Hi, im building a large hotwire foam cutter for my shop. I have been planning on using a pair of linear rails on each end, two per axis but Im wondering if I could get away with a single heavy rail. If you arent familar with what im talking about, Ill try to describe the load situation. If the rail were mounted flat on the floor, i will have two "trucks?" on the rail connected with a metal plate. extending upward from this plate will be a 50 inch tall tower holding its own lighter duty linear rail. There will be a side load in the form of spring tension on the upright rail at all times, and this will be transfered into the main rail at the bottom. When the spring load is near the bottom it would be almost direct side load on the linear rail and im not worried about it, but the spring load is up at the top of the 50 inch tower it will put a good deal of torsion on the linear bearing. I this within the limits of a bearing like this, I know that ideally it would take a huge downward or direct side load but do you think the bearing would hold up with that torsional tension? Is 20 lbs so small compared to what it can handle that it shouldnt even be considered? It will be moving at very low speeds and never have any shocks or sudden impact under normal opperation, only steady spring tension. The reason that I cant simply connect the top or bottom of the towers to support the spring tension, is because each tower will be required to move independant of the other so any connection other than the wire is impossible. I also realize that i could put a track and roller at the upper end of each tower to support the side load, but that makes the machine bulky and hard to load/unload.
ok, let the opinions begin.
since you are using a hotwire cutter, there will be almost no load on the actual cutter, so as long as you deal with the flex of the rest of the system, one rail would probably work. you could always make provisions in your design to add a second rail if the single is not giving you desired results.