Tuesday, September 20, 2005


First non-circular object printed

Last night I ran off the first non-cylindrical shape from the Meccano prototype RepRap in EVA. It's shaped a bit like a keyhole and tapers as it goes up. It was done by programming the PICs rather than sending commands from a PC, pending my fixing of the serial control software that I mucked up. Here it is:

This illustrates several useful things:

o We can produce non-circular artifacts!

o EVA Produces fine filliaments on some corners, which are easily brushed off.

o The indexing of the turntable by means of a magnet and reed switch is sufficiently consistent in operation.

o It is possible to produce tapered objects.

All the layers fused beautifully, but the initial base layer was a little patchy possibly due to me depositing on cardboard. The turntable initially located itself under the head automatically, and after checking the EVA feed I created a stable and well-bonded base by running the bottom layer repeatedly without adjusting the height. Then it was just a question of enabling automatic control of the vertical axis and the object formed before my eyes.

Vik :v)

Huh... I put in a comment and it got erased. Weird...

Anyhow, congrats Vic!
Oh, now I see. I forgot to publish it. Silly me! :-(
That's amazing! Well done!
So how durable is it? How long did it take to complete it?
Durable? Heh, not very. It won't fall apart, but it squishes fairly easily - it's just EVA hot-melt glue. I can make them with thicker walls, but the accuracy diminishes with deposition width.

The whole thing took 5-10 minutes; I didn't time it. I was running with a very slow deposition rate to reduce the amount of goop dribbling out of undesired orifices. The Polymorph extruder should be faster.

Vik :v)
Two walls should be quite practical. However, I am having some difficulty with the SDCC compiler and have only just got the serial comms going on one PIC again.

Rather than hard-code more functionality into the PICs, I'd like to try and get the PC controlling the RepRap's movement. Once that's done, creating scripted objects should be much simpler and I'll try depositing some solid, filled objects.

A Polymorph extruder is not too far away from my little lab now, so assembling and controlling that will have to be slotted in too. Then there's the documentation. Busy days ahead!

Vik :v)
I once stumbled on a website where people had made a Lego RP machine that extruded chocolate under computer control (and what better working material could one imagine?). Like a fool, I failed to bookmark it. If anyone knows where it is, tell me and I'll blog the URL.
This may be what you remembered. It's pretty kinky.

I've been meaning to test plaster of paris reinforced with fibreglass insulation. Should insulate and be fairly heatproof, as well as being structural.

Vik :v)
Wow! Great pic! again congrats!
plaasjaapie's was the one. Thanks!

Vik - when plaster of paris sets it's a hydration of calcium sulphate hemihydrate to calcium sulphate dihydrate. I suspect you may find that, when it gets near 100 C, the water of crystalisation (which is effectively where the water went) starts to come out again and it turns back to a powder. But I could be wrong.
I use plaster of paris to cast lead in. Once it's had residual moisture cooked out of it, it retains its structure and strength. Even quite fine details are preserved - reproduction coins can be cast.

Vik :v)
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