i'm doing a series on mechanical rigidity of 3D printing frames, and came to the conclusion that the Fisher's use of panels is absolutely superb. The typical Kossel is easily susceptible to rotation and shearing, but the addition of those three panels to the Fisher almost *completely* eliminates that. the analysis page is here: [reprap.org]
There is only one potential flaw, and it's this: the top of the open frame hole in each panel face needs bracing, but it can only really be done on the outside as the z-axis mechanisms would otherwise be interfered with. Horizontal Extrusion (or even L-Plate) needs to go on the outside just over the top of each of the open holes in each face, attached in three places each, with each bracing then joined (externally and rigidly) to each other but leaving a gap sufficiently large that each Z-axis travel mechanism can still go through it without interference. Actually... a single flat piece of acrylic could equally well do the job, a quick sketch is attached. Attachment points are shown in green.
Could anyone who has a Fisher say if the panels are actually loose or not? I suspect that they are. Do they wobble about at all (outwards or inwards), and also, what happens if you try to push the top of the Fisher side-to-side when the base is firmly attached to the ground? I would expect the panels to bow and flex (and the top to move about as a result), but it would be nice to have that confirmed.
A specific video demonstrating the concept (which took only minutes to do instead of hours for 3D CAD design and days to weeks to create a first prototype) is here: [youtu.be]
Always looking to improve the quality of 3D printing.