Is it time to upgrade the Tevo Z-axis?

Sure is....

The Tevo's standard cantilevered X axis has always concerned me.  Usually I'd position the print so that any skew in the Z axis did not matter - after all, I'm not making production-ready products. Usually 2 orthogonal axis out of 3 is good enough - Do the egss in the refigerator egg tray really care if they lean a few degrees?

I crossed a threshold a few months back and attacked the problem. I have automatic bed leveling but still had z axis skew. What was up with that? Eventually the light bulb moment occured and I realised that having the X axis parallel to the bed and the frame being perpendiclar to the printer base, does not mean that prints have an orthoganl Z axis.

The  bed was parallel with the droopy X axis so all the layers were nice and levelled but the z axis was off. After a day of printing test prints and using grbl's firmware skew correction, I finally got rather good orthoganal prints. A few percent out is easily ignored.

Pondering what should be the next Tevo upgrade - multiple print heads, automated server driven print head clear, but settled on a stable Z axis as everythign else would probably cause greater skew issues so dealing with the problem now will reduce future issues.

I finally received all the parts I need for an upgrade after a very long time (who would have thought to check the number of lead screw starts when ordering? Ugh - 2 more months later...)

My Tevo is rather constrained space-wise with all the mods so I have forced myself to model the important parts ensure it all fits. So far, so good. The model even highlighted a problem that was all sweet in my mind but was a physical impossibility.

Now I could go and finish the model before printing parts but that is no fun. It looks good to me so lets print a part or two and get some weekend's satisfaction. As I have only one printer, I do have to make sure I have all the bits needed before physically upgrading - once it is in bits, there is no chance to make alterations.

First rough test print for the bottom mounting bracket proves the concept works. A shaft collar pressing on a thrust bearing to take the load and a normal radial bearing to centre the shaft. Each bearing doing the job it's designed for. A definite overkill but it moves so very smoothly under load...

A few days later.....

The model seems to be prety good so now it is time to "go all in" and print some parts with proper densities. I pondered if it was worth risking an 18 hour print job for all the bits needed especially when the printer had frozen on me for the very first time only a couple days ago. But all seemed good after an evening's printing and I was keen to see what awaited me in the morning....

So many nice pieces but unfortunately the printer had frozen. Some low parts were salvageable. After a few more smaller print runs, it was time to try and assemble one axis that did not affect the printer operation.

Ugh!!! How can it be out of alignment when it is generated from the cad model? Seems I dimensioned the model to the bottom of the acrylic sheet rather than the top so I was 4.3mm out. Bugger! Back to the cad drawing board....

Bit still, the oldham coupler seems to do its job - not obvious when I wiggle both the shaft and the camera, but you get the gist.

I also discovered that the X axis hits the Z axis bottom mounting bracket. That will teach me for using approximate model measurements and assuming everything will be fine. Time to model the real world accurately rather than picture it all in my mind. More components to be printed....