Saturday, 27 August 2016

Printing with flexible filament is fun

I'm just about out of the purple Innofill plastic. For purposes of printing things for our kitchen, I'm looking for a matching red color. Turns out there's a color scale I hadn't heard of until recently, namely RAL, and some things I spraypainted were RAL 3003, a nice deep red. So let's see if that's available in filament!

At they offer any color filament you can pick out of RAL, but you have to buy 10 kg at a time, which is a bit much. They don't state the RAL for their regular spools.

At I find exactly the right color, at an almost suspiciously low price, 16€ for 800g. Looks like they're quite active on the forum, and I don't see any complaints there. (argh! When did "berlin" become a top-level domain?) has a nice overview of their colors, but alas no 3003. it is. Got here just before we left for the US, but not in time to do anything with it. Also got a sample of PETG, which I hadn't heard of before, but sounds like it's worth trying.

I'll need to do a better filament setup. From what I'm reading, the way I've just had the spool hang loose with no guiding and letting go of the end, I've set myself up for the tangles I now suffer from. I broke the spool holder that came with the kit, plus it was for larger spools AFAICT, so now I'll just use the rest of this spool to print the holder for the next.

For a quick test print, I reduced infill from 20 to 5%, set 1 top and 2 bottom solid layers, set infill_only_when_needed to true. Then I printed a reduced version of this filament holder to check that it matches my spools. Looks good, though it was probably designed to just let the spool sit loose and accept the bit of friction. I started designing a spool holder rolling on four ball bearings, so there's practically no friction, but then it struck me that a bit of friction may be a good thing. Instead I might just want to guide the filament better, maybe with a bit of PTFE tubing and a longer way from the spool to the extruder. Only problem with that is that cold pulls become harder.

And because I was running low on the normal filament, I decided it was time to try out the flexible filament. At the same settings as my regular PLA, it came out quite nice:

This is not an extremely flexible filament, just enough that I can compress the sides of this cube. I was going to print at 25% speed, but it didn't get picked up, and printing at 100% worked just nicely. Let's move on to testing ObPhoneCase by intersection the design with some cubes and printing that.

I realize now that placing the design centered in 0,0 would have made some things easier, for instance scaling.

Looks like I set the Z adjustment a teeny bit high, but the flexible filament doesn't seem to curl when cooling, so all that does is make the bottom layer less flat. That simplifies things!

The trickiest part of the phone case is getting the holes right. While some overhang is doable, it's not so predictable. However, printing with support doesn't work so well for this kind of structure, the support generated by Slic3r is fairly heavy-handed and doesn't come off nicely in this case:

Overall the case looks good, though:

Eventually I just decided to do my own support for the holes, with little cubes literally hanging in mid-air, but with a fraction of a millimeter distance. That actually came out really nice:

They come off at a light touch (actually some fell out just due to the bending when getting the print off the bed) and leave only the smallest of marks.

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