RE: [rp-ml] Design for (Rapid) Manufacturing

From: Yasser Hosni <>
Date: Tue Mar 10 2009 - 06:22:40 EET

Add to that the following:
(1) Rapid tooling (soft and hard) using stereolithography (RP) is a
valuable step to Rapid Manufacturing of higher than 10 unit batch sizes!
 Examples include dies for plastic injection or pattern and mold making
for casting.
(2) spare parts for older equipment where reverse engineering is
integrated with RP to produce the parts.
Dr. Yasser Hosni
Professor of Engineering
University of Central Florida

9:19 PM >>>

Whilst I do see where you’re coming from I can’t say that I agree with
RM is cost effective if the batch sizes are small enough. I build parts
for use on our race cars using SLS, and as the batch size rarely exceeds
10, RM is a perfect fit for us. Tooling for such low volume would be
ridiculously expensive and the lead times involved prohibitive. On the
odd occasion where batch size has been up in the hundreds, I’ve still
managed to manufacture parts in-house significantly cheaper than
outsourcing to injection moulding.
Aerospace companies are putting parts on military aircraft every day.
I’m not sure that I could consider parts used on fighter aircraft as
joke products. They obviously pass all the requirements for the product,
and if it wasn’t a cost effective way of producing the parts, I’m pretty
sure they’d be doing it another way.
Pat [] On
Behalf Of Joe Kerer
Sent: 09 March 2009 22:11
Subject: Re: [rp-ml] Design for (Rapid) Manufacturing

The best way to design for RM is to put something into your design that
is going to make it extremely difficult to manufacture the products
using more conventional means.


Lets get real. A good designer designs for manufacturing, not RP. RM
(RP) should only be used in rare occasions, as this is generally not a
good manufacturing method.


Look at many of the parts that the RP/RM manufacturers are showing as
RM parts. They are mostly a joke, as they can be manufactured via other
methods with better and cheaper results.



--- On Fri, 3/6/09, William Watson <> wrote:

From: William Watson <>
Subject: [rp-ml] Design for (Rapid) Manufacturing
Date: Friday, March 6, 2009, 2:11 PM

I was recently asked by our local IDSA chapter to write a short note on
designing for rapid manufacturing processes. Although there is a lot of
documentation on design constraints for other manufacturing processes
(injection molding, sand casting, et al.), there is little help for
designers in the additive fabrication space.
I thought I would open this conversation up to the RP community with
the hope of finding more help for the designers looking for better
prototyping guidance as well as developing support for accepted DDM
The article below was written for the industrial designer with little
or no experience with rapid manufacturing. Obviously there is much more
detail and depth than I covered. Hopefully this is a good place to
The original can be found at:
 Here is the text:
Design for (Rapid) Manufacturing
Rapid Prototyping (RP), Additive Fabrication, Direct Digital
Manufacturing, 3D Printing are just four of the many different ways to
describe the twenty-two -year old industry based on technologies that
build parts up, layer by layer. For the designers new to the technology,
the promise is the same:
Everything drawn in 3D CAD can be sent to a 3D Printer.
If only product design was that easy. When your design process involves
rapid prototyping, knowing about the materials and process can improve
the outcome of your prototype.
There are two equally false thoughts about prototyping materials:
  • RP parts are super fragile and super expensive – DON’T DR
  • RP materials come from “unobtainium” and are a perfect match for
all designs and assemblies
Although the first notion was probably true ten years ago, things have
improved dramatically. Materials are stronger and better mimic the
engineering polymers intended for production parts. Also, lower cost
processes have reduced the overhead of many suppliers. For many
processes, ordering a second piece only adds a fraction of the cost of
the first. Since your marketing manager is going to keep the first
model, might as well order two so you have one to use to communicate
with engineering and manufacturing.
Of course, the thought that RP machines can make everything is equally
false. If your design includes sheet metal, expect to make some
thickness changes before sending the STL file to the model shop. Many
assemblies incorporate multiple materials to optimize the design for
strength or weight. Do not expect one RP material to cover that very
wide range of material properties.
So, what is a designer to do? First, think about your design and
product development goals. Then pick a prototyping strategy that best
meets those goals.
General design considerations:
  • When Outsourcing
    - Match your design with the right process
      • Small medical device? SLA
      • Color concept model? Z Corp
      • Over molded plastic/rubber? Objet
    - Be realistic about lead times
      • Start to finish with shipping time, outsourcing takes a week
      • Give your supplier a heads up when projects are on the way
    - Understand cost and time drivers
      • Material Volume
      • Build Envelope
      • Post Processing
  • In House 3D Printing
    - Know the strengths and limits of your process
      • Modify the design to make post processing easier
      • Know when to use assemblies, and when to manually assemble
      • Use hollow or sparse builds to minimize costs
    - Understand support materials and post processing
    - Determine how to make the build more efficient. What drives time?

Just like most other manufacturing processes, RP appreciates good
design. Simple rules like constant or similar wall thicknesses help make
growing and processing the parts much more efficient. Cantilevered beams
often need support, and sheet metal features need to be thickened. Most
importantly, using good design sense and understanding how your parts
are made will help you make better designs in less time with less money

Bill Watson, IDSA is the managing partner of Anvil Prototype & Design
( ( )), a Z
Corporation partner and RP service bureau based in Charlotte, NC.
Bill Watson
Anvil Prototype & Design ( )
4101 Stuart Andrew Blvd. Suite F
Charlotte, NC 28217 (
Voice: 704-527-8171


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Received on Tue Mar 10 06:23:49 2009

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