Bracing is your friend. My current design is using all 6x6 and 3x3 extrusions. Box all your corners and keep the lengths to a minimum. Most machines I see made out of 80/20 are designs that are better suited to steel or cast iron as a material. Not much thought is put into the weakness of the material OR it's strengths.
Aluminum is actually a very rigid material and if you take the extrusions internal honeycomb design into consideration with your design in regards to force loading you will have no problems building a rock solid machine.
When designing for strength remember to keep lengths to minimun. You'd be suprised how much rigidy can be gained by taking an inch off a moment arm when dealing with high forces created in material removal. That being said, do you really need 6 inches of travel on your Z axis?
Bridgeports are great machines but what happens when you get to the end of your travel on the X axis? Shudder city. Leaverage is a powerful force multiplier. Use it your advantage. See the forces working againt you and gain leverage againt them. If you're able to keep that mental picture in your mind while you're designing, the design will tell you exactly what it wants to be. It sounds simplistic, but machines design themselves, just be watchfull of what the design is telling you and don't be stubborn if the machine is not wanting to be what you originally had in your mind.
I design filling machines for a living and I'm not proclaiming that to raise my stature here or anywhere else, it's just a job. But a lot of what I'm saying comes from some hard lessons as well as some great triumphs in a professional environment. Good luck to all. Use your imagination but listen to the design.
Jim  |