Electric material send to manufacturer for assembly purpose

Respected Sir,

We are purchasing electric material from M/s. ,..............INC.- Japan on purchase order then we will pay material value to supplier.

Afterwards we will give order with material to local vendor for manufacturing of our product  and we will send electric material to same vendor for assembly purpose.

After manufacturing the final product (After assembly the electric material) our vendor will send material to us.

In this case please clarify below mentioned point from GST point of view.

1)Which document is required to prepare for sending electric material to vendor ?

2)How to bring back material from vendor ?

Please advice.