maandag 22 december 2014

ABS polishing

After polishing an ABS print for a weekend, I decided there should be a faster method than polishing with ever finer grit by hand..

(For more information about this polishing job and model, please see here)

So when cold acetone vapor techniques came around, I decided to give it a try. Turns out that for delicate/mechanical models you really don't want them in the vapor for too long, which means you probably want to sand them a bit first to get nice results. And you also want some kind of rotating device probably, to avoid the tops of objects to collapse inwardly..

But if we have to sand anyway, and we have a pretty precise printer (as shown below), do we still need acetone vapor to get a nice finish..? While experimenting a bit, I found that for objects printed on my kossel mini, it's pretty quick to sand with grit 150 or so (to get rid of any ridges), then with 300 or so (to give a much smoother feel) and then to finish things off with a bit of steelwool. The result is an almost lego-like (though matte) finish.

In the meantime, I actually tried a vibrating tumbler (with some serious cutting action, but it didn't make a scratch) and various dremel brush heads, but so far nothing I've tried comes close to good old manual sanding. I'm sure that in the future there will be a faster (chemical?) smoothing process, but for now I will stick with manual sanding.

donderdag 11 december 2014

delta printer precision

I more or less finished my Kossel Mini build, and after some easy calibration steps (just following along with the think3dprint3d documentation), I am already amazed with the printing quality that I'm getting.

I was never able to get really uniform z layer heights on my Mendel Max, but for delta printers this does not seem much of a problem. A colleague helped me to make a close-up photo of a print with 0.2 mm thick layers, and as you can see the precision seems to be insane, in every direction. There also seem to be much less surface artifacts caused by vibration.

In fact, with this kind of precision it probably becomes a lot easier smooth the surfaces in post processing. After a bit more calibration to avoid ABS warping, I hope to start looking into this.

maandag 1 december 2014 kossel mini kit

I just finished printing the plastic parts for my new 3d printer, a Kossel Mini, to be built from a very nice kit sold at

Some issues I ran into so far:
-the extruder motor spacer was missing (quickly added by think3dprint3d)
-the legs on the LCD panel were a bit long and would only fit when heightening the printer considerably (quickly fixed by think3dprint3d, awesome!)
-the z-probe pin hole is modeled way too big. while the pin is only 1.5mm thick, the hole is 2.6mm, so I had to print the z-probe holder twice.
-the hole made in the effector is only 4mm deep, whereas the hotend I received requires a 4.8mm hole.
-the anti-chatter parts are a bit ugly, so I replaced them with pull springs, attached with zipties.
-I couldn't find the new extruder mounter, so took it from elmuchacho's thingiverse account -homing speed by default is set a bit high in the provided marlin firmware. it at least made me turn off my printer very quickly while homing for the first time.

Other than these issues (which you mostly won't run into with the provided plastic parts), I can highly recommend this kit to anyone who would like to build a reprap-style delta printer (with out-of-the-box heated bed). For me the biggest thing which is still missing is dual extrusion, to enable dissolvable support structures.

I hope to report after calibration on the resulting precision of printed parts. If it's really good (z-precision wise), I intend to also play with cold acetone vapor to see what happens to precisely printed mechanical parts.