For many geometries (especially complex or thin-walled shapes), 3D printing is faster than milling. Many medical devices are made largely out of plastic, espec

For many geometries (especially complex or thin-walled shapes), 3D printing is faster than milling. Many medical devices are made largely out of plastic, especially the disposable parts that are currently in short supply. 3D printers (FDM and SLS) commonly produce parts in many of these same plastics. Mills are generally used on metal, and the programmers and operators may not be as comfortable fabricating complex shapes from plastic. Mills are especially slow making thin plastic pieces, as they have to limit the feed- and pull-out-forces, and the heat generated, by the tool. 3D printers have little difficulty in making flexible / compliant parts (like close-fitting masks), because they exert nearly zero force on parts as they make them. Mills are even slower at making flexible plastic parts, because they have to operate at even higher RPMs, lower feed rates, and shallower depth-of-cuts in order to not deform the flexible part, even as they rip material off of it. 3D printers convert nearly all of the material you give them in to finished parts. Mills produce a lot (sometimes an awful lot) of waste that has to be shipped away and recycled back into usable material. VW probably relies on CNC mills in their normal production pipeline, but may not have hard dependencies on their 3D printers. It might be much less disruptive for them to offer much or all of their 3D printing capacity to humanitarian efforts. --- The highest-output way to utilize CNC mills for bridging the shortage of ventilator / PPE parts would be to fabricate molds for injection-molded parts. VW (and other automakers) can definitely do this. The big holdups would be in acquiring designs for the parts (who knows how long that would take?), and in designing the molds (on the order of a week or two). Milling a mold takes hours or days depending on how complex it is. (The different pieces of a mold can be made by different machines.) Once fabricated, assembled, and inspected, a mold could produce hundreds of parts a day. The necessary delay in designing, fabricating, and iterating molds (and other assemblies for the mass-manufacture of plastic parts) means that 3D printing will always beat it to the punch. For the next couple of weeks, expect most unofficially-manufactured medical parts to be 3D printed. The supply of traditionally-manufactured medical parts should significantly increase later this year. The parts and assemblies to do that are/will-be made on CNC mills in the intermediate time.