Hi, could anyone help me on this…

what is the difference among scrap on item, scrap on BOM and scrap on Routing? Are they different?

Scrap in routing is Scrap% that is expected in a specific machine center.

Item card and BOM Card From online help.

So if you define all three all three are considered - load an example up and process it through to have a look.

i usually use the scrap quantity on item card for items that loose weight by nature

on routing line i specify the scrap that is caused by a specific manufacturing operation