Insignias

I really didnt know where to ask, do insignias stack, if i have windwalker insignias on all armor pieces will that give me +75 armor with 3 ench?

Thx in advance

No they don't. With 3 enchantments and windwalker's on every piece of armour you have +15AL. If you use, say, radiant on a piece, you have less armour.

To put it more clearly, each +armour insignia only gives you that bonus to the piece of armour it's been applied to.