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newSchoolWorks.com › VoTechWorks › Manufacturing & Marine › Industrial Maintenance › Certification Exam Preparation: NCCER Industrial Maintenance & MSSC CPT › Lesson 3
MFG-INDU16-10 · Lesson 3 · 28 clock hours · practice

Targeted Domain Review: Electrical, PLC, Predictive Maintenance & MSSC Quality/Production Modules

Objective. After instructor-led review and timed drill covering electrical fundamentals, PLC ladder logic interpretation, predictive maintenance technologies, MSSC CPT Quality Practices & Measurement, and MSSC CPT Manufacturing Processes & Production, the learner will score 75% or higher on each domain practice set.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed engineer or certified journey-level tradesperson or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

Why This Session Matters

You are now close to sitting the NCCER Industrial Maintenance credential exam and the MSSC Certified Production Technician (CPT) assessments. Both credentials test you across several domains in a timed, multiple-choice format. Research into trade exam performance consistently shows that learners who practice domain by domain — drilling each topic until they hit the pass mark before moving on — outperform learners who only review broadly. Today's session uses exactly that strategy across four domains: Electrical & PLC, Predictive Maintenance, MSSC Quality Practices & Measurement, and MSSC Manufacturing Processes & Production.

Domain 1: Electrical Fundamentals and Motor Control

Ohm's Law ties voltage (V), current (I), and resistance (R) together: V = IR. Power in a DC or single-phase AC circuit is P = VI. In a three-phase system, total power is P = √3 × VL × IL × PF, where VL is line voltage, IL is line current, and PF is power factor. Exam problems will give you two of the three Ohm's Law variables and ask for the third, or ask you to identify why a fuse rating must be recalculated when a motor load changes.

NEC wiring diagrams use standardized symbols. On the exam, expect to identify a normally open (NO) contact, a normally closed (NC) contact, a coil, a fuse, and a disconnect. Motor control circuits add a starter coil, overload relay contacts, and a holding contact. Three-phase concepts tested include the difference between wye and delta connections, how to identify a phase-to-phase versus phase-to-ground fault from a voltage reading, and the purpose of a motor overload relay.

Safety note: Electrical work in industrial settings falls under NFPA 70E arc-flash requirements. Before any live troubleshooting, a qualified person must perform an arc-flash hazard analysis, and the correct arc-flash PPE (face shield rated for the incident energy, arc-rated clothing, and insulated gloves) must be worn. Lockout/tagout (LOTO) per OSHA 29 CFR 1910.147 is required before any work on de-energized equipment. On the exam, questions about PPE selection and LOTO sequence are common.

Domain 2: PLC Ladder Logic

A PLC executes its program in a continuous scan cycle: read inputs → execute logic → update outputs → housekeeping, then repeat. Input addresses reference field devices (sensors, pushbuttons); output addresses reference actuators (coils, solenoids, motor starters). A normally open (NO) contact passes power when its associated bit is ON (1); a normally closed (NC) contact passes power when its bit is OFF (0).

Timer rungs most commonly use the TON (timer on-delay) instruction. When the rung goes TRUE, the timer accumulates time; when the accumulated value reaches the preset, the timer's done bit energizes. Counter rungs (CTU — count up) increment each time the rung transitions from FALSE to TRUE. For fault-finding from a ladder printout, trace the rung left to right: find the first contact that is open (not passing power) when you expect it to be closed, then go to the field device at that address.

Domain 3: Predictive Maintenance Technologies

Predictive maintenance (PdM) detects failure trends before breakdown occurs, avoiding unplanned downtime. The four technologies most heavily tested in NCCER are:

On scenario-card exercises, assign the technology by matching the fault type to the technology's detection mechanism — do not guess by elimination.

Domain 4: MSSC Quality Practices & Measurement

Statistical Process Control (SPC) uses control charts to distinguish common-cause variation (normal) from special-cause variation (a signal that something changed). On a standard X-bar chart, out-of-control rules include: one point beyond a control limit; a run of consecutive points on the same side of the centerline; or a trend of consecutive points moving in one direction. The exam will show you a plotted chart and ask you to identify whether the process is in control and, if not, which rule is violated.

GD&T (Geometric Dimensioning and Tolerancing) symbols appear on engineering drawings. Basic symbols tested include flatness, circularity, perpendicularity, and true position. Measuring tools: a vernier or digital caliper measures outside diameter, inside diameter, and depth; an outside micrometer measures outside diameter with greater precision; a CMM (coordinate measuring machine) measures complex geometry automatically from a programmed routine.

