BOM Line with Fixed Quantity

The purpose of this page is to discuss how to update iDempiere to use a BOM Line with a fixed quantity.

Example - Here is an example to best describe the scenario. Let's assume we are producing stainless steel tubing. We have a bill of material that calls for the use of a plug to manipulate the characteristics of the tubing. We use one plug per production order regardless of how many meters of tubing we are creating in that order. Therefore, we need the Production window => Line subtab => Quantity Used field to always be 1.

Implementation - iDempiere does not support this feature out of the box; however, the implementation is quite easy to accomplish. Here are the steps to update iDempiere:

• Add a new Product window => BOM subtab => Fixed Quantity field. Set the default value to zero.
• Create a new Model Event plugin (IEventTopics.PO_AFTER_NEW) for the Production window => Line subtab to update Line => Quantity Used field to that of the newly created Product window => BOM subtab => Fixed Quantity when the Fixed Quantity value is non-zero.

If you need help implementing this feature, let me know. I can help you find someone who can assist you.

Math - To complete this implementation, we need to discuss some math. First, let's introduce the concept of an assumed batch size. This is the typical or average number of finished good units that are created in a single Production order. Set the Product window => BOM subtab => BOM Qty field to the following:

• Fixed Qty / Assumed Batch Size

Discussion - the following are points related to this scenario:

• If you create a Production order where the Production Quantity is equal to the assumed batch size, the Line => Planned Quantity will be equal to the Line => Quantity Used. There will be no manufacturing variance posted as a result of this situation.
• If the Production Quantity is less than the assumed batch size, the Line => Planned Quantity will be less than the Line => Quantity Used. As a result the Production order will post a debit balance to a manufacturing variance expense account. This situation effectively increases your cost of goods sold.
• If the Production Quantity is greater than the assumed batch size, the Line => Planned Quantity will be more than the Line => Quantity Used. As a result the Production order will post a credit balance to a manufacturing variance expense account. This situation effectively decreases your cost of goods sold.

Summary - If any part of this page is unclear, please do not hesitate to let me know via the mailing list or below comments.