From the category archives:

mechanical engineering

3d printing hack

It’s not going to replace Makerbot or your local rapid prototyping house anytime soon, but still a pretty impressive hack.

Tagged as: 3d printing, hacks, makerbot, rapid prototyping

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For those of you who aren’t familiar with the industry, Makerbot is the (in my opinion) at the leading edge of the RepRap movement. Or, with less jargon: Makerbot is a build-it-yourself robot. It makes things out of plastic. It’s worth checking out their website for the details, in the meantime check out my buddy Nick’s [...]

Tagged as: 3d printing, makerbot, rapid prototyping

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liquid metal (as awesome as it sounds)

design

Just came across LiquidMetal today. Wow. At first I thought it was just a twist on Metal Injection Molding (MIM). Digging in a little further I realized that the really cool part isn’t the process, it’s the material. Liquid Metal isn’t actually a material, but a class of alloys, check out their website for more [...]

Tagged as: alloys, liquid metal, metal injection molding, springs

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6-32 screw warning

mechanical engineering

Came across this fun fact today… 6-32 screws have the worst ratio of torque that can be applied to torque necessary to shear the screw. In other words, they are the screws most likely to shear off. Good to know.

Tagged as: fasteners, screws

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hard anodizing

materials

A while back I had the need to get some sheetmetal (every spell check in the world keeps telling me it’s “sheet metal” and not “sheetmetal”, but I digress) and machined parts hard anodized. I’ve been meaning to post my notes on the process for some time… and now I am. what is hard anodizing? A [...]

Tagged as: aluminum, anodizing, hard anodizing, hard coat, plating

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using diamond pins for locating

mechanical engineering

When two parts need to be precisely aligned. It’s tough to beat a two pins. One goes into a hole (that fixes X + Y translation), and the other goes into a slot (that fixes rotation). It works great, but it’s always seemed a little sloppy to me. Then I was turned on to diamond [...]

Tagged as: diamond pins, locating, pins

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recycled resins: sometimes they’re just better

mechanical engineering

The biggest hurdle to overcome with regards to using resin containing recycled content is something I like to call the performance bias. Our performance bias tells us that in most cases, second hand materials aren’t going to perform as well as their brand new counterparts. It’s a bias that generally serves us well, but during [...]

Tagged as: Injection Molding, recycle, resin, Valox iQ

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how side actions work

mechanical engineering

When I first heard the term “side action”, I got what it was… but couldn’t quite envision how the tool worked. I was told that: A side action is something that allows you to create a feature with a pull direction that is at an angle to the primary pull direction. In hindsight that seems [...]

Tagged as: cam, Injection Molding, side action

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statistical tolerance analysis basics: Root Sum Square (RSS)

mechanical engineering

In my last post on worst-case tolerance analysis I concluded with the fact that the worst-case method, although extremely safe, is also extremely expensive. Allow me to elaborate, then offer a resolution in the form of statistical tolerance analysis. cost A worst-case tolerance analysis is great to make sure that your parts will always fit, but [...]

Tagged as: example, manufacturing, root sum square, RSS, rss tolerance stackup, rss tolerancing, spc, statistical tolerance analysis, tolerance analysis fundamentals

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First Cut prototype

mechanical engineering

I’ve heard some bad things about First Cut. Some complained about the poor tolerances, others that First Cut won’t tap holes, still others complaining about maximum part size. They’re right, each one of them. But if you’re willing to accept tolerances of ±0.005 (give or take) and tap your own holes, First Cut is a solid [...]

Tagged as: CNC, machining, prototyping

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statistical tolerance analysis basics:
worst-case tolerance analysis

mechanical engineering

fair warning: if you’ve never heard the phrase “tolerance analysis”, you’ll likely never have to perform it and should just spend the next 5 minutes elsewhere. Otherwise… A well-performed tolerance analysis will add years to your life. No worrying about parts fitting together, no worries about sloppy fits. A well-done tolerance analysis both proves the [...]

Tagged as: example, root sum square, stackup, tolerance analysis, tolerance analysis fundamentals, worst-case tolerance analysis

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urethane castings: 3 things to ask before you hit ‘send’

mechanical engineering

A while back I shared some things you should know about urethane castings. I focused mainly on when you should use them, and not so much on some of the actual design considerations. So here you go… design considerations. The overarching theme is that rapid prototyping houses like to do things a certain way. Sometimes though, [...]

Tagged as: example, product design, prototyping, urethane casting guide

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CNC Motorcycle Helmet

mechanical engineering

This ridiculous video made the rounds on some forums a while back, I was just reminded of it today. It’s a motorcycle helmet CNC ripped out of an aluminum billet.

Tagged as: CNC, machining

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sealing medical cushions:
RF vs ultrasonic welding

design

Once your kickass memory foam design has been molded or fabricated, it’s probably going to need to be covered. That means upholstery. When you think of upholstery, you probably think of stitching and sewing. If you’ve got some practical experience, stapling might even come to mind. But when you start talking about designing medical cushions, [...]

Tagged as: fabrics, medical, RF welding, ultrasonic welding

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507 Mechanical Movements PDF: another great mechanism resource

mechanical engineering

Not too long ago I told you about three great mechanism references, one of which was the not-so-cheap Mechanical Devices Sourcebook. Well times are tough, and I’ve been reminded of the Sourcebook’s Grand-daddy: 507 Mechanical Movements. The link is a free PDF (507 has long since crawled out from under copyright protection) and there is no [...]

Tagged as: 507 mechanisms, mechanism design, mechanisms and devices, references

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Dear SolidWorks and Pro|Engineer:
fix these problems

mechanical engineering

Everyone has their preferred CAD package, and most look down their nose at all the others. The Solidworks guys rag on the Pro|Engineer guys, a few yucks are had, and you go back to work. But isn’t what we really want for one of these CAD programs to really get their act together? To decimate [...]

Tagged as: CAD, Pro Engineer, SolidWorks

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CAD job trends: or why I pity students that learn Unigraphics

mechanical engineering

There is an interesting thread over at eng-tips regarding current CAD job trends. The content itself isn’t so groundbreaking, but the recommendation of Indeed.com’s Job Trends tool made it worth the read. “Finally!” I thought. “Some objective data to prove that Unigraphics is dying!” I wasn’t disappointed: (note: I think the “inventor” is inflated, as job [...]

Tagged as: CAD, Pro Engineer, SolidWorks, Unigraphics

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a quick tip for preventing PCB-induced stress

mechanical engineering

Most of the products we design have at least one Printed Circuit Board. The design process usually goes something like this: Specifiy the components (sensors, batteries, switches, etc.) required for the device to perform it’s desired function. CAD-up the components per their respective spec sheets. Drop them into the CAD assembly to see how much [...]

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three great mechanism references

mechanical engineering

Mechanisms are awesome, but they don’t seem to get much love in the search engine world. All told, these are the three best references I’ve seen that actually help in mechanism design. Flying Pigs Paper Animation has some nice flash of your standard mechanisms. Boston’s Museum of Science has a wall of mechanisms, so be [...]

Tagged as: mechanism design, references

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free body diagrams in product design

mechanical engineering

Free body diagrams are old-school, and when I was in school I didn’t think I’d use them much. Truth is, I actually use them alot. When I’m doing a feasibility study for a mechanism concept or calculating rough safety factors and don’t have time for an FEA simulation, free body diagrams are the best tool [...]

Tagged as: FEA, free body diagrams, statics

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