Z-Axis_Brake
Description
Note 7 July 2021: It worked, though I had to stiffen it up after a while. But it is superfluous since I use one 8x4 lead screw in stead of the usual 8x8 one, despite the relatively heavy load of a 326x326x6mm etc. I could not find a cheap one, so I used a Robotdigg "Tr8*4 400mm Leadscrew Threaded Linear Nema17" - part no. 17HS3001-400N84, which is a combination lead screw + motor. This thing prevents the bed of a Core_XY 3D-printer going down after power-off. It is greatly inspired by the Anet A8 Z Axis Brake by Gear_Down_For_What, https://www.thingiverse.com/thing:2238760. 1 motor with 1 lead screw can easily handle my 330x330mm >4kg bed assembly. Except for the going down, which is hardly their fault. It is a familiar problem but I didn't see any simple solution, until I saw what Gear_Down_For_What had come up with. Great idea. Thanks. The usual stepper motors with 5mm axes are build to withstand sideways forces, but I use a motor with build-in lead screw and I don't know about that. (I use that combination because I didn't find a lead screw with enough accuracy). So I thought it safer to exert pressure on two sides. And to have some control over the braking force too. I don't need a motor coupling, but it would be nice to have some smooth metal to brake on, like in the original, not something printed. Something like that half of a coupling which fits the 8mm lead screw or the 5mm motor axis. With the help of a saw (it is only aluminium) that's easily provided for. Check for sharp edges. In that way people who use the usual configuration can use it also by putting this below the normal motor coupling in their "motor + coupling + lead screw" setting. If one has a coupling with 2 8mm bores and uses a built-in lead screw one can use that as a dummy without sawing, of course. A M2 bolt gives better control over the braking force than a M3 bolt, though there is just enough room for a M3 bolt, when one would like to try that. An earlier lighter design gave way pretty soon, so I hope this sturdier one will keep. Otherwise it is easy enough to make it still more stiff and exchange the open version. So don't hesitate to ask for it, when you see your bed going down after a while. Remember: one would like to use as little pressure as possible to just prevent the bed going down. Experiment a little with the M2-bolt. There are 2 variations: an open one in 2 parts and a closed one. The open one can be mounted and replaced without having to unmount anything else. I used: 2x M3x8 2x M3x12 4x M3 washers and nuts 1x M2x15 1x M2 washer and locking nut 2x M4x4 socket set screws to replace the originals (M4x6) which stuck out 1/2x flecible motor coupler (see text) PLA
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