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newSchoolWorks.com › VoTechWorks › Manufacturing & Marine › Robotics / Mechatronics › Externship / Worksite Placement › Lesson 3
MFG-MECH15-09 · Lesson 3 · 100 clock hours · field

Independent Supervised Tasks and Expanded Responsibilities

Objective. With general (not direct) supervision, the student will independently execute at least three different categories of mechatronics technician tasks — drawn from robotics, fluid power, electrical/PLC, or sensor/instrumentation work — demonstrating safe work habits and progressively decreasing need for guidance as documented in supervisor notes.

⚠ 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.

Working Independently: What This Phase Means

By this point in your externship you have observed, assisted, and completed tasks under close supervision. This phase raises the bar: your supervisor steps back to a general oversight role, checking your work rather than directing every step. You are expected to select the correct procedure, gather the right tools, execute the task safely, and document what you did — all without being prompted. This mirrors real shop-floor conditions, and it is precisely what employers mean when they say they want a technician who can "work independently."

Progress is measured two ways: your supervisor's signed task-completion notes, and your field log entries reviewed by the school coordinator. Together they must show at least three distinct competency categories — fluid power, electrical/PLC/sensor, and robotics — before this phase is complete.

Safety Before Every Task

Independent work does not mean shortcuts. Apply the hierarchy of controls every time.

Task 1 — Troubleshooting a Fluid Power Fault

A systematic approach prevents random part-swapping and wasted time. Work from the source outward:

1. Verify supply pressure at the compressor or pump outlet using a calibrated gauge. Compare to the system's rated pressure specification.

2. Check the filter/regulator/lubricator (FRL) unit. A clogged filter or a misadjusted regulator is a common cause of low downstream pressure.

3. Trace to the directional control valve (DCV). With supply confirmed, energize the valve solenoid and listen/feel for spool movement. Use a gauge on each work port to confirm the valve is shifting and passing flow.

4. Inspect the actuator. Calculate expected cylinder force: F = P × A, where A = π × (bore radius)². If measured force or speed is lower than calculated, suspect a worn seal or an undersized orifice.

5. Document as-found conditions, your diagnosis, the repair taken, and as-left readings in your field log. Note which PMMI Mechatronics Fluid Power competency area each step addresses.

Task 2 — Sensor Calibration or Replacement

For a 4-20 mA analog transmitter, the standard scaling formula maps loop current to engineering units:

EU = EU_min + [(I − 4) / 16] × (EU_max − EU_min)

Where I is the measured loop current in mA. After installing or calibrating a sensor:

1. Open a work order through the site system before touching the machine.

2. Record as-found values: current loop reading (mA) and the PLC's engineering-unit display.

3. Apply the zero and span adjustments per the sensor data sheet, or replace the unit.

4. Verify the new signal at 0%, 50%, and 100% of range using a loop calibrator or a mA-capable multimeter.

5. Apply the scaling formula to confirm the PLC display matches expected engineering units at each point.

6. Record as-left values, close the work order, and have the supervisor sign off.

For discrete sensors (proximity or photoelectric), verify switching distance, output state (NPN/PNP), and correct LED indication before closing the work order.

Task 3 — Robot or PLC Program Edit

Even a small program change must follow a structured process:

1. Define the task in writing before touching the teach pendant or programming terminal.

2. Back up the existing program to a USB drive or network share before any edits (a FANUC CERT core habit for HandlingTool programs).

3. Make the edit — a position register change, an added instruction, or a timer adjustment — in ROBOGUIDE simulation first if live edits are not permitted by site policy.

4. Test at low speed with all personnel outside the safeguarded space before running at production speed.

5. Document the original logic, the change made, and the test result. Reference the IEC 61131-3 language used (ladder diagram, function block, structured text, etc.) or the FANUC HandlingTool instruction applied.

6. Supervisor reviews and signs the task-completion note.

Completing This Phase

Your field log for this phase must show three distinct competency categories with signed task-completion notes for each. The school coordinator checks that the entries are detailed enough to demonstrate independent judgment, safe practice, and correct technical execution. "Satisfactory" on all supervisor signatures plus coordinator acceptance of the log = phase complete.

