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blog | July 29, 2015

Break the Bottlenecks

Bottlenecks in production remain one of the largest impediments to productivity on the shop floor. The irony is that one or two machines can slow the entire throughput of...

By WorkWiseSoftware

Bottlenecks in production remain one of the largest impediments to productivity on the shop floor. The irony is that one or two machines can slow the entire throughput of a production operation to a crawl. This is much like the one or two accidents on the freeway, which brings the entire freeway speed to a painful stop and go.

Finding the bottlenecks

The first step in handling bottlenecks is the process of identifying them. There are several techniques for doing this.

WIP inventory– Sometimes, the fastest way to find bottlenecks in your operation is to look for the large stacks of WIP in front of individual operations and ask the reasons why the WIP is sitting there. The answers will quickly lead to the operations that are the bottlenecks.

Visual scheduling– A more accurate and easy method to identify bottlenecks is to use your ERP Visual Scheduler for the shop. This tool provides a visual picture of problem areas. It can also provide you the ability to reschedule your short term bottlenecks immediately.

Other reports to identify your bottlenecks include:
• Longest queue time
• Lowest production rate
• Highest utilization rate
• Longest duration as a bottleneck

Remember to monitor your bottlenecks to determine whether those bottlenecks are short term or long term bottlenecks. Short term bottlenecks may only be temporary, and not worth fixing at this time. Examples would include short term bottlenecks caused by special orders, or other one- time events.

Cost of bottleneck

It’s important to know the cost of the bottleneck so you can evaluate the value of eliminating it.

One hour of entire shop cost per hour held at the bottleneck – Some people project that the cost of a bottleneck is equal to the cost of one hour of time across the entire shop. The thought process is that the bottleneck is constraining you from filling any more capacity because it just isn’t possible to push any more through the bottleneck. For every hour that you can open for the bottleneck, one more hour is available for the entire shop to produce product. Now, in complex larger operations, it’s rare that one operation would hold up the entire shop, but this certainly helps to understand the cost in more simplistic plants. Nonetheless, it’s also easy to imagine the impact on any sized organization.

Lost sales – Another method of looking at the inherent cost of bottlenecks is to review the cost of lost sales to a customer. If you have the ability to sell more to customers, but are constrained by your capacity, you can total the value of those lost sales to understand another value of un-clogging a bottleneck. Some would argue that there are other costs involved in making those sales, but they would only be correct for material costs. Other production costs have already been made, and are merely idle due to the bottleneck.

Lost customers – Yet another way to view the cost of the bottleneck, is to evaluate the value of a customer lost because of late deliveries. If you are continuously running a bottleneck, you are also running late deliveries.

Resolving the Bottleneck

Use alternative methods of scheduling.

Backward – One simple way to control bottlenecks is to backward schedule until the bottleneck reaches full capacity. The goal is to fully utilize the bottleneck operation, but to not over schedule. If the capacity and timing is not acceptable to your customer, you will need to find other methods to help clear the log jam.

Forward – In some businesses, customers are quite willing to accept delivery dates, as long as you can stick to them.

Bottleneck centered – In this method, everything is first focused on the bottleneck operations and then scheduled to other operations

Visual scheduling – Visual scheduling provides a full view of the shops planned activities and an early view of schedule items to be resolved. With enough advanced notice, and an ability to visually view the schedule, creative schedules can be created.

Create alternative methods of production.

Cross train – Cross training works well for absenteeism, breaks, cleanup and the like. A bottleneck should never stop running for any external reason.

Capacity planning – Sometimes, there is just a capacity problem that cannot be solved by alternative methods. Through capacity planning, you can determine the bottlenecks in advance, and the cost of boosting that capacity. Many people are surprised that their entire throughput is governed by a relatively inexpensive piece of machinery.

Overtime or shifts – This is often the first alternative that many people consider. However, it’s important to consider the cost of another shift including plant costs, supervision costs and other incremental costs.

Maintenance management – One of the least costly methods for resolving your bottleneck problem is the maintenance of your bottleneck operation to near 100% uptime. Many manufacturers leave the maintenance to chance and suffer the consequences. Your ERP software can help you plan preventive maintenance and identify breakdown trends. This way, you can implement a “repair before it breaks” program, and keep your bottleneck running as near to 100% as possible.

Minimize the setup time– Setup time is also equipment downtime. If the operation is unavailable, it’s not running at full capacity. Sometimes small adjustments and focus can make a big difference. Other times, the cost of the downtime may well justify more sophisticated setup reduction (SMED, for example).

Subcontracting– Yet another method for certain types of operations is the outside sourcing of the missing capacity. This works particularly well for non-core competency type items.

Increase buffers at constraint– Again, the objective is to keep the bottleneck at full capacity. If you shop is subject to high levels of schedule shocks, it’s an intelligent move to build some buffers in front of the bottlenecks.

Inspection prior to bottleneck– This method is often forgot, but still the cause of bottlenecks. Every item that goes to the bottleneck operation should be of the highest quality.

Reduce quality and rework– Every poor quality part that comes from the bottleneck, is one unit of capacity lost. Make sure your quality programs highlight these bottleneck operations first.

Reduction of cycle time– This method is self-explanatory: faster speed equals more capacity. But also remember, speed with low quality still equals low capacity.

Real time MES– Sometimes the best way to fix problems is to know about them as fast as possible. With formal alerts, real time data collection, and feedback dashboards, you can be on top of any capacity depleting activities.

Eliminating non-value added time– As lean and 5s have taught us, non-value added time must be eliminated. This is even truer, at bottlenecks. Is your process slow, or is your layout slow?

Updated Standards– Even though this will sound oxymoronic, if you plan with poor standards, you plan to fail. If your lead times, move times, cycle times and the rest of your times are wrong, how can you possibly plan control your bottlenecks?

Summary

Bottlenecks can down throttle your entire shop, and limit your through put while hurting your costs and fill-rates. Sometimes the solutions to these bottlenecks are easily found, and sometimes it can take extensive work to find, and resolve them. It’s always a good idea to put the systems in place to monitor these bottlenecks, and to know about these bottlenecks far in advance of their consequences.

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