Warped sheet material can result in poor lasering and cutting results. Partially cut sheets are particularly vulnerable to bending. Regardless of your efforts to keep all your materials from warping, it is not always easy to keep it flat in your laser even with good hold-down suction. Storing your acrylic sheet stock flat is the first step to preventing warping.
I use pieces of rolled steel as weights. They can be purchased at hardware stores. I use both 1-1/2-inch X 1/4-inch flat steel and 1/2-inch square bars. They are both heavy enough to flatten materials from 1/64-inch to 1/8-inch thick.
The flat steel can sit low enough that it does not interfere with my focusing plunger on my lens head. Placing them around the engraving area assures good lasering results the first time.
You will need to cut them to the variety of lengths you want. I have used both a hack saw and a metal cutting blade on a rotary tool. A little filing takes any spurs off.
-Bob Hagel, Eagle’s Mark