Robert, welcome to The Grumble, I am sure you will become a major contributor to this forum.
Hoffmann Machines sells a really swell saw that not only will cut both miters at the same time, it will rout the miters to accept the Hoffmann dovetail wedges. All you have to do is hammer the wedges in, and your frame is made. You can even forgo using glue if you like. Once the Hoffmann dovetail inserts are in the frame, it will not come apart. This system will give you perfect frames, every time. If I remember correctly, you can snap one of these bad boys up for around twenty five thousand.
If the Hoffmann system is a little too fast for your operation, you could consider a ten or twelve inch double miter saw from CTD Machines in Los Angeles, California. The man to talk to there about your cutting requirements is Larry. Larry will be able to advise you on what is best for you. He is a straight shooter and will not oversell you.
Please be clear about one major point. You can purchase the best saw in the world, but if you skimp on the blades, you may as well stick with your hand miter box.
A decent set of cut off blades will run you around two hundred and fifty dollars each blade. Listen to the people who supply your new machine about what is best for it. We have all learned the hard way about blades, save yourself some time and money, purchase the proper blades.
If your operation is manufacturing, you may want to look into some of the production joining machinery as well. Joining machines are like saws, they can start from a few thousand and go into the many thousands, depending on your needs.
Please let us know what type of saw you purchase, and how you like it once it is in production.
John