FINAL PROJECT TWO: BACKDOOR WIRING HARNESS USING CATIA V5

OBJECTIVE:

This project aims to demonstrate the practical application of wiring harness routing and design principles on a car's backdoor/tailgate using CATIA V5 software. The main objective is to showcase the implementation of industry best practices and packaging rules studied throughout the course by creating a properly routed wiring harness and a flattened view drawing. The project will incorporate the use of appropriate protection coverings and available connector 3D data from www.te.com to ensure a realistic and comprehensive design.

The project will focus on generating essential reports, including clearance, clipping/clamping selection, harness fixing requirements, harness continuity, and any necessary assumptions. These reports, along with the CATIA 3D data, will be submitted to provide a complete overview of the design process and decisions made.

Completing this project will demonstrate proficiency in electrical component definition, catalogue creation, proper bundle routing, support part selection, flattening, and drawing creation using CATIA V5's flattening and drafting workbenches. The project will be evaluated based on the criteria outlined in the grading policy, ensuring that all aspects of the wiring harness design process for the car's backdoor/tailgate are adequately addressed and presented.

 

STP FILE THAT WE IMPORTED INTO CATIA V5:

 

WHY WIRING HARNESSES ARE ESSENTIAL IN MODERN VEHICLES:

Modern automobiles are complex machines brimming with electronic components. Gone are the days of simple electrical systems with just a few lights and a starter motor. Today's vehicles rely on a network of wires, connectors, and protective elements bundled together – the wiring harness – to perform a multitude of critical functions:

Power Delivery: The harness carries electrical current from the battery to power various components like lights, sensors, actuators, entertainment systems, and engine control units.

Signal Transmission: It acts as a communication channel, transmitting low-voltage signals between sensors, control units, and other electronic modules. This allows for functionalities like engine management, airbag deployment, and anti-lock braking systems (ABS).

Data Transfer: With increasing vehicle automation, wiring harnesses facilitate the transfer of data between different ECUs (Electronic Control Units) enabling features like navigation, driver assistance systems, and vehicle diagnostics.

In essence, the wiring harness is the nervous system of a modern car, ensuring proper communication and power distribution for all electrical and electronic functions. Without it, a car would be nothing more than a hunk of metal.

 

Factors to consider while designing a wiring harness layout for an Automotive Backdoor/Tailgate:

As a wiring harness designer, there are numerous factors to consider when designing an automotive backdoor/tailgate wiring harness for newer vehicles. These factors ensure the harness's functionality, durability, and compatibility with the vehicle's electrical systems. Here's a detailed explanation:

1. Electrical Requirements:

   - Identify the electrical components in the backdoor/tailgate, such as power locks, windows, rear wipers, defrosters, and cameras.

   - Determine the power requirements for each component, including voltage, current, and peak loads.

   - Consider the use of advanced features like gesture-controlled tailgates, proximity sensors, and anti-pinch technology.

 

2. Connector Selection:

   - Choose appropriate connectors based on the electrical requirements, environmental conditions, and space constraints.

   - Consider using sealed connectors to prevent water and dust ingress, ensuring reliable connections in harsh environments.

   - Evaluate the use of high-speed data connectors for cameras, displays, and other advanced features.

 

3. Wire Selection:

   - Select wire gauges based on the current-carrying capacity and voltage drop requirements of each circuit.

   - Use high-temperature, abrasion-resistant, and flexible wires to withstand the harsh environment in the backdoor/tailgate area.

   - Consider using shielded wires for sensitive circuits to minimize electromagnetic interference (EMI).

 

4. Routing and Packaging:

   - Design the harness routing to minimize the risk of chafing, pinching, and stretching during door/tailgate movement.

   - Utilize protective sleeves, conduits, and grommets to protect wires from sharp edges and moving parts.

   - Optimize the harness layout for easy installation, and serviceability, and to minimize the overall weight and cost.

 

5. Modularity and Scalability:

   - Design the harness with modularity in mind to accommodate different trim levels and optional features.

   - Use standardized connectors and interfaces to enable easy integration of additional components or future upgrades.

   - Consider the use of subassemblies or pre-terminated cables to simplify the assembly process and reduce installation time.

 

6. Safety and Compliance:

   - Ensure the harness design complies with relevant automotive standards, such as ISO, SAE, and FMVSS.

   - Incorporate safety features like short-circuit protection, overcurrent protection, and proper insulation.

   - Conduct thorough testing to validate the harness's performance, durability, and resistance to environmental factors.

 

7. Vehicle Integration:

   - Collaborate with the vehicle design team to ensure proper integration of the harness with the backdoor/tailgate structure and mechanisms.

   - Consider the impact of the harness on the vehicle's weight distribution, centre of gravity, and overall performance.

   - Evaluate the need for additional support brackets, cable ties, or adhesives to secure the harness in place.

 

8. Manufacturing and Assembly:

   - Design the harness with manufacturing feasibility in mind, considering aspects like wire routing, connector orientation, and assembly sequence.

