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Work Breakdown Structures

This article is about how to apply Work Breakdown Structures to engineering development and construction projects.

Before we start

To clarify the terms: the work breakdown structure is also called the project structure plan (PSP). Before the approach or method for creating a work breakdown structure is presented, here are a few points for general classification.

What is a Work Breakdown Structure?

It is a rule-based hierarchical representation of project goals, phases, product components and tasks or actions. A work breakdown structure is used in projects as an aid to structuring project content.

Why do you need a Work Breakdown Structure?

A work breakdown structure is always required when a project takes on a scale and complexity that is no longer easy to survey. This is the case, for example, when many people are working on a project and there are dependencies between the work results. The WBS is the basic skeleton of the project and enables the project team and suppliers to have an objective view of the work steps required in a project or a project section.

Character of the Work Breakdown Structure

A work breakdown structure can have different levels of detail. This depends on the complexity of the respective sub-step. It may also be necessary to revise a WBS during the course of the project -- i.e. expand, change or reduce it. If, for example, the product structure is worked out in a development process in the first phases of the project, it can only be included in the WBS later and the corresponding work steps assigned.

Is my project to small for a Work Breakdown Structure?

The answer is: unlikely. It doesn’t take long to set up a WBS. In principle, at the beginning it is a kind of checklist for project planning (and thus, among other things, an instrument for risk management, here an article regarding risks in projects), which during its creation in most cases leads to work steps that have not yet been considered being recognized and can be taken into account. If this is not the case and the project is structured very simply, then the WBS may be obsolete.

Method of creation

In general, a work breakdown structure can be freely designed. The following classification criteria, which can also be combined with one another, are common:

  • Project phases
  • Sub-tasks or sub-projects
  • Work content
  • Product structure

When mixing the classification criteria, care must be taken not to include duplicate content in the work breakdown structure or the WBS. This can be avoided if only one criterion is used, but this does not make sense for larger projects. There can be sub-tasks where the usage of a different criteria are useful than in the rest of the project.

In development and construction, a WBS should contain information from the following areas:

  • Project target (most common the top node of the WBS)
  • Project phases
  • Product structure
  • Engineering process

The different information from these elements is assigned to the levels of the hierarchy. The number of levels can be freely selected; 4 levels are defined below.

1Product (Overall System)
2Main elements of the product as well as a summary of cross-element processing steps, such as test and validation, project management, data organization
3Sub-elements to level 3, both with regard to the product components and the overarching processing steps
4Work packages for the product elements (alternatively: further breakdown of the product structure, but the lowest level of the WBS should always contain work packages)
Ebenen der Work Breakdown Structure

In individual cases, work packages can already be settled at higher levels -- depending on the complexity of the sub-step.

Example Work Breakdown Structure

A company wants to develop a machine that automatically regrinds punching tools. So far there is no comparable product, but we already have a vague idea of ​​what this grinding machine could look like, i.e. what elements it will essentially consist of. The aim of the project is to develop a prototype and provide proof of functionality. In this case, the work breakdown structure could look like this (the image can be moved with the mouse and the zoom can be changed with the mouse wheel):

Zoom: 1
Grinding Machine 6 Workpiece fixture 7 Tool head 1 Project Management 2 Documentation 3 Control 4 Power Supply 5 Housing 8 Prototype 8.2 Manufacture 8.3 Assemble 8.4 Test 8.4.2 Realization 8.4.1 Definition 4.1 Interfaces 4.2 Engineering 4.3 Integration 5.1 Frame 5.2 Cover 2.3 Engineering Calculations 2.2 Proof of conformity 2.1 Manual 1.5 Requirements Management 1.4 Work Organization 1.4 Data Organization 1.3 Controlling 3.1 Hardware 3.2 Software 7.1 Kinematics 7.2 Design 3.1.1 Concept 3.2.2 Programming 3.2.1 Concept 1.2 Design Reviews 1.1 Process organization 7.1.1 Concept 7.2.2 Engineering Design 7.2.1 Concept 8.1 Procurement of materials 4.1.2 Engineering design 4.1.1 Concept 5.1.2 Engineering design 5.1.1 Concept 5.2.2 Engineering design 5.2.1 Concept 6.2 Engineering design 6.1 Concept 3.1.2 Engineering design 3.2.3 Test

The steps listed here are examples and of course depend on which development steps are typically implemented in a company. On the basis of a well-developed WBS, it is also possible to outsource work to external suppliers, since the interfaces are then already well defined.