Specialized Technique #13: Therblig Analysis to Master Productivity in Fine Assembly (Scenario 2025)

In an industrial ecosystem where machinery OEE (Overall Equipment Effectiveness) has been optimized to near technical limits, residual variability and efficiency losses hide almost exclusively in the human factor.

For industrial engineers and plant managers in high-precision sectors—such as electronics, Tier-1 automotive, or medical devices—the 2025 challenge is clear: traditional timing is dead for short cycles. When cycle time drops below 0.8 minutes, the “snapback” methodology is incapable of capturing process reality.

The only way to reduce cycle times without compromising quality or ergonomics is Forensic Method Engineering: the atomic decomposition of manual work into its 17 (or 18) fundamental motions, known as Therbligs.

This article breaks down the Confidential Technical Report TE-13 from Cronometras, revealing how to transform work measurement through micro-motion segregation and MTM (Methods-Time Measurement) systems use.

The Collapse of Traditional Timing in Micro-mechanics

Attempting to optimize a fine assembly line with a stopwatch and a pace rating table (Performance) is technical negligence in the current scenario.

Analyst Physiological Limitations

The human eye has a critical perception latency. It is physically impossible for an analyst to consistently capture time intervals of less than 0.04 minutes (2.4 seconds). In fine assembly, where a “Grasp” motion can last milliseconds, conventional timing introduces an unacceptable statistical error.

Fine Assembly Technical Definition

To apply Technique #13, we define the work environment under the following critical conditions:

• High Repetitiveness: Short cycles (< 0.8 min).
• High Visual Load: Constant focus needed.
• Micro-mechanics: Handling components with dimensions < 10mm.

The Subjectivity Risk (Rating)

Without a Predetermined Time System (PTS) like MTM-1 or MOST, valuate “Performance” or “Pace” in high-skill tasks becomes subjective. An operator may appear fast by moving hands quickly but generating technical waste. Technique TE-13 eliminates this subjectivity: standard time is a function of the method, not apparent speed.

Anatomy of Technique #13: Efficient vs. Inefficient Therblig Segregation

Frank and Lillian Gilbreth’s concept is not ancient history; it is the fundamental basis of Cobot programming and current MTM standards. Technique #13 relies on a relentless binary classification of motions:

1. Value Therbligs (Advancement)

Are the only ones the customer is willing to pay for, as they physically transform the product or advance the operation:

• Grasp (G): Take control of the object.
• Assemble (A): Join two parts.
• Use (U): Manipulate a tool.

2. Waste Therbligs (Fatigue)

Do not add value to the product, only add time and ergonomic load to the operator:

• Search (Sh) and Select (St).
• Hold (H).
• Inspect (I) (unless it is a defined critical quality operation).

Mathematical Objective: Maximize Value Therblig density within total Cycle Time, driving Waste Therbligs to zero.

[Suggested Visual Element: Pie Chart comparing “Cycle Time Distribution: Value Added vs. Inefficient Therbligs (Before and After)“]

The 3 Cycle Time “Vampires” in Fine Assembly (Field Data)

According to data analysis from report TE-13, 40% of time in non-optimized lines is lost in three critical inefficiencies.

1. The Hidden Cost of Search (Sh) and Select (St)

• Root Cause: Chaotic arrangement of bulk materials and lack of gravity feeding.
• Cognitive Impact: These are “Mental Therbligs”. They increase cognitive load and visual fatigue, penalized by OHS Law and new psychosocial risk regulations.
• Technical Solution: Apply the Fixed Location Principle. The part should never be “searched for”; it must appear at an exact point (vibratory or gravity feeders). If the eye has to travel to find the part, the method is incorrect.

2. Position (P) and Tolerance Penalty

In MTM systems, not all positionings are equal.

• MTM Data: There is a difference of up to 5.6 TMU (Time Measurement Units) between a Class 1 positioning (loose/no pressure) and a Class 3 (exact fit/pressure).
• Tooling Engineering: The methods engineer must collaborate with tooling design to implement conical guides and physical Poka-yokes. The goal is to reduce motion “Class”, allowing fluid assembly without need for precise visual alignment.

3. Hold (H): Maximum Inefficiency

• Technical Verdict: “The human hand is a high-complexity assembly tool, not a bench vise”.
• Correction: Any instance of Hold (left hand holding base part while right works) is a 50% inefficiency in limb usage. Implementing quick-action fixtures is mandatory to free both hands and allow a balanced Simo-Chart.

”Cronometras Std.” Measurement Methodology (Step by Step)

To audit and correct these micro-motions, we don’t use stopwatches, we use imaging technology.

1. High Speed Capture: Video recording at minimum 60 fps to “freeze” micro-motion and analyze frame by frame.
2. Simo-Chart (Simultaneous Motion Cycle Chart):
   • Y-Axis: Time (expressed in TMU or ten-thousandths of an hour).
   • X-Axis: Left Hand vs. Right Hand Activity.
3. Imbalance Detection: Visual analysis allows identifying gaps.
   • Technical Example: If RH performs Assemble (A) and LH is in Hold (H) or Wait (UD), we have a flagrant imbalance that must be corrected by redistributing workload or improving tooling.

[Suggested Visual Element: Simo-Chart fragment showing RH/LH imbalance and its correction via fixture]

Regulatory Framework and Ergonomics (Spain 2025)

Justifying standard times in 2025 requires solid regulatory backing, especially before works councils and safety audits.

• UNE-EN ISO 11228-3: This standard regulates handling of light loads at high frequency. Therblig analysis is documentary proof to validate that motion frequency is not injurious.
• Standard Justification: By basing standard time on MTM and Therbligs, discussion shifts from “operator speed” (subjective) to “work method” (objective).
• Allowances Reduction: By eliminating fatigue Therbligs (Bend, Body turn, Static hold), rest coefficients (fatigue allowances) can representatively be adjusted downwards legitimately, resulting in a more competitive but less arduous standard for the worker.

Cronometras Technical Solution: Plant Implementation

For plants seeking to adopt Technique #13, we propose the following consultative workflow:

Step 1: Micro-motion Audit

Mapping potentially Type II (Delays) and III (Mental Elements) Therbligs via video analysis at bottleneck stations.

Step 2: MTM-1 Normalization

Converting observed times to predetermined times. This eliminates operator variability and establishes a base time founded on human motion physics.

Step 3: Job Redesign (Micro Layout)

Moving Grasp (G) zones closer to the Normal Work Zone (35-40cm radius from elbow). The goal is minimizing classes C and D of Reach (RE) and Move (M) motions, which consume most time and generate most shoulder fatigue.

Expected ROI: Experience dictates an 8-12% cycle time reduction solely by eliminating Search and Select, without requiring massive automation investments.

Conclusion: Precision Methods Engineering

In the 2025 industrial scenario, we cannot afford to pay wages for motions that do not transform the product. Specialized Technique #13 is not just a measurement tool; it is an efficiency philosophy integrating technical productivity and occupational health.

Fine assembly requires precision, and precision requires data. Stop timing waste and start designing value.

[Suggested Visual Element: Infographic of 17 Therbligs with their standard symbols, categorized into Efficient and Inefficient]

Is your plant losing efficiency in micro-motions invisible to the human eye? Request a micro-motion audit with MTM and Technique #13 specialists from Cronometras today.

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