The tutorial mission on how to use the grinder machine is not very in-depth. It has you put in three of the same rarity weapons (in this case, white), and it gives you a better, blue gun.
Other than that it mentions that you have to experiment with different recipes and that if you grind with moonstone you are more likely to get better results.
I have tried the grinder quite a few times and sometimes I put in three weapons of the same rarity, and it does not allow me to grind them.
I have listed a number of specific questions, but would like to just know as much as possible about how exactly the grinder works.
What other requirements must be met in order for you to be able to grind weapons?
Is it just that some weapons don’t mix, such as different elemental weapons?
Does the weapon class have anything to do with it (pistol, shotgun, etc.)?
Is it possible to grind purple weapons (or higher)?
According to the wiki, you need to input specific recipes into the grinder. The recipes, are as follows, and require items of the same rarity in every case but the legendary case:
- Legendary of desired type: 2 legendary weapons + 1 purple weapon of the desired type
- Up one rarity level (specific type): 2 weapons of the desired type + 1 other weapon
- Up one rarity level (any type): 3 weapons of different types
- Up one rarity level (non-weapons) 3 items of same type (grenade mod, shield, etc)
- Assault Rifle: 1 SMG + 1 Sniper Rifle + 1 Shield
- Rocket Launcher: 2 weapons of any type + 1 Grenade Mod
- Shotgun: 1 Pistol + 1 SMG + 1 Shield
- SMG: 1 Assault Rifle + 1 Pistol + 1 Shield
- Sniper Rifle: 1 Assault Rifle + 1 Shotgun + 1 Shield
For all except the legendary recipe, these recipes work for anything up to and including blue inputs, with the potential to output a weapon of the same rarity or greater. If fed moonstones, the grinder will always output an item of increased rarity, and has a chance to add a luneshine effect to the weapon.