Some thoughts on the Z stop end

One of the most frustrating aspects of my Reprap printer was the Z stop end. For those non-reprappers out there, a stop end helps the machine to feel the boundary of its printing bed. It (usually) comprises of a mechanical switch secured to a supporting structure within the printer.

 

 Image stolen from http://www.nextdayreprap.co.uk

The problem with traditional stop ends is that they are usually secured to the metal rod as shown above. For X and Y stop ends, the rods used are usually tangent to the X and Y motion of the extruder respectively hence it is not as problematic. The same cannot be said for the Z stop end (refer to pic above for more details).

Since the motion of the extruder is parallel to the supporting rod of the Z stop end, every time the extruder touches the Z stop end, the Z stop end shifts down a few hundred nanometers.In the end, the reprapper ends up calibrating the Z stop end almost every time before use.

Z stop end V2.0 with an independent support which is more secure.

Z stop end V2.0 was designed with Autodesk Inventor (very good for speed modelling as compared to AutoCAD) and was engraved with Blender (free artistic 3D modelling software). The picture did not show the engraved words as those are on the other side. This stop end eliminated the problem I had with V1 (the first stop end design), however time proved that V2 had its complications as well.

Words are hard to describe what I faced. A well annotated picture best represents the problem.

This problem is harder to identify. Initially I thought it was the new Z stop end that was not secured. Found out that the bridge itself was prone to offsets.

And so, after a few more thought processes and some analytics, I came up with Z stop end V3. (I think the inspiration for V3 came from one of the designs found in thingiverse, www.thingiverse.com). Basically V3 directly reads the Z position of the extruder instead of the bridge (not sure the proper technical term for it) supporting the extruder and mount. Hence, it avoids the problems faced by V1 and V2 (hopefully). It does however, require some manual homing of the Z axis before each print. This is a much better tradeoff (trust me, a seemingly automatic Z homing design like V1 and V2 with a "fixed" position may ended up having the reprapper wasting more time recalibrating the Z stop end instead). Meanwhile, only time will tell if V3 can provide the reprapper with a more enjoyable reprap experience.