Railcore II Kinematic Bed Mounting

cults3d

I created this kinematic coupling system to overcome the problem of z-axis binding on the Railcore printer. BOM: The printed parts 6x M3 screws of appropriate length 6x M3 nuts & optional washers 2x 8mm Steel ball bearings (Amazon link below) 7x 8mm long, 6mm OD M3 threaded sleeve rods (Amazon link below) The kinematic coupling avoids over constraint of the bed and allows the z-axis to move freely regardless of any misalignment in the z-rails. Using the Kelvin kinematic coupling arrangement allows the majority of positional control to come from the front left rail, which is easiest to align. The back left rail will have reduced effect on bed position, and the right hand rail will have almost no impact on the bed position, other than keeping it level. It is also possible to use the same parts to generate a Maxwell coupling, which will average out the alignments of each rail. I don't see much benefit from that in this application, unless vibration from the printer being passed through to the bed proves to be a problem. The Kelvin configuration might be more susceptible to hard accelerations in the y-axis, compared to the Maxwell. (This is actually a modified version of the Kelvin coupling, since I have use two crossed cylinders for the single point contact position, rather than a ball and a flat. This has no effect on the functionality, but allows us to use only two types of component.) This is a work in progress, I've run several prints without problems, but my Railcore is new so I don't have much before and after data, and I'd really appreciate feedback. A word of warning, with the current design, the bed is just resting on the mounts, a significant lateral force could knock the bed off, and cause damage. Take extra care when removing prints, or working on the printer. I suggest lifting the bed off and resting it in the bottom of the printer when not in use. You'll also need to reduce you max z-height by ~10mm. Also note, the upper mounts will be at bed temperature, so it is probably best to go straight for ABS or PC. All parts print without supports, in the orientations shown in the screen shot. If this proves to be effective, the next step will be to add floating pre-tensioning screws to keep it in place. The Fusion 360 file is a mess but I've added it. The diagrams show how it goes together, the rods can be screwed in, the balls just pop-fit for me. Parts: Uxcell a16050300ux0563 M3 304 Stainless Steel Threaded Sleeve Rod Bar Stud Round Connector Nuts 10pcs https://www.amazon.com/dp/B01HSTUZW8/ref=cm_sw_r_cp_apa_i_AwRgDbDY8JVKA 100 8Mm Chrome Steel Bearing Balls https://www.amazon.com/dp/B008M3584K/ref=cm_sw_r_cp_apa_i_LiVgDbXHMNW6C Reading on kinematic couplings:https://en.wikipedia.org/wiki/Kinematic_coupling https://www.precisionballs.com/KINEMATIC_ENCYCLOPEDIA.php#k1