> On May 13, 2024, at 1:45 PM, Todd Zuercher via Emc-users > <emc-users@lists.sourceforge.net> wrote: > > Anyone have any brilliant ideas to stiffen a woefully inadequate cross beam > on a gantry router without adding too much mass? What is there now is a 4" x > 8" rectangular 3/8" walled extrusion that is 145" long. > > Under normal jogging commands the two servos control the ends of this gantry > reasonably well, but while the axis is homing the thing shakes and wobbles > terribly bad. Also If I put a dial indicator in the center of the bridge and > hit the bridge forward or backward it will flex and wobble enough to displace > the dial indicator +/-0.03 and it takes nearly a dozen wobbles to dampen it. > But on the ends the servo's only have a few thousandths of give. > > I'm less concerned about the actual stiffness and more worried about > dampening the wobble.
What is the extrusion made of, I assume it is some kind of aluminum alloy. The simplest but expensive option is to replace it with a stronger/stiffer material with the same dimensions. Of course Titanium comes to mind but that is maybe not in the budget. Carbon fiber could work and it is possible to DIY carbon fiber beams with just hand tools. I have made 4 meter long racing kayaks with carbon, using just a paint brush and scissors in one weekend. The first class way is to make a female mold and polish it well so the part looks nice. The cheap way is to make one like they make surfboards. You start with a foam block, shape it then wrap it in fiber and resin. The neat thing about carbon composite is that you are not limited to the extrusion shape. I would make the entire beam a compound curve with no flat or straight or cylindrical sections, Maybe like a very elongated American football but with ovil cross section. I like to use the car hood story. A flat sheet of sheet steel is bendable by hand. But after they stamp it into the shape of a car hood it becomes rigid. So rather then a square tube, way not oval but with a larger diameter in the center where all the bending force is? The way you make it is to first make a full-size model out of wood and bondo. Do a test-fit and give it an automotice grade paint finsh and then paste wax. Make a fiber glass mold, then from that your part. Yes that is a lot of work. This is why you have an aluminum extrusion there now, because that was easy and cheap. > > Todd Zuercher > P. Graham Dunn Inc.<http://www.pgrahamdunn.com/index.php> > 630 Henry Street > Dalton, Ohio 44618 > Phone: (330)828-2105ext. 2031 > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
