> -----Original Message-----
> From: O'Reilly, Sean (S.B.)
> Sent: Friday, August 06, 1999 2:58 PM
> To: firstname.lastname@example.org
> One additional dimension on the FFF as a manufacturing process. In my
> experience (which, of course is limited to manufacture for the auto
> industry) one of the critical items is process throughput - how many
> parts/pieces per hour. I don't know how representative of the entire
> injection molding universe the following numbers are but, here goes:
> For a small, simple part like an instrument cluster lens, the entire cycle
> - close the press, inject the plastic, allow to cool, open the press
> remove the part - can be accomplished in under a minute depending on tool
> material, tool cooling and part material. In addition, most IM molds are
> 2-, 3-, or 4-cavity molds meaning 2,3 or 4 parts are molded in one shot.
> The cycle time will go up for this kind of mold, but not a whole lot.
> For large parts - say 3 ft. long or bigger, the cycle time can be in the
> 5 - 10 minute range.
> For the sake of estimation, let's say that a "small", simple part can be
> made in 30 seconds and a "big" part in 8 min.
> It's hard to imagine any FFF process (which will use an additive,
> layer-by-layer building process) being able to build a full sized part in
> 30 seconds. I spent some time several years ago, measuring the "cycle"
> time of various FFF machines. The fastest (at that time) was the Cubital
> machine which had a per-layer "cycle time of about 1 min.
> Cubital had the advantage of forming the layer in one single flash of its
> UV lamp and as a result the cycle time was independent of the size of the
> cross-section currently being built. Most of the others (SLA,SLS, and
> saw an increase in the per-layer cycle time as the current cross-section
> got bigger.
> (One paradox was that the bigger -meaning more material- a layer was, the
> faster the LOM could build it - recall that the LOM "removes" material -
> in a sense) The worst was about 4 minutes per layer.Now, let's assume a
> space-age FFF cycle time of 30 seconds per layer. At layer thicknesses of.
> say 0.005 in. our hypothetical FFF machine will take about 200 min. to
> complete a build of 1 inch. Even if we assume multiple parts per build,
> the "throughput" will be VERY FAR from 30 sec per part.
> At the risk of sounding repetitive, the REAL strength of FFF is its
> ability to build astoundingly complex parts at about the same rate that it
> builds "simple" parts and the ability to build anything solid that can be
> modelled in CAD. Most "complex" products today are made up of a bunch of
> "simple" (to manufacture) parts.
> The idea of a truly complex part being built in a single "operation" is
> what FFF offers. To take advantage of that we need a new mindset.
> Sean O'Reilly
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