Why do I have problems gluing Acriglas® to my stock acrylic sheet?
The problem, if you want to call it that, may lie in the fact that you are using a fast solvent with dissimilar materials, which absorb the solvent at different rates. If you are using something like a stock clear material like Acrylite® FF, which is extruded, it will absorb methylene chloride solvent faster than the Acriglas®, which is cast acrylic. The softer extruded material will starve the glue joint because it has soaked up the bulk of the solvent before the harder cast material has had a sufficient time to soften and fuse together with the extruded.
The solution is simple. You can either make sure you use a sufficient amount of solvent to ensure a good bond, or slow down the rate of absorption by cutting the solvent with 10% Glacial Acetic acid, or buying a slower absorbing solvent to begin with. This will also give the two dissimilar materials enough time to fuse together. Between an adjustment to your gluing technique and a different solvent, you should no longer experience any difficulties.