Precision Piezo 20mm disc to LM8UU bearing mount

thingiverse

Edit 8/13/2018: So... I actually built and tested this thing out, and I've got some updates to share. The long version is now deprecated in favor of the small one, which is more than strong enough and has plenty of advantages that make it worth using instead. I've addressed a couple of issues with the new version: Using the 4 screws to hold everything together puts stress on the piezo disc, which can cause problems if your printer isn't made exactly to dimensions or if your LM8UU bearings are slightly larger than spec. This results in a lack of sensitivity and may not be good for longevity. Solution: I've made the two holes in the plunger piece larger so that the socket head cap screws can float, which allows you to tighten them to keep pressure on the bearings while still holding everything together. Using 2 screws to mount the assembly to the bed was unnecessary and excessive. A single screw at each location is more than enough to prevent lateral motion of the bed, especially if it's mounted tightly as intended. You could also use a single screw to allow for spring tension height adjustment for levelling, but I'm not sure what this will do to sensitivity. It was possible to mount the system so that the disc was already at the allowed maximum motion, which is a combination of factors including making the two screws float. To address this, I increased the depth of the opening and raised the plunger by 0.25mm, which should not damage the piezo ceramic even if the plunger is pressed fully to the disc mount cup. Original description follows: Mounting system for heated bed - you'll need three of these (although I see no reason why you couldn't use four). There are two versions included: one is 30mmX50mm, and the other is 30mmX30mm. The smaller version might be a little weaker because the screw holes are closer to the actual bearing opening, but it will save some space. Each set holds one 20mm piezo disc sensor, and there's a plunger piece that mounts to your bed via two screws spaced at 40mm. The plunger piece should hold two standard 3mm nuts (5.5mm wrench size). Each set has four pieces: an upper and lower "cap" piece to hold the LM8UU bearing, and a bed to hold the 20mm piezo disc. The assembly works by sandwiching the disc and the LM8UU bearing together with a slight pre-tension applied via the four screw/nut combinations holding it all together. The mounting deck should be between 21.5 and 22.5mm from the centre point of the LM8UU bearing, with some allowance for the piezo disc itself. The upside to this is that automatic bed leveling should be a breeze, but the downside is that there's not much room left over for making adjustments. The piezo disc itself is about 9mm away from the bed material, which should insulate it from the heated bed adequately for function. This is still a work in progress, and I'm publishing this as an addendum to my beltless printer design because I had to redesign the bed mechanism anyway, and I want to implement the Precision Piezo sensors. It seemed like a good idea at the time!