5S (Sort, Set in Order, Shine, Standardize, Sustain) is a lean foundation tool. Lean's eight wastes (transportation, inventory, motion, waiting, overproduction, over-processing, defects, and unused talent — sometimes taught as seven) appear in manufacturing process questions. Identify waste types by the scenario description, not by memory of a list.

Scoring and Re-Drill Protocol

After each timed drill, update your Domain Tracker immediately. If your score is below 75% on any domain, you complete a 20-item re-drill in the same session before the class moves to the next topic. Your instructor will initial your completed re-drill. The pass mark for this lesson is 75% on each domain practice set or a documented successful re-drill — no exceptions, because the actual credential exams do not offer second chances on exam day.

Key terms10

Ohm's LawThe relationship V = IR, stating that voltage across a conductor equals current through it multiplied by its resistance; the foundation of electrical circuit calculations.
Scan CycleThe repeating sequence a PLC executes: read all input states, solve all logic rungs, update all outputs, then perform housekeeping before starting again.
TON (Timer On-Delay)A PLC timer instruction that begins accumulating time when its rung goes TRUE and energizes its done bit when the accumulated value reaches the preset value.
FFT (Fast Fourier Transform)A mathematical process used in vibration analysis to convert a time-domain vibration signal into a frequency spectrum, revealing individual fault frequencies.
Infrared ThermographyA PdM technique using a thermal camera to detect surface temperature anomalies caused by high-resistance connections, overloaded components, bearing faults, or steam trap failures.
SPC Control ChartA run chart with a centerline and statistically calculated upper and lower control limits used to distinguish common-cause variation from special-cause signals in a process.
GD&T (Geometric Dimensioning and Tolerancing)An engineering drawing language using standardized symbols to define the permissible variation in form, orientation, location, and runout of part features.
5SA lean workplace organization method with five steps — Sort, Set in Order, Shine, Standardize, Sustain — used to improve safety, quality, and efficiency.
Lockout/Tagout (LOTO)An OSHA-required procedure (29 CFR 1910.147) for controlling hazardous energy by isolating and de-energizing equipment before maintenance, then applying a lock and tag to prevent re-energization.
Oil AnalysisA PdM technique that tests a lubricant sample for viscosity, water content, particle count, and wear metals to detect internal component wear or contamination before failure.

Worked examples4

1. A 120 V single-phase circuit feeds a resistive heating element. The measured current is 8 A. Calculate the resistance of the element and the power it consumes.
  1. Step 1 — Find resistance using Ohm's Law: R = V ÷ I = 120 V ÷ 8 A = 15 Ω.
  2. Step 2 — Find power using the power formula: P = V × I = 120 V × 8 A = 960 W.
  3. Step 3 — Confirm with the alternate power formula: P = I² × R = (8)² × 15 = 64 × 15 = 960 W. Both methods agree.
Answer: Resistance = 15 Ω; Power = 960 W.
2. A TON timer rung in a PLC has a preset of 5 seconds (PT = 5 s, time base 1 ms, so preset register = 5000). The rung has been continuously TRUE for 3 seconds. State the accumulated value, whether the done (Q) bit is ON, and what will happen next.
  1. Step 1 — Determine the accumulated value: the rung has been TRUE for 3 s = 3000 ms, so the accumulated value = 3000 (in 1 ms increments).
  2. Step 2 — Compare accumulated to preset: 3000 < 5000, so the preset has not been reached.
  3. Step 3 — State the done bit status: the done (Q) bit is OFF because the accumulated value has not reached the preset.
  4. Step 4 — State what happens next: the timer will continue counting. When the accumulated value reaches 5000 (at the 5-second mark), the done bit will turn ON, energizing any output coil controlled by that done contact.
Answer: Accumulated value = 3000; done bit is OFF; the timer will energize the done bit at 5 seconds.
3. A micrometer reading shows the sleeve scale at 0.275 in and the thimble scale adds 0.013 in. What is the measured outside diameter?
  1. Step 1 — Read the sleeve (barrel) scale: the last visible line past the reference line reads 0.275 in.
  2. Step 2 — Read the thimble scale: the thimble line aligned with the sleeve centerline reads 0.013 in.
  3. Step 3 — Add both readings: 0.275 in + 0.013 in = 0.288 in.
Answer: Outside diameter = 0.288 in.
4. On an SPC X-bar control chart, the centerline is 50.0 mm, the upper control limit (UCL) is 52.5 mm, and the lower control limit (LCL) is 47.5 mm. The last nine consecutive plotted points are all above the centerline but below the UCL. Is the process in control? Identify the applicable out-of-control rule.
  1. Step 1 — Check for points beyond a control limit: all nine points are below 52.5 mm (UCL), so no point is outside the limits.
  2. Step 2 — Apply the run rule: a run of nine or more consecutive points on the same side of the centerline is a recognized out-of-control signal (the exact count used varies slightly by standard — commonly eight or nine points; your MSSC/NCCER study material specifies the count used on your exam).
  3. Step 3 — Conclusion: even though all points are within the control limits, the run indicates a non-random (special-cause) shift. The process is out of statistical control.
Answer: The process is out of control due to a run of nine consecutive points above the centerline, signaling a special cause even though no individual point exceeds the control limits.

