DIY 3D Printing is easy

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.

First printed objects - two calibration cubes, two starfish, and my wife's name extruded 20mm high

The results of my first 5 print runs.

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.)

Calibration cubes are stringy and irregular

Calibration Cubes

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.

The underside of the first cube is very open and spiderweb-like, while the second cube has a much firmer base, due to the Z-height being better.

Beneath the stringy cubes

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.

Stringy Starfish Closeup

Stringy Starfish Closeup

Organic Shapes: no-one knows how distorted they are

I chose the Starfish by sconine as my next print for two reasons:

  1. My wife is a mad rockpool enthusiast, and blogs about rockpool critters constantly, and
  2. 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!

Oblique extruded letter J

20mm tall extruded letter J

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.

The underside of the extruded J is smooth

Underneath the extruded J all is smooth

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.

The vertical edge of the extruded 'O' has tiny loops

The vertical edge of the extruded 'O' has tiny loops

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 top of the extruded letter 'J' shows a lattice pattern

Latticework pattern on extruded letter 'J'

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.

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8 Responses to DIY 3D Printing is easy

  1. your J top isn’t solid because it’s extruding slightly too little plastic. You can either go nuts bashing filament diameter and packing density, or simply leave those alone and adjust your E steps. If you’re using Sprinter firmware, simply send M92 Ennn to set a new value (mid-print!) It will lose this value every time it resets, so once you find one you like, stick it in your configuration.h and re-flash.

    Every roll of filament will have a slightly different diameter, so will need its own slightly different E steps. Most of mine are happy with 110, but my yellow needs 126! Your number should be closer to 1300 I think, using the makergear stuff and standard settings.

    I use the magic number of 1.128379 for filament diameter regardless of my actual filament diameter, which changes my numbers significantly! If I put in 3mm, my E steps is close to 700.

    apart from that, looks like you’re off to a flying start! It still amazes me how easily people get excellent results with a good kit, compared to those who struggle with a bad kit or self-sourcing without consulting us in irc://irc.freenode.net/#reprap !

    • BrazenArtifice says:

      So does this mean that instead of adjusting the filament diameter in skeinforge (or slic3r, when I get to that), I’d adjust the last float in axis_steps_per_unit[] in configuration.h of Sprinter? And the higher this figure, the more plastic is pushed out (thus thicker extrusion)?

      Just before the extruded text print I measured my filament as averaging closer to 1.72mm than 1.75mm and changed the numbers in skeinforge to reflect that. Do you recommend resetting that to 1.75 and instead developing a table of E-step values for the different PLA rolls in Sprinter, and re-compiling any time I change a reel?

      I can test this out once I re-tighten various bits that sounded a little rattly after my first one-hour print! Thanks for the advice.

      • Basically, filament diameter, “packing density” and E steps are all used to convert the volume of each segment (layer height * extrusion width * segment length) into a number of steps to send the stepper. Personally I don’t see the point in having 3 things to fiddle with that all only affect one number, especially when changing two of them requires re-skeining, whereas changing the third can be done on-the-fly, even mid-print!

        Read more at http://wooden-mendel.blogspot.com/2011/09/volumetric-stage-two.html and http://reprap.org/wiki/Triffid_Hunter's_Calibration_Guide

        Yes, float axis_steps_per_unit is the thing to adjust in sprinter to save a value permanently.

        If you do go down this road and find success, please update my calibration guide in the wiki with your excellently detailed instructions and explanations!

        • BrazenArtifice says:

          Ok, I understand what you’re saying. As long as some slicing software developer doesn’t start to rely on E-steps to somehow really be E-steps, that’s a good approach.

          I’ve just printed 2 more 20mm cubes. One at 110% of my current E-steps settings, and one at 130%. I can see the difference, and its going in the right direction, but there is still a gap between the two outer perimeters, and also between the diagonal fills. If I’m out by 70% I’ve probably still got a wrong number hidden in skeinforge somewhere, I suspect. The print at 130% is noticeably better in other ways too.

          Last time I read your wooden mendel post, the second and third paragraphs made my eyes glaze over 🙂 And your method on the wiki starts by suggesting a micrometer, “or a vernier caliper will do”. I don’t think I’ve even seen a vernier caliper since high-school.

          Now that I can see the effects on my own prints, I’ll read them again with more concerted attention, and see if I can take your elegantly concise description and turn it into a multi-page penny-a-word pulp paperback version that I can understand. (She walked into my office like she owned the joint. “You’re not pushing enough” she snarled. I flopped my noodle on the desk, and she rolled her eyes in disgust. “Its too skinny to impress me” she said as she stalked out…) I know I’m verbose, and tend to over-explain things. Your compliment on my writeups means a lot to me. I’m hoping I’ve found an environment where my chattiness is useful!

          • one spot where slicing software does rely on E steps to really be E steps is the retract distance. I’ve found it’s not really much of a problem, I just set it a hair higher than I need, and the minor variations in E steps aren’t enough to make it problematic.

            I /know/ I’m too much of an engineer to write effectively for non-geeks. It seems to me that you’re somehow able to straddle the worlds, understanding the issues at stake and translating them into non-geek terminology 🙂

            Let me know if my calibration guide makes more sense now that you’re actually printing!

            • BrazenArtifice says:

              Yep, it makes more sense now. I think I may need to draw myself some diagrams, but its past midnight and I don’t do maths well late at night. I’ll get back to you 🙂

  2. Cath Clark says:

    Oooh, shiny! Well done for bringing concept into manifestation, Andrew!

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