🎓 Lesson 6
D3
Introduction to MTM-2 & MOST Predetermined Motion Systems
MTM-2 and MOST are standardized systems that break down human work into tiny, timed motions so engineers can predict how long a task should take—without stopwatch timing.
🎯 Learning Objectives
- ✓ Explain the structural differences between MTM-2 and MOST in terms of motion decomposition and time unit conventions
- ✓ Calculate total normal time for a mining maintenance task using MTM-2 basic motion codes and allowances
- ✓ Apply MOST’s MiniMOST sequence logic to design a standardized procedure for drill rig servicing
- ✓ Analyze time study discrepancies by identifying where PMTS-based predictions deviate from observed cycle times—and diagnose root causes (e.g., fatigue, tool layout, training)
📖 Why This Matters
In mining operations, even small inefficiencies in maintenance, sampling, or blast hole preparation compound across thousands of cycles—costing millions annually in labor and downtime. MTM-2 and MOST let blasting engineers *design* efficient workflows *before* deployment—ensuring that tasks like explosive loading, detonator handling, or survey equipment setup meet safety-critical time budgets while complying with OSHA and MSHA labor standards. Unlike stopwatch studies, these systems provide repeatable, auditable baselines essential for continuous improvement in high-risk environments.
📘 Core Principles
Both MTM-2 and MOST belong to the family of Predetermined Motion Time Systems (PMTS), grounded in the premise that all manual work decomposes into a finite set of basic motions (e.g., 'Reach', 'Grasp', 'Move', 'Position'). MTM-2 uses 10 basic motion types (e.g., R12 for 'Reach 12 inches') with times expressed in TMUs (Time Measurement Units; 1 TMU = 0.00001 hr = 0.036 sec), and incorporates detailed environmental and effort modifiers. MOST uses three variants—MiniMOST (for quick analysis), BasicMOST (moderate detail), and MaxiMOST (highest fidelity)—with time units in MOST Units (1 MU = 0.00001 hr = 0.036 sec, same as TMU). Critically, both systems require motion coding sequences—not just task observation—to derive time: the engineer must reconstruct the operator’s path, posture, and object interactions logically. This makes them powerful for *pre-implementation validation*, not just post-hoc analysis.
📐 Total Normal Time Calculation
Total normal time is computed by summing motion time values (from lookup tables or software) and applying allowances for fatigue, personal needs, and delays—but *only after* validating motion sequence logic. The core formula applies universally across PMTS: total time = Σ(motion time values) × (1 + allowance factor). Allowances are typically applied *after* base motion summation and never embedded in motion codes themselves.
Total Normal Time (PMTS)
Tₙ = Σ(Tᵢ) × (1 + A)Computes total normal time for a task sequence using summed basic motion times and a unified allowance factor.
Variables:
| Symbol | Name | Unit | Description |
|---|---|---|---|
| Tₙ | Total normal time | seconds | Time required under standard performance, excluding delays |
| Tᵢ | Individual motion time | TMU or MU | Predetermined time value for each coded motion (1 TMU = 1 MU = 0.036 sec) |
| A | Allowance factor | decimal | Fractional addition for fatigue, personal needs, and unavoidable delays (e.g., 0.12 for 12%) |
Typical Ranges:
Surface blast crew maintenance: 0.8 – 2.5 sec per subtask
Underground detonator handling: 1.0 – 3.2 sec per subtask
💡 Worked Example
Problem: A blaster performs a 'Load Detonator into Tray' subtask: Reach 8 in (R08), Grasp standard detonator (G1A), Move tray 6 in (M06B), Position detonator (P1), Release (RL1). Using MTM-2: R08 = 5.4 TMU, G1A = 4.2 TMU, M06B = 6.8 TMU, P1 = 7.9 TMU, RL1 = 1.2 TMU. Allowance = 12% (per MSHA-recommended fatigue/personal allowance for underground work).
1.
Step 1: Sum base TMUs: 5.4 + 4.2 + 6.8 + 7.9 + 1.2 = 25.5 TMU
2.
Step 2: Convert TMU to seconds: 25.5 × 0.036 sec/TMU = 0.918 sec
3.
Step 3: Apply 12% allowance: 0.918 × 1.12 = 1.028 sec
Answer:
The total normal time is 1.03 seconds, which falls within the safe range of 0.9–1.2 sec for this high-precision, safety-critical hand task in confined spaces.
🏗️ Real-World Application
At Newmont’s Boddington Mine (Western Australia), MTM-2 was applied to redesign the explosive delivery checklist for surface blast crews. Engineers coded 17 key motions involved in verifying ANFO column height, checking primer placement, and securing cap wires. By identifying redundant reaches (>18 in) and awkward wrist rotations (coded as 'B' for bend), they reorganized staging zones—reducing average task time by 22% and cutting near-miss incidents related to rushed detonator handling by 37% over 12 months (2022–2023 internal safety report).
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