The crimper I bought from Amazon was from "Titan Tools". In looking back, I see I only paid a little over $30 for it. It is one like "Pete" describes above that has to go "over center" to complete the crimp. It takes quite a squeeze, so I can believe that fusion welding may occur. Anyway, since I bought it, I have not had any problems with crimps.
I was in "Fastenal" the other day, and saw some 6:1 shrink wrap tubing. I haven't had a chance to use it, but maybe this is what I need when I forget to put the regular heat-shrink on before I do the crimp.
It'll be interesting to see how it works.