Implement parallel and non-parallel operations in a Production BOM

A Production BOM defines each step of a production operation, its duration, and the components and resources required to complete each step. In many production operations, you may need to schedule parallel operations. This can involve:

  • Fork queues: Incoming operations are split into several operations to obtain finished products or components for further production simultaneously.
  • Join queues: Multiple incoming operations are joined into one operation for further production.


You should be familiar with the basic Production BOM setup before implementing parallel operations and fork-join queues as described in this article.


Prerequisites


Table of Contents

Fork-join queue examples

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Parallel sequences in a Production BOM can be set up by adding the previous operation name in the Previous step column dropdown field. Selecting Step 0 here indicates that no previous operations must be completed before the operation can begin. 


Below you can find some examples to see how such operations can be implemented in DEAR. 


Important information:

  • Operations with the same sequence number are started at the same time.
  • Operations can be started when the "previous step" operation/s have been completed (for all operations of that sequence number, if there is more than one).
  • It is allowed to miss out sequence numbers. 


Scenario 1: Join queue (simple)

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Two operations are executed in parallel. Both operations are then joined into the next operation in the sequence. 

  • The Cutting and Polishing operations do not require a previous operation, so both have Previous Step: 0.
  • Packing (Step 2) operation requires previous operations Cutting (Step 1) and Polishing (Step 1) to be completed. 
  • Both Step 1 operations will be carried out in parallel.
  • Step 2 cannot be started until both of the previous operations have been completed. 


Scenario 2: Join queue (complex)

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The queue of two operations is executed in parallel with the queue of the other two operations. Each queue has a sequence of the operations inside it. Both queues are joined into a single operation. Such a sequence is set up using the same sequence numbers for the operations which define that these operations will be executed in parallel.

  • The Cutting (Step 1) and Polishing (Step 1) operations do not require a previous operation, so both have Previous Step: 0.
  • Painting (Step 2) operation requires previous operation Cutting (Step 1) to be completed.
  • Drying (Step 2) operation requires previous operation Polishing (Step 1) to be completed. 
  • Step 2 operations can be started only when Step 1 operations will be completed. 
  • If the Step 1 operations have a different duration, Step 2 can be started only when the longest operation of Step 1 is completed. Step 2 operations are started simultaneously. Step 3 can't be started when at least one of the previous operations is not completed.


Scenario 3: Fork queue (simple)

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In a fork queue, one operation is split into two queues. Each queue has a sequence of the operations inside it. Both operation sequences in the split will run in parallel. 

  • The Cutting (Step 1) operation does not require a previous operation has Previous Step: 0.
  • Polishing (Step 2) and Drying (Step 2) operation requires previous operation Cutting (Step 1) to be completed.
  • Step 2 operations can be started only when Step 1 operations have been completed. 
  • If the Step 1 operations have different durations, Step 2 can be started only once the longest operation of Step 1 has been completed. 
  • Step 2 operations are started simultaneously. 


Scenario 4: Fork queue (complex)

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In a fork queue, one operation is split into two queues. Each queue has a sequence of the operations inside it. Both operation sequences in the split will run in parallel, no matter the number of operations in the sequence. 

 

  • The Cutting (Step 1) operation does not require a previous operation has Previous Step: 0.
  • Polishing (Step 2) and Drying (Step 2) operation requires previous operation Cutting (Step 1) to be completed.
  • Step 2 operations can be started only when Step 1 operations have been completed. 
  • If the Step 1 operations have different durations, Step 2 can be started only once the longest operation of Step 1 has been completed. 
  • Step 2 operations are started simultaneously. 
  • Step 3 can't be started until both Step 2 operations have been completed.
  • Step 3 operations are started simultaneously. 


Scenario 5: Fork-join queue

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Fork and join queues can be combined in the same Production BOM. 

  • The Cutting (Step 1) operation does not require a previous operation has Previous Step: 0.
  • Polishing (Step 2) and Drying (Step 2) operation requires previous operation Cutting (Step 1) to be completed.
  • Step 2 operations can be started only when Step 1 operations have been completed. 
  • Step 2 can be started only once the longest operation of Step 1 has been completed. 
  • Step 2 operations are started simultaneously. 
  • Step 3 can't be started until both Step 2 operations have been completed.
  • Step 3 operations are started simultaneously. 
  • Packing (Step 4) operation requires previous both operations Assemble (Step 3) and Painting (Step 3) to be completed.


Scenario 6: Fork-join queue with non-parallel execution

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Not all steps in an operation sequence will be happening in parallel. Drying (Step 3) below is an example of a non-parallel step. 

  • The Cutting (Step 1) operation does not require a previous operation has Previous Step: 0.
  • Painting (Step 2) operation requires previous operation Cutting (Step 1) to be completed.
  • Drying (Step 3) is a non-parallel step. The previous step for it is 0 which means that it is scheduled as soon as resources are available during the Step 1 and Step 2. 
  • Assemble (Step 4) operation requires previous both operations Drying (Step 3) and Painting (Step 2) to be completed.
  • Washing (Step 5) and Packing (Step 6) are not parallel steps. Step 5 and Step 6 can be scheduled as soon as Step 4 is completed. 
  • Step 5 and Step 6 do not have to be executed simultaneously or have the same scheduled start date. 


Scenario 7: Fork-join queue (complex)

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Production BOM supports complex combinations of fork-join queues to ensure your production operations can be accurately mapped. 

  • The Cutting (Step 1) operation does not require a previous operation has Previous Step: 0.
  • Polishing (Step 2) and Drying (Step 2) operation requires previous operation Cutting (Step 1) to be completed.
  • Assemble (Step 3), Painting (Step 3) and Varnishing (Step 3) operations should be started simultaneously, after both Polishing (Step 2) and Drying (Step 2) have been completed. 
  • There is no Step 4 - this is allowed by DEAR. Missing operation sequence numbers can be used when it is likely another process may be added to the sequence at a later date.
  • Fanning (Step 5) is a non-parallel step. The previous step for it is 0 which means that it is scheduled as soon as resources are available. It could be carried out at any time before the next step in the sequence.
  • Packing (Step 6) and Staining Wood (Step 6) operation require all three Step 3 operations to be completed. Both Step 6 operations will be started simultaneously. 
  • There is no Step 7
  • Decorating (Step 8) and QA (Step 8) operation require Packing (Step 6), Staining Wood (Step 6) and Fanning (Step 5) to be completed. Both Step 8 operations will be started simultaneously.
  • Re-painting (Step 9) can be started only when both operations: Decorating (Step 8) and QA (Step 8) are completed. It can be started before or after Step 10, as these steps are not parallel. 
  • Transporting (Step 10) can be started only when QA (Step 8)is complete. It can be started before or after Step 9, as these steps are not parallel. 
    • NOTE: Depends on previous step, not previous operation sequence number.


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