Looking to make a 6mm piece for a mold

Hi Guys,

This is my first post, so glad to make all you acquaintance.

I have a Ortur Laser Master 2 with a 60l air assist compressor and tried to cut through 6mm black acrylic today. It nearly cut al the way through, but not after hours running at 100 speed and 97 power.

I need to cut a material at 6mm which has sharp and straight edges so that i can make a rubber cast mold from it so i can epoxy replicas.

Can anyone suggest how this might be achieved as I desperately need to find a solution?