Monday, February 17, 2014

More fun with the Printrbot Simple, and an easy spool solution

I have spent some time calibrating my Printrbot Simple, and am having excellent results. It took some experimentation and a good set of calipers and about a dozen little test prints, but I think it's there. :-)

I found that though the X/Y/Z steps per mm were right on, I was overextruding by about 8%. This didn't show up when I measured the amount of filament being moved - in fact, with the stock settings, it appeared that I should be under-extruding. But the symptoms were consistent - my prints were about .3mm too big in all directions on the external dimensions, and holes and slots were printing too small. Dialing back my extrusion multiplier to .9250 did the trick - prints are smooth and fit together.

I also switched filaments to Zen Toolworks PLA in white, and I am very pleased. I found that in my cool basement I had to run it at 210C to get good layer adhesion, but once I figured out that, man, it's nice.

I found a simple way to hang a filament spool, which eliminates tangles on long prints. I had a wide hook designed for hanging things on garage walls that was the right size. I had binding until I removed the rubber coating, exposing the steel. Works great.

Sunday, February 2, 2014

Estimating Cost of 3D Prints in PLA

When I first decided to get a 3D printer, I had no real understanding of what it cost to operate. It's useful to be able to know what a part costs before you print it.

It turns out this is pretty easy. Repetier Host (and probably anything that uses Slic3r as the slicing tool) will output the length of filament, as well as the volume, that the print will consume. For example, the print below shows that it will need 3.5 cubic centimeters of PLA plastic to complete.

An internet search shows that the density of PLA plastic is 1.25 grams per cubic centimeter. A 1 kilogram (1000 gram) spool of PLA costs about $30.

Now we can set up a simple ratio:

1000 grams/$30.00 = 1.25 grams/ (dollars per cubic centimeter)

Dollars per cubic centimeter = 0.0375, or just shy of 4 cents. So the above sample print, at 3.5 cubic centimeters, would cost about (4 x 3.5) = 14 cents.

If your design does not require printed support scaffolding, you can also easily calculate what it will weigh. This is useful for robotics and RC models. 3.5 cubic centimeters x 1.25 grams per cubic centimeter is about 4.4 grams.