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Dialog Box March 2007

1 Mar, 2007 By: Cadalyst Staff

Readers have their say.


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SLS Most Robust Process
After reading "Rapid Prototyping" in February's "MCAD Modeling" column, I have to say: SLS not robust? Sorry, but that is not accurate. Of all the RP processes around now, SLS is probably the most robust. Also the image of the vase -- is that not a Z Corp. shot? Z Corp. machines are not SLS -- I'm not sure I have ever seen or come across a multicolored SLS machine. Metal parts from FDM? Again, surely this is SLS. All in all a very inaccurate article, not up to your usual high standards.
—Kevin Quigley, Shrewsbury, United Kingdom

Mike Hudspeth responds
Mr. Quigley has some good points. First, I never said in the article that SLS wasn't a robust technology. But no additive RP technology will produce parts that will be super-rugged (at least without secondary operations and/or thick walls). I have seen many examples of SLS models, and they all have a semi-rough texture. It can be sanded smooth, but it doesn't come out of the machine that way. This is also why it is not the best choice for tiny parts. The resolution just isn't there. By tiny, I mean something like the hub of an insulin needle or a jewelry setting. SLA is a superior choice in tiny, detailed parts. I stand by that statement.

Yes, the vase is a Z Corp. image. Technically, Mr. Quigley is correct. Z Corp. doesn't use a laser but a print head. It might more accurately be described as an SCS (selective chemical sintering) process. It uses a chemical binder to hold the building powder together. I should have made that distinction. The Z Corp. machines' biggest claim to fame is their ability to do multicolor parts. This is due to color added to the binder.

The metal object shown was produced on an Arcam EBM S12. Mr. Quigley is also correct in that this isn't an FDM machine but is more like SLS. Arcam uses an electron beam to fuse metal powder. I apologize for the confusion.


Finding a Tutor
Can you advise how to find a private tutor to do CAD training at the architectural firm I'm working for in Philadelphia?

—David Arfaa, Philadelphia, Pennsylvania

Robert Green replies
In the greater Philadelphia area, I would contact Synergis Technologies for tutoring resources. Synergis handles all sorts of CAD products. You might also want to contact local technical schools to see if any instructors are willing to do part-time tutoring. Last, get on the AUGI (Autodesk User Group International) Web site and post a request labeled CAD TUTOR NEEDED IN PHILADELPHIA, including your e-mail address. (The AUGI site is open to all users who complete the free registration.) I'm 99% willing to bet you'll find something following these recommendations.


Putting People First
Cadalyst is a fine magazine with many insights and much information. However, in reading the January 2007 issue, I was sorely disappointed. Language is the medium through which a magazine distributes its information. It's through language that ideas are formed. Without language we could not express thoughts, ideas, dreams or desires.

On page 14, your "Tech Trends" column, "Building a Better Box Cutter," identifies the recipients of the design competition as disabled people. That is an expression with which I take exception. By placing the adjective "disabled" ahead of the subject "people," the word disabled is given greater importance than the word people. I would like to propose the phrase "people with disabilities" as an alternative.

As a person with a disability, perhaps little things like this are more important to me. But in my defense, I would argue that the fact that I am a person is of greater importance than that I am disabled. It follows that in describing me, it is more accurate to say that I am a person with a disability rather than that I am a disabled person.

Just as your mission in life is to promote the use of CAD, my mission in life is to raise the awareness of the general public on disability-related issues. Let's put people first.

—Cornelius Van Dyke, Yellowknife, NWT, Canada


About the Author: Cadalyst Staff

Cadalyst Staff

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Lynn Allen

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