Two different extrusion diameters ?

Hello,

Not yet a reprapper, I have ordered plastic parts for a Huxley (at www.eckertech.com)...
(sorry for my english, feel free to correct if I am using wrong words)

I am thinking about the extruder, and would like your thoughts on an (unclear) idea : would it be possible to switch between two extrusion diameters, a thin one for all extern surfaces, and a wider one for printing the inside parts ?

I thought of an old "Criterium" pen where the 1mm graphit mine is blocked between four pieces.

Same pieces may join together at the end of a "standard" extruder, and reduce the extrusion diameter. Conic pieces are not required, pyramid shape with four triangles may do the job as well.

A vague idea for the mechanism to push pieces together.


I have still to find a way to guide the four pieces so they do not fall, join precisely, and something to pull them again.

Does someone have skills in mechanics, and may tell us if such a thing can be assembled, with the required precision ? It is probably too complicated, but why not ask...

(Uploaded with ImageShack.us)

... as you extrude with high pressures against the orifice, the mechanical structure has to be very rigid and can't have any gaps (even microscopic ones), or the plastic will go through the gaps, solidify outside and block the sliding mechanism.

Actually the best idea is to use two (or more) extruders with different nozzles and/or materials ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Well, thanks for the advise. I will read more on multiple extruders.

How about something closer resembling a Camera Shutter?

This is made to be completely closed to light, maybe a slight mod could be made to that design?

I found this on a Steampunk website:

[www.youtube.com] - Click on link, not sure how to properly embed.

There's a few more on there, I particularly like "Lego Stargate Iris" - quixotic!

I was considering something similar to get around the "In Fill" time for parts: you only need the resolution near the outer skin of parts, maybe build up two layers and then infill with a bead twice the diameter of the outer skin.

If it can be made precise enough, this may circumvent the biggest problem of the nozzle: drilling the 0.5mm aperture. It completely removes that problem and puts up several other accuracy problems!!!!


-AS






(Images ripped off from someone's work at: Brassgoggles, Steampunk community)

... as said before, this shutters won't work proper with pressure from one side and fluid and/or hardening material blocking the sliders ...

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Viktor,

The Pressure problem "could" be solved, but the molten abs seeping in would always be an issue. Probably more so in the "True Iris" shown on the Youtube Clip as it will have elements sliding over each other.

....not to mention the Co-eff thermal expansion on a mechanism.....

I never say never, unless it violates laws of Thermondynamics, though I thought this mechanism may be of interest to anyone who stumbles on this later looking for interesting mechanisms that they may wish to replicate.

-AS

Edited 1 time(s). Last edit at 02/05/2011 12:28PM by andysuth.