The math in this lesson3

Learners read an X-bar control chart against UCL and LCL to judge process control.
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Brush up in the math halls at newSchoolWorks.com:
In class: Electrical and PLC domain sprint (12 hours): instructor reviews Ohm's Law and power calculations with sample exam problems, NEC wiring diagram symbol recognition (residential and industrial), motor control circuit reading, and three-phase concepts; learners complete a 50-item electrical timed drill; then instructor reviews PLC scan cycle, input/output addressing, normally open/normally closed contacts, timer and counter rungs, and basic fault-finding from ladder logic printouts; learners complete a 40-item PLC timed drill; all scoring and debrief using the 'why wrong / why right' protocol. · Predictive maintenance technology review (8 hours): instructor uses projected thermal images, vibration trend charts, and ultrasound spectral plots (drawn from NCCER Predictive Maintenance module and industry reference images) to review route-based vibration analysis terminology, infrared thermography applications, oil analysis interpretation, and ultrasonic leak detection; learners sort 30 scenario cards into the correct PdM technology category, then complete a 30-item timed practice set with immediate scoring and peer discussion. · MSSC CPT Quality Practices & Measurement and Manufacturing Processes & Production modules (8 hours): instructor reviews SPC control chart reading (identifying out-of-control conditions by rule), GD&T basic symbol recognition, measuring tool selection and use (micrometer, caliper, CMM concept), 5S principles, and basic lean/waste identification; learners complete a 50-item MSSC-formatted timed drill covering both modules, score in pairs, and update their Gap Analysis Worksheets; instructor leads a 30-minute debrief targeting the ten most-missed items class-wide.
Materials: NCCER Contren Electrical, PLC, and Predictive Maintenance module texts; MSSC CPT Quality Practices & Measurement and Manufacturing Processes & Production study materials; projected thermal images and vibration trend charts (instructor reference set); PdM scenario cards (instructor-prepared set of 30); 50-item electrical drill, 40-item PLC drill, 30-item PdM drill, 50-item MSSC quality/production drill; scientific calculators; Gap Analysis Worksheets; Domain Tracker sheets.
Check: Domain Tracker updated after each drill; learners below 75% on any drill complete a targeted 20-item re-drill in the same session before the next topic begins; instructor initials each completed re-drill. Pass mark: 75% on each domain practice set or documented successful re-drill, recorded on Domain Tracker.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

NCCER Industrial Maintenance — Electrical
1. A technician measures 24 V across a resistor and 0.5 A through it. What is the resistance?
NCCER Industrial Maintenance — Electrical / Motor Control
2. In a motor control ladder diagram, a normally closed (NC) overload relay contact is wired in series with the starter coil. When the motor overloads and the relay trips, what happens to the contact and the coil?
NCCER Industrial Maintenance — PLC
3. A PLC scan cycle executes in which order?
NCCER Industrial Maintenance — Predictive Maintenance
4. A maintenance technician reviewing a vibration frequency spectrum notices a new, sharp peak appearing at the ball-pass frequency outer race (BPFO) of a motor bearing. Which predictive maintenance technology produced this finding, and what does it indicate?
NCCER Industrial Maintenance — Predictive Maintenance / Safety
5. During an infrared thermography inspection of an energized motor control center, a technician identifies a hot spot on one bus-bar connection. Before approaching the panel to investigate further, what is the FIRST safety action required?
MSSC CPT — Quality Practices & Measurement
6. On an SPC X-bar control chart, a quality technician sees one data point plotted above the upper control limit. What is the correct interpretation?
MSSC CPT — Quality Practices & Measurement
7. A machinist uses a GD&T drawing that shows a perpendicularity symbol with a tolerance of 0.02 mm applied to a bore surface. What does this callout control?
MSSC CPT — Manufacturing Processes & Production
8. During a lean manufacturing walk-through, an observer notices that a CNC operator must walk 40 feet to a remote storage rack to retrieve cutting inserts for every job changeover, adding several minutes each time. Which of the eight lean wastes does this BEST represent?
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