If I make the bed longer then 1 meter, it is recommended to support the middle of the tubes. how do you support the moving x and y tubes ? Or do I have this wrong in my mind.
You only support the rails. The gantry can’t be supported, so they sag in the middle, but not as much as all of it sagging in the middle. When mine was 5 foot square I think I had a 16th of an inch sag before the supports were added. It’s not much, but if you’re V carving signs it could be enough to mess up a carving. That’s why Ryan designed the lowrider. SS tube doesn’t sag as much, and it’s designed to be that long.
without supporting the gantry, there will be sag. then I assume this won’t be a problem ?
we are about to pull the trigger on this, but I want to sort out all f the issues before we jump.
You could add a counterweight to the center gantry ro reduce the sag.
Attach a string to the gantry, go over a pulley attached to the ceiling and hang some weight on it, 2-3kg would probably be enough…
That won’t work very well. It will also try to pull the gantry back to the center of the table all the time.
@gene, how big do you want to go? If it’s only a meter square, you’ll probably be alright. The recommended is about 2 feet square, which is a little over a half meter. Any bigger than that, I’d go with a lowrider.
We are looking to see what size we really need. first thought was 4ft x 2ft, really larger that we need, thinking mabee 3 ft x 3 ft ,or 3 ft x 2 ft. that should work with no problem.
Otherwise buy some better tubes, it will greatly reduce the sag. Some materials are way harder than other and higher tube thickness will help, at the cost of higher inertia, so lower accelerations (should be no problem for carving though, only for high speed 3D printing but I understand that’s not what you plan to do anyways).
Here is a calculator that might help you:
In my case I’m using 4130N DOM steel with very thick walls, it is a close second to titanium in terms of strenght and I was unable to measure any sag with my comparator.
We plan to use 25.4mm stainless steel, this should be able to handle 1 meter x 1 meter ?
I would think so. I’d throw some supports on the outer rails if needed, but the full sheet lowriders are longer than that on the 4 foot span, and it doesn’t sag enough to make much of a difference.