A Therblig Is a Basic Motion: Understanding the Building Blocks of Efficient Work
Introduction
In the world of industrial engineering and human factors, a therblig is a basic motion that serves as the fundamental unit for analyzing and improving work processes. First introduced by Frank and Lillian Gilbreth in the early 20th century, therbligs break down every task into simple, observable actions such as “grasp,” “move,” “release,” or “inspect.” By cataloguing these motions, engineers can pinpoint unnecessary movements, reduce fatigue, and boost productivity. This article explores the origins of therbligs, explains each of the 18 standard symbols, demonstrates how they are applied in modern workplaces, and offers practical tips for using therblig analysis to design leaner, safer operations.
The Birth of Therbligs: A Brief History
The term therblig is an anagram of the word “Gilbreth,” with the letters rearranged and a slight alteration to avoid direct naming. Frank B. Gilbreth and his wife Lillian M. Gilbreth pioneered scientific management by focusing on the human element of work. While Frederick Taylor emphasized time studies, the Gilbreths introduced motion study, arguing that the way a worker moves is just as crucial as how long a task takes Simple, but easy to overlook..
In 1917, the Gilbreths published Motion Study: A Method for Increasing the Efficiency of the Hand, presenting a set of 18 basic motions—later called therbligs—each represented by a unique symbol. In real terms, their goal was to give managers a visual language for describing work, enabling systematic elimination of wasteful motions (what we now call muda in lean methodology). Over the decades, therblig analysis has been integrated into ergonomics, time‑and‑motion studies, and even modern digital workflow tools Simple, but easy to overlook..
The 18 Standard Therbligs
Below is a concise reference guide to the 18 classic therbligs. Each symbol consists of a simple geometric shape, making it easy to sketch on a motion‑study chart.
| Symbol | Therblig | Description | Typical Application |
|---|---|---|---|
| ⧈ | Search | Locating an object or information | A worker scanning a shelf for a part |
| ⧈ | Find | Successfully identifying the needed item | Grasping the correct component after searching |
| ⧈ | Select | Choosing among alternatives | Picking the right tool from a set |
| ⧈ | Grasp | Taking hold of an object | Hand closing around a bolt |
| ⧈ | Hold | Maintaining grip while repositioning | Holding a piece while aligning it |
| ⧈ | Transport Empty | Moving without a load | Walking to a workstation |
| ⧈ | Transport Loaded | Moving while carrying an object | Carrying a finished sub‑assembly |
| ⧈ | Position | Placing an object in a specific spot | Aligning a component before fastening |
| ⧈ | Assemble | Joining two or more parts | Screwing a bolt into a hole |
| ⧈ | Use | Operating a tool or machine | Turning a wrench |
| ⧈ | Inspect | Checking quality or correctness | Visual verification of alignment |
| ⧈ | Pre‑Position | Preparing a location for a later action | Setting a jig before machining |
| ⧈ | Release | Letting go of an object | Dropping a part after assembly |
| ⧈ | Rest | Pausing without productive output | Waiting for a machine to cycle |
| ⧈ | Delay | Intentional waiting for a later step | Waiting for a material to cure |
| ⧈ | Plan | Mental preparation for the next move | Deciding the order of tasks |
| ⧈ | Unavoidable Delay | External interruption beyond control | Power outage |
| ⧈ | Hold (Passive) | Passive holding without effort, e.g., a part resting on a support | Part supported by a fixture |
Note: The visual symbols are omitted here for brevity, but in practice each therblig is drawn as a distinct shape on a flow chart.
Why Therbligs Matter in Modern Workplaces
1. Ergonomic Insight
Analyzing motions at the therblig level reveals repetitive strain patterns. Here's a good example: excessive Grasp → Hold → Release cycles can indicate a need for tool redesign or automation to reduce hand fatigue. By redesigning workstations to combine or eliminate certain therbligs, companies can lower the incidence of musculoskeletal disorders (MSDs) Worth keeping that in mind..
2. Lean Manufacturing Alignment
Lean principles focus on eliminating waste. Therbligs give a microscopic view of waste: any Search, Find, or Rest that does not add value is a candidate for removal. Mapping a process with therbligs helps identify non‑value‑added (NVA) motions, which can be streamlined or eliminated through layout changes, better inventory management, or standardized work instructions.
3. Training and Standardization
When new employees learn a task, presenting the sequence of therbligs clarifies expectations. A visual chart showing Plan → Search → Find → Grasp → Transport Loaded → Position → Assemble → Release serves as a concise checklist, reducing learning curves and variation in performance Less friction, more output..
4. Digital Integration
Modern motion‑capture systems (e.g., wearable IMUs or video analytics) can automatically tag motions with therblig categories. This data feeds into dashboards that highlight bottlenecks in real time, enabling rapid Kaizen events.
