Machining Your Own Vs. COTS

[Cory]

The answer is it depends.

If you have something that needs to be extremely accurate, or you need to make a bunch of them, or it has angles and contours, then you'd want to use the CNC.

If you have a simple part you can make with a bandsaw and a power drill, you wouldn't want to use the CNC.

My formula for buying COTS vs making your own would be to decide:

Can we get the same functionality out of a COTS part as a custom?
How much more will it cost to go COTS?
How much longer (or shorter) will it take to get the COTS part?
Am I going to spend more than price premium of the COTS part to actually make it myself?
What else could I be making with my CNC, that isn't available as a COTS part?

If the answers to those questions favor COTS parts, then it's probably a worthwhile investment.

[Chris Fultz]

to add to Cory's comments -

use the off-season to learn the machines.

then, during build time -

if the part an easily be purchased, purchase it.

focus your design and fabrication time and attention and your machine tools on the parts that you cannot buy and need to be custom made for your robot.

[usbcd36]

One thing that becomes obvious after a few years of this competition is that you can't make everything yourselves. If you can buy what you need, that's better than making it, unless you're under severe time constraints (which almost never happens to us, since we're literally within driving distance of McMaster-Carr).

Personally, I would reserve the new tools for the complex parts, and try to stay away from using them unless they're actually necessary.

[Akash Rastogi]

Doesn't it also depend on the precision required for the product and cost/quality ratio?

[EricH]

Or, as in the case of sprockets (one example), you can get COTS and modify them using the machines, e.g, lightweight them.

[sdcantrell56]

I would say to do a combination of the 2. If you can purchase something that works just a well as what you can make and is cost effective then by all means purchase it. That will save machining time for other more complex things that need to be machined.

As far as using mills to do large things, I somewhat favor it, especially for fabricating drivetrain plates, or things like that just because the accuracy is so much greater than could be achieved with just measuring and a drill press and band saw.