For the longest time have been aspiring to build a Rockwool/fire rated drywall/green-glue/resilient-channel enclosure given trim router noise…
Complete with fancy polycarbonate pivoting door to bang my head on…
Lately though, am wondering whether it’d be just as effective, and cheaper time/material to just switch to a water cooled spindle (70db?), with NO enclosure. SteveMPotter has a nice setup, consider checking out.
My LR3 was doing wheelies while engraving polycarbonate. Not enough weight I thought… So I bought bunch of steel blocks at my local MetalSupermarket from their offcuts and scraps section. Each piece was 1-2lbs. Tried shoving different number of blocks into/onto the gantry. That helped a bit, until I started losing steps in part because my leadscrews were not well aligned and lubed, and my current was too low.
Unfortunately I was fixing the wrong problem, created new ones… Fortunately I discovered and fixed some existing performance bottlenecks related to my assembly quality.
Main cause for the lift and popping wheelies was me trying to use a symmetrical v carve bit. Unfortunately, the v bit has a flat tip and doesn’t pull through material like a new sharp 1/8" single flute uncut upcut carbide bit would. So the fix for me was to use a different bit, was engraving so specifically switched to an offset v carve bit, much better outcome thanks to JeffE’s suggestion.
During these misadventures I did observe that adding weight to the YZ plates (not the gantry), helped reduce unwanted lifting by using some Bowflex dumbbells. I understand not everyone has Bowflex, so maybe a 
six-pack holder for the YZ would be a more practical way to weigh down YZ plates.
Am switching from 4 start to 2 start leadscrew even though Ryan showed off how much weight a well assembled stock LR3 can handle.
Curious what combination of bit, material and speed is causing unexpected lifting? Have seen suboptimal and/or dull bits burn a bunch of people’s time.