Sunday, 21 January 2018

Valuable prints

OctoPrint is still being weird. It thinks the print time left is either 2 hours or 6 hours, depending on when I look at it, out of a total print time of... an hour. I guess when they say "approximate", they really mean it.

For a friend in the US, I printed a holder for a set of Euro coins. It came out pretty well. I didn't include any fudge factor for the holes, but with my perimeter adjustment set to 65%, it was so close that applying a rubber mallet was enough to get the coins in.

Perfectly fitting holes

I painted the legends with a silver Sharpie, the only pen I found that would stick properly. I like how the €2 coin seems to glow from within.
I'm also printing more fan mounts for my project of adding some air movement around our radiators. I've lasercut enough boards for it that I can start running tests soon. I wish I had some more temperature loggers, but I haven't been able to find any below about €50. Since I want to have several of them around for various purposes, I don't want them that expensive. It's not like the hardware is costly.

I've upgraded to Slic3r PE, which is under a lot more development than regular Slic3r. Also, it includes an interesting feature: You can adjust the layer height before slicing. Not only does this allow for slightly faster printing on simple verticals, it can also make slight inclines look nicer.

Sunday, 14 January 2018

Lots of calibration prints

Ran across a couple of calibration pieces by +Jeff Parish  which include instructions on what to adjust if they don't come out right. Since I haven't had things fit just right together, I thought I'd give them a shot.

First the simple U-pieces. Initial print was with 2.85mm diameter (white PLA from DasFilament) at 220ยบ. Fit together slightly loosely, increasing the nominal diameter to 2.90, then 2.95, then 3.0, before realizing that I should decrease the diameter. At 2.5, they could only barely be squeezed together, at 2.7 they fit only with a slight looseness.

A curious blip on the temperature graph:

Notice during the first of these two prints, at about -22 minutes, the temperature drops by about 10 degrees, stays there for maybe a minute, then goes back up. This didn't happen on the next print of the same piece. Weird.

Since holes are one of the hardest things to get right, I decided to make my own piece, with blackjack and hookers pegs and holes. To be able to test them against something independent, I made one hole+peg combination be 3.5mm, so a standard headphone jack should match, and the other 1/4" hexagon to match a screw bit.

I printed this piece with a 2.6mm nominal filament diameter, only to find that they fit even tighter than the original piece at 2.5mm. Unsurprisingly, none of the holes or pegs matched anything. Trying again at 2.7mm, they still don't fit, despite the pegless ones fitting at this calibration. At 2.85, they fit very tightly together, roughly as easily as the 2.5mm one with the original piece. That is a huge difference in material - overextrusion is clearly visible on the top of the 2.5mm pieces, and the corners are sloppy. Why they fit well I cannot tell.

 Now to try to get the pegs to work. I have a few knobs to tweak for this. I can change the number of perimeter layers - I currently have 2. I can change the extrusion speed of perimeters, small perimeters, and external perimeters, which are currently set to 60 mm/s, 15 mm/s, and 50% (i.e. 30 mm/s) respectively, the defaults. I can also set the perimeter width manually (in mm or %). That last one is promising.

To start out drastic, I set the perimeter width to 75% - and it was almost perfect! The hex bit fits tightly in the hex hole, the hex peg goes into the hex screwdriver easily, the headphone jack almost goes into the 3.5mm hole, and the headphone peg almost fits its hole. The notch fit is still rather tight, but fitting. At 65%, there is no appreciable difference.

In other news, I printed an art piece as a gift for a friend (that I won't show here lest they see it). The full piece at 0.2mm layer height took about 7 hours to print. When doing a test with 0.1mm layer height, printing roughly 1/10th of it was estimated to take 16 days. Wut? OctoPrint can't agree with itself how long it takes. It was actually only 3 hours.

Also heard about Slic3r PE, the variable layer height is a nice idea, and it's good to have somebody actively working on Slic3r. I have an idea for better support structures that I'll get back to in another post. I tested it out with the same peg piece, seeing little difference, then tried the CtrlV complex test print. Better than ever, except for the overhangs.

Nice roundings and a pyramid free of clutter, unlike the blue version
The text never came out this nice on previous prints
The overhangs are a bit sloppier than with the red filament test, but that might be a filament difference.

Thursday, 4 January 2018

Various prints, and thoughts on Z offsets

As I've been printing this and that, my Z offset has gradually increased to over 2mm. I have two remaining hypotheses for what causes this: Either the nuts holding up the X axis move slightly over time, or the two Z axis rods get slightly out of sync. The first hypothesis seems like it should change Z the other way, but when I did a check of Z offset on the left and right side, there was a huge difference. Adjusting the right side down to match the left side brought my Z offset back down to 1mm.

I still have a distance probe to add, but even after that I should keep an eye on the unevenness, since print quality undoubtedly will be better if the Z axis doesn't have to move when printing a layer.

Other things I've printed recently:

A properly rescaled AAA battery organizer (on the left without the fan duct active since the plug had fallen out):

Notice how the corners one the left one look melted. Fan support saves corners!

A McBenchy for my new red filament. Slightly weak on the brow, but overall good quality:

One-and-a-half McBenchy for my blue filament, done without fan by accident. Total brow failure:

Painter's stands for holding painting projects up:

A funnel sized to make it easy to fill our peanut container: