Manual, walking and machine time

Manual, walking and machine time

An operator balance chart totals work, but it can hide when automatic processing overlaps manual activity. A combination table puts those activities on a shared time axis. Distinguish hands-on time, walking and automatic machine time, then trace the actual sequence. Check when the person is free, when a machine requires attention and where waiting occurs. Do not add all machine time to labor content or assume that any apparent overlap is feasible. Safe access, sequence and quality requirements remain binding. Use repeated observations and trial the proposed pattern with the operator before revising the method.

Follow the method

1. Load
2. Automatic cycle
3. Separate manual task
4. Wait / observe
5. Unload

Explain fifty elapsed seconds without losing any work

Fictional machine-and-bench case: loading takes 10 seconds, the automatic cycle then runs for 30 seconds, a separate manual task takes 20 seconds during that cycle, and unloading takes 10 seconds after it ends. Analyst Theo must explain the supplied 50-second arrangement without double-counting overlap.

Follow the method

1. Manual work
2. Automatic process
3. Operator waiting
4. Elapsed sequence
5. Incorrect sum

Thirty automatic seconds are not thirty extra labor seconds

Plot manual work, automatic time and waiting on one timeline, reconcile elapsed and work-content totals, and test whether a proposed overlap is actually permitted.

Fictional machine-and-bench case: loading takes 10 seconds, the automatic cycle then runs for 30 seconds, a separate manual task takes 20 seconds during that cycle, and unloading takes 10 seconds after it ends. Analyst Theo must explain the supplied 50-second arrangement without double-counting overlap.

Role: Process analyst observing with the operator and equipment owner.

Normal condition

No person or machine is assigned incompatible simultaneous work, and access, precedence and quality conditions are respected.

The gap

The draft estimate adds 40 manual seconds and 30 automatic seconds and calls the result a 70-second observed cycle.

• The overlap is hypothetical and permitted only for this teaching calculation.
• Task availability, machine access, walking and repeat-cycle feasibility require real verification.

1. Draw one common clock

   Theo places each activity on its own resource lane using the same zero point and second scale. Loading ends at 10; only then can the machine start its 30-second interval.

   Why: Independent time bars without a shared clock conceal whether work actually overlaps or violates precedence.

   Evidence: Automatic lane runs from 10 to 40, not from zero to 30.

2. Place the separate manual task

   Put the 20-second task from 10 to 30 on the operator lane while the machine runs. Leave the operator’s 30–40 interval visible as waiting.

   Why: The manual task overlaps machine processing but not loading or unloading. It cannot be counted twice or assumed possible during prohibited access.

   Evidence: Operator lane: load 10, separate task 20, wait 10, unload 10 seconds.

3. Reconcile the totals

   Sum manual work as 10 + 20 + 10 = 40 seconds. Automatic time is 30 seconds and elapsed sequence time is 50 seconds. Do not add overlapping resource durations to obtain elapsed time.

   Why: The three totals answer different questions. The ten seconds of waiting remains part of elapsed time but is not manual work content.

   Evidence: Manual 40 sec; automatic 30 sec; waiting 10 sec; elapsed 50 sec.

4. Challenge the assumptions before improving

   Confirm that the separate task is ready at second 10, that the automatic phase requires no operator attendance, and that required walking or checks have not been omitted.

   Why: A combination table can expose an opportunity, but it cannot make an unsafe or unavailable overlap real.

   Evidence: Validation list names access, attendance, task readiness, walking and repeat-cycle checks.

5. Record an observed alternative distinctly

   When a trial supplies different times, redraw the intervals from those observations and compare the full sequence. Retain the original supplied model as a prediction.

   Why: A work-content total alone does not show the repeatable output interval, especially where machine and operator cycles interact across units.

   Evidence: Actual trial timings and operating conditions accompany any proposed standard revision.

The separate task takes longer

In a hypothetical variant the separate task takes 35 seconds, starting at second 10.

It ends at 45, five seconds after the machine. Unloading is then 45–55 if all access assumptions still hold.

There is no operator wait before unloading; the machine instead waits five seconds. The original 50-second sequence no longer applies.

Manual content 55 sec; automatic 30 sec; elapsed 55 sec; machine wait 5 sec.

Run a practice session

Materials

• Timeline grid and separate operator/machine markers
• Original and longer-task cards

1. Declare the lanes · 4 minutes

   Who is doing each activity?

2. Build the 50-second sequence · 8 minutes

   Where are the 20 seconds counted in both lanes?

3. Solve the changed model · 8 minutes

   When can unloading actually begin?

4. Review reality checks · 5 minutes

   Which condition cannot be proven by arithmetic?

Debrief

• Ask why the longer task creates machine rather than operator waiting.
• Do not accept a 70-second elapsed label for the supplied model.

Draw the lanes to scale and check every shared-resource overlap before consulting the answer.

Transfer into the work

Owner: Process engineer with operator and equipment owner

Record: Resource combination table plus observed access, timing and quality conditions

Review: After a controlled timing trial and before standard revision

Evidence: Feasible precedence, complete work content and representative observed sequence timing

Retain the approved method; revise the model from actual evidence and reassess proposed overlap.