Most manufacturing teams still rely on static documents and 2D drawings to guide assembly and production—despite building increasingly complex, highly engineered products. Model-based work instructions change this by putting the 3D product model at the center of every step the operator performs.

This approach bridges the gap between design and the shop floor, reduces misinterpretation, and provides a dynamic foundation for continuous improvement.

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What are model-based work instructions?

Model-based work instructions (MBWI) are digital work instructions that use the 3D CAD model and associated product data as the primary source of truth for communicating manufacturing and assembly steps.

Instead of:

• Writing purely text-based instructions, or
• Embedding static 2D drawings or screenshots in documents (PDFs, Word, PowerPoint)

Model-based work instructions:

• Reference the live 3D model
• Capture manufacturing intent directly on that model
• Present interactive, step-by-step guidance to operators

They are usually delivered via a manufacturing execution system (MES), a dedicated work-instruction platform, or a web-based viewer integrated with PLM/ERP.

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How model-based work instructions differ from traditional instructions

1. Source of truth

Traditional:

• Based on manually created documents
• 2D drawings, annotated images, and text
• Often recreated or duplicated from engineering data

Model-based:

• Driven directly from 3D CAD and Product Manufacturing Information (PMI)
• Changes in the model (e.g., design updates, tolerances) can flow into instructions
• Single, unified source of truth across engineering, manufacturing, and quality

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2. Format and interaction

Traditional:

• PDF or printed work travelers
• Linear text, tables, and snapshots
• Operators interpret views and connector locations from static images

Model-based:

• Interactive 3D views (rotate, zoom, explode, cross-section)
• Step-by-step sequences tied to specific model states
• Parts or features highlight automatically per instruction step

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3. Change management

Traditional:

• Engineering change orders (ECOs) trigger manual updates to documents
• High risk of outdated instructions on the shop floor
• Hard to ensure all copies are replaced

Model-based:

• Instructions are linked to the underlying model and BOM
• Updates can be propagated centrally and instantly pushed to the shop floor
• Version control and traceability become part of the system, not manual tasks

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Key components of model-based work instructions

While implementations vary, strong MBWI systems typically include:

1. 3D CAD model and PMI

• Native or neutral 3D models (e.g., Creo, NX, CATIA, SolidWorks, JT, STEP)
• PMI such as:
  • Dimensions and tolerances
  • GD&T
  • Surface finishes
  • Weld symbols
  • Notes and callouts

The PMI often replaces traditional 2D drawings, enabling Model-Based Definition (MBD) that feeds directly into instructions.

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2. Manufacturing Bill of Materials (mBOM)

• A manufacturing-centric view of the product structure
• Defines the exact parts, assemblies, and consumables needed at each operation
• Aligns with:
  • Routing and operation steps
  • Work centers and stations
  • Tooling and fixtures

The mBOM is essential for linking real-world operations to the 3D model.

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3. Operation steps and task breakdown

Each operation is broken into discrete steps, for example:

• Operation 20 – Subassembly Build
  • Step 20.10: Load base plate
  • Step 20.20: Install bracket A with fasteners F01
  • Step 20.30: Torque fasteners to 15 Nm using Tool T03

Each step includes:

• Associated 3D view (specific orientation, exploded state, hidden/show parts)
• Textual instructions and safety notes
• Visual cues (highlighted parts, arrows, balloons, callouts)
• Required tools, materials, and consumables

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4. Work-instruction viewer on the shop floor

Operators access model-based instructions via:

• Touchscreen terminals at workstations
• Tablets or ruggedized devices
• Augmented reality (AR) headsets in advanced setups

The viewer typically supports:

• 3D navigation (rotate, zoom, pan)
• Step navigation (next/previous, jump to step)
• Embedded quality checks and data capture (measurements, pass/fail, signatures)
• Media: photos, videos, short animations

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5. Integration with PLM, MES, and QMS

Model-based work instructions are most effective when integrated with core systems:

• PLM (Product Lifecycle Management):
  • Manages CAD, PMI, EBOM/mBOM, configurations, and change history
• MES (Manufacturing Execution System):
  • Manages routings, work orders, scheduling, and real-time execution
• QMS (Quality Management System):
  • Captures inspection results and nonconformance data linked to steps

These integrations ensure instructions always align with current product and process definitions.

