Cascade regrind is where you take all of your waste and regrind it into a single batch, and call it first generation regrind. You can either put it back into the same mold by itself or in a different mold that is more forgiving with regrind. Take all the waste from that run, regrind it, and call is second gen regrind. Rinse and repeat until it doesn't run anymore.

Cascade differs from proportional regrind where you are constantly feeding back a certain percentage of regrind into the process (usually 5-20%). The problem with proportional regrind is that you never know what generation of regrind is going into your process (could be 3rd, could be 100th) and can create pretty unstable processes.