dimples in jigs

I have only been doing this a short time. I have been seeing dimples like places in some of the jigs after I take them out of the mold....I have a 40 cavity and 10 cavity mold I am seeing it in both. it is not the same cavity and sometimes it is at the bottom part of the mold and sometimes it is at the top half and some times it is on the left side of mold and other on the right....I have tried heating the molds before I inject them. still does it. could any one give me any tips on what I can try........thanks

Shoot your plastic cooler, hold some pressure on the injector after it stops and be sure to top off the sprue when you remove the injector from the port. You can try sandwiching your molds between to others too which will help pull some heat away from the mold you are shooting. For the most part I'd just start shooting the plastic cooler....instead of around 350 to 340 degrees allow your cups to cool down to around 330 or even 320 degrees.