MMAW NC II common mistakes
MMAW NC II · Understand the traps and how to avoid them.
Treating 5S as a one-time cleanup and answering that the final step (Shitsuke/sustain) means 'finish the cleaning', rather than describing a recurring audit, visual-standard, and habit-reinforcement routine.
Many candidates learn 5S from posters that list only the five Japanese words, so they memorize the sequence but never learn that sorting uses red-tagging, set-in-order uses floor marking and shadow boards, and sustain is a management system with scheduled audits.
What to do instead
Study 5S as five separate tools: Seiri = red-tag area with disposition dates; Seiton = address/label system, floor tape, shadow boards; Seiso = cleaning as inspection with a checklist; Seiketsu = written visual standards and photos; Shitsuke = audit schedule, assigned owners, corrective-action log. When a question asks 'what happens next', pick the option that creates a repeatable routine, not a one-off action.
Reading a drawing's dimensions off the printed picture instead of the stated values, and ignoring the title block, revision block, projection symbol, and general tolerance note.
Candidates who have only seen drawings on a screen or in training handouts assume the drawing is to scale, and they skip the title block because it looks like boilerplate.
What to do instead
Drill a fixed reading order on every drawing: title block (part number, material, scale, units) → revision block (compare against the work order revision) → projection symbol (first vs third angle) → general tolerance note → datum callouts → dimension values. State explicitly in your answer that dimensions govern, never scale, and that a revision mismatch means stop and query.
Using a caliper or micrometer without checking zero, without considering the vernier/graduation resolution, and without applying the correct reading technique (parallel jaws, ratchet stop, no excessive force).
Candidates conflate the instrument's resolution with its accuracy, and they practice reading scales only on clean, round numbers, so they freeze when the thimble falls between graduations.
What to do instead
Build a routine: wipe measuring faces, close jaws/anvils and confirm zero (note any zero error and its sign), select the instrument whose resolution is about one-tenth of the tolerance, apply the ratchet or friction thimble, then read main scale plus thimble/vernier and record with the correct number of decimals. Practice between-graduation readings and zero-error correction until they are automatic.
Choosing a multimeter function and range by habit - leaving the leads in the current jacks when measuring voltage, or measuring resistance on a live circuit.
Candidates memorize 'black on COM, red on V' but never internalize that the current path is a near short circuit through the meter, or that an ohmmeter injects its own current and needs an isolated component.
What to do instead
Adopt a pre-measurement checklist: identify the quantity (V, A, Ω, continuity), move the red lead to the matching jack, select the highest range or auto-range, verify the meter on a known source, then probe. For resistance and continuity, isolate and de-energize the component and confirm no parallel path. Practice the failure consequence: leads in the A jack across a supply blows the meter fuse or trips the circuit.
Describing a pneumatic or hydraulic circuit from its symbols without distinguishing a 5/2 from a 3/2 valve, or confusing a flow control with a pressure regulator, so the described actuator motion is wrong.
Candidates learn symbol shapes separately from circuit function, so they can name a component but cannot trace which port is pressurized in each valve position or explain meter-in versus meter-out speed control.
What to do instead
For every circuit question, redraw the valve as boxes with arrows and trace the flow path for the energized and de-energized states, stating which port exhausts. Learn the standard distinctions: number of boxes = positions, number of ports = ways, spring return vs double solenoid, and that a flow control throttles flow (speed) while a regulator limits pressure (force). Confirm with the actuator: extend, hold, retract.
Wiring a sensor to a PLC input without matching the sensor's output type (PNP sourcing vs NPN sinking) to the input card's common configuration, and without checking the load current.
Candidates treat all discrete inputs as interchangeable and have not traced the actual current path through the input opto-isolator for sinking versus sourcing arrangements.
What to do instead
Before wiring, write down three facts: sensor output type, input module common (sink/source, shared common or shared supply), and sensor load current versus input rating. Trace the current path from supply through the sensor output transistor, through the input terminal, through the opto-isolator, and back to the opposite rail. If the types mismatch, specify an interface relay or the correct module variant rather than 'just wire it'.
Troubleshooting a PLC-controlled machine by rewriting or editing the program first, instead of verifying inputs and outputs and using the program's monitoring/forcing functions to localize the fault.
Candidates equate 'the machine misbehaves' with 'the logic is wrong', and they are more comfortable editing ladder than reading field devices, so they change code and lose the original state.
What to do instead
Follow a fixed sequence: confirm the symptom and safety state → check supply, breakers, and the PLC run/fault indicators → monitor the relevant rung and compare actual input states with expected → check the output device and its driver circuit → only then examine logic. Never edit or force without recording the original program and getting authorization; remove all forces before returning the machine to service.
Answering alignment questions with 'tighten it until it runs smoothly' rather than naming the measurement method (dial indicator, feeler gauge, laser alignment), the tolerance, and the correction (shimming, soft-foot removal).
Candidates know alignment matters but have not learned the procedure, so they describe outcomes instead of the measurable steps that produce them.
What to do instead
Learn alignment as a measurement loop: check for soft foot first, mount the dial indicator or laser system, take readings at defined positions (0/90/180/270 or the tool's specified points), compare against the manufacturer's tolerance, then correct with shims or adjustment and re-measure. State the tolerance and the re-check in your answer; 'runs smoothly' is never the criterion.
Jumping to a component replacement during fault diagnosis without first reproducing the fault, gathering evidence, and forming a testable hypothesis.
Candidates under time pressure equate action with competence, and they have not practiced a structured diagnostic method, so they substitute parts and hope the symptom disappears.
What to do instead
Use a documented loop: observe and record the symptom and conditions → gather information (drawings, error codes, maintenance history) → form a hypothesis → test the hypothesis at the cheapest, safest point → confirm the root cause → repair → verify by re-running the original condition and recording the result. In written answers, show the sequence and the evidence at each step; a named root cause beats a list of swapped parts.
Treating lockout/tagout and pre-commissioning safety checks as a formality to mention once, and omitting the isolation, verification, and restoration steps when describing a task.
Candidates memorize hazard categories for recall questions but do not apply them to procedural scenarios, and they assume de-energizing a switch removes all stored energy.
What to do instead
For any scenario involving intervention, write the full sequence: identify all energy sources (electrical, pneumatic, hydraulic, gravitational, stored capacitive/spring) → isolate → lock and tag → release or block stored energy → verify zero energy by test → perform work → remove tools and personnel → restore guards and energy → notify and functionally test. In pneumatic and hydraulic answers, explicitly mention bleeding residual pressure and blocking suspended loads.