Next increment. Started with a cheap Core-XY printer, with a lot of faults. As a first iteration, moved all the electronics to a common backplane. Found the cube was askew. Iterated on braces for the corners. Placed the new braces on six of eight corners (and brought all the belts into plane).
This is where things get interesting.
We really want to brace and square the top frame. But big braces would interfere with mechanical motion.
Easy to add braces to the bottom frame. Even a single bottom brace noticeably stiffens the entire frame. Four bottom braces lock five of six faces of the cube into alignment. (Each corner is shaped to exactly guide all three extrusions.) This tends to lock down the last face.
Add two braces to the top-front (easy to do), and you lock all faces into strict and stiff alignment.
Even three (trial) corners did much to square the cube. Had to do a thorough re-level at that point.
Ripped out and added (final) braces to six corners. Started a print, which finished perfectly … without in any way re-levelling the bed.
Hi @Preston_Bannister , i like your setup. Would you mind showing more pictures, from how the bed is hold.
I have a couple of rigidbots myself and i was planning on modify one to a corexy like yours.
Also, at present, staring at the gantry. There is slight play in the assembly holding the print head to the gantry. Think I am seeing this in some of the prints. Not loose, but a bit of force can move the head.
Definite play in X. The assembly is on three wheels - two above and one below. The wheels seem to be firmly against the V-grooves in the extrusion … but there is some “give” somewhere.
Some play in Y, but this seems to mostly be the light extrusion flexing when loaded in torsion. Not sure how much side-force is exerted on the nozzle during a print. Might just punt on this (for this printer).
Also the part cooling fan/duct is quite weak, only from one side - and there are obvious print artifacts.
I want to use a lasercutter to make the six sides of the cube with cut in mesh holes, such that it will be square and alligned every time. All maker spaces have laser cutters, why not use it for building our 3d printers?
@Baldur_Norddahl There are times when I love to have a CNC router (or the like), to cut aluminum, acrylic, and wood sheet. Likely there is a maker space somewhere in the area.
Not so much a fan of acrylic for main structural pieces. Joining together pieces so as to avoid stress concentration (and cracking) is trouble. You have to add some complexity.
Aluminum extrusion is straight, stiff, strong, and light. With a t-nut and a screw, we can mount (and re-locate) things anywhere along any of the rails, which adds agility for future experiments.
Though acrylic frames do look cool.
I would rather do the frame with extrusion, and use largely non-structural acrylic sheet for the enclosure. In fact,I have some hollow acrylic greenhouse panels that will need to be cut when later building an enclosures.
But it is precisely because you can relocate that the build ends up being not square. Use a laser cutter to make holes and joins means you get as square and alligned as the laser cutter itself.
@Baldur_Norddahl As it turns out, with properly designed printed plastic corner braces, the frame can only be assembled in exact alignment. Also the resulting frame is very rigid, is “dead” to vibration. Also minimizes the part count, and simplifies assembly.
This started as a slightly dubious experiment, but turns out to work as well, and better, than I expected.
