System Design, Safety Planning, and Project Kickoff

Why Design and Safety Planning Come First

Every professional mechatronics and robotics build starts with paper, not wire. Rushing to assemble before the design is complete is a leading cause of rework, equipment damage, and injury. For your capstone project, no physical build activity—wiring, plumbing, mounting, or robot programming—may begin until your instructor has signed off on a complete, internally consistent design package. This lesson explains each document in that package and the safety standards that shape it.

The Five-Document Design Package

1. Scope Document

The scope is a one-page plain-language statement that answers four questions: What does this system do? What are its inputs and outputs? What safety interlocks are required? What does "done" look like (success criteria)? A well-written scope keeps the project from growing uncontrolled and gives your instructor a clear target to approve. List every sensor signal coming in, every actuator going out, and every interlock—for example, "E-stop de-energizes all robot motion and closes the pneumatic supply valve within 500 ms."

2. Block Diagram

A block diagram shows every major subsystem as a labeled box and every signal path as an arrow. Typical blocks for a capstone cell include: PLC, robot controller, servo or VFD drives, HMI touchscreen, sensor cluster (proximity, photoelectric, vision), pneumatic or hydraulic sub-circuit, and power distribution. The block diagram is not a wiring schematic—it is a communication tool. Once the instructor approves the block diagram, you convert it into detailed drawings.

3. Electrical and Pneumatic/Hydraulic Schematics

Schematics use standardized IEC or ANSI drawing symbols so that any technician can read them. Every component receives a tag number (for example, PB1 for push button 1, SOL-A for solenoid A) that will appear on both the drawing and the physical component. Electrical schematics show control-voltage circuits separately from power circuits. Pneumatic schematics show directional control valves, actuators, flow controls, pressure regulators, and the air supply using ISO 1219 symbols. Hydraulic schematics follow the same symbol set. Consistent tag numbers across all documents—scope, schematic, BOM, and JHA—are required for sign-off.

4. Bill of Materials (BOM)

The BOM is a spreadsheet listing every component: tag number, description, manufacturer, part number, quantity, and the specification that drives the selection (voltage rating, bore size, current capacity, etc.). The BOM proves that every item on the schematic has been identified and that ratings are appropriate for the application.

5. Job Hazard Analysis (JHA)

The JHA is the most safety-critical document. It must identify every hazardous energy source—electrical, pneumatic, hydraulic, gravitational, mechanical stored energy—and assign a control for each one.

Safety Standards You Must Cite in the JHA

OSHA 29 CFR 1910.147 — Control of Hazardous Energy (Lockout/Tagout)

This standard requires that all energy sources be isolated and locked out before servicing. For each energy source on your system, the JHA must state the isolation point, the lockout device used, and the verification step (test for absence of stored energy). Your JHA will walk through this sequence: notify affected employees → shut down equipment → isolate energy → apply lockout/tagout devices → release or restrain stored energy → verify isolation before touching.

NFPA 70E — Electrical Safety in the Workplace

NFPA 70E governs arc-flash and shock hazards. Before working on or near energized conductors, a qualified person must determine the arc-flash boundary and the shock protection boundary. PPE (arc-rated clothing, insulated gloves rated for the voltage, face shield) is selected based on the incident energy at the work location. Your JHA must specify the PPE category or calculated PPE for any energized-work task, and must note that an Energized Work Permit is required whenever work inside the arc-flash boundary cannot be avoided. The preferred practice is to verify absence of voltage with a tested, rated voltage tester before touching any conductor.

OSHA 1910.212 — Machine Guarding

All points of operation, ingoing nip points, rotating parts, and flying chips or sparks must be guarded. Your JHA must identify each machine-guarding requirement: for example, a conveyor drive requires a belt-and-pulley guard; a pneumatic press requires a two-hand control or light curtain at the point of operation.

ANSI/RIA R15.06 / ISO 10218 — Industrial Robot Safety

If your project includes a robot cell, ANSI/RIA R15.06 governs the safeguarding design. The standard requires a risk assessment before the cell is built. Safeguarding options include hard barriers with interlocked gates, safety-rated light curtains, area scanners, or—for collaborative applications—speed-and-separation monitoring. Your JHA must document the risk assessment outcome and the safeguarding method selected.

Design Consistency: The Golden Rule

Every tag number that appears on the schematic must appear in the BOM and in the JHA. If SOL-B is a pneumatic solenoid on the schematic, it must be listed in the BOM with its voltage and flow rating, and the JHA must address the pneumatic energy stored downstream of SOL-B when the system is de-energized. Inconsistencies are the most common reason design packages are returned for revision.

Advancing to Build

Once all five documents are complete, consistent, and free of unresolved safety gaps, your instructor will sign the design package. That signature is your build permit. Any change to the design during build—a substituted component, an added sensor, a rerouted cable—requires a red-line update to the affected drawings and, if the change introduces a new hazard, a JHA revision before work continues.