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.

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