A bottleneck in manufacturing is a point in the production process that has less capacity than the demand placed on it. For example, if you can make a batch of dough for 100 cookies in an hour but your oven can only fit 48 of them at a time, then the oven is a bottleneck in the cookie making process even if you have space to cool 100 cookies after they are baked. As a manufacturing process becomes more complex, more factors can cause a bottleneck. It could be as simple as a machine that is too small, as with the oven, or it could be related to the way batches are scheduled, employees are put to use, or other managerial decisions.
Create a flowchart that depicts the the production process as a series of steps based on the instructions used to manufacture the product. Each step should represent the use of a resource such as an employee or a machine. For example, in clothing manufacture a press will need to cut out fabric pieces in one step and in the next step a person might be sewing pieces together. The cutting step must be complete before the sewing step can begin.
Calculate the theoretical capacity resource profile, or percent usage, for each step. Begin with the number of units per hour that can go through the first step. Then carry that number through to each step, even if the answer is not possible. For example, if the press can cut out enough pieces of fabric for 40 shirts each hour, but the sewing team can only complete 30 steps per hour, the capacity of the sewing team is at 40 divided by 30 (times 100 to make it a percentage), or 133 percent of capacity. If the next step was folding and 60 shirts could be folded in an hour, then the theoretical capacity of that step would only be 66%, or (40/60)*100, even though in reality there would never be more than 30 shirts reaching the folding step per hour.
Compare the percent of capacity for each step. The one with the highest value is the current bottleneck.
Confirm your calculations by observation. Watch the production process as it occurs. Talk to the operators, the supervisors, and other related personnel. You are looking for places where something is not flowing smoothly. This may be an inventory pile-up, people waiting for something to do, or something that when it breaks brings the entire process to a stop. If the calculated answer indicates a true bottleneck then there will be physical evidence.
Repeat the process as often as necessary. Fixing one bottleneck will reveal another until the entire production process is running below full capacity.