Ultra Stable Kinematic Mount for 3D Printer Bed12/23/2017 at 03:39 • 1 comment
My latest 3D printer, UMMD, uses a kinematic mount, often used to mount lenses and beam splitters on optical tables, to mount and level the bed. The mount constrains motion in 6 DOF, yet allows the bed to expand when heated without creating any lateral forces that cause either the bed or support structure to flex. It has proven so stable that after initial leveling, it has not needed releveling even after transporting the machine on its back in my car.
The kinematic mount uses three leveling screws, two with spherical heads. One of the spherical head screws, the reference, sits in a chamfered hole that allows the bed to tilt but prevents lateral motion.
The other spherical head screw, used to adjust the bed's pitch in the X axis, sits in a chamfered slot that allows the bed to tilt for leveling and to expand when heated but prevents rotation around the reference screw.
The third screw, the roll adjuster, is simply a flat screw that touches the underside of the bed and allows it to tilt for leveling and to slide to accommodate thermal expansion .
The 300x300x8mm MIC6 tooling plate bed is held down onto the leveling screws with springs. Nothing stands above the bed's PEI print surface, which minimizes the danger of the extruder nozzle crashing into clips or screws.
Belt Lifted Z-Axis for 3D Printer12/23/2017 at 03:11 • 0 comments
My latest 3D printer design uses a belt lifted Z axis that has proven to be a very good performer. The 300x300x8mm MIC6 bed and its support (3.5 kg) are lifted on two linear guides using two steel core belts. The belts are driven by a NEMA-23 motor mounted on an OnDrives Rino 30:1 worm gear reducer that prevents the bed from dropping when power is shut off. Maximum speed is 20 mm/sec (the motor is spinning at 333 rpm!), even with a 4 kg print load. The motor is rated for 1.8A, but I operate it at 1A and it never gets more than 5C above ambient temperature. It is driven directly by the driver chip on a SmoothieBoard controller. I have measured belt stretch and determined that it is negligible.