So I want to run this by people to see if there is a good reason not to do this.
Rigidity is a big part of all kinds of mechanical systems. Of course the CNC machine, but also things like the handling of a car. There’s a trick that many racers use for street vehicles which has large measureable improvements in a car frame’s rigidity.
Basically take spray foam insulation, and fill the frame rails (But not overfill!) with foam. The foam itself isn’t very strong, but applied over the area of the inside of the frame rails, it has a marked effect on the ability of the rails to flex under strain. The filled steel has much less flex to it, which has a desireable effect on the car’s handling.
So… I want my MPCNC rails and gantry to be stiffer, but not much heavier. If a few ounces of spray foam can make the gantry rails stiffer, would that be worth the downsides?
I have some leftover 1" tube from my MPCNC cuts, which I think are long enough to serve as rails for a LowRider2 at 49" of X. If nobody has a compelling reason not to do it, I may set up an experiment to see if I can get some quantifiable data for stiffness. My experiment would be to use a good straightedge, say my 3’ journeyman level to measure deflection of the 1" steel tube when suspended across a 4’ gap, and supporting a weight, say 2kg. This is more than the strain that carrying a router should have, as that is typically split across 2 rails, but ought to give me measureable deflection.
The main downside that I can see is that people often run wiring harnesses through the gantry rails. Once the foam is added, the wires will not be able to be easily removed. I believe that if I do this, I will run enough wire through the tube before I put the foam in for a LowRider2 gantry, and terminate it in such a way as to be able to plug in motors and endstops, and never need to replace the wire running through the tube.
Anyone have a compelling reason why this is a bad idea?