Time is the hardest currency in industry. Both REFA and MTM promise reliable time data on predominantly manual work processes for planning, calculation, and control, but they start at very different points. REFA provides a broad range of tools for recording, evaluating, and designing existing processes, while MTM breaks down processes into granular building blocks, making workflows measurable even at the planning stage. This article classifies the two most popular methods of process analysis and optimization, highlights similarities, strengths, and limitations, and provides recommendations on when each method makes more sense.
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The REFA Fachverband e. V. was founded in Berlin in 1924 and is now based in Darmstadt. REFA focuses on methods of work design, business organization, and corporate development.
At the core of REFA is time study. Real processes are described, divided into process sections, measured, and evaluated. The performance of the person being observed is assessed relative to the REFA standard performance; this results in basic times and, with surcharges, the target times for planning and calculation.
This determines the care and accuracy of the study.
The work task, work procedure, and work method used must be specified in detail.
The process is divided into stages and measuring points are defined. The times determined in this way are documented in the REFA time recording sheet.
The measured power is normalized to a reference power, known as the REFA standard performance.
The times determined are checked for statistical validity. If necessary, measurements must be taken again.
of the work process by adding up the target times of the individual process steps.
To this, basic time, recovery times, distribution times, and any other surcharges are added.
The result is the target time per unit, fully documented for planning, calculation, or remuneration.
Like REFA, MTM is both an organization and a method. The MTM method pursues similar goals, but starts earlier. While REFA measures the existing work system, MTM can already be used to plan manual processes.
MTM describes manual work using standardized movement and activity modules. Each module has a standardized time value in TMU (time measurement unit), whereby 1 TMU corresponds to 0.036 seconds. The time values are set so that they can be achieved by an average skilled employee over an entire working day.
Typical building blocks are reaching, grasping, bringing, joining, or releasing; target times are calculated from their time values without a real production line existing.
In practice, there are different system levels: MTM-1 works very finely, while MTM-UAS and MTM-MEK are condensed and therefore significantly faster to use. This allows the analysis effort to be scaled to suit the question at hand without losing reproducibility.
Modern workflows also allow MTM analyses to be derived from VR/motion capture data, resulting in valid planning times even at very early stages.
Both methods provide standardized time data for planning, calculation, and control. Quality is achieved through clear task descriptions and correct application. The difference lies in the approach: REFA evaluates actual performance based on the real process, while MTM generates target times from predefined movement modules.
In practical terms, this means that new launches and variant comparisons benefit from MTM because layouts, cycles, and ergonomics can be evaluated prospectively. Series production, remuneration issues, and audits often require REFA time studies because they are based on actual data and are compatible with collective agreements and works agreements. Many plants use a combination of both: MTM provides the target value, while REFA calibrates and validates during ramp-up and series production.
MTM and REFA are not rivals, but tools for different phases of the same task: REFA measures, MTM models. Depending on the issue at hand, one provides a robust basis for the current situation, the other provides reliable target values. The most effective approach is a combination of the two: MTM for setting goals, REFA for verification in everyday practice.
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