What Is a Time Study?

A time study is a structured observation and measurement of the time required to perform specific tasks. In electrical engineering, it is used to break down the process of building circuits—from component placement and soldering to testing and troubleshooting—into discrete elements. The goal is to establish a standard time for each operation, which serves as a benchmark for efficiency, workload planning, and cost estimation. Pioneered by Frederick Winslow Taylor in the late 19th century, time study remains a cornerstone of industrial engineering. For circuit assembly, it helps identify micro-inefficiencies such as reaching for tools, repositioning components, or waiting for solder heat-up, enabling engineers to streamline workflows and reduce assembly time by 15–30%.

Key Techniques for Conducting Time Studies in Circuit Assembly

Process Breakdown (Elemental Analysis)

Dividing the assembly process into small, repeatable tasks—called elements—is critical. For example, a typical PCB assembly might be broken into: pick component, position on board, secure with solder, inspect joint, and clean residue. Each element should have a clear start and end point (e.g., “hand touches component” to “hand releases component”). This granularity allows analysts to pinpoint bottlenecks, such as a long travel distance for a particular part or inconsistent solder-feeding motions.

Direct Observation and Timing

Using a stopwatch or digital timer, an observer records the time for each element across multiple cycles. The continuous timing method (running clock) captures the cumulative time, while snap-back timing zeroes after each element. For circuit assembly, snap-back is often preferred because it isolates task times without cumulative drift. At least 10–20 cycles should be observed to account for variability caused by operator fatigue, component variation, or ambient conditions.

Standardization and Method Sheets

After identifying the fastest, most consistent sequence of movements, a standard method is documented. This includes tool placement, body posture, and component orientation. For instance, placing resistors in a bin by value and using a “cattle-rack” PCB holder can reduce handling time by 0.5 seconds per component. The method sheet becomes the baseline for training and performance evaluation.

Multiple Cycles and Statistical Averaging

To obtain a reliable standard time, data from several cycles (and optionally several operators) are averaged after adjusting for performance rating and allowances. The formula is:

Standard Time = (Observed Time × Performance Rating) + Allowances

Performance rating adjusts for operator pace (e.g., 100% normal, 110% skilled), while allowances cover personal needs (5%), fatigue (4–7%), and unavoidable delays.

Motion Study and Therbligs

Frank and Lillian Gilbreth extended time study with motion study, breaking tasks into 17 fundamental movements called therbligs (e.g., reach, grasp, transport, hold, position). In circuit assembly, the number of therbligs can be reduced by using gravity-fed component feeders, automatic screwdrivers, or clip‑on heat sinks instead of fasteners. A 10% reduction in therblig count often yields a 15% reduction in cycle time.

The Science Behind Time Studies: Methods and Motion Economy

Predetermined Motion Time Systems (PMTS)

Systems like Methods-Time Measurement (MTM) and MOST (Maynard Operation Sequence Technique) provide pre-measured times for basic motions (e.g., reach 20 cm = 0.5 seconds; grasp a small object = 0.3 seconds). For circuit assembly, an MTM analysis can compute a theoretical standard without physical timing: placing a DIP-8 IC takes 4.8 seconds using MTM’s 118 code. This helps design assembly lines before prototypes exist.

Principles of Motion Economy

These ergonomic guidelines reduce wasted effort:

  • Hands should begin and end motion simultaneously – when inserting connectors, use both hands to pre‑align wires.
  • Use momentum whenever possible – place components in a chute so sliding brings the next part to hand.
  • Tools and materials should be within a normal work area – a 40 cm radius for seated assembly minimizes reaching.
  • Use jigs and fixtures to hold the board – eliminates the need to manually stabilize the PCB.

Performance Rating and Normalizing

Operator pace varies. A trained analyst uses Westinghouse rating system (skill, effort, conditions, consistency) to adjust observed times to a “normal” pace. A fast but inconsistent operator might receive a 110% rating for effort but 90% for consistency, yielding an overall 99% rating. This ensures fair standards across different workers.

Application in Electrical Engineering: Specific Circuit Assembly Steps

PCB Through-Hole Assembly

Inserting axial leads into plated through‑holes requires: lead forming, insertion, clinching, and soldering. A time study might reveal that clinching leads in a 45° angle takes 0.8 seconds vs. 1.4 seconds for clinching flat—a 43% improvement. Using an automatic lead former can further reduce the “lead form” element from 2.1 seconds to 0.3 seconds.

