Production management, as we know, has been a hot topic within our industry for some time now. And we’ve looked at it from just about every angle. No doubt. But what about the actual visual output of our management systems? What visual tools are available to ensure good production and how do we affirm the approach?

Work Sampling Analysis

When it comes to gathering data, Work Sampling Analysis (WSA) is often used to measure production effectiveness and it is the most accurate process available to gauge labor utilization. With this methodology, data is collected by analysts who observe workers at varying times and locations with the intent to determine work efficiency. How are the workers spending their time? Are they being productive, doing support tasks, non-productive work, or idle? These observations are then cataloged into three main categories with productive/direct work being the category most necessary for completion:

• Productive work (direct work or time on tools)
• Supportive work (transport, travel and instruction)
• Idle time (personal and idle)

Production Management Systems in Building Construction

As we know, the Last Planner© concept of Lean construction improves construction outcomes utilizing CPM or other methods of time management to ensure project delivery meets contract requirements. And Takt production within Lean construction is growing and gaining momentum as IGLC now lists 84 papers with “takt” as a keyword through 2022. Even Shingo points out in his works on balanced production that “there is a proper balance between capacity and load,” making Takt production a central feature in the Toyota production system [1]. Why is Takt gaining so much momentum within our industry?

Takt Production Methods

In a nutshell, Takt production utilizes a stable pace of sequential trade work through work zones as the foundation for balancing customer needs with available production time and capacity. Common representations of Takt production include:

• Line of Balance (LOB)
• Flowline Scheduling
• Short Interval Production Scheduling (SIPS)
• Takt Production Matrix (TPM) Methods

We will be focusing specifically on how TPM methods relate to direct work and flow efficiency. The TPM visual output software utilized in the discussion presented here is a software implementation called the Clear Flow Matrix© (CFMx).

Takt Production Matrix

In the CFMx TPM example below, work zones (areas) are represented by rows labeled in the first column and ordered in the logical work sequence (path of construction) throughout the project. The trades (may be multi-trade teams) are then listed and labeled in logical trade sequence across the columns. The two axes in the CFMx TPM align with Shingo’s ideas expressed in the Toyota production system that the two flows in production (operations and process) should be displayed orthogonally [1].

As you can see, each TPM cell represents work for the respective zone/trade during a Takt period that often measures one week in duration for substantial projects. Production progress then advances with time in logical trade/zone sequence from the first Takt/zone/trade cell at the upper left to project completion at the lower right.

The diagonal link of TPM cells highlighted below represents planned or actual progress of trade/zone work for that takt period, while the time sequence of linked cells represents production progress that balances the completion date with the production capacity of the crew. This time-sequence of trade/zone work is the balanced production front (BPF) of crew work that follows the planned trade sequence and physical path of construction through zones. Any work off the BPF does not increase overall throughput but does increase work in process (WIP) without contributing to throughput.

Work zone throughput time (each row below) is measured in Takt periods by the number of trade steps (column count). Similarly, total throughput time (in Takt periods) for the entire TPM is clearly visible as the number of work zones, plus the number of trade steps, less 1, and is equal to the duration derived from the appropriate form of Little’s Law for this Takt production application. During construction trades, managers and customers may plan and track production using this same TPM information.

CFMx WSA Field Studies Verify Improved Direct Work

As a means of validating the effectiveness of TPM methods, CFMx software was applied to three building construction projects in 2018 and WSA data was collected by construction management students from the University of Texas at Austin [2]. For those of you who may not know, CFMx is a software solution that provides a clearer, more condensed view of production trade flow through work zones that has proven to establish and maintain efficient workflow through consistent zone/trade handoffs.

As you can see in the above stacked column chart, the consistent workflow and trade/zone exchanges achieved by the CFMx TPM method provide impressive direct work ratios averaging 51% across three varying project types (multifamily, school and hospital), which cataloged some 12,000 observations to generate the data for the study [2].

When it comes to construction industry direct work, recent IGLC research reveals a concerning downward trend in direct work decreasing by about 2.5% each decade in the period of 1972-2018, ultimately falling from 50% to below 40%, as shown in the chart below [3]. The authors of the meta-analysis of published direct work data suggested a direct work baseline of 30 - 40% +/- 10% for system comparison purposes.

What does this tell us? TPM methods like CFMx may improve labor effectiveness by reducing nonproductive work through improved flow efficiency demonstrated by the CFMx direct work data of 51% [2], which is an improvement over the direct work baseline of 30-40% suggested in [3].

TPM Improves Flow Efficiency

Flow efficiency relates to the capacity of any balanced production management system to streamline processes to improve labor utilization and increase direct work. So, the 50% direct work ratio achieved on the CFMx TPM projects shows that TPM methods can lead to improved flow efficiency. We therefore conclude that the use of a TPM provides project teams with a simple, efficient, and consistent visual management tool for improved flow balancing production to meet customer demand.

REFERENCES

[1] Shingo, S. and Dillon, A.P., (1989) A Study of the Toyota Production System: From an Industrial Engineering Viewpoint. CRC Press, Boca Raton.

[2] Tiezzi, Augusto Vitorio, (2018) A study of the effectiveness of the Clear Flow Matrix in building construction projects, MS Thesis, University of Texas at Austin.

[3] Wandahl, S., Neve, H. H., and Lerche, J., (2021) What a Waste of Time, Proc. 29th Annual Conference of the International Group for Lean Construction (IGLC29), Alarcon, L.F. and González, V.A. (eds.), Lima, Peru, pp. 157–166, doi.org/10.24928/2021/0115, online at iglc.net.