π Lesson 3
D2
Cycle Time, Takt Time, and Lead Time: When to Use Which
Cycle time is how long one worker or machine takes to finish one complete task; takt time is how fast you *must* work to match customer demand; lead time is the total time from when a job starts until itβs fully delivered.
π― Learning Objectives
- β Calculate cycle time for drilling, loading, and stemming operations using field timing data
- β Determine takt time for a given monthly ore production target and available shift hours
- β Analyze lead time components in a surface blast sequence to identify non-value-added delays
- β Explain the operational consequences of mismatched cycle and takt times in a multi-shift blasting schedule
- β Apply lead time decomposition to prioritize improvement actions using value-stream mapping principles
π Why This Matters
In mining/blasting operations, confusing cycle time, takt time, and lead time leads to chronic overburdening of drill rigs, misaligned shift handovers, unsafe rush-loading practices, and missed production commitments. For example, if your drill rigβs cycle time is 18 minutes per hole but takt time requires 15 minutes to sustain ore delivery, youβll accumulate backlog β forcing overtime, compromising stemming quality, or triggering unplanned blast delays. Understanding which metric governs *what* β capacity, pacing, or end-to-end accountability β is foundational to labor efficiency, safety compliance, and reliable mine planning.
π Core Principles
Cycle time is an *observed, physical measure* of process capability β rooted in equipment performance, crew skill, and geotechnical conditions. Takt time is a *demand-driven constraint*, derived from business requirements (e.g., mill feed rate) and calendar availability (shifts, maintenance windows, weather). Lead time is a *system-level metric*, spanning functional boundaries: it includes engineering (design review), procurement (explosive delivery), execution (drilling β loading β firing β muck-up), and verification (fragmentation analysis). Critically, takt time sets the 'heartbeat' of the operation; cycle times must be β€ takt time *at every critical path step* to avoid bottlenecks; lead time reveals where systemic waste (e.g., 4-hour wait for blast permit sign-off) erodes responsiveness.
π Key Calculations
Three distinct formulas apply β each with different purposes and units. Cycle time is measured directly or averaged across repetitions. Takt time is calculated from demand and time availability. Lead time is summed across sequential and parallel process stages, including waits. Using them interchangeably causes planning failures β e.g., optimizing drill cycle time while ignoring 2-day explosive logistics lead time yields no throughput gain.
π‘ Worked Example
Problem: A surface copper mine targets 1.2 million tonnes/month of run-of-mine ore. The crushing plant operates 20 days/month, two 10.5-hour shifts/day (21 hrs/day total), with 92% equipment availability. Blasting supplies 100% of plant feed. Calculate takt time per blast round (assuming each round produces 12,000 tonnes).
1.
Step 1: Compute available production time = 20 days Γ 21 hrs/day Γ 0.92 = 386.4 hrs = 23,184 minutes
2.
Step 2: Determine required blast rounds/month = 1,200,000 t Γ· 12,000 t/round = 100 rounds
3.
Step 3: Takt time = 23,184 min Γ· 100 rounds = 231.84 minutes/round β 3h 52min per round
Answer:
The takt time is 232 minutes per blast round. This means the *entire sequence* β from blast design finalization to verified muck-up completion β must average β€232 min to sustain demand. If current lead time is 42 hours, the gap reveals major opportunities for improvement.
ποΈ Real-World Application
At Newmontβs Boddington Mine (Western Australia), a 2022 labor efficiency review found drill cycle time averaged 14.2 min/hole (within spec), but blast lead time averaged 58 hours due to sequential approvals: 8h for geotech sign-off, 16h for explosives logistics, 12h for safety committee review, and 22h for superintendent authorization. Though takt time was 210 minutes/round, the team redesigned the workflow using parallel approvals and digital sign-offs β reducing lead time to 19 hours without changing cycle time. This enabled a 30% increase in weekly blast frequency and eliminated weekend overtime.
π§ Interactive Calculator
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