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Top 10 Design Principles

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DougM21   11/4/2011 9:36:54 AM
The article and the linked pdf make a great refresher, and should also be required reading for designers in training. 

One design element you might add to the pdf is the bonded rubber bushing (as used in automotive suspension linkages).  It's a special case of flexures, and darned useful.

Nick Name
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Design Basic Principles
Nick Name   11/4/2011 10:45:26 AM
I highly appreciate the systematic approach over the more than 40 years of activity in machine and instrumentation design I developed a similar list and I am pleased to see the convergence of both. I consider that if those basic rules are respected many possible errors are avoided and the development is more straight and economical.

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Add One
Tool_maker   11/4/2011 2:51:31 PM
Very useful list to which I would add: When making changes to improve or correct a design, make sure you can change it back to the way it was in case your idea does not work. There are few things more frustrating than making a permanent alteration that does not achieve the desired results.

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Two more...
Amclaussen   11/7/2011 12:03:32 PM

The design of many of the late model cars and trucks seem to be made by Monkeys, but it is the complete lack of respect for the need to maintain and service the newer cars that is the common flaw.  CAD software has given way too much easy to the "designers", so that a dexterous computer draftsman is all that appear to be needed by industry.  But it happens that those draftsmen must have never hold a wrench in their hands, much less know how to handle it, or even what the hell that object is!

Today it is common to find that the machines or assembly jigs needed to assemble a given component, are too costly or complex.  This can be traced to less that good design for the produced part causes it.  The KISS principle should be the golden rule.  A good design usually has an intrinsic easyness to be disassembled and reassembled, thus the prototypes can be freed from design flaws faster and more throughly.

Dave Palmer
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Buckling and elastic stability
Dave Palmer   11/18/2011 12:27:55 PM
The admonition to beware of buckling of compression members is a good one.  It's important to remember that buckling has nothing to do with strength! If you look at the buckling equations, you will not see any strength terms.  The only material property you will find is the elastic modulus - which happens to be one of the few material properties you can't change through heat treatment or mechanical processing.

Too often, if a part is breaks, the answer is always "make it stronger." But if the failure is occurring in buckling, making the part stronger won't fix the problem.  You need to increase the second moment of intertia (either by increasing the cross-sectional area or changing the cross-sectional shape) or decrease the effective length (either by making the part shorter or by changing the end conditions).

Jack Rupert, PE
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Jack Rupert, PE   11/22/2011 3:24:42 PM
Very interesting list.  I'm dowloading the PDF and passing around the link.  I especially like the point about "self-help".  Since I do both control-automation hardware and software, I've always tried to include that.

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bobjengr   6/21/2012 6:05:24 PM

 Excellent list—very straight forward.  Ockham's razor states "all things considered, the most straight-forward design is the best design".  You mention that as one of your points.  Number 10 is also very interesting in that "tribology" (friction, wear, lubrication) is cautioned to be a consideration when designing mechanisms.   I will also state that I agree with one commenter in that designing for repair and / or replacement is a good idea and will keep customers coming back ( certainly repair men).  As a kid working his way through college, I ran an appliance repair operation.  The ability to repair quickly is a marvelous design feature when successfully accomplished by design engineering teams. 


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