Re: Minimum feature sizes on RP parts

From: Candi Majewski (
Date: Wed Jul 24 2002 - 12:54:22 EEST

Dear Ed and list!

Thanks for all the replies so far, it has been interesting to see some of
the comments people have!

Many of you have questioned the exact definition of 'feature size', so now I
would like to put another question to you all.

What do people out there working with RP feel would be the most useful
definition? Would it be the minimum wall thickness that could be produced,
or would you rather know the smallest radius achievable? Or would the
minimum possible height of a protrusion, or the minimum depth or width of a

Once again I am looking forward to your comments!


Candice Majewski
Rapid Manufacturing Research Group
Loughborough University
Tel: +44 (0) 1509 227564
Fax: +44 (0) 1509 227549

>Subject: Re: Minimum feature sizes on RP parts
>Date: Fri, 19 Jul 2002 10:29:10 EDT
>Dear Candi:
>Other folks will have better, more up to date comments, I'm sure, but
>never stopped me. "Feature size" is not quite the same as "resolution." Is
>there an exact definition? I don't know. I suppose a lot depends on the
>nature of the feature, but here goes:
>In a message dated 02-07-19 08:54:59 EDT, you write:
><< Below is a list of the processes I am looking at, along with the feature
> sizes I have down at the moment.
> I am interested in any comments anyone may have - are these numbers
> reasonable, have you successfully produced smaller features than these,
> are these sizes unrealistic?
> Stereolithography - 0.1mm
>***EG: There are special systems, and special techniques that can go down
>a fraction of a mil using what we think of as "classic," moving-laser
>stereolithography. Generally what you give up is part size. Other
>techniques, such as those used by microTec in Germany can produce a
>resolution in the single micron range. Quite a bit of work is going on at
>the nanometer level in the MEMS area, as well. Is all this SL? It all uses
>photopolymers shaped by light, so depends on your definition. I'd say it
> Fused Deposition Modelling - 0.2mm
> Direct Metal Laser Sintering (EOS) - 0.2mm
>***EG: EOS recently introduced a steel powder capable of producing 20
>layers. Min feature size may stay in this range though, depending on how
>robust details are. Finishes are certainly improved.
> Laser Sintering (3D Systems) Metal - 0.2mm
> Laser Sintering (3D Systems) Plastic- 0.2mm
> Laser Sintering (3D Systems) Sand - 0.5mm
> Wax Jet Printing - 0.2mm
> 3-D Printing (Soligen) - 0.5mm
> 3-D Printing (Pro-metal) - 0.2mm
> 3-D Printing (Z-Corp) - 0.5mm
>***EG: Both starch and plaster materials produce layer thicknesses well
>this number. Mostly people seem to be using plaster these days and I
>the typical layer thk is about 0.004". Looking at parts, I'd say the min
>feature size might be twice that or around 0.008". Whatever it is, it's
>probably better than 0.020".
> Laminated Object Manufacturer - 0.5mm
>***EG: Some of the parts made by Kira seem to be quite a bit better than
> Ink Jet Printing (Objet) - 0.05mm
> >>
>***EG: The existing machines produce 20 micron layers and have different
>resolutions in the x-y directions of 300 x 600 dpi. It would seem that min
>feature size would have to be greater than 0.05mm. Incidentally, 3D is
>to introduce a copy based on their MJM machines.
>Please post a summary of the responses you get, or please send me an email.
>This could be a pretty interesting subject and inquiring minds want to
>Hope this helps,
>Ed Grenda
>Castle Island Co.
>19 Pondview Road
>Arlington, MA 02474 USA
>781-646-6280 (voice or fax)
> (email)

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