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

From: Shane Collins <>
Date: Tue Mar 10 2009 - 19:57:57 EET

In addition to Pat and David's comments, over 2000 people can now walk
without pain because they received a total hip replacement where the
titanium acetabular shell was manufactured with Arcam's EBMR technology.
The additive manufacturing technology of EBM allows for engineered surface
porosity to ensure bone in-growth. I would call this a serious, series
RP/RM application as well.



Shane Collins

805 427 0019

-----Original Message-----
From: [] On Behalf
Of David K. Leigh
Sent: Monday, March 09, 2009 9:34 PM
Cc: Joe Kerer
Subject: RE: [rp-ml] Design for (Rapid) Manufacturing


I'd have to agree with Pat.


There are many reasons you may consider a traditional RP method for RM:

* Unique Design (unmoldable, combined assemblies, etc.)

* Mass Custimization (hearing aids, orthodontics, etc.)

* Batch Size (1 car)

* Unique material properties

* Production volume (<1000 per year. . . ag products, business jets,
military, etc.)

* Rapid Engineering Changes or revisions (amortized tooling costs >
RP part cost)

* Test market in cases where tooling costs could be prohibitive
(sales samples prior to mass production)

* Time to market considerations (safety upgrades)

* Reverse engineering (obsolete or unsupported products)

* etc.

Many many applications for RM. . . not just "neat-O" design competitions.




From: on behalf of Warner, Pat
Sent: Mon 3/9/2009 8:19 PM
Cc: Joe Kerer
Subject: RE: [rp-ml] Design for (Rapid) Manufacturing

Whilst I do see where you're coming from I can't say that I agree with you.


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.





From: [] 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 constraints.

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 start.

The original can be found at:
ml 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

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 DROP THE

  . 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

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

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 19:54:37 2009

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