Personally, i think that the plate is bound to the soul of it's wearer, and that it is forged by regular means but changed somehow to become actual plate. i believe the blades are also formed likewise. my personal opinion is that the blade and plate are created/gifted by spren such as honor spren (sly ect) when in a time of need. if you read the released stuff that people have managed to collect about the second book, teft (i think) mentions how kal's eyes glowed. this would link to the blade causing the light in their eyes. also, i believe that any weapon could be made a shard with this method. a spear perhaps?
also, hi i'm new to the site