KodinLanewave
commented
4 years ago Another option is design a "zero-set" tool offset ...setter. Basically just a simple tool head carrier with a z-screw and a piezo sensor. When you build or modify an existing tool, set it on the device, activate it, and it lowers the head down to the piezo sensor, then records the offset into whatever tool table entry you designate. Think of it like a tool probe offset fixture on a CNC mill, just not bolted to the machine. Probably complete overkill, but it'd be both fast and easy to build or modify tools without spending an hour getting the offsets perfect. I'm not even sure you'd need the stability of a full linear rail since you're just measuring Z offset length. Just a length of aluminum extrusion, a really short leadscrew, (40-60mm?) a stepper, some wheels designed to run along aforementioned extrusion, and the piezo sensor, along with whatever rendition of the tool changer lock mechanism makes sense. (can be hand-actuated to keep cost down)
I went trough the design and I have a suggestion for an autolevel that would detect the offset of any tool and tram the buildplate.
Using a dummy tool with only a PrecisionPiezo and a known length from the anchoring point of the toolchanger to the dummy "nozzle" one can tram the bed and set Z to 0.
Using a microswitch sensor on a platform controlled by a stepper and a lead screw, one can set the height difference between the known dummy tool and any other tool. The toolchanger in the startup routine can change Z to the small leveling platform, Home Z with the dummy by raising the platform until it hits the microswitch. Next, changing the tools, it can set the offset for each and every tool with M585.
It can then lastly home and tram the real bed with individual lead screws.
Perfect for changing nozzles. Only the X/Y offset has to be known.
I considered another Piezo for the platform but they are too sensitive to Z movement.