How to Improve Efficiency and the Bottom Line in High-Mix ... › 2015 › 04 › how... · situation where the changeover time rather than line utilization is imposing limits on

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HOW TO IMPROVE EFFICIENCY AND THE BOTTOM-LINE FOR HIGH-MIX PCB PRODUCTION

MARK LAING, VALOR DIVISION OF MENTOR GRAPHICS CORPORATION

How To Improve Efficiency and the Bottom-Line for High-Mix PCB Production

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INTRODUCTIONAlthough production volumes for PCB manufacturers may have remained the same or even increased, the number of unique product designs in the production schedule has increased significantly. Some individual products are still being built in large quantities but the majority of PCB manufacturers are now operating in a high-mix environment.

With this move from low-mix to high mix-manufacturing, the need for absolute throughput or optimization on a single product has been reduced in favor of optimizing throughput across multiple batches of different products. Overall line utilization is now being limited by changeover times rather than the build start and end times.

MOVING BEYOND INFINITE VERSUS FINITE PLANNINGThere are some planning software solutions for manufacturing production that are based on infinite algorithms, which means they do not understand the many complex constraints of high-mix PCB manufacturing scheduling. Also there are others that use finite algorithms that have much more constraint awareness; however, they are significantly more expensive. Although the software is created to understand due dates, material availability, and labor dependencies, they still lack a solid understanding of how a product

is built through surface mount technology (SMT) lines, which means that activities on SMT that occur in PCB manufacturing are ignored in the planning solution.

In contrast to both of these methods, the Mentor Graphics Valor Production Plan software comes with detailed knowledge of SMT machines, lines, feeders, parts, and reels, as well as other standard manufacturing issues, which enables it to provide a more accurate production schedule for high-mix environments.

The Valor Production Plan tool was created with the fundamental knowledge of how raw PCB components are assembled onto circuit boards and how boards can be brought together to create assemblies. It links to electronic resource planning (ERP) systems to obtain feed material availability and work order information to ensure accuracy. The software can

be integrated with existing manufacturing software systems.

REMOVING THE INFORMATION GAP BETWEEN SUPPLY CHAIN/LOGISTICS AND THE SHOP FLOOR TO IMPROVE PROFITS

Many supply chain or logistics people believe that their shop floor scheduling tasks are covered within their existing solution. However, the ERP system is not aware of the details of typical SMT production activities. It can only build a schedule based on the typical product tact times, overall part availability, and required

Figure 1: Example of a typical situation where the changeover time rather than line utilization has put limits on production.



work-order due dates. The shop floor production people know this information is limited because they are estimates based on what has happened in the past and a typical set-up configuration for each batch. The result is an on-time delivery of 98% but difficulties remain in maximizing profit.

Some planning solutions can perform simple multiple-product grouping, creating an SMT setup for more than one PCB product. Other planning solutions can perform work-order sequencing based on due dates. Only Valor Production Plan to date brings both of these capabilities together into a single planning solution.

TYPICAL EXAMPLEAlthough companies are manufacturing in a high-mix environment with reasonably low batch sizes and many different batch sizes, for historical reasons or because of lack of automation, each batch is built with its own dedicated feeder setup. Even with a significant amount of commonality between products that could reduce the number of different setups, a low line utilization is accepted as normal and not addressed. Unfortunately

though, the more feeders are changed from product to product, the higher the chance that mistakes will be made.

Figure 1 shows a typical high-mix production plan created by a planning and supply chain ERP and then carried out on the shop floor. A setup is created for each work order, which is repeated for each subsequent work order during the day. For the 10 products shown in the figure, there is approximately 8 hours of set-up time and an actual build time of just over 4 hours, for a combined total of approximately 12 hours of manufacturing and 33% line utilization. This is typical of a situation where the changeover time rather than line utilization is imposing limits on manufacturing capability.

Figure 2: This is an example of where good grouping capability increases line utilization dramatically, decreasing setup time and improving production efficiency.

Figure 3: Comparison of the production plan timelines between the two different approaches.



HOW TO IMPROVE LINE UTILIZATIONIn contrast to the typical, traditional, example used in Figure 1, the Valor Production Plan software is able to analyze the parts on each of the boards and combine all the products into a single setup as shown in Figure 2.

In the new example, the overall build time is approximately 8 hours with a set up time of less than 90 minutes. This translates to line utilization higher than 80%. This is example illustrates the benefit of proper grouping applied to individual setups to increase line utilization.

Figure 3 compares the production plan timeline for the two approaches. With good grouping, setup is completed 4.5 hours earlier than the setup per product approach as is typical in many high-mix production facilities. With only one set up for all 10 products, once the configuration is verified, the chance of mistakes also is reduced.

A MORE EXTENSIVE EXAMPLE: OPTIMIZING THE PRODUCTION PLAN FOR 341 WORK ORDERS PER WEEK

Let’s take a look at how a different approach could affect a week’s worth of production, 341 work orders, a number that manual planning methods, or even semi-automated with spreadsheet programs, would not be able to handle. The work orders usually would be filtered to prioritize the ones with the closest due dates. Then individual work orders are assigned to each of four SMT lines. In this high-mix environment, the SMT lines often are all different from each other, meaning that, for example, there is one line that supports Assembleon machines,

Figure 4: An example of the dynamic multiple-line analysis that can be done using Valor Production Plan software.

