Here are some considerations and links to the style of heavy-gauge crimpers I like. (Measure the dies to make sure it works with your crimp terminals.) But grinding custom crimpers out of bolt cutters is a good idea. I'd make a few test crimps before using it on a robot.
I don't like it when people crimp and then solder; either one, properly, is sufficient. But crimping is generally a whole lot easier to do properly.