Key terms10

General supervisionA level of oversight in which the supervisor checks completed work and is available for questions but does not direct each step; the technician selects and executes the procedure independently.
Lockout/tagout (LOTO)The energy-control procedure required by OSHA 29 CFR 1910.147: de-energize all hazardous energy sources, apply personal locks, and verify zero energy before working on equipment.
4-20 mA loopA two-wire current-signal standard used in industrial instrumentation; 4 mA represents the minimum (0%) of the measured range and 20 mA represents the maximum (100%).
As-found / as-left valuesDocumented measurements recorded before a calibration or repair (as-found) and after the work is complete (as-left); required for quality records and work-order closure.
Directional control valve (DCV)A valve that routes hydraulic or pneumatic fluid to one port or another to extend or retract an actuator; can be shifted electrically by a solenoid or mechanically by a pilot signal.
ANSI/RIA R15.06 / ISO 10218The primary North American and international standards for industrial robot safety, covering safeguarding, teach-mode speed limits, collaborative operation, and work-cell design requirements.
IEC 61131-3The international standard defining five PLC programming languages: ladder diagram, function block diagram, structured text, sequential function chart, and instruction list.
Loop calibratorA portable instrument that can source, simulate, or measure a 4-20 mA current signal; used to verify transmitter output and check PLC analog input channels without the process variable present.
ROBOGUIDEFANUC America's offline robot simulation software used to create, test, and verify robot programs without risk to production equipment; a core element of FANUC CERT HandlingTool training.
Arc-flash boundaryA distance defined by NFPA 70E inside which a worker could receive a second-degree burn from an arc-flash incident; determines required PPE category and approach limits.

Worked examples4

1. A pneumatic cylinder with a 2-inch bore is fed at 85 psi. Calculate the expected extend force. Then the technician measures actual force at 110 lbf. What does this suggest?
  1. Find the piston area: A = π × r² = π × (1 in)² = 3.1416 in²
  2. Calculate expected force: F = P × A = 85 psi × 3.1416 in² = 267 lbf (rounded to whole number)
  3. Compare to measured force: 110 lbf is well below 267 lbf — less than half of expected.
  4. Conclude: The large discrepancy is too great to be explained by friction alone; likely causes include a worn piston seal allowing bypass, significantly reduced supply pressure at the cylinder (check gauge at the cylinder port, not just at the FRL), or a partially closed flow-control valve on the supply port.
Answer: Expected force ≈ 267 lbf; measured 110 lbf indicates a serious fault such as a blown piston seal or a throttled supply — not a minor calibration issue.
2. A pressure transmitter is ranged 0–200 psi (4 mA = 0 psi, 20 mA = 200 psi). The loop calibrator reads 12.4 mA. What pressure should the PLC display?
  1. Identify values: EU_min = 0 psi, EU_max = 200 psi, I = 12.4 mA
  2. Apply the scaling formula: EU = EU_min + [(I − 4) / 16] × (EU_max − EU_min)
  3. Substitute: EU = 0 + [(12.4 − 4) / 16] × (200 − 0)
  4. Calculate numerator: 12.4 − 4 = 8.4
  5. Divide: 8.4 / 16 = 0.525
  6. Multiply: 0.525 × 200 = 105 psi
Answer: The PLC engineering-unit display should read 105 psi when the loop current is 12.4 mA.
3. The same transmitter (0–200 psi, 4–20 mA) shows 20.0 mA on the calibrator but the PLC displays 198 psi instead of 200 psi. Is this within a reasonable tolerance, and what is the percent-of-span error?
  1. Calculate expected reading at 20 mA: EU = 0 + [(20 − 4) / 16] × 200 = (16/16) × 200 = 200 psi
  2. Find the error: 200 − 198 = 2 psi
  3. Calculate percent of span: error / span × 100 = 2 / 200 × 100 = 1.0%
  4. Evaluate: Whether 1.0% is acceptable depends on the process requirement listed in the work order or instrument data sheet; many industrial sensors specify ±1% or ±0.5% accuracy — the technician must compare to the site specification before closing the work order as acceptable.
Answer: The error is 2 psi, or 1.0% of span. Acceptability depends on the site's stated accuracy requirement for that loop.
4. A hydraulic cylinder with a 3-inch bore must extend at a speed of 4 inches per second. The pump delivers 8 gpm. Using the hydraulic speed formula, will the cylinder meet the speed requirement?
  1. Find piston area: A = π × (1.5 in)² = π × 2.25 = 7.069 in²
  2. Convert gpm to in³/min: 8 gpm × 231 in³/gal = 1848 in³/min
  3. Convert to in³/sec: 1848 / 60 = 30.8 in³/sec
  4. Calculate cylinder speed: v = flow rate / area = 30.8 in³/sec ÷ 7.069 in² = 4.36 in/sec
  5. Compare to requirement: 4.36 in/sec > 4 in/sec required, so the pump flow is sufficient.
Answer: The cylinder will extend at approximately 4.36 in/sec, which meets the 4 in/sec requirement.

