X axis 1530 versus 3030

[NGinuity]

Hey everyone,

I'm looking to build a T-Slot design 3 Axis machine that's 8 feet on X and 4 feet on Y (I've already decided on 6030 for Y). I found a company that has brackets that allow you to attach cold roll to either 1530 or 3030, and I was wondering, is 1530 strong enough to not deflect if I'm using a wood router operation? Or should I pay more for the 3030 for strength? It seems that the cold roll that the linear carriages will ride on will make even 1530 very rigid and would merely act as a support structure, as well as taking the brunt of deflection. In addition, since I'm running rack and pinion, the rack will stiffen the bottom all the more.

So, after I've bored everyone with that diatribe, is 1530 strong enough for what I'm trying to do?

[ahren]

Deflection is primarily caused by bending loads, and is a function of the sectional moment of inertia of the beam resisting the load. The inertia is a function of the width of the beam times the height cubed, so the orientation of the extrusion is far more important than the series -- in one orientation, 3030 is only twice as stiff as 1530, but in the other orientation it's ~8x stiffer. That being said, deflection is also a function of how long of an unsupported span you have, so just some additional supports can help you save cost on extrusion.

There's a lot more that goes into selection of your framework (how tall your gantry is, cutting forces you expect to see, etc.) But for a practical answer, I can tell you that our kits are based on 1530 for the X, and 3060 for the gantry, just as you have proposed, and it works very well for the proportions we have settled on -- you can check out our plans here:

CNCRouterParts

Good luck with your machine!

Ahren
CNCRouterParts

[NGinuity]

Ahren,

Fantastic! I'm glad you frequent these forums, because your company is the one I referred to when I said "I found a company that has brackets", in addition to many other items I am looking for. Prepare to receive some of my money in the very near future.....