Your plan says the job finishes Thursday. The floor says Monday. Nobody is lying, and usually nobody has made a mistake. The plan was built on an assumption that quietly does not hold.
What infinite capacity actually means
Classic MRP works backwards from a due date using lead times. It calculates when a job should start so it finishes on time. What it does not do, by default, is check whether the machine is free.
That is infinite capacity scheduling. The maths assumes the work centre can absorb whatever you give it. On paper it is tidy. On the floor you end up with forty hours of work booked onto a machine that has eight hours in the day.
An infinite capacity plan is not wrong about what needs doing. It is wrong about when it can be done, and it will not tell you.
How you know this is happening to you
- The schedule is rebuilt by hand every morning, usually by the same person.
- Promised dates are set by whoever feels most confident, not by the system.
- Two jobs are booked on the same machine at the same time and nobody noticed until the operator did.
- The plan is technically live but everyone works from a whiteboard.
If the real schedule lives in somebody’s head, you do not have a scheduling problem. You have a single point of failure who cannot take a holiday.
Finite capacity, in plain terms
Finite scheduling adds one rule: a work centre can only do one thing at a time, and only during the hours it is actually available. If the slot is taken, the job goes to the next free slot rather than on top of the existing one.
The consequence is uncomfortable and useful. Your delivery dates get later and they get honest. You find out in the planning stage that you have promised more than you can build, instead of finding out in week three.
| Infinite | Finite | |
|---|---|---|
| Checks machine availability | No | Yes |
| Can double-book a work centre | Yes | No |
| Dates it produces | Optimistic | Achievable |
| Tells you that you are overloaded | Not until it happens | While you are still planning |
| Needs accurate routing times | Less so | Yes |
The catch, because there is one
Finite scheduling is only as good as your routing data. If an operation is recorded as taking one hour and it really takes three, the system will confidently build a plan that fails, just in a different way.
You do not need perfect times to start. You need honest ones on the operations that constrain you, which is usually two or three work centres rather than all of them. Fix those first and the plan gets useful quickly.
What to check before you buy anything
- Ask the vendor to double-book a machine in a demo. Watch what happens.
- Ask whether the Gantt lets you drag a job, and whether it stops you dropping it on a full slot.
- Ask whether capacity planning is in the plan you are buying or a tier above it.
- Ask what happens to downstream operations when one job runs late.
Some MRP systems do this properly and some do not, and the marketing pages rarely make it obvious. It is worth ten minutes in a demo rather than a year of manual rescheduling.
Where Brytebuild stands
Brytebuild plans finite. A work centre cannot be double-booked, and the Capacity Planner lets you drag work around within what the workshop can actually take. It is included from the Basic plan rather than sold as an upgrade.
If you want to see how that compares with what you are using now, the comparison pages set it out system by system, including where a rival handles it just as well.