The extrusion die was due to arrive at the factory today. I haven’t heard anything to the contrary yet, so I assume they’ll get cracking with the extrusion on Monday. (Of course, I’ll give them a call to check up on them; watch this space.)
Things are moving, but slower than I would like. A new die is being made, and should be done next week. After that, it works like this:
- Extrusion: a billet of aluminium alloy (a thick, solid cylinder) is heated and pushed through the die by a powerful hydraulic press. The profile emerges from the die, much like macaroni from a pasta-making machine.
- Cut: the resulting raw profile is cut in long lengths (three to six meters).
- Anodizing: the long lengths are submerged in a solution of sulfuric acid and a current is passed through the parts. This creates a thin, clear coat of aluminium oxide on the surface of the profile. Another step is required to seal the pores in this coating, which improves corrosion resistance. The thickness of the coat on standard MakerSlide gives it good corrosion resistance, and some resistance to abrasion: perfect for acetal (Delrin) wheels, but not good for steel wheels. To withstand those, a much ticker and denser layer of oxide is needed. Because the oxide is an insulator, once the layer grows thick enough it prevents current from flowing through the part and stops more oxide from being created. To work around this, and to create a much tougher layer, hard coat anodizing is done slowly, in a different concentration of sulfuric acid, at temperatures near freezing. The refrigerated tanks and the much longer time mean the process is expensive. In our case, it costs more than the extruded aluminium itself.
- Cut to size: the long lengths are cut to the sizes we need by a CNC saw.
- Packaging: parts are wrapped in plastic tubing.
- Shipping: the wrapped lengths are placed on pallets (with more packaging to protect them) and transported to us by truck.
The current estimate of when this fabled truck will arrive and deposit its load in our garage is end of February.