The math in this lesson2

Learners scale 12.4 mA to psi and judge a 198 psi display against full-scale tolerance.
F-LE.1G-MG.2
Brush up in the math halls at newSchoolWorks.com:
In class: Independently troubleshoot at least one pneumatic or hydraulic circuit fault (such as a slow cylinder, a pressure loss, or a valve not shifting) using a systematic approach: check fluid power supply, inspect directional control valves, measure cylinder bore and calculate expected force (F = P × A), and document the diagnosis and repair in the field log, cross-referencing PMMI Mechatronics Fluid Power competency areas. · Calibrate or replace at least one sensor (proximity, photoelectric, or analog 4-20 mA transmitter) on a live machine, following the site's work-order system; verify the new signal by monitoring PLC I/O or a loop calibrator, apply the 4-20 mA scaling formula to confirm the engineering-unit reading is correct, and record the as-found and as-left values. · With the site mentor's permission, create or edit a simple robot program segment or PLC routine (even in a simulator if live edits are not permitted) to solve a minor production improvement task suggested by the supervisor; document the task, the logic change, and the test result, referencing FANUC CERT HandlingTool or IEC 61131-3 ladder/function-block concepts.
Materials: Site production equipment, pneumatic/hydraulic test gauges, loop calibrator or multimeter with mA measurement, sensor data sheets, PLC programming terminal or ROBOGUIDE simulation laptop, work-order system access, student field log binder
Check: Each independent task must have a signed task completion note from the site supervisor confirming the work was done safely and correctly; school coordinator reviews log entries for this phase and checks that at least three distinct competency categories are represented; pass = supervisor signs all task completion notes as satisfactory and coordinator accepts log entries as complete.

Practice check8

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

PMMI Mechatronics — Fluid Power / Safety
1. Before opening a hydraulic line on a press that has both electrical and hydraulic energy sources, the FIRST action required by OSHA 29 CFR 1910.147 is to:
PMMI Mechatronics — Industrial Electricity / Siemens SMSCP Level 1
2. A 4-20 mA temperature transmitter is ranged 0–500 °F. The loop calibrator reads 8 mA. What temperature should the PLC display?
Siemens SMSCP Level 1 — Electrical Components / Safety
3. When replacing a proximity sensor on a running conveyor line, which NFPA 70E practice best protects the technician from electrical shock?
PMMI Mechatronics — Fluid Power
4. A technician finds that a pneumatic cylinder with a 1.5-inch bore extends slowly even though supply pressure is correct. The NEXT step in a systematic troubleshooting approach is to:
PMMI Mechatronics — Programmable Logic Controllers / Siemens SMSCP Level 1
5. Which IEC 61131-3 programming language uses horizontal rungs with contact symbols (normally open, normally closed) and coil symbols to represent logic, most closely resembling a relay ladder schematic?
FANUC CERT — HandlingTool Operation & Programming
6. Before making any live edits to a FANUC robot program, the FANUC CERT curriculum specifies that the technician should first:
FANUC CERT — Robot Safety / ANSI/RIA R15.06
7. Per ANSI/RIA R15.06 / ISO 10218, when a technician must enter a robot work cell to verify a fixture position, the safest permitted condition is:
PMMI Mechatronics — Industrial Electricity / Externship Documentation
8. A field log entry for a sensor calibration task is considered complete for externship documentation purposes when it includes:
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