How would that make a difference in the manufacturing process?
The issue withe several lot numbers that is prepared at the same time in the same machine (annealing oven) still exist. As far as I can see. So please explain that flow in more detail!

Thanks. But our difficult is that Odoo make a new manufacturiong order for every lot number you register. The annealing process got a high cost, that we want to add to the product cost. (We use FIFO costing). If we have i.ex. 4 drums = 4 orders they would all collect the same full cost of the operation. And since the number of drums in processing varies, I cannot see a good solution. Without the costing issue, we could do with separate orders for every drum - I think.

4 drums = 1 MO with component as 4 drums and 1 operation (annealing) component further breakup to 4 MOs, similar to back-orders.

When you mean number of drums vary is that due to size of drums and in which process does it vary annealing or the process prior?

The annealing process is like a big oven. Can be heated up to 600 C. Depending on the diameter of drums, there is room for different number to process together. The operation before this is when the cable is coiled - in its specific delivery lenght specific for the customer - on the drum.
Important also: This is the last operation in the manufacturing process. (But not all products go through this process.)

I think we need to develop something specific for this.

Not possible. The quantity on one drum is some thousand meter. With serial number every 1 M will get a serial number. We don't produce 1 drum. We produce a qty of meter cable on the drum. This is how the cable business work. One drum is one Lot number that have a specific lenght of cable.

But thanks for answering.

your manufactured product is drum[with cable] and your BOM is cable, right? Please explain

you are producing multiple drums of cable and you want to track every drum, right?
So every drum needs to be identified, right?

You might say we produce cab le on a drum. (Not drum on a cable).
BOM looks like: 1000 M of cable, use 10 000m of wire.
Order then might look like: Deliver 20 000 M on drum wit 5000 M on each drum.
Manufacturing order = 20 000M. For every druim / lot number you confirm Odoo create a backorder - as one manufacturing order only can deliver one lot number
This works very good. Except when we introduce the annealing oven. You can put 4 - 8 drums (depending on size) into the annealing oven.
The ideal is to process this in one work order. So we can also collect the cost of the operation. But cannot configure out any way to set this up.

Every drum needs tracking - from raw materials to finished and delivered. Every drum got quality measures.

okay, got it, you want to get rid of the process of creating multiple backorders.
You can customize the manufacturing order.
Found this, please check in detail https://apps.odoo.com/apps/modules/14.0/hv_manufacturing_mass_sn/

Your product is configured as cable sold in length with UOM meters and/or Drum = 5000M... having this the LOT would be for the cable how do you assign a Lot for a Drum?

In your example 20000M cable would be a lot number distributed into 4 drums. Drum is more like a package option here.

Unless your product is defined as drum in units .. in which case your SO would be 4 Drums and you would have a MO/ operation to convert units to length