Decommissioning the Micro Kossel

Micro Kossel

    After almost 18 months of heavy use the Micro Kossel was long overdue for maintenance and wear checking, so I decided to partly disassemble it last week, this unfortunately lead to the discovery of several fatal flaws that would have required basically replacing the frame to correct, so I decided that it was time to retire it.

Micro Kossel parts after disassembly

    Most of the flaws were wear and tear issues that some of the PLA parts hadn't stood up to well at all, specifically the AMZ3D transparent red carriages and SEACANS.com green rails and corner/motor brackets. I don't have photos but the motor corners were warped badly enough that the motors were stuck pointing about 20 degrees up from the normal horizontal position, making any attempt to tighten the drive belts pointless, they'd just slip off the mounts or the plastic would just melt further and worsen the problem over time. 

Micro Kossel frame rail with cracked section

Micro Kossel frame rails with cracked sections

     As you can see, the Seacans green PLA fractured across the layers on these sections, a highly atypical failure for a printed part, normally you'd see fracturing along the layer lines with PLA, not this glass-like fracturing. It's worth noting that the Tinkerine Lavender PLA shows only minor damage where stuck nuts and bolts were removed, and that's mostly cosmetic, so I'll probably be reusing those parts in a future project. 

Carriage plate showing stress fractures

    The AMZ3D PLA carriages are by far the most alarming of the parts, two of them cracked at the hinge point (lower left of the image above), and all three where showing some alarming stress fractures that you can just see in the picture above, I've warped the contrast to make it a bit clearer, my camera has a hard time seeing them but they're very clear to the naked eye. Taken together, these issues mean that it was just a matter of when, not if, that the hot-end would come off axis during a print and make a complete mess at minimum, start a fire at worst, so I've dismantled the frame and salvaged the electronics for a new project, here's a preview, but more on that next time.

Mystery parts for next project

Stress Testing the Mega Kossel: Building C. Laimer's Tourbillon Watch

Tourbillon Clock

     After the painting project from last time, I decided to try building a more mechanically complex project, Christoph Laimer's Tourbillon Watch (thing:1249221). It's a very complicated model with very tight printing tolerances, all the parts need to be as close to perfect as possible or the clock won't work properly. 

Printing the mainspring pinion gear on the Mega Kossel

     Obviously the first step in this project was lots of printing, about 100-120 hours in total, perfect for shaking out any glitches in the printer. Aside from a couple of spaghetti incidents caused by the print bed shifting on it's mounts, actually printing the parts was the easiest part of the project, tracking down compatible screws was the hardest part, I ended up reaming most of the screw holes to accept M2 screws since those were the closest that I could find.

Clock parts organized for assembly with mainspring being assembled

Mainspring clamped for assembly with printed machine vise

    Actually building the clock took a few days, the virtual walkthrough and assembly videos were invaluable for this stage, always making it clear what part was installed next at every step of the process.

Mainspring fully installed with outer casing in place

Clock parts set out for assembly

   I ended up using some 14-gauge wire cut to length for the gearing axles, long needle nose pliers are crucial for installing them in the upper center plate. Other tools I used were a 3/64-inch drill bit for reaming the gears mounting holes and a Philips screwdriver for the M2 screws. After a couple of days work I had it assembled and mostly working, one of the gears is a bit sticky on its axis, but it's mostly complete.

Test fitting Clock face components

Completed Tourbillon Clock