high mix manufacturing

 

CalAmp, Inc.

  DEHART CONSULTING, INC.'s flow-based manufacturing methods enabled California Amplifier to significantly reduce floor space, manufacturing cycle-time, and overhead staffing requirements, reduce our material costs by nearly 20%, while over tripling California Amplifier's inventory turns to 10+...  


Fred Sturm, President and CEO California Amplifier, Inc.

Since the early 1980's, the benefits of producing a given production volume throughput with the minimum amount of inventory have been well documented.  Beginning with the Just-in-Time methodologies, using Kanban cards for inventory replenishment, to Demand Flow methodologies, like that posited by Suri (Paired-cell Overlapping Loops of Cards with Authorization, or POLCA) of the Quick Response Manufacturing Institute in 1998, and that patented by Costanza (US 6,594,535) in 1999, and more recently JDA Software's patents of 2009 (US 8,989,879) and 2015 (US 8,965,539). See also R. Suri, “QRM and POLCA: A Winning Combination for Manufacturing Enterprises in the 21st Century,” Technical Report, Center for Quick Response Manufacturing, May 2003.

    A goal of production businesses is a high return on investment.  Thus, if the same throughput (return) can be achieved with a smaller investment (inventory), methods of reducing inventory for a given throughput provide businesses with a competitive advantage.

    The use of Kanban scheduling was championed early by Toyota Motor Company in its high volume, low variety automobile factories. Kanban cards were assigned to batches of inventory and when consumed at a production operation, they were sent back to be replenished at an upstream operation.  Using this "demand-pull" method, production at an operation would only take place with an authorizing Kanban, and this resulted in:

1.    Limiting the amount of inventory in a factory to that determined by the number of Kanbans issued; and

2.    Stopping production at upstream operations if production was stopped at some stage. This is because the Kanbans would stop flowing upstream.  This synchronized production and enhanced quality, and reduced cost, because if a defect was found at one stage upstream, production would be automatically stopped until the problem was solved.

    Suri recognized in his 1998 innovation that the Kanban method does not work well in high variety production environments.  This is because any individual part may only be made once, or at least infrequently, and replenishment based on batches of similar units is not possible.  To implement his push-pull system (POLCA), the pull-signal is based on the number of production hours that a batch of work (the Work Order, or WO) represented in its destination Work Center (WC). This normalizes all production parts based on the hours required to accomplish the work in a given WC.  

POLCA has been successfully implemented and has been shown to be a solution to the high-variety production problem.  This disclosure describes another approach to this problem that is based on matching the flow times of WOs to their downstream demand requirements.

  • DCI Introduces Vortex Demand-Pull Technology +

    Since the early 1980's, the benefits of producing a given production volume throughput with the minimum amount of inventory have been well documented.  Beginning with the Just-in-Time methodologies, using Kanban cards for inventory replenishment, to Demand Flow methodologies,



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  • Vortex Introduction +

    The time-based demand-pull system (“demand-pull system”) technology of the described demand-pull system provides an implementation of demand-pull scheduling for various production operations/systems/factories.  It works in conjunction with a Material Resource Planning (MRP) or Enterprise Resource Planning (ERP) system, which creates production WOs and houses associated data, such as workflows and operational standard hours, to pull work through a factory with results similar to that of POLCA. 



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  • Production Priority-setting Examples +

        There are numerous methods of setting priorities in a production environment, too numerous to discuss in total in this paper, but some of the more prevalent methods are discussed below.



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  • First Authorized - First Processed Work Flow +

        When looking at work flow through a factory from the perspective of minimizing cycle time and honoring demand-pull policies, work should be processed on a first authorized, first processed (FAFP) basis. In other words, once a WO has been authorized within a WC’s queue, it should be pulled into production on a FAFP basis.  Deviating from this policy can result in an increase in the average cycle time, unless batching of WOs will reduce their aggregate cycle times due to machine capacity.  For an example of the latter situation, a machine may be capable of simultaneously processing ten pieces, and if there are two five-piece (or fewer) WOs, they could both be processed at the same time to reduce their aggregate cycle time, improve efficiency and maximize capacity.  