Figure 5: Results of the multi-line analysis can be viewed under the Planning tab.



one may be Fuji, one is Juki, and one is Universal. This means that each machine’s software is different and therefore does not have visibility to the products that are being built on the other lines.

In comparison, the Valor Production Plan software can be used to select all 341 work orders, and its multi-line analysis capability can be used to determine which line to assign orders to. They can also be grouped to appropriate setup configurations. Figure 4 shows an example of this multi-line analysis. The software can be operated at the start of the month, for example, to assign an initial work order based on the starting point for the month. The Valor Production Plan software can then dynamically adjust the assignment of work orders as due dates change, new work orders appear, and material stock levels change.

Once the multiline analysis has completed, the Planning tab in Figure 5 shows the results; in this case, 5 groups for line 1, 2 groups for line 2, and 3 groups for lines 3 and 4.

This also presents the first opportunity to see the effect of lack of materials. The Messages column of the Planning tab shows that parts are missing, which indicates that the proposed work orders cannot be produced based on the current stock levels.

Material availability can be connected to the Valor Shop Floor system, or a simple scheduled export from whichever ERP system is in use can create a list of part numbers against quantity. This file can be auto-matically scanned to keep it updated as material is consumed. The group can be expanded to reveal which product or products

Figure 6: Examples on both lines of CPH with and without the setups included.

Figure 7: This timeline shows that the grouped setup is completed much earlier than the non-grouped setup.



are affected by the lack of material, and the work orders can be quickly re-sequenced to push them out to when restocking will occur.

KEY PERFORMANCE INDICATORSKey performance indicators (KPIs) provide a simple yet powerful way to compare different what-if scenarios through various different metrics. The first KPI we will use for our example is line utilization in conjunction with components per hour (CPH). Figure 6 shows examples on both lines of CPH with and without the setups included. Following the KPI comparisons, we see the over-line cost modeled through operator cost, line cost and material cost. Again, the grouped setup significantly reduced the line cost between the two what-if scenarios.

The production plan timeline in Figure 7 shows that the grouped setup is completed much earlier than the non-grouped setup. The methods make it easy to compare different strategies, comparing and contrasting them to determine the one that delivers best on the current production goals.

No matter how much we plan for upcoming production, change happens and our plans must adapt. New work orders need to be integrated into the existing plan, material stock for certain parts are exhausted, priorities for existing work orders change, and lines suddenly stop working and need maintenance. Typically, the existing approach is to stop what is currently being produced and switch over to the latest priority of the hour, which is inefficient because it affects the schedule

much more than it has to. With the Valor Production Plan software, new work orders can be added to the existing work orders in process, determining at which lines and at what point to inject them in to the schedule. Due dates, changeover times, and schedule disruptions can all be considered to determine how best to deliver on the changing production demand.

Dynamic grouping options also can be used to analyze changes in production requirements and to see how best to include them in the upcoming sequence. Also static setting may be developed that fixes a part of the setup across multiple products or groups to provide easier integration of new products, or existing products, to the current sequence.

Figure 8 shows the current state of 120 work orders where we have some open capacity on line 1. Once we import 30 new work orders, we can use the multi-line analysis capability to decide how best to integrate these new work orders into the existing production schedule. Figure 9 shows that most of the new work orders have been assigned to line 1 and that all work orders have been accounted for. The status row at the bottom of the screen indicates that 150 work orders (120 +30) have been assigned and none remain unassigned.

Figure 8: Existing work orders.



The Planning tab in Figure 10 shows the new overall product sequence. Each line can be reviewed to see how many groups are needed and whether we have any part shortages with the new plan. If so, then the schedule can be sequenced again to account for upcoming part deliveries.

Figure 9: New work orders.

Figure 10: New product sequence.


©2015 Mentor Graphics Corporation, all rights reserved. This document contains information that is proprietary to Mentor Graphics Corporation and may be duplicated in whole or in part by the original recipient for internal business purposes only, provided that this entire notice appears in all copies. In accepting this document, the recipient agrees to make every reasonable effort to prevent unauthorized use of this information. All trademarks mentioned in this document are the trademarks of their respective owners.

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SUMMARYThe scenarios discussed here are typical of using Valor Production Plan to improve a real-world production high-mix environment, taking constraints on material, lines, machines, and shift patterns into account. However, the Valor Production Plan software is powerful enough that it can also be used to run what-if scenarios with different constraints or to adjust what limits are put in place for existing constraints. Questions can be analyzed such as: what could be achieved if another line was added, what could be produced if another machine was added to existing lines, or what could be built if there was a machine with more feeders. The ability to simulate how manufacturing can be improved allows for more scenarios to be considered and evaluated to decide if they will contribute to the overall company goals.

The Valor Production Plan software for manufacturing has been show to help address the challenge of improving efficiency as well as the bottom line in high-mix PCB production environments. For more information, visit http://go.mentor.com/planning.

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How to Improve Efficiency and the Bottom Line in High-Mix ... › 2015 › 04 › how... · situation where the changeover time rather than line utilization is imposing limits on