Especially if you concentrate on organic, irregular shapes! Here are photos of the first five objects to come off my printer’s bed, with no more alignment and setup than (mostly) leveling the bed. Oh, and eventually finding out where to enter my filament diameter and desired layer height.
The Overview Photo
The green cutting mat is marked in centimetres, so you can judge the scale. The red PLA plastic was included with my kit by MakerGear. I didn’t know any PLA was included, so I ordered a bunch of clear and of silver PLA with the printer. The red is so cheerful and intense I chose to print with it first. (Good choice, MakerGear.)
The square objects are 20mm test calibration cubes. The first one is very short because the length of filament ran out part-way through. I hadn’t built my filament reel at that point, so I used a short length just to test that everything worked. You can see how irregular and stringy it is. Contributing factors were:
- I hadn’t levelled the print bed yet.
- I had the Z end-stop set too high, so the nozzle wasn’t smooshing the PLA down onto the bed.
- I had the filament diameter set at 3mm instead of 1.75mm, so the printer was printing much thinner lines than it intended to.
- I had the layer height set to 0.4mm, when my nozzle is only 0.35mm.
The end result is thin, stringy lines of plastic, not really becoming part of the layers beneath. Still, look how shiny and cool the result is! And despite its stringiness it hasn’t delaminated at all.
What’s the underside like?
Turning the cubes over, you can see that the first cube is stringy all the way through. The software that slices the models puts two layers of tightly packed plastic down as the bottom of the object, but with the wrong Z height, they never stuck to the bed.
By the second cube I’d got the starting Z height more correct, and set the filament diameter correctly, so the printer laid down an almost solid platform of plastic as the base of the cube. You can see the difference (though I apologise for the shallow depth of field – I can’t learn everything at once!) Inside the cube is mostly hollow, with a thin interlocking mesh of lines that give strength without using huge amounts of plastic. The ratio of plastic to air inside objects is called ‘infill’. You can set it on a per-print basis to make your parts either stronger or lighter.
Organic Shapes: no-one knows how distorted they are
I chose the Starfish by sconine as my next print for two reasons:
- My wife is a mad rockpool enthusiast, and blogs about rockpool critters constantly, and
- They’d look cool no matter how badly they printed.
If you look at the overview photo at the beginning of the post, you can see the two starfish are not the same. The first starfish has the tips of its arms more bent. Though they were both printed from exactly the same file, and the extruder moved along exactly the same path to print them, they are clearly different.
Again, it is down to problems with height. This time its the layer height that was wrong in the first print. So the extruder was dragging the filament behind it, like walking through spider webs, instead of sticking it down to the layer beneath. It happened mostly on the tips, probably because the changes of direction were more extreme there.
Still, its nicely textural. My wife was thrilled, and has requested that I print a third starfish with the same wonky settings so she can use them to make a sea-themed necklace. The designer of the original starfish has posted a new, more squiggly, variant for those whose printers actually do what they are asked to do!
Joy to the world, I can extrude Text!
One of the tasks I set myself very early in my obsession with 3D printing was to be able to extrude text. Happily, bright people had already solved the problem.
There is a plugin for Inkscape that can output objects as STL format files. It’s a bit fiddly, and I’ll write a post on it when I can find my notes, but it does work. Then you can extrude the STL outline in OpenSCAD. The closeup of the side of the letter J makes me proud! It’s not quite perfect, bit it’s close. Smooth and well aligned, with only one noticable discontinuity. My settings are getting better. Layer height set to 0.3mm, enough less than my nozzle size of 0.35mm that the nozzle is smooshing down the previous layer slightly, as it is supposed to, in order to build strong inter-layer adhesion.
Perfectly smooth bottom
With these settings, the underside of the ‘J’ is absolutely solid and smooth, taking on the texture of the blue painter’s tape. The edges look like they are slightly flared out, so maybe I’m laying down too much plastic here, which would be a first.
Vertical Edges get loopy
I took this shot to highlight the oddness that happens where the layer height changes on the circular form of the letter ‘O’. The loops and bulges are, I think, the result of too much PLA being extruded while the nozzle is moving from the letter ‘J’ to the letter ‘O’ between layer changes. There is a function called ‘oozebane’ that somehow retracts a little bit of filament back into the nozzle when long non-extruding moves are needed (like between the letter forms here). I haven’t set that up – I don’t understand how yet – but I suspect that would help reduce those bumps.
The texture on top of the letter ‘J’
While this is not what I wanted from this print, it is a good illustration of how things work. You can see that the letter is outlined with two lines of plastic, which start and finish at the bottom-left. Inside that outline is a diagonal pattern of two lines close together, then a gap. Through the gap you can see that the diagonal lines go the other way on the level below. So we can assume that they alternate with each level (I don’t need to assume, I watched it happen – its hypnotic).
Why is it not good? Because the two outlines should be hard up against each other, smooshed together. The latticework in the middle, the ‘infill’ should have stopped being ‘infill-y’ two layers below the top, so the top two layers are as solid as the base was. I don’t yet know why that didn’t happen here, but that’s ok. Finding out is great fun.