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  • Demand-Based Production from a Flow-Time Versus Need-Time Perspective +

    From a flow-time perspective, Work Orders should arrive in a Work Center's queue at precisely the time when they are needed to be worked on.  This minimizes both production cycle-time and inventory investment. The desired time for the next WO to arrive for processing is when the currently-authorized work in a WC and its upstream-adjacent (UA) WCs has been started into the WC and cleared the first operation in the WCs routing. This assumes that demand exists for the WO at the next downstream work cell.



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  • Examples of the Vortex Authorization Process +

    The examples set forth in the table below illustrate the WO authorization process resulting from the pull-test in different circumstances.  In all the examples, a set of WCs such as shown in the following Figure is used.  There are two WCs (WC 130 and WC 135) that feed into a third WC (WC 145) and the downstream WC (WC 145) is presumed to be healthy (reference the discussion of Work Center Performance Testing) so that the pull-testing for this WC is active. 



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  • Calculating Flow Time in a Work Center +

    Using Standard Labor/Machine Processing Hours
    In the case where all units in a WO are processed as a discrete set, the Flow Time of a WO in a WC is equal to the Standard Process Hours of the WO.



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  • Demand-Based Production from a Work-Volume Perspective +

    When looking at authorizing work in upstream stages of production, the traditional Kanban system establishes quantity buffers, or queues, at each WC. Then when the buffer quantity hits a minimum value (the Queue Policy), the Kanban card is returned to its originating WC for replenishment. 



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  • Table of Definitions +

    The following is a Table of Definitions for the articles describing the Vortex technology.



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  • An Optimum Queue Policy +
  • An Automated Demand-Pull System Embodiment +

    The Figures below illustrate an embodiment of the demand-pull system, which can be implemented using a software system with a database.  In this embodiment, a .NET service bus and MSSQL database running on a networked Microsoft Windows server are connected via the local area network (LAN) to individual clients in the various WCs. 



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  • Comparison of Time-Based Demand-Pull versus POLCA +

    POLCA (Paired Overlapping Loops of Cards with Authorization) is a prior art system to produce solutions to the application addressed herein, that is, demand-based shop floor control in a high mix, or high variety, production environment. 



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  • Vortex Shop Floor Control for Discrete Manufacturing +

    Is your manufacturing environment order-driven? Do you Engineer-to-Order or Customize-to-Order? Do your spaghetti diagrams look more like a network than continuous flow? If you struggle with production cycle-times that are too long and inventories that are too high, we have a solution!


    Introducing Vortex, a Shop Floor Control system designed to minimize your production cycle time and reduce inventory. Vortex works to pull production through your factory exactly when it’s needed! It predicts when a work center will be in need of more work, identifies the highest priority batch in all upstream work centers, and then authorizes the batch to be started just at the right time for it to reach the work center exactly when it is needed.


    Upstream work is only released if there is downstream demand, thus implementing one of the basic tenets of Lean Manufacturing – demand-pull production – in the high-variety, order-driven factory.


    Sounds simple, right?  In theory, yes.  However, if you’re talking dozens of work centers, dozens of different work flows and varying batches of sizes and flow times – predicting the time at which more work than is currently authorized for production will be needed can very quickly get complicated – the real-time calculations piling up pretty fast.

     
    Vortex streamlines the thousands of computations with a patent-pending algorithm, which works not only to synthesize all the math, but also integrate those solutions directly into your production system.


    Vortex’s modern, standards-based API is compatible with most ERP and Shop Floor Control systems.  The fully featured API allows your ERP and other internal systems to always stay up-to-date with the status of work on the shop floor. Vortex relies on your existing ERP system to create Work Orders according to your existing planning policies and inject them into the system through the API.  From there, Vortex handles the Starts into each work center based on demand-pull policies – minimizing both cycle-time and Work-in-Process inventories.  


    Check out our demo based on the following 5 products with individual work flows through 10 work centers. To view the demo, please click the link on this page - or drop us a line and we will take you for the tour.



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