Need Help!- Deflection Calculation

[Freff]

Hi guys, and thanks for your words of confidence. The whole machine is made of 12mm aluminum plate except the Z plate which is 10mm. The travel on the X axis is about >16" the Y axis is >24" and the Z is >5" which will be reduced to about >3 1/2 when the bed is installed.

Mike
At the time I think the rationale for the X rails behind the gantry was to keep the centre of gravity between the gantry sides and therefore not having the router way out front and increasing the leverage on the rails. Not sure if there is any mileage in this thinking.

As I said earlier, most of the work will be on light ply and balsa with the very rare occasion when a bit of light milling on aluminum may be necessary. On my first machine (MDF) I never used any bit bigger than 1/8" with no trouble, other than the questionable tolerances and having to keep tightening all the bolts.

The Y axis rails will be bolted to a 2"x2" box section frame running about 3" below the bed, in effect shaped a bit like a squashed H on it's side. (hope that makes sense)

[.xXACEXx.]

caught all this a lil late...i started to reply when you first made the post and no one had made a reply but couldnt remember any of the numbers or material i used...so i did some deflection test today...

.519 diameter "A2" tool steel unhardened ,supported each end in a v block with a 7 1/2 pound weight sitting in the middle ,with 20 inches free unsupported length deflected 15 thousandths (.015 inch)

under the same length and support the same 7 1/2 pound weight deflected a 1 inch "4140" unhardened steel rod only 1 and 1/2 thousandths (.0015 inch)

i know this dont really help ya any now ,but maybe it will help some one who is considering using bronze bushings and "drill rod" steel shafting for linear rails ...it may have been a simple test but ...looks like "bigger is better"