Negotiate copper price

Hi I need some advice.

I am new in the copper industry started two months ago. My company buys and sells copper rod. I am meeting the supplier tomorrow to negotiate a lower price.

How much percentage decrease can i ask for and what facts can I use to motivate my request. I order about +- 200Tons a month from the supplier.

Interesting use of this site bosslady - nice one! Mixed bag of expertise call this site home so I'll be interested to read the responses. Good luck!