Rigidity of the frame is key for accurate and safe subtractive manufacturing.

You do not want your frame to flex while a spindle is cutting aluminium at 20kRPM. See Marco Reps and Kris Temmerman on youtube, they built formidable high precision CNC mills out of steel and concrete. For machines that rely on frames made out of extruded aluminium, flexing has always been an issue, even with much sturdier designs such as the Avid CNC machines.

Also, FYI, in a lathe the workpiece spins, and in a mill the tool spins.

This thing is not very rigid and the interconnections are made of plastic. There is a lot of flex and anything other than soft materials can not be milled with any precision.

One main reason professional 5 axis CNC machines are so expensive is because they are very rigid yet can move quickly and precisely.

That cantilever design is known for having rigidity problems for 3D printers and isn't used at all for subtractive manufacturing. Compare it to a MaxNC 10[0] or a Taig[1] micro mill and you'll be able to see how much more robust their construction is.

[0]http://millingaccessories.biz/2015/04/07/maxnc-10-cnc-millin... [1]https://lh3.googleusercontent.com/-TkXnpUUXqLg/T4Qj3qVU9JI/A...

And they were built using solid cast iron. Meanwhile this machine consists of one big aluminum extrusion and a thin extrusion. It's clearly built for speed not rigidity.

> Meanwhile this machine consists of one big aluminum extrusion and a thin extrusion.

With long cantilevers (i.e., supported at only one end) on both, to boot. Long cantilever, thin material = slop.

Even a small bench top lathe has hundreds of pounds of cast iron in the bed and ways, as you said.

That aside, a lot of the jobs they show in the video (pen-plotting, wood-burning, 3d printing, etc.) don't really demand a huge amount of rigidity. I wouldn't want to try any serious milling or turning with this machine, for sure, but for those jobs it looks like a totally reasonable design.

And I do like the fact that it's designed to be 3D printed itself (other than the extrusions and stepper motors, etc.), so well done on that.

Lathes are kind'a more rigidly built though and I think that is what GP tries to point out.