It would be nice if the rails were stiffer.
Why don’t we print some sort of lightweight lattice structure that can be pinned/bolted/whatever together in sections, and then jammed into the EMT conduit?
Some sort of… /////////// type thing? If it’s light it wouldn’t have enough weight to pull down the conduit.
I have some ideas, but just wanted a sanity check before I sit down with CAD.
What’cha all think?
How big is your machine? At normal sizes EMT should not noticeably flex, and you can go up to stainless.
What you are asking for can be had if you check thingiverse for “MPCNC midspan supports”. A single support 1/2 way increases rigidity by 4x. I might even have it linked on the size page.
Yes, I see the midspan supports. This is not that. This would go INSIDE the EMT.
Like a little bridge truss, helping to stiffen it up.
I do not wish to go up to stainless. I LIKE the idea of using commonly available parts.
You would have to figure out how to affix the truss to the conduit at all the midpoints, otherwise, the truss would just flex with the tubing. Plus you would probably be dealing with the plastic breaking from stress fractures as the metal tried to flex it.
In the end, you wouldn’t gain anything for the amount of pain it would cause.
Well…
I’m going to try it. Nothing ventured, nothing gained, and trying stupid things is what gets us ahead sometimes.
Also, I’m probably that guy that wandered over the hill in prehistoric days and got eaten by a bear, warning everyone not to go over there. 
That won’t work, because it won’t make contact inside the tube. Even if you make it a bit bigger than your tube diameter, it will be grinded off when you’ll jam it inside.
If you really want to put something inside your tubes (which I really doubt will make any difference unless your tubes are made of some kind of chewing gum), you should probably try to use some polyurethane foam. Easier, cheaper, faster and it will probably make it a tiny little bit stiffer.
just brainstorming how about threaded rod as long as the tube slightly longer for the ends. and with a series of nuts and washers either made of wood or 3d printed thick 5mm+ with the same OD as the ID of the tube spaced out 10 mm apart and at the ends of the tube an oversize washer with nut and jam nut to pull on each end acting like a spine
For? Tension could be a good thing but compression is not really what we would want.
While we’re on the topic of Sanity Checks…
I’m starting my build in a few weeks.
I was thinking of standing the tubes on end and filling them with resin (with or without glass fibers) to stiffen them as I want to build a 4x3 foot machine without mid-span supports. I cant think of any possible downsides to filling the outside pieces, but filling the inside pieces will add weight.
Has anyone done anything like this? It would be quite a bit cheaper for me to do this than to go to stainless.
I don’t think anyone has tried this yet. Neat experiment though! Does epoxy change shape/volume as it cures? I can’t remember if it does or not.
By my calculations, that’s about 1/3gal of epoxy or resin. without spilling. Another 1/6gal for the center. Add in allowances for slop and maybe a f-up? A gallon costs about $75 or so? Looking at amazon, I’ve never bought it.
Just sanity checking your cost math.
If you do this. Find a set width span. Like 40". Put a weight on it, hook it on the exact center and measure the deflection before and after. That would be pretty informational.
You should also know. The LR is great at that size and also, there are some “mid span supports” for the outside pipes for mpcncs that big. That was the size of my mpcnc and it is workable (I didn’t use supports or fill the EMT). Just don’t expect to cut aluminium and you might have to work harder on your CAM if you want precision.
Look into micro balloons. They are exreamly small glass spheres that are used to lighten epoxies.
Ok, I’m talked out of it. For the price and hassle, I’ll just skip it as I don’t plan on doing anything serious. Mostly laser work which doesn’t need rigidity anyway.
Thanks for the input.
Darn. Someone is going to try it…
I happen to have a gallon jar full of micro balloons. I am in need of a rebuild so I might have to give this a try, unless anybody can convince me to convert my MPCNC into a lowrider (it may not take much)?
Do it.
Maybe do the flex test first and then make a low rider.