Gantry routers, rigidity and aluminum

As an endmill cuts, it pushes against the spindle and moves the whole machine slightly. If you try to remove too much material, the whole machine will skip back and forth, causing the endmill to bang against the workpiece. That’s what’s happening in that video (at 0:31).

On the other hand, if you remove too little material, the heat starts to build up, eventually turning the aluminum into a thick, sticky goop.

For hobby routers, there are a lot more challenges. Small spindles don’t have a lot of torque, but they spin really fast, so you have to keep the head moving or else the aluminum will melt. Also, as the parts get lighter, they are more susceptible to resonance, like a tuning fork. It’s basically a balancing act trying to minimize the forces without melting the metal.

Those are some pictures from the desktop photography course. Despite the issues, the part was within 0.2 mm and held threads. With some improvements and creative use of the plasma cutter, I would be surprised if I couldn’t get some usable parts out of carbon steel.

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These two videos may be of interest now that the Shapeoko 3 has the HDZ upgrade installed.

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