Machines that make machines / Prusa MK4
I got an Original Prusa MK4 kit for Christmas.
Remarkably little. One print let go of the bed and welded itself into a blob around the hotend, which took a while to pick off. The fans failed and were replaced. The one that still annoys me: run out of filament mid-print and the printer can get stuck in a loop, refusing to admit that new filament has arrived. Separately, and written up below, a firmware update quietly broke printing altogether.
Nothing about the choice. I looked at Bambu and went Prusa because it is open, and Bambu have since been closing off access to their own software, which settled the argument retrospectively. The only real limit is build volume — I want to print a BB-8 but that's massive. That wants a bigger printer, and I would rather build that one than buy it.
FreeCAD
I have been learning FreeCAD - forcing myself at first to use it, now after watching lots of videos from MangoJelly I'm really enjoying using it. V1.0 release was very good, it's an awesome piece of software - just with a bit of a learning curve. For my speaker project I did a full assembly of it in FreeCAD.
Fixtures
Most of what I print is functional: robot parts, brackets, adapters, cabinet fittings, workshop jigs and wot not.
Open tools
I chose the Prusa partly because it is open and understandable. Same reason FreeCAD has become the default: if a tool is part of the workshop, I want to be able to inspect it, fix it, and keep using it when the vendor tries a bait and switch.
Actual modelling
I absolutely love the parametric nature of FreeCAD, and the solver for sketches is super cool, takes a while to get used to but it's epic.
It is Christmas after all.
My wife asked me to fix this while I was building the printer. Fair enough.
a serious repair to a seasonal object.
Yes, the Christmas decoration made it onto the welding table.
Uprights and plates.
Small screws can be tricky.
I've got an idea for these big bearings.
Printed brackets becoming part of the machine that will print more brackets.
Build arc
Sorting screws into little piles.
Rods, blocks, and carriage.
Cool gantry.
The hot end.
Airflow hardware.
Print head.
Cable routing and controller wiring.
Finding more bits.
assembling more bits.
Wiring the machine.
The nearly finished MK4 on the bench.
Such a nice kit to build, very straightforward.
you spin me right round, baby right round
Yeah so I'm not the best presenter.
The foam tray, the loom, and a leaflet that says HAPPY PRINTING.
Parts bins on the bench, instructions open on the laptop.
The board and its connectors.
Grease first, then slide.
Carriage, rods and belt.
Printed parts out of the bag and onto the frame.
Small crimps, done by hand.
Small parts, overhead.
Onto the X carriage.
Screen, board and housing.
Standing on the bench, screen on.
The overhead angle, and me in shot for once.
Debugging / firmware regression
While printing ARCTOS robot-arm gears, I hit repeatable layer shifts after updating the Prusa MK4 firmware. The first checks were mechanical: belts, screws, calibration, slicer settings. Nothing obvious explained it.
Rolling back from firmware 6.2.x to 6.1.3 made the same parts print successfully. Same printer, same class of part, different firmware behaviour.
I added the result to the public Prusa-Firmware-Buddy issue threads. Other users reported similar failures, Prusa tied the regression to internal ticket BFW-6795, and firmware 6.2.2 was later released with a fix.
Off the bed
Filament storage
Some filaments are hygroscopic, and when the water in the filament boils in the print head it can lead to bad prints - a rough surface, weak parts. Nylon and TPU are hygroscopic. I'm not sure about PETG and so on, but I keep them in these containers anyway.
A 2.5L Lock & Lock airtight food container takes a 1kg spool really well and clips shut on a rubber seal. A cheap hygrometer from Amazon sits in the middle of the reel so I can see whether it is actually working.
