairing STLs for free. With that, the dispenser actually printed right:


I printed a little mount thing for putting up my name sign at work. Unfortunately, I'm not exactly sure where the name sign is.

I started printing a solder fume extractor, but it ate a lot more filament than I expected, I had to stop halfway through when my white filament ran out. Now I have a useless white thing.


This was also the largest rectangular thing I printed so far, at 13x13 cm, so I was extra careful to keep an eye on the clips on the side. The duct fan mount is just high enough that it doesn't hit the clips here. Oddly, the print wasn't really on the center of the bed, but towards the back:



I had a sample of PETG lying around from an earlier order from dasfilament.de. Since my white ran out. I figured it'd be a good time to try that. I did a Bugz because it's small and I had problems with it sticking together in PLA.

When that came out well (and was able to move), I did a McBenchy, of course, which came with a much better bow and almost-readable letters, but dangling filament atop the windows:

Nice overall, but some sagging at the window

Look at that nice, smooth bow

Still some gaps in the foredeck

Stringing in several places - I suspect more retraction would be needed.

The name can almost be read. But what's with the hole in the bottom left?

On a second partial print with higher start position, you can almost read the undertext.

Unfortunately, the Rubinrot (RAL 3003) offered is not quite the shade of red we want in the kitchen, we want Kirschrot. And the filament that they call Kirschrot is misdescribed as Rubinrot, so not I don't really know what it is.

One problem with PETG is that it doesn't print into thin air as easily. Not only does it sag in horizontal prints, unless PLA which can actually print straight across nothing, but it also requires support at a much higher overhang angle. An attempt involving a halfcircle fell down despite support material at an overhang of 40 degrees.



I'm starting up my balcony garden, now that it's nice weather again, and I want to use the two semi-spherical plant boxes I have, However, they don't come with a good holder, nor a good hole to stick a holder through. So rather than drilling a little hole, I of course design a matching holder:


I believe the PETG would be the appropriate material for this, having better structural integrity as well as probably being able to withstand the weather better. I should probably print it sideways to not put the stress on the layers, but across them, and to avoid the overhang problem above.

An advantage of using Octoprint is that I can go back and see what I have printed, hence the many things listed this time.