Grinding Force Weapons?

[Jabedoben]

I've seen some FAQs about the importance of grinding Force weapons?

I can't seem to figure out how to do it. I go to the right weapon upgrade shop with a matching grinder and the screen says I have no grinders to upgrade the weapon with?

What am I doing wrong?

[Itsuki]

You need to turn the grinder bases into grinders. You do this by buying grinder boards (they are sold on the second floor of Colony), then going to your PM and synthing the grinder bases into grinders.