Scheduling Logic: Inventory Constraint

The Inventory constraint feature is used to detect the material and when it is about to run out. By rescheduling, the operations will be assigned taking into account the state of inventory on a certain date and time.

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You can only get inventory information with help of the Inventory graph. While inventory constraints of the items are not set up, knowing the inventory whether it is too large or not does not matter. However, problems may occur during purchase of items. So let’s use the Inventory constraint flag property in the Item table – set the Inventory Constraint Flag to Yes for items A and X.

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Then, run the reschedule button. There are no changes on the Gantt chart or Inventory graph, but you will see a warning message as an output in the Message window.

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By double-clicking the message, the details will be displayed and you can confirm the concerned operations.

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You will be able to see clearly when and at which stage of production the shortage happened.

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In addition, you will be able to know easily which item, when and how many is about to run out.

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You can also check to understand the whole situation in the Operation table or even in the Input Instruction table.


To learn more about Asprova specific to this sample demonstration, you may visit Asprova’s online help and search Operation Split or its e-Learning videos at http://lib.asprova.com/ (see 24. Scheduling Logic).

Material Requirement Calculation

In Asprova, the required quantity of items can be calculated and the input time from the manufacturing time to setup time can be moved. This article will explain how to register the requirement and time settings.

In the Integrated Master Editor, when producing item “AX”, we need 1 item of the Resource/Item “A”.

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In the Order Table, order “1” has been set so as to produce 10 items of “AX” by 15:00 on June 5th.

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Run the reschedule button to see that the order “1” is assigned at the Resource Gantt chart.

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Go to the Inventory Graph by right clicking the table, go to Drilldown, then Inventory Graph.

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The initial inventory of “A” is 0 and is reduced to -10 when order “1” starts. This means that 10 items of “A” have been used by the start time of order “1”.

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To see the consumption change, go to the Integrated Master Editor and adjust the Production to 1.5 and reschedule it.

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In the Resource Gantt chart, the consumption of “A” changes to 15.

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Now, set 1.5 as Setup and 0 as Production. Run the reschedule button.

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You will see that 15 items of “A” have been used when the setup of order “1” starts instead of start of production.

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To learn more about Asprova specific to this sample demonstration, you may visit Asprova’s e-Learning videos at http://lib.asprova.com/ (see 24. Scheduling Logic).

 

 

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When calculating the material requirement, Asprova can check the inventory of the raw material and parts and automatically generate replenishment orders. This is the Auto-Replenishment function of Asprova.

There are two ways to generate replenishment orders: 1) we can replenish one to one for each order, or 2) calculate the total requirement and replenish at once by registering the lot size.

In this Integrated master editor table, the only items to be produced are shown. Item “AX” is produced by assembling the production item “A” and the purchase item “X”.

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Three sales orders are registered in the Order table.

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As the manufacturing order has not been registered yet, rescheduling it would mean item “AX” is out of stock.

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Let’s set up the auto-replenishment order for items “AX” in the Item table. Since we want to give manufacturing instructions for each sales order of item “AX”, update auto-replenishment as “Yes (one-to-one production)”.

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Run the reschedule button. By doing this, the manufacturing order will be automatically registered when the inventory of item “AX” runs out of stock.

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On the other hand, as the stock of items “A” and “X” will also run out, we need to set auto-replenishment as well.

For items “A” and “X”, since we produce and purchase these items at once, set “Yes” for the [Auto-replenishment flag] and register the lot size. For item “A”, register 500 for production lot size MAX. For item “X”, as it is a purchase item, set “Purchase” for the Obtain method property. Then, register the lot size at the Purchase lot size MIN/MAX at 5000.

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Run the Reschedule button. The schedule changes to produce item “A” with a quantity of no more than 500 items at once. As we purchase “X” in a large quantity, only one purchase order will be generated.

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The one-to-one replenishment order is often used for made-to-measure items or individual items
and the replenishment order with lot size is often used for mass-production.

There are a lot of additional features based on the auto-replenishment, for example: time period grouping and inventory control. To learn more about Asprova specific to this sample demonstration, you may visit Asprova’s online help and search Operation Split or its e-Learning videos at http://lib.asprova.com/ (see 24. Scheduling Logic).

 

Operation Split

There are two methods on how to split the operations. One of them is to register the lot size for the equipment. In this sample, input 200 as the Resource split size MAX in the equipment Cutter 1.

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This method is used when the quantities, which can be processed, are different for each piece of equipment. Run the reschedule button and you will see that the operations have been split.

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During the assignment of operations, which were split as mentioned above, the corresponding instructions can be assigned separately.

