high mix manufacturing

 

Xilinx, Inc.

 DEHART CONSULTING has provided innovative solutions to our operational space planning and facility design needs on several occasions.  DCI consultants bridge the gap between operations and facility management to assure that we arrive at win-win solutions for our stakeholders ... 

Forrest James, Sr. Director, Global Real Estate and Site Services at Xilinx, Inc.


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

#

Item Description

Variable

Formula / Explanation

1

Flow Time for WO1 through WCN-1

tWO1, n-1

2

Transit Time for WO1 from WCN-1 to WCN

tT,N-1,N

This is a constant value entered by admin staff.

3

Remaining Clear Time of the WO in process at WCN with the least remaining Clear Time.

tR,N

4

Sum of the Clear Times for WCN of all WO's in its queue.

QN

5

Sum of the Clear Times at WCN for all authorized UA WOs

YN

6

Number of capacity units within WCN

CN

This is a constant value entered by admin staff.

7

Remaining Clear Time at WCN-1 for the WO with the least remaining Clear Time

tR,N-1

8

Sum of the Clear Times for WCN-1 for all authorized UA WOs in the WCN-1 queue.

tQ,N-1

9

Number of capacity units within WCN-1

CN-1

This is a constant value entered by admin staff.

10

Batch Size

B

This is a constant value entered by admin staff. If the WO will not be serially split, the B is equal to the WO # Units.

11

Number of Operations within the WC for a given WO

ON

This is a constant value based on the WO’s Work Flow, or Routing.

12

Clear Time

tC

the elapsed processing time required for a WO to complete the first operation in a WC.

13

Flush Time

tF

The elapsed processing time required for a WO to complete all operation subsequent to the first operation. 

14

Max Split Ratio

RC

15

Flow Time Ratio

R

The ratio of Flow Time to Standard Process Hours in a balanced line.

16

Clear Time for WCN for WO1.

WN

- the elapsed processing hours required to complete WO1 from start to finish at a given WC. This is Clear Time + Flush Time. If a WC has a single operation, Flow Time is equal to Clear Time, and R=1.

17

WCN Queue Policy

XN

18

WO Quantity

# Units

This is a property of the WO that is initially provided with the WO details, but may change if defects arise during production.

19

Standard Hours per Unit

HPU

This is a property of the WO that varies per WC and represents the total standard work hours per unit for the WC.

20

Operation Hours per Batch

OHPB

 

21

WO Flow Time

WOFT

22

WO Standard Hours

WOSH

23

Queued Hours

Q

Sum of Flow Times for all WOs in a WC Queue.

24

UA Authorized Hours

Y

Sum of Flow Times for a WC of all WOs with open PTs at UA WCs.

25

Workflow

 

refers to the sequence of defined operations required to convert raw materials into a finished unit. This is also commonly known as a routing.

26

Work Center

WC

an organization of resources that facilitates the performance of an operation or plurality of operations in a production Workflow.

27

Work Order

WO

refers to a set of similar units to be processed as a group at a WC.

28

Upstream Adjacent

UA

refers to a WC that is next prior to a given WC in a Workflow, i.e, WCN-1 would be UA to WCN.

29

Pull-Tag

PT

is a work authorization property assigned to a WO. Work may be performed on a WO if, and only if, a PT has been assigned to it and the PT is in an Open state.

30

Work Order One

WO1

the WO that is UA, has been assigned the highest priority relative to other UA WOs, and not yet assigned a PT.

31

Work Center N-1

WCN-1

the WC in which WO1 is queued.

32

Balanced Line

 

a sequence of processing operations, each of which requires the same time to complete.

  • 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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