Wednesday, December 11, 2013

Prototype: Omnijug

I got exciting news today! I got a full scale prototype of the omnidirectional jug made up. A lecturer I had from college was able to help me to produce a 3D printed prototype of the jug and it was ready for me to collect. I was, to put it mildly, giddy.

I had produced a full scale model of the jug from foam board which helped me get a feel of the general hands on experience of using it but this model would not stand up to the rigours of slip moulding so I needed something a bit more rigid and durable for this purpose. The model was produced on a z-corp 3D printer. This type of printer is a bit different from some other types of 3D printer. It does not produce plastic models by extrusion like FDM and it doesn't cure a resin using a laser like stereolithography it prints in powder.

Basically powder-resin 3D printers work by laying down a thin flat sheet of powder. A layer of your 3D object is then printed on this in resin using what is essentially an inkjet printer head, the machine then lays down another layer of powder and repeats the process until your model has been produced.This type of prototyping has lots of advantages.

  • First off it's cheaper than a lot of other 3D printing, the powder material you use is fairly simple and the resin is relatively cheap.
  • It's pretty quick, the build time even for multiple objects can be much faster than single objects using other methods.
  • It's more economical, because the object that's printed ends up basically embedded in a basin of powder there is no need for support material. This also allows for the printing of overhangs and other features that would require more planning using other methods.
  • You can add colour, as I said before the resin is printed in a way very similar to inkjet printing, you can add inkjet cartridges to certain machines to create material deep colourings. This has been exploited to great effect in medical scanning or engineering prints where features of scans or stress tests can be viewed physically very effectively.
  • The surface finish is easy to manipulate. Because it's not a plastic most surface treatments can be applied to it without fear of melting. You can also sand the surface to smooth it out.
When the object first comes out of the machine it does need to be treated to give it extra rigidity. When I was in college we'd give it a coat of cyanoacrylate (AKA superglue). This could be messy sometimes but made for a really strong part (Sometimes too strong such that sanding became a right pain in the ass). I was informed today that a solution of Epsom salts is what they use now and while not quite as tough as the cyanoacrylate it's certainly tough enough, cheaper and decidedly more health and safety friendly than spreading a glob of strong solvents all over your model.

Anyway. lets get to the pictures...

First up is a front on view. Bear in mind this model is yet to be sanded and treated so the surface is still rough but regardless I think you get a good sense of the facets and the way the light acts differently on them in this photo.

The next two show the "forever leaning" illusion. From several angles (well three, or six technically) the jug appears to be leaning to one side. I say this is an illusion because in reality the jug has is balanced and has three-way symmetry.

From the front view in the first photo the jug's rectangular section can be seen, the below view gives it more of a lozenge shape almost.

Finally, while my initial idea was that the jug should be held across one side and around two angles towards the top, playing with this prototype has shown a lot of other ways to hold and use the jug exist, some might be even better!

A couple of other aspects of this design struck me from the prototype. The jug holds a very decent 2 litres but people who've seen it have been surprised by this. I think one reason may be the thinning effect of the faceted sides. Front on, at the jugs widest, the jug appears rectangular in section, though the sides fall away from view particularly at the top where it's most noticeable. The side on view where the jug appears to be leaning is the thinnest view and from this perspective you can see only two sides that again appear to recede backwards. Perhaps this is the reason for the deceptive volume.

Another thing I noticed was, as I mentioned earlier, the alternative ways of holding it that didn't occur to me. Even though I had the card model I think the rigidity of this prototype and the ability to really grab it made a difference in evaluating it. Something to bear in mind for future card prototypes... build em strong!

So that's it for now. I must sand, sand, sand and possibly spray, then sand, then spray or otherwise smooth out the prototype before using it to form the slip-casting mould. I just got in contact with a potential kiln owner/operator which is a rather exciting development.

John O'Shea

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