Design Resources

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Development Guide



General Design Tips


The elements are the foundation of hardware design. Get to know the important ones and how they interact with each other in different environments.

Ptable: Periodic Table of Elements

Needs: quality videos explaining the most relevant elements (ex. Hydrogen, Oxygen, Carbon)

Useful Materials


Assembly Mechanisms

Forming Mechanisms

Transport Mechanisms

A Short Guide to Moving Stuff

A Short Guide to Keeping Stuff Together



Quick Connect/Terminal Block/Cable

Common Electronics Misconceptions Clarified



Synthetic Chemistry

Optics and Lasers





A machine base, regardless of how light and stiff it might be, will elastically sag between supports from its own weight. While fabricated structures generally have a better strength to-weight ratio than cast structures, the weight induced sag is an important issue neverthe less because it causes supposedly flat surfaces to warp. The traditional way of dealing with this symptom is the following: the machine base is milled and ground on a machining cen ter large enough to hold the entire base. With the base evenly supported, all precision sur faces are machined to specification. Next, the base is put on its supports which are commonly located in the corners of the base and, depending on the overall length, some times even in between. Because the support is now localized and no longer uniform, the structure will sag, which is removed through scraping. Scraping is a manual finishing pro cess whereby a a thin layer of ink is spread over the surface of interest. Next, a straight master surface, usually granite, is put on top and rubbed against. The ink will wear off at the high spots but remain untouched at the low spots. Next, a scraper is used to remove all high spots and then the process is repeated until the surface is sufficiently flat. Due to its low forces, scraping is a tremendously accurate but also very time consuming process that requires very skilled workers.


Originally Posted by digits View Post

   ....I guess a more interesting question is how do you use a mill to build a bigger mill than itself? ...

It's the old bootstrap question.

So let's say you were stranded on a deserted island, with nothing but a bridgeport mill and a huge pile of material. It's a funny picture, a guy standing on the beach next to a Bridgeport mill sticking out of the sand! So instead let's also assume it is located in a covered shop (with utility services) and you have unlimited consumables (fasteners, bearings, motors, wire, endmills, paint, structural tubing, hand tools, food) but no other machines.

I imagine you could not make the larger machine directly. You might first have to build fixtures and build some intermediate machines. For instance, you might start by building a lathe and then a surface grinder.

Any parts too large to fit inside the cutting envelope of your Bridgeport would be either made by indexing the part through the cutting area or as multiple pieces bolted together. The biggest problem would be making a substitute for what is normally a gigantic iron casting -- the machine base. This part will be too big to simply index.

The main casting can be made of individual pieces bolted together. This is where the suface grinder comes in handy, to make a flat surface across multiple pieces. We're not talking perfecly flat or perfectly square. Just "good enough." This first round of machines will have to be made adjustable, because you are certain to accumulate error while building large pieces from many small ones.

I think something about this concept is appealing, even though it is unlikely that any of us will attempt it. Perhaps this is what made Dave Gingery's books so popular! I know I've thought a long time about how each generation's biggest machine was made -- obviously it was made on a smaller machine.

For any of this to work -- to build larger machines from smaller ones -- or to build more accurate machines from less accurate ones -- requires something that the DIY world does very, very well. It's a cross between the "get 'er done!" manta and "let's do something completely different!" For instance, most of the DIY router machines on this site are built with skate bearings on gas pipe! As a manufacturer, you would reject that concept because of all the time it takes to adjust each machine into tolerance. But if you need to do something new (say building a larger machine from a smaller one), then you are willing to put up with less-than-ideal solutions and make them work manually.

All sorts of possibilities open up when you have more time than money! That's better than having more money than brains anyway.

When you finished with the second generation machines (larger, but perhaps less accurate), then you would manually scrape and tinker and adjust those machines. They might be accurate only in a certain configuration, or for a certain setup. But then you could build the next generation that was yet more accurate, and needing less adjustment.

Essentially, isn't that how today's modern machines got here?