Hi, I utilize my LR2 to primarily cut acrylic LED signage and have encountered a lot of the same challenges you are experiencing.
My signs typically include a routed channel / groove in which I inlay neon leds. Depending on the leds, I need I 5-7mm wide channel and I cut that channel a little more than half way into the 6mm acrylic. And once the channels have been carved, I move onto the profile cut.
For my channel cuts I like to use a single flute upcut bit. I initially tried trach cutting, but it was annoyingly slow, and today I typically just grab whatever single flute endmill I need for the channel (I keep a good selection of single flutes handy). If I need a 5/32" channel, I grab that bit and setup estlcam for an egrave an set it to 3.5mm deep, 1 single depth pass.
For my profile cuts, I found switching down to a 1/8" single flute worked the best. I seem to be able to push the smaller bit through the 6mm acrylic much faster than a 1/4 end mill. I typically do 2-3 passes (depending on the shape), with a single finishing pass.
I found my best results by slowing my router down to near its lowest speed setting (1.25-1.75ish on my Dewault, my LR3 will use the Makita for better selection of RPMs). Any faster and I notice that the acrylic gets a bit gummy and wants to fuse back together.
I also start to get a bit nervous of the outcome when I try running past 8-10mm/s. This might just be me or my build, but I’ve had numerous instances where steps were missed leading to a lot of scrap acrylic over here.
For the actual engraving of text onto the acrylic, I haven’t personally used it, but I’ve seen many videos where a spring loaded diamond engraving drag bit is used. The spring loaded element helps keep it in contact with the material. The router is just holding the bit while the machine moves, router not powered on for this.
For finishing the edges, I ended up buying a belt / disk sander. I also start somewhere around 400 and keep increasing (2000+). I then use a cutting compound and work that in. This is a lot of work, flame polishing is WAY quicker and looks beautiful…when it works. My flame polishing results are a mixed bag. When it works, its beautiful, but propane cant do it, the fake mapp gas equivalent provides mixed results. Shy of getting a better torch & fuel set, consistent good flame polished results still out of reach for me. Protect your front and back surfaces from the wrap around heat.
Thanks for sharing your efforts and results, it was a good read and has me wondering if I can go push more speed. I may have to go revist the troch method to see if there speed to be had there.