Re: [rp-ml] New machines could turn homes into small factories (My 2 cents..)]

From: Adrian Bowyer (
Date: Sat Mar 26 2005 - 16:45:35 EET

Quoting Eitan Priluck <>:

> What sort of system do you envision that wont have some sort of likely
> patent infringement issue. Im most curious to know which type of rp
> technology you think has the least landmines for you to worry about.
> Quoting Adrian Bowyer <>:
> > I love inkjet-based systems too, but - for my project - I think they suffer
> from
> > at least one technical and one legal problem:

I had an idea last night (at 4 a.m., much to the annoyance of my wife: "For
God's sake! What are you getting up _now_ for?"), so I think I'll retract the
above. Here is the idea:

Lay down white (or light-coloured) powder for sintering as in SLS, but run an
inkjet printer head over it. In the printhead there is a substance pretty rare
in RP printheads, namely black (or dark) ink. Behind the printhead you have a
strip-heater the width of the scan. Now, the black printed-on powder will
absorb more heat than the white, so you adjust the strip-heater temperature
until the black powder just sinters and the white stays raw.

This is the opposite of Behrokh Khoshnevis' Selective Inhibition
Sintering; let's call it SPS - Selective Promotion Sintering.

A quartz-halogen heater would probably be best. You could have the strip heater
I just suggested, or you could flash the whole area once the printhead was out
of the way.

It might be a good idea if the ink did not wet the powder, as that way you would
get a denser black because it would not soak in.

You could apply the ink in any way you like; you wouldn't have to use an inkjet
- though I suspect that would be simplest.

You may also have to flood the thing with CO2 or N2 to stop oxidation.

The nice things about this are

  1. It doesn't use any expensive bits;
  2. The printhead is completely standard; filled with ink and just as bought
       from the supermarket;
  3. You can get all sorts of subtle temperature/sinter control by printing
       shades of grey instead of black.

I've had a look through the patents (particularly concentrating on patents that
cite the SIS patent, number 6589471) and I can't find this. Does anyone know
if it's been done?

If not I hereby, herewith, and hereafter (just to sprinkle a bit of lawyer-speak
about) give the idea away free; this puts it in the public domain, and it's also
on my project website; anyone can use it for whatever they like.

Floreat emptor!



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