I am currently upgrading my 24 x 30 inch frame (diode laser from China) to a 4 x 8 foot table size for those big projects.... cause bigger is better, right? I bought 20 and 20 x 40 framework from 80/20 and assembled it, but am concerned because the carriage has a bit of side to side flex. I think the C-channel would be a much better fit for what I need but I see the max length is only 1500mm, when I actually need 2,452mm (8 feet) Can they be joined smoothly and strongly enough, or can I get an 8 foot length? Doug
If you made the gantry the short way (ie only 4 feet long) there would be less flex. Then you could put multiple supports along the long axis to keep it from sagging and flexing. But, you would have to buy another piece of 20x40 since it looks like you cut it up already. If you were to join two pieces end to end, I would put a 3d printed v slot connector in the joined ends and have extra wheels on the gantry cart to make a smoother transition over the joint. I would also reinforce the joint with a flat aluminum plate with a whole bunch of 5mm socket cap screws and t nuts. You will also get a lot of belt stretch over that length so I would consider a dual belted system (sort of like a poor man's rack and pinion).
Thanks for the response. Haven't cut anything yet. The short piece of 2040 on the left is the carriage from my original frame. You can see the burns in the table where it use to sit. I will try this out first and see what happens. Perhaps by turning down the acceleration and decel it will reduce any sway caused by momentum. I use T2Laser for engraving and BenCutLaser for...cutting, and I believe I can edit the G-code within those programs for smooth starts and stops.
The problem you're going to face with a Cbeam is they're heavy, 1.45 pounds per foot heavy. That's nearly a 12 pound beam you're wanting to put on a system that should be kept as light as possible if you want any kind of speed out of it. I can't see how your carriage is laid out from the photo but if you're determined to keep the long beam I would suggest bonding a thin walled 1.5" square x 1/16" aluminum tube to the back side. Overall though, I have to agree with Craig. Turning the gantry to the short direction will give you much better results because you can make is so much lighter.
If you decide to go with longer C-Beam, we may be able to help. Just drop an email with your size request to http://support.openbuilds.com/support/home.