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Why manufacturers are adopting model-based work instructions

1. Reduced errors and rework

• Visual, interactive 3D makes complex assemblies easier to understand
• Operators see exactly which part, orientation, and location are required
• Less reliance on tribal knowledge or guesswork from 2D prints

Example:
In a wiring harness assembly, 3D routing paths and connection points can be shown clearly, reducing misrouting and connector swaps.

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2. Faster training and onboarding

• New operators ramp up faster with clear visuals and guided steps
• Less time spent shadowing experienced workers
• Consistent instructions reduce interpretation differences between shifts

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3. Shorter time-to-update for changes

• ECOs and design updates propagate into the model and, from there, into the work instructions
• Manufacturing engineering adjusts step sequences and views once, centrally
• The shop floor sees updated content the next time they load the work order

This is critical for high-mix, low-volume environments where variants change frequently.

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4. Better alignment between engineering and manufacturing

• Manufacturing engineers use the same 3D data that design engineers use
• Feedback from the shop floor can be tied directly to features on the model
• DFM (Design for Manufacturability) and DFA (Design for Assembly) decisions become more data-driven

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5. Stronger traceability and compliance

• Each instruction step can log:
  • Who performed it
  • When it was completed
  • Which tools and torque settings were used
  • Measurements and inspection outcomes
• Traceability records link back to the exact product configuration and revision of the instructions

This is vital in regulated industries like aerospace, defense, medical devices, and automotive.

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Practical examples of model-based work instructions

Example 1: Mechanical assembly station

Scenario: Assembling a gearbox subassembly

Model-based instruction for a step might show:

• A 3D exploded view of the casing and gears
• Highlighted gear #G03 in green
• A callout for:
  • Part number
  • Orientation arrow showing correct face and direction
  • Instruction text: “Install gear G03 with chamfered side facing bearing B02. Apply grease type G-124 to teeth.”

Operators can rotate the model to confirm orientation and fit before proceeding.

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Example 2: Electronics and PCB assembly

Scenario: Placing components on a printed circuit board

Model-based instructions can:

• Display the 3D board model
• Highlight the exact pads and orientation for each component
• Link to test points for downstream functional testing
• Embed process notes like preheating, soldering parameters, and ESD precautions

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Example 3: Service and maintenance procedures

While often used for new manufacturing, model-based work instructions also support:

• Field service technicians performing repairs
• Maintenance teams executing preventive tasks on machines or assets

They can access the 3D model, isolate components, and follow guided disassembly/reassembly steps.

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How model-based instructions are created

1. Prepare model and product data

• Ensure 3D CAD models are clean, up to date, and appropriately simplified for shop-floor use
• Capture PMI so that 2D drawings are not the only source of critical information
• Build or validate the mBOM that reflects manufacturing reality

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2. Define process flow and operations

• Work with process planners and manufacturing engineers to define:

  • Operation sequence
  • Work centers
  • Required resources (tools, fixtures, materials)

• Map each operation to specific product structure elements in the mBOM

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3. Author instruction steps

Using a model-based authoring tool, manufacturing engineers:

• Create steps and associate them with:
  • Parts, assemblies, and features in the 3D model
  • Operation and work center data
• Define 3D views:
  • Camera angle
  • Exploded states
  • Hidden/shown parts
  • Highlighting and annotations
• Add text instructions, safety notes, and quality checkpoints

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4. Validate with the shop floor

• Review instructions with experienced operators and supervisors
• Confirm:
  • The sequence matches the real workflow
  • Visuals are clear and meaningful
  • Timing and ergonomics are realistic
• Adjust steps and views based on feedback

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5. Release and control versions

• Link instructions to specific:
  • Product revisions
  • Configurations or options
  • Work orders or serial numbers
• Establish governance so changes follow approvals and are auditable

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Best practices for implementing model-based work instructions

Start where complexity is highest

Focus first on operations that:

• Have high defect or rework rates
• Are difficult to describe in text or 2D diagrams
• Require heavy use of tribal knowledge
• Involve many variants or options

This is where MBWI will deliver visible value quickly.

