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 220º. 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.

No comments:

Post a Comment