   - Optimize the harness design for automated assembly processes, such as wire cutting, crimping, and connector insertion.

   - Develop clear and concise assembly instructions and diagrams to ensure consistent and error-free production.

 

9. Testing and Validation:

   - Perform rigorous testing to validate the harness's functionality, durability, and reliability under various operating conditions.

   - Conduct environmental tests, such as temperature cycling, humidity exposure, and vibration testing, to ensure the harness's performance in real-world scenarios.

   - Verify the harness's compatibility with the vehicle's electrical system through integration testing and on-vehicle validation.

 

10. Cost and Supplier Management:

    - Collaborate with suppliers to identify cost-effective materials and components that meet the harness's requirements.

    - Evaluate the use of alternative materials or manufacturing processes to optimize cost without compromising quality.

    - Establish strong relationships with reliable suppliers to ensure consistent quality, timely delivery, and technical support.

 

By considering these factors and incorporating the latest technologies and design practices, a wiring harness design engineer can develop a robust, efficient, and future-proof backdoor/tailgate wiring harness for newer vehicles in the market.

 

 

PACKAGING RULES:

1. Routing should facilitate ease in manufacturing, accessibility, removal, and maintenance of attached equipment and wiring harnesses.

2. Avoid routing through small structural holes and openings to minimize chafing and handling during installation.

3. Avoid routing and clipping in the blind zone of the operator during harness assembly or service.

4. Protect against potential damage caused by common misuses, such as being handheld or used as temporary support for test equipment.

5. Allow additional slack in the harness according to the surroundings and bending requirements.

6. Ensure routing meets clearance requirements with different surrounding parts.

7. Provide sufficient slack for each branch to avoid additional stress on the wire and terminal crimping joint, while preventing harness fouling due to extra slack.

8. Avoid routing over bolts or near bolted joints to prevent harness damage or puncture. Keep harnesses away from panel mounting screws.

9. Provide protection when routing near sharp edges is unavoidable.

10. Maintain a maximum distance of 200mm between two clips on a straight branch.

11. Use clips and clamps if the harness bends at multiple locations.

12. Minimize the use of sheet-metal brackets.

13. Ensure branch lengths are greater than 50mm.

14. Maintain a minimum distance of 25mm between the clip and the branching point.

15. Keep a minimum distance of 50mm between two branch breakouts.

16. Use rubber grommets when the harness passes through sheet metal panels.

17. Position harness connectors higher than the routing and branching points to prevent water entry due to gravity.

 

ESSENTIAL ASSUMPTIONS:

1. Provide clips/clamps as required and use additional clips/clamps to avoid falling cases.

2. Allow 5-10% slack if needed.

3. Avoid routing over bolts and bolted joints to prevent harness puncture.

4. Provide protection when routing on sharp edges.

5. Adhere to clearance distances and keep the harness away from heat-generating components.

6. Protect according to the surrounding temperature.

7. Avoid direct support for harnesses on fuel lines routed in the engine.

8. Use plastic guiding channels if necessary.

9. Maintain branch lengths greater than 50mm.

10. Keep a minimum distance of 50mm between two branch points and 25mm between the clip and the branch point.

11. Minimize the use of sheet metal brackets on the engine, utilizing available threaded bosses or requesting them.

12. Ensure the wiring harness is easy to assemble and access.

13. When using dummy connectors, ensure that the defined positions are practical, and bundle diameters and placements are properly defined for wire harness routing.

14. Consider creating a harness channel for routing and protection in tight packaging areas with numerous constraints.

 

 

CONNECTORS, CLIPS AND CLAMPS USED IN OUR LAYOUT:

1. TYPES OF CONNECTORS USED:

CONNECTOR ONE:

 

CONNECTOR TWO:

 

2. TYPES OF FIR TREE CLIPS USED:

 

3. CLAMPING EQUIPMENT:

P-CLAMP:

 

WIRING HARNESS ROUTING, PACKAGING AND FLATTENING PROCESS FOR OUR BACKDOOR:

First, we'll import the STP file that was provided to us into the CATIA environment and save it as a part file.  

Next, we're going to create the context assembly as it serves as a central repository for the backdoor wiring harness design, encompassing three distinct sub-assemblies.

WHAT IS A CONTEXT ASSEMBLY?

A context assembly is a top-level product file within the CATIA V5 environment. It serves as the central container for all the components that constitute the wiring harness.

It typically encompasses three main sub-assemblies:

Geometrical Bundle (or Assembly): This sub-assembly defines the physical layout of the wiring harness within the vehicle. It includes the actual routing of the wires, connectors, clips, clamps, and other supporting features.

Electrical Bundle: This sub-assembly contains all the electrical data associated with the harness. This includes information on wire gauge, colour coding, pin assignments, and connector specifications.

Annotations: This sub-assembly holds any notes, comments, or additional information relevant to the wiring harness design.

 

WHY IS THE CONTEXT ASSEMBLY IMPORTANT?

