Tuesday, 4 August 2009

More PLAying

Way back in April last year I tested a sample of PLA and got as far as making a test block with it and establishing that the warping was much less than the other plastics and you don't need a raft. I finally got round to making some objects with it last week.

The first bed material I used was balsa wood. That works well without a raft. The only downside is that when the object is peeled off it takes a few fibers from the wood with it. No big problem for functional objects, but it does spoil the aesthetic appearance a bit. The top and sides of the object are nice and shiny, but the base is cloudy.

I tried MDF, that gives a smoother finish, but I could not get it to stick reliably. Vik suggested 3M blue masking tape, but I didn't have any to hand, so I tried some sticky back plastic instead. That made objects with a nice glossy base but I could not get the outline to stick reliably.

The lid on the left was made on balsa. I think the black flecks are bits of black ABS which was the last plastic I used in the extruder. The one on the right was made on sticky black plastic. It looks much nicer, but on the top right you can see a bit of missing outline.

I also made this screw-able jewelry box, which looks nice in PLA.

PLA is very nice to extrude. It has a higher melting point than the other plastics but it viscosity falls rapidly with temperature so you can extrude it at lower temperatures. I did the first outline at 210°C, the first layer infill at 200°C and the rest of the object at 180°C. It does not seem critical.

I run the fan after the first layer to make it set quickly. I also needed a fan blowing on the heatsink of my extruder. Otherwise it can heat up past the glass transition of the PLA, which is only about 70°C. When that happens it jams fast and has to be drilled out.

Not needing a raft saves a lot of machine time and also my time removing it.

Even larger objects don't show any warping. I made this contraption to hold a scope probe in place for a job I am doing at work.

Vias are so small nowadays that attaching a wire is difficult and risks ripping the tracks off. Here it is in operation: -


  1. Neato! Does the PLA work with the old M5 driven extruder, due to the bend in the feedstock required? And can you have a kg or so coiled up, ready to go?

    Also, does it smell bad or off gas something nasty when you extrude it?

    I've been messing with heaters and turkey bags trying to cut down on the warping and smell of ABS, but I'm not having a lot of luck so far, and it complicates the build setup a bit. Got to find some PLA and try it out myself.

  2. Great work ... Where do you buy the PLA from... in the UK?

  3. Wade,
    Yes the PLA bends just enough to feed from a large hanging basket and get past the bend in the extruder. It tends to rotate in the extruder so the basket has to rotate. The coils can whip around violantly, at one point I was wearing googles as it nearly took my eye out.

    It doesn't give off much in the way of fumes. If anything it smells slighly sweet and looks quite like molten sugar. I am sure you could spin it into candy floss for a joke.

    I used to notice the smell of ABS but now I don't. I think I must have retrained my nose to ignore it.

    I bought it from Vik in NZ, so the shipping was slow and expensive, but no worse that when I buy filament from the US.