# How to combine wires into a cable maximizing cable length while minimizing waste?

A customer brought us this problem and we're looking for ideas to help them. It seems to be a flavor of cutting-stock but without the demand profile.

They have varied length spools of different types of wire that need to be combined into a cable. For example, 2 spools of red of length 100 and 200, 3 spools of blue of length 80, 100 and 100, and one spool of black of length 250. Cables can be composed of up to 15 wires.

They want to make the final cables as long as possible yet minimize the spool ends of the wire. We've been told spool ends are discarded but I expect if the spool end is long enough it's put back into inventory.

• How long is the cable? – Ray Butterworth Aug 24 '20 at 13:11
• this seems like a very odd production issue. No manufacturer plans to make cables as long as possible, to the extent of wire on the spool. Are you saying if they paired the 80' blue spool with the 200' red spool, they would throw away 120' of red? – AirSquid Aug 24 '20 at 15:39
• I agree that it seems odd, I think we are missing some information, but looking for suggestions with what we've been told. They would use the 120' feet leftover of red to combine with one of the remaining blue spools and what was left on the black spool. – mcfenelon Aug 24 '20 at 16:40
• The part about "up to 15 wires" in a cable raises all sorts of questions. Is there a minimum number of wires in a cable? Is there a minimum number of wire types in a cable? Are all cables considered equally valuable/profitable? – prubin Aug 24 '20 at 18:28
• It's not obvious what kind of answer is required. E.g. you could make three cables with all three colours, two 200 long and one 50 long, leaving enough for a red/blue cable 30 long, and a 20 cable with a single red wire. No left-overs. So what's the problem? – Ray Butterworth Aug 25 '20 at 12:02