Re: Selective Solar Sintering

From: Jim Mallos (
Date: Fri Feb 04 2000 - 19:55:35 EET

David Maxfield wrote:

> Does this mean that when I used a magnifying glass to start wood on fire
> I was using just 2 watts?

Roughly, yes. My own magnifier is about 7.5 cm diameter, or about .0044
m2 in area. Bright direct sunshine at sea level is about 930 w/m2.
Allowing 10% for absorption and refelection losses at the glass, mine
should be about 3.7 watts.

> > Suppose we pick a 100 watt power rating, that scales us up to a spot of
> > 2.5mm diameter. That sounds awful as a resolution if we are raster
> > scanning, but it is not so awful as a minimum wall thickness if we are
> > smoothly tracing the contours of a cross-section.
> Are we going to be able to fuse more than thermoplastics, without going to
> a vacuum?

Concentrated sunlight can melt anything. (Historically the first melting
of platinum was accomplished in a solar furnace.) The problem is that it
cannot melt things as fast as a laser can. In that brief time heat
diffuses below and to the sides, degrading the resolution in a
selectively sintered part. I don't think going to a vacuum would be much
help in this regard.

Jim Mallos
Heliakon Solar Sintering Lab

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