Secondary operation cost analysis project

Hello all,

I am currently an intern for a company manufacturing medical devices. I am trying to create a cost analysis study to determine how much time is spent walnut blasting parts and what the operation is costing us. I need to justify my future proposal to automate this operation.

Can anyone help me figure out what my study should focus on to determine cost? The obvious variable is time, but what other important variable should be focuses on?

Thanks in advance!