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Keep steps granular and focused

• Avoid long, multi-part steps that bundle several actions
• Each step should be:
  • Actionable
  • Tied to a specific model state
  • Easy to confirm as “done”

Granular steps make it easier to track issues and improvements at a detailed level.

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Design visuals for the operator, not the engineer

• Use simple, clear perspectives—often close to the operator’s real viewpoint
• Avoid cluttered callouts or overly dense PMI views
• Use consistent color schemes for:
  • New/added parts
  • Existing parts
  • Fasteners and tools

Pilot with actual operators and refine.

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Integrate quality checks into the flow

• Embed inspection points directly inside the work instruction:
  • Torque verification
  • Visual inspection confirmation
  • Measurement entry fields
• Make these checks mandatory before advancing to the next step when required

This helps catch issues early and connects quality data directly to the process and configuration.

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Plan for connectivity and device ergonomics

• Ensure devices at workstations:
  • Have sufficient performance for 3D visualization
  • Are usable with gloves or in production environments
• Plan offline modes or caching if connectivity is unreliable
• Minimize clicks and navigation—operators should not have to fight the interface

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Challenges and how to address them

Data preparation overhead

Challenge: Converting legacy 2D-based processes to model-based can be resource-intensive.

Mitigation:

• Start with new products or major redesigns where 3D and MBD are already in place
• Use automation tools to generate baseline views and steps, then refine manually
• Prioritize high-impact assemblies before trying to convert everything

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Organizational change and training

Challenge: Engineers and operators are used to drawings and printed travelers.

Mitigation:

• Train manufacturing engineers in the authoring tools and MBD practices
• Run small pilots demonstrating tangible benefits (fewer errors, faster builds)
• Involve operators early and incorporate their feedback into instruction design

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System integration complexity

Challenge: PLM, MES, ERP, and QMS may be fragmented or disconnected.

Mitigation:

• Define a clear data ownership model:
  • PLM for product definition
  • MES for execution and scheduling
• Use standard integrations or APIs where possible
• Start with loose coupling (e.g., URLs, identifiers) and tighten integration over time

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When model-based work instructions make the most sense

Model-based instructions are especially valuable when:

• Products have complex geometry or assemblies
• There are many variants, options, or customer-specific configurations
• Quality and compliance requirements are strict
• You’re moving toward MBD, digital thread, or Industry 4.0 initiatives
• There is a need to shorten time-to-market and respond faster to change

For simple, repeatable, low-variation processes, traditional work instructions may still suffice. But as complexity and change frequency grow, MBWI typically provide a more scalable and reliable approach.

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FAQ: Model-based work instructions in manufacturing

Are model-based work instructions the same as Model-Based Definition (MBD)?
Not exactly. MBD is about embedding all necessary product definition (dimensions, tolerances, notes) in the 3D model instead of 2D drawings. Model-based work instructions use that MBD data to create and deliver manufacturing instructions. MBD is the foundation; MBWI is a downstream application.

Do operators need CAD training to use model-based instructions?
No. The viewer is designed for non-CAD users. Operators interact with simple controls—next step, rotate, zoom, and highlight—through a focused user interface.

Can model-based work instructions be used without a full PLM system?
They can, but benefits increase significantly when integrated with PLM and MES. Without PLM, you can still load 3D models into a dedicated work-instruction tool, but you’ll need clear processes to manage revisions and changes.

What about printed copies—are they still needed?
In a model-based environment, the goal is digital-first on the shop floor. Some organizations still print limited reference materials or emergency backups, but the interactive 3D experience is where MBWI delivers most of its value.

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Summary

Model-based work instructions replace static, document-centric directions with dynamic, 3D model-driven guidance that is directly tied to the product definition and manufacturing process. By leveraging CAD, MBD/PMI, and integrated PLM/MES systems, they:

• Reduce assembly errors and rework
• Accelerate training and onboarding
• Improve responsiveness to engineering changes
• Strengthen traceability and compliance

For manufacturers dealing with complex products and frequent change, model-based work instructions are a foundational element of a modern, connected, and resilient production system.