I have had to modify CAD drawings to accommodate new design changes. This involved changing the rev number, adding redlines, and adjusting the bill of materials (BOM). Once the redlines drawing was approved, I had to go back and remove all strike-throughs and red font text and replace it with all black font with the final revision indicated in a table that’s usually on the bottom right hand corner of the drawing. I have not dealt with engineering change order yet, but I’m sure I will as I gain more industry experience. My understanding of an engineering change order is that it is initiated when an issue is pointed out and the solution leads to changing the product slightly or significantly, depending on the issue. Once the change is approved, the physical product change is executed and the ECO is used to throughout the process to sum up what the modifications need to be made, finalize the details, and obtain all the approvals needed to implement the change order.