HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Comments
View Comments: Newest First|Oldest First|Threaded View
Dave Palmer
User Rank
Platinum
The case of the breaking brakes
Dave Palmer   6/24/2011 3:03:42 PM
NO RATINGS
Powder metal parts can cut costs, but (as with any material or process) it's important that there be a good match between the application and the material.  The award-winning parts seem to be good examples of this.

Unfortunately, I've also seen examples of parts which never should have been powder metal.  For example, I was once involved in a failure analysis for a mechanical brake actuator which consisted of a hub with a long shaft.  Since the compaction direction was along the axis of the shaft, and the length of the shaft was more than twice the diameter of the hub, it was difficult to achieve a high density in the shaft.  The shaft was subjected to torsion and bending loads.  Depending on the exact size and location of porosity, fatigue cracks would initiate at the base of the shaft.  With repeated actuations, the shaft would snap off, rendering the brake inoperable.

Making the part out of powder metal may have saved money in the short term, but this could have been a very expensive problem if anyone had been injured or any property had been damaged (fortunately, this never happened).  As it was, a significant sum of money needed to be spent on this issue.

Of course, there are PM techniques which could have been used to solve this problem.  For instance, double press / double sinter would have made it possible to achieve a higher density.  Powder forging would have allowed an even higher density.  But once the part was already in production, either of these options would have required significant new tooling expenditures.  Ultimately, after examining a number of options, it was found that it was cheaper to machine this part from an inexpensive forging.

There are many applications for which PM is a great option.  However, design engineers need to make sure that it is a good fit for the application.  PM suppliers should also be careful to bring up any potential areas of concern during the design review process, so that any potential issues can be resolved before the part goes into production.



Partner Zone
Latest Analysis
A bold, gold, open-air coupe may not be the ticket to automotive nirvana for every consumer, but Lexus’ LF-C2 concept car certainly turned heads at the recent Los Angeles Auto Show. What’s more, it may provide a glimpse of the luxury automaker’s future.
Perhaps you didn't know that there are a variety of classes, both live and archived, offered via the Design News Continuing Education Center (CEC) sponsored by Digi-Key? The best part – they are free!
Engineer comic Don McMillan explains the fun engineers have with team-building exercises. Can you relate?
The complexity of diesel engines means optimizing their performance requires a large amount of experimentation. Computational fluid dynamics (CFD) is a very useful and intuitive tool in this, and cold flow analysis using CFD is an ideal approach to study the flow characteristics without going into the details of chemical reactions occurring during the combustion.
The damage to Sony from the cyber attack seems to have been heightened by failure to follow two basic security rules.
More:Blogs|News
Design News Webinar Series
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
12/10/2014 8:00 a.m. California / 11:00 a.m. New York
11/19/2014 11:00 a.m. California / 2:00 p.m. New York
11/6/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Jan 12 - 16, Programmable Logic - How do they do that?
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  67


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service