Centralized Management: The context assembly provides a single, unified location for managing all aspects of the wiring harness design. This allows for efficient organization, version control, and collaboration among engineers working on the project.

Visualization and Packaging Analysis: By incorporating the geometrical bundle within the context assembly, engineers can visualize the complete routing of the harness within the 3D model of the vehicle. This allows for early identification of potential packaging issues, such as interference with other components or insufficient space for proper routing.

Design Verification and Validation: The context assembly facilitates the verification and validation of the wiring harness design. With all the electrical data and annotations readily accessible within the same file, engineers can ensure the design meets all functional and electrical requirements.

Manufacturing and Assembly Support: The context assembly can be used to generate manufacturing documentation, including flat-pattern drawings and bills of materials (BOMs). This information is crucial for efficient harness fabrication and assembly.

 

Issues Without Using a Context Assembly:

Data Fragmentation: Without a central location, electrical data, routing information, and annotations could be scattered across multiple files, leading to confusion, version control issues, and potential inconsistencies.

Packaging Challenges: The inability to visualize the complete harness layout within the vehicle could result in significant packaging problems later in the design process. Clashes with other components or insufficient space allocation for the harness might require costly redesigns.

Design Errors and Omissions: The lack of a centralized location for design verification could lead to undetected errors or omissions in the electrical data or routing configuration. These issues might not be discovered until later stages of development, causing delays and rework.

Manufacturing Difficulties: Generating accurate manufacturing documentation becomes challenging without the centralized data organization provided by a context assembly. Incomplete or inaccurate BOMs and drawings can lead to production delays and potential quality issues.

 

CONCLUSION:

Context assembly is a vital element in CATIA V5 for designing effective and well-packaged automotive wiring harnesses. By providing a centralized platform for managing all aspects of the design, it streamlines collaboration, facilitates verification, and helps avoid costly errors down the line.  Using a context assembly ensures a more efficient, reliable, and well-coordinated wiring harness design process.

 

Next, In CATIA, we will initiate the design process by establishing a new product. This product will function as the context assembly and serve as the central hub for managing all data about the backdoor wiring harness.

1. Backdoor Model Incorporation: Subsequently, we will import the existing part file of the backdoor into the newly created context assembly. This establishes a reference for the backdoor geometry within the design environment.

2. Dedicated Harness Assembly: Next, we will create an additional product within CATIA. This product will be specifically designated for the wiring harness assembly. Naming the product appropriately, for example, "Backdoor Wiring Harness", will enhance clarity and organization.

3. Component Import and Routing: All necessary components, including:

• Connectors
• Mounting equipment
• Supports
• Any other relevant elements

These components will be imported into the dedicated wiring harness assembly product. Within this dedicated product, the essential tasks of:

1. Wiring harness routing: Defining the physical path of the wires within the backdoor compartment.
2. Packaging operations: Ensuring optimal placement of the harness components to avoid interference with surrounding parts and achieve efficient space utilization, will be undertaken.

 

4. Independent Design: It's crucial to emphasize that the wiring harness assembly will be designed entirely independently. This means:

No direct reference will be taken from the engine model geometry.

The harness will be designed as a self-contained assembly, ensuring it functions independently within the backdoor compartment.

By adhering to these steps, we establish a well-structured and organized approach for designing the backdoor wiring harness in CATIA V5. This approach fosters clarity, and efficient data management, and minimizes the risk of errors during the design process.

 

Next, We'll access the dedicated wiring harness product by double-clicking it. Then, using a right-click, we'll open it in a separate CATIA window for focused routing and packaging.

 

As a wiring harness design engineer, it is crucial to strategically place all the required fir tree clips on the inner panel of the backdoor, which faces the vehicle's interior. This placement serves multiple purposes:

1. Secure Harness Routing: The fir tree clips provide a robust and reliable means of securing the wiring harness along its intended path. By carefully selecting the clip locations, we ensure that the harness follows a designated route, minimizing the risk of interference with other components and preventing potential chafing or damage.

 

2. Optimize Packaging Space: The inner panel of the backdoor offers limited space for harness routing and component placement. By judiciously positioning the fir tree clips, we can optimize the use of available packaging space, ensuring that the harness is efficiently routed and does not obstruct the installation or operation of other backdoor components.

 

3. Facilitate Assembly Process: The strategic placement of fir tree clips simplifies the harness installation process during vehicle assembly. By aligning the clip locations with the harness routing and connector positions, we streamline the assembly sequence, reducing the time and effort required for harness integration.

 

4. Ensure Aesthetics and Functionality: The inner panel of the backdoor will be subsequently covered, concealing the wiring harness and maintaining the visual appeal of the backdoor's interior. By carefully selecting the fir tree clip locations, we ensure that the harness is securely fastened and remains hidden from the customer's view, preserving the aesthetics of the backdoor while allowing for the proper functionality of all connected components.

 

5. Enhance Serviceability: In the