FW: FDM real concerns

From: Cooper, Ken (Ken.Cooper@msfc.nasa.gov)
Date: Thu Jan 30 1997 - 15:34:03 EET

We've been FDM users for several years now, with our 1500 upgraded to
1600. I think QuickSlice is definitely a user friendly interface, but
two concerns we have are repeatability and porosity. For example we can
build a part and deliver one day, but three or four weeks later the
same file might not build well at all. On the porosity end, we
attempted to use some FDM'd parts for wind tunnel nozzle testing, but
the ABS wouldn't hold pressure until massively coated with polyeurethane
and wax (there go the dimensions). Other than that we've had very good
luck with our Stratasys machine, except for a recent problem with the

Ken Cooper
NASA Rapid Prototyping
>From: Roberts, Floyd E III
>Sent: Wednesday, January 29, 1997 4:26 PM
>To: Cooper, Ken
>Subject: FDM real concerns
> The FDM as used for wind tunnel models still has problems with the
> control and minimization of the start up and stop beads. We often
> spend a great deal of time imperfectly trying to get rid of these
> defects. Additionally the feed rate while adequately controlled for
> most modeling but it is remarkable inconsistent when you must have
> high density large scale parts. Cosmetically these defects in
> density do not show up but they often result in strength variations
> or porosity difficulties.
>Floyd Roberts

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