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11. How to calculate Availability of parallel processes

Parallel processes and OEE often generate serious discussions. Here is one:

Q: I would like to know how to calculate available time if there’s 2 processes working parallel to produce 1 batch of product. For example: 1st batch Process A works from 9:00 – 11:00 and Process B works from 9:30 – 12:00. 2nd batch Process A works from 11:00 – 15:00 and Process B works from 12:00 – 15:30

Arno Koch •   OEE calculates the effectiveness of a MACHINE. What you describe is a situation of (at least) TWO machines working in parallel.

What you are probably looking for is to synchronize capacities of the two machines in order to have the right quantities of the two product available a te right (same) time in order to proceed to the next step.

Knowing the availability of the two machines together does not give an answer to this question. Neither does knowing the two separate availabilities, since you may be facing differences in max speeds, performance and quality rates.

What does makes sense is to do is this:

When

• Machine A can run a max speed of 100 pcs/hr
• Machine B can run a max speed of 80 pcs/hr

then what happens when both machines run at 50% OEE:

• Machine A produces 50% x 100 pcs = 50 pcs/hr
• Machine B produces 50% x 80 pcs = 40 pcs/hr

In order to get the same quantity of product after the same amount of time:

• Machine can slow down to 40% x 100 pcs to produce 40 pcs/hr
• Or Machine B can speed up to 62,5% x 80 pcs to produce 50 pcs/hr

In this way the two machines are in sync again and the proceeding proces can proces either 2 times 40 or 2 times 50 products.

Of course you may also have the slower machine run longer, but that would force into more stock, longer shifts etc. OEE could help here to achieve a more balanced situation. Since you already have a parallel process, there is little need for batching: you could gain significant advantages when going towards ‘flow’ of very small quantities (batch to one piece flow conversion).