Bill of Materials Rollups 101 using OpenBOM
By: Openbom, Openbom.Com
Tags: Bill Of Materials, Manufacturing, Bom Cost, Hardware

When it comes to Bill of Materials, roll-ups are super important. Because roll-up calculations allow you getting an assessment about cost, weight, or other key data.

There are multiple roll-up features available in OpenBOM and we’ve been doing many improvements. We’re not done by any means. Today, I want to give you a systematic view on OpenBOM roll-up system.

OpenBOM can do single level and multi-level roll-ups.

Single level roll-up

The first one is simple — just a sum of values in any columns. It can be easily applied and controlled by the “Total” function in BOM.

Any property can be totaled by using “Enable rollup totals”:

The results are the total values displayed in BOM:

The calculation is based on the formula in the total cell. Technically you can edit it if needed:

Multi-level roll-ups are designed to help you sum value from multiple levels.

OpenBOM is automatically organizing data in hierarchical relationships based on Part Numbers. Read more about it here.

OpenBOM has 2 types of multi-level roll-ups: 1. quantity embedded roll-up; 2. custom value roll-up. Let’s talk about quantity roll-up first, because it is easier.

Quantity roll-up — flattened BOM

Quantity roll-up is embedded in OpenBOM and becomes available via Quantity property and Flattened BOM function.

To make quantity roll-up calculation you need to use “Quantity” property in your BOMs. It is the default one and is also used by all OpenBOM CAD integrations.

Check this video for a detailed explanation:

Multi-level roll-up

Multi-level roll-up is a mechanism that allows you to roll-up any custom property (eg. Cost, Mass, etc.). It is totally flexible but requires applying some rules and creating a custom property for roll-up values.

Sometimes it can cause confusion. For example, the fact of having “cost” property, won’t automatically roll-up it because you will need to create Total cost (property) to collect values between levels and Quantity property to multiply it.

The following picture should “fix” it for you. Here is an example of multi-level and how it is calculated:

OpenBOM calculates roll-up of specific property (eg. Cost, Mass) bottom-up and places roll-up for each level on the upper-level BOM. You can see it in the picture above the cost of screw, wheel, and axle (3.2+4.8+2) is combined and placed in the Cost property for Axle assembly (SK1–102). This value (10) is used in the next calculation where it was multiplied with Quantity (2) and combined with cost of screw and board on the top level.

The following video demonstrates the step by step process of creating a multi-level roll-up:

More information about formulas are rollups is available in our online help — Formulas, Totals, and Rollups.

Conclusion

OpenBOM provides a flexible and robust mechanism for roll-up calculation. It is your ultimate roll-up machine. You can easily get totals but the biggest value of OpenBOM are total values between levels while taking into account quantities and assembly-component relationships.

To learn more and experiment with some of the roll-up features, register at OpenBOM.

Best, Oleg

P.S. Let’s get to know each other better. If you live in the Greater Boston area, I invite you for a coffee together (coffee is on me). If not nearby, let’s have a virtual coffee session — I will figure out how to send you a real coffee.

Want to learn more about PLM? Check out my Beyond PLM blog and PLM Book website.