Conducting a Therblig Analysis: Step‑by‑Step Guide
-
Select the Target Process
Choose a high‑impact operation—such as a workstation that accounts for >15 % of cycle time or has a high injury rate Which is the point.. -
Record the Motion
Use a high‑speed camera or a simple video phone. Capture at least three full cycles to account for variability And that's really what it comes down to.. -
Break Down the Task
Replay the video frame‑by‑frame, assigning each observable action to a therblig. Write the sequence on a therblig sheet with timestamps. -
Classify Value‑Added vs. Non‑Value‑Added
- Value‑Added (VA): Assemble, Use, Inspect (when inspection is required for quality).
- Non‑Value‑Added (NVA): Search, Find, Rest, Delay, Transport Empty, etc.
-
Calculate Percentages
Sum the time spent on each therblig and compute the proportion of total cycle time. This quantifies waste Less friction, more output.. -
Identify Improvement Opportunities
- Combine: Merge Search → Find into a single Select by improving labeling or storage.
- Eliminate: Remove Rest by synchronizing upstream/downstream processes.
- Automate: Replace repetitive Transport Loaded with a conveyor.
-
Redesign the Process
Sketch a new therblig diagram reflecting the proposed changes. Validate with a pilot run. -
Implement and Monitor
After implementation, repeat the motion study to verify reductions in NVA time and confirm ergonomic benefits.
Real‑World Example: Assembly of a Small Electric Motor
Original Therblig Sequence (per unit)
- Plan – 2 s
- Search – 4 s (locate rotor)
- Find – 1 s
- Grasp – 0.5 s
- Transport Loaded – 3 s (walk to bench)
- Position – 1 s
- Assemble – 2 s (insert rotor)
- Inspect – 1 s (visual check)
- Release – 0.3 s
- Rest – 2 s (await next part)
Total cycle time: 17.8 s, with 11.5 s (≈ 65 %) classified as NVA Not complicated — just consistent..
Therblig‑Based Redesign
- Implement a shadow board to eliminate Search and Find (now Select takes 0.5 s).
- Introduce a rotating rack that brings the rotor within arm’s reach, removing Transport Loaded (now Transport Empty of 0.5 s).
- Add a fixture that holds the rotor in the correct orientation, merging Position and Assemble into a single Assemble of 1.5 s.
- Integrate an in‑line sensor that automatically confirms correct insertion, reducing Inspect to 0.2 s.
New sequence: Plan (2 s) → Select (0.5 s) → Grasp (0.5 s) → Transport Empty (0.5 s) → Assemble (1.5 s) → Inspect (0.2 s) → Release (0.3 s) → Rest (0.5 s) = 6.5 s total.
Result: Cycle time reduced by 63 %, NVA motions dropped from 65 % to 25 %, and worker fatigue decreased dramatically.
Frequently Asked Questions
Q1: Are therbligs still relevant in a highly automated factory?
Yes. Even fully automated cells consist of robotic motions that can be mapped to therblig equivalents (e.g., Transport Loaded becomes a robotic arm move). Understanding these motions helps optimize robot paths, reduce cycle time, and prevent collisions.
Q2: How many therbligs should be tracked in a complex process?
All observable motions should be recorded, but focus on those that consume >5 % of total time or appear repeatedly. Over‑granular tracking can obscure major waste Easy to understand, harder to ignore..
Q3: Can therblig analysis be applied to knowledge work?
While originally designed for physical tasks, the concept extends to cognitive steps: Plan (mental preparation), Inspect (review), Delay (waiting for information). Mapping these can uncover bottlenecks in software development or customer service Simple, but easy to overlook..
Q4: What tools assist with therblig documentation?
Traditional paper sheets, spreadsheet templates, and specialized software such as MTM‑UAS or Process Analyzer can capture and visualize therblig data. Modern video‑analysis platforms often include built‑in therblig tagging Less friction, more output..
Q5: Does therblig analysis replace time‑and‑motion studies?
No. Therbligs complement time studies by providing qualitative insight into how time is spent, not just how much. Together they give a complete picture of efficiency.
Benefits Summary
| Benefit | How Therbligs Deliver It |
|---|---|
| Reduced Cycle Time | Eliminate or combine NVA motions |
| Lower Injury Risk | Identify repetitive strain patterns |
| Higher Quality | Standardize Inspect and Plan steps |
| Cost Savings | Decrease labor hours and equipment wear |
| Continuous Improvement | Provide a clear visual language for Kaizen teams |
Conclusion
Understanding that a therblig is a basic motion unlocks a powerful analytical framework for anyone seeking to improve work efficiency, safety, and quality. By dissecting tasks into 18 elemental motions, organizations can see exactly where waste hides, how ergonomics can be enhanced, and where automation offers the greatest return. Whether you are a seasoned industrial engineer, a lean practitioner, or a manager looking to empower frontline workers, mastering therblig analysis equips you with a universal language for designing smarter, healthier, and more productive workplaces. Embrace the therblig mindset, map your motions, and watch your processes transform from a collection of random movements into a symphony of purposeful, value‑adding actions That's the part that actually makes a difference..