Furthermore, it is also possible to shorten the lead time, by setting the Time constraint method as “ESE”.

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Run the reschedule button and you will see that the operation has been finished earlier than the previous sample.

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Another method of operations splitting is to register the Production lot size MAX for each item at the [Item table].

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When the production quantity is larger than the lot size of the item, the operations will be split and then assigned.

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This is used when the production quantities are different for each item.

Also, when there are several pieces of equipment, parallel production becomes possible and can reduce lead time. This can be done by changing the Time constraint method to “SSEEE”.

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Note also that the operation split function has plenty of effects, such as split by rate, switching workers by shift, etc.

To learn more about Asprova specific to this sample demonstration, you may visit Asprova’s online help and search Operation Split or its e-Learning videos at http://lib.asprova.com/ (see 24. Scheduling Logic).

 

 

Time Constraint

In this article, we will study the time constraint by which we can specify how to connect the previous operation with the current one given the time delays for each resource and item.

In the case where the next operation starts after completing the previous operation, we can set “ES” as the Time constraint method which means End-Start.

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You then set the time delay between the operations at the Time constraint MIN as seen below.

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Press the Reschedule button and you will see that the operation will be assigned after the end of the interpretational time delay as set in the Time constraint MIN.

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In this sample, the interpretational time delays for resources are different wherein the transfer of the operations can lead to delivery delays, which will also be displayed.

In cases where the previous process and the next process operates at the same time, we can set “SS” as the Time constraint method, which means “Start-Start”.

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By setting “SS” as the Time constraint method for the Injection process, we can get a schedule wherein the Press and Injection resources will operate side by side.

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But you will notice that the next process will be completed earlier. Therefore, this cannot be operated.

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In order to finish the next process after the previous process has completed, we will use “SSEE” as the Time constraint method.

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By doing this, after the previous process ends, the next process will be finished.

The next sample, we will explain how to register different times between operations for each item.

In this case, let’s register the Time constraint method and Time constraint MIN for Input instruction.

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By taking the end time of the previous process for each item and time constraints into consideration, we can calculate the operation’s start time (or end time in the case of a backward operation) and generate the schedule.

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To learn more about Asprova specific to this sample de9monstration, you may visit Asprova’s e-Learning videos at http://lib.asprova.com/ (see 24. Scheduling Logic).

 

Material Requirement Calculation (Yield, Scrap)

Yield rate and scrap quantity can be specified in the Integrated Master Editor for the Input Instruction and Output Instruction. An input instruction specifies the item and its quantity to be input to the given operation. An output instruction specifies the item and quantity to be output from that operation.

In the order table, order 1 requires to produce 9 items of “AX”.

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You can view order 1 in the Resource Gantt chart.  By looking at the Inventory graph, you will see that 9 items of “AX” are required.

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Please set 0.9 as the yield rate for the output instruction and press the reschedule button.

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As 9 items of “AX” will be supplied to the next process, 10 items of “AX” will be produced and 10 items of “A” will be used. This is because the yield rate is set as 0.9.

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Then, set 1 as the scrap quantity.

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Press the reschedule button and confirm that the required quantity of “A” is increased by 1 to 11.

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Next, let’s set 1 as the scrap quantity for the input instruction and press the reschedule button again.

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The manufacturing quantity of “AX” remains 11 items but the required quantity of “A” was increased to 12 items.

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If we set 0.8 as the yield rate for the input instruction and reschedule it, the required quantity of “A” will change to 15.

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To learn more about Asprova specific to this sample demonstration, you may visit Asprova’s e-Learning videos at http://lib.asprova.com/ (see 24. Scheduling Logic).

 

Set up Time (Resource)

In Asprova, it is also possible to schedule the setup time for changing molds and jig tools. This can be specified in the Integrated Master Editor. This article will show you how to generate a schedule setup by switching the main resource and the sub-resource.

In this sample, we will produce item “AX”. Press 1 will be used as a main resource. Mold 1 and Mold 2 will be used as a sub resource.

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Let’s register in the Resource setup table a 120m-setup-time to switch Mold 1 to Mold 2 on Press 1.

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In addition, let’s set a 20m-setup-time to switch Mold 2 to Mold 1.

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Press the reschedule button to see the result. At the Resource Gantt chart, you will see that there is a 120m-setup-time on Press 1 when Mold 1 to Mold 2 is switched. Subsequently, there is a 20m-setup-time on Press 1 when we change Mold 2 to Mold 1.

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To learn more about Asprova specific to this sample demonstration, you may visit Asprova’s e-Learning videos at http://lib.asprova.com/ (see 24. Scheduling Logic).