Run Solver w Macro, returns no feaseble solution.

[Fredrik S]

Hello Experts out there.

I am trying to make a sheet that will compute the best blend optimum of 3 products in order to minimize cost, but still be within the constraints that i have set up.

The products have different properties, the critical one being a temperature tolerance level.
This formula is quite messy, and I wonder if this is a problem for Solver.

Per default I know that the example data in the sheet have a solution.

Please advice

[PingPing]

I can't see any problems with the code. Is there a feasible solution with your given constraints? If not, try relaxing some constraints and work up from there to find the binding constraint. If there IS a feasible solution, try 'seeding' solver with values on your input variables A, B and C that provide a feasible (though not optimal) solution and then run Solver.

FWIW I've found Solver to be helpful but a PITA sometimes because of problems like the one you're experiencing.

[Fredrik S]

Yes - there is a feasable solution. (For instance 50 of volume A and 50 of volume B and 0 volume C. Not optimal, but close.) I have tried 'seeding' the input, but alas - same same...

[Alf]

Hi Fredrik

Have a look at the file I've atached and see if this helps you.

There is one problem related to gasoil blending i.e. cloudpoint does not blend liniarely. In order to get a correct answar cloudpoint must be converted to index. If you are interested send me a private mail since a discussion on gasoil properties are probably not of common interest in this forum.

If you just are interested in using Solver try this link: http://www.solver.com/

HTH

Alf

[Alf]

Hi Fredrik

This is a better model I think for what you aim to do.

Alf