Delrin/Acetyl isn’t THAT brittle and it takes a LOVELY finish. One must keep in mind what their project is. Treated properly, Delrin/Acetyl is extremely tough.
There are multiple grades available. The most common Delrin is “100” and it serves for many purposes. I’ve seen it used for gears under quite a bit of stress.
Nylon is an excellent plastic to machine but it is often more difficult to find than other plastics (which can result in some priceiness to it). I would only touch it with Onsrud plastic handling end mills. It is a bit twitchy, especially for finishing. A single flute Onsrud does wonders.
…however the PA6 grade is incredibly tough…
You got that right!
There is a gotcha - Nylon melts a bit too easy for my taste; it gets “stringy” when machined improperly. Coolant - with no water in it (Nylon is seriously hygroscopic (it attracts water)) - is appropriate. A micro drop dispenser would be perfect for this job.
Use G-Wizard and I cannot see why the Nomad cannot machine Nylon just fine.
My “go to” plastic WAS HDPE (for many prototyping jobs). I’ve been spending a lot of time with Starboard and I have to say I’ve been won over. It machines just like HDPE… well it is a modified HDPE… but is a bit tougher and it’s UV resistant (good for outdoor uses).
When I need something a bit tougher, I use PVC. PVC is a bit brittle but it is also a bit forgiving. It take a nice finish.
When I want toughness, durability and awesome finish, it’s Delrin/Acetyl all the way.