Surface-Mount (SMD) Soldering

SMD placement by hand involves: aligning the chip with a microscope, lowering it with tweezers, and reflowing with a hot‑air pencil. A study at a prototype lab showed that “position and tack” for a 0805 resistor averaged 7.2 seconds. By adding a vacuum pickup tool and a stencil, the time dropped to 4.5 seconds. Allowances for eye fatigue (8%) were also factored in.

Wire Harness Assembly

Cutting, stripping, crimping, and inserting contacts into connectors are repetitive. Using an automatic wire stripper and a rotating crimp head can reduce the “strip and crimp” element from 6.8 seconds to 2.3 seconds per wire. A time study also highlights the benefit of pre‑labeling wires to eliminate the “search for correct position” element.

Testing and Debugging

Testing involves: connecting power, probing test points, and comparing readings. Time studies often reveal that test preparation (cable connection, fixture alignment) consumes 44% of test time. Designing a spring‑loaded pogo‑pin test fixture can cut that to 18%.

Modern Tools and Technologies

Video Time Study Software

Tools like UmtPlus, Proplanner Time Study, and iObeya allow recording video of assembly and then analyzing frame by frame. An analyst can mark element boundaries on the timeline and automatically compute times, performance ratings, and statistical control limits. This is especially useful for high‑mix, low‑volume circuit assembly where repeated manual timing is costly.

Lean Manufacturing Integration

Time study data feeds into Value Stream Mapping (VSM) and kaizen events. For electrical assembly, the VSM might show that soldering accounts for only 15% of total lead time, while waiting for inspections accounts for 35%. Time studies help target those waiting elements with parallel processing or inline inspection cameras.

Ergonomic Assessment Tools

Assembly tasks with high repetition (e.g., using a screwdriver hundreds of times) risk hand‑arm vibration syndrome. Time studies combined with RULA (Rapid Upper Limb Assessment) can flag unsafe cycles and suggest tool redesign, such as using a torque‑limited nutrunner.

Benefits Beyond Efficiency: Quality, Training, and Ergonomics

A well‑executed time study in circuit assembly delivers more than speed:

  • Consistency in Quality – standard methods reduce variation. For example, a study by RocketEMS showed that standardizing “solder tip dwell time” (3.5 seconds per joint) reduced cold‑solder defects by 56%.
  • Faster Training Curves – new technicians can compare their times against the standard, identifying which element they need to improve. The standard serves as a clear performance target.
  • Ergonomic Savings – by removing unnecessary motions (e.g., twisting neck to look at a monitor), time studies also reduce cumulative trauma disorders. One case study from a power supply manufacturer saw a 22% drop in shoulder complaints after re‑arranging the workbench based on motion analysis.
  • Cost Reduction – labor cost per board is directly tied to cycle time. A 10% reduction in assembly time on a product with 5,000 units annually saves approximately $12,000 per year (assuming $20/hour labor).

Common Pitfalls and How to Avoid Them

Ignoring Operator Input

If the technician feels they are being spied on, they may work slower or faster than normal, skewing data. Solution: explain the purpose (process improvement, not performance appraisal) and involve operators in the analysis. Let them suggest improvements—they know the micro‑moves best.

Insufficient Sample Size

With less than 10 cycles, the average can be heavily influenced by outliers (e.g., a dropped component). Use statistical limits: calculate the mean and standard deviation, then continue sampling until the confidence interval width is within ±5% of the mean.

Neglecting Allowances

Some analysts use only observed time plus a flat 10% allowance. But for circuit assembly, allowances vary: hand soldering requires more fatigue allowance (9–12%) than machine‑assisted assembly (4–6%). Ignoring this leads to unrealistic standards and worker burnout.

One‑Time Study

Processes evolve—new components, new tools. A time study from six months ago may be obsolete. Perform refresher studies at least annually or whenever a significant change occurs (new solder alloy, new feeder, etc.).

Conclusion

Time study is not merely a paperwork exercise; it is a practical, data‑driven method for continuously improving circuit assembly operations. By breaking down tasks, observing with precision, applying motion economy principles, and using modern software, electrical engineers can achieve measurable gains in productivity, quality, and worker satisfaction. As automation and miniaturization advance, the techniques of time study become even more critical to design assembly processes that are both fast and reliable. Whether you are assembling one‑off prototypes or managing a high‑volume production line, mastering time study will give you a competitive edge in delivering efficient, high‑quality electrical systems.

For further reading and practical guides, see the IISE guide to time study methods, a case study on time & motion in electronics assembly, and MOST system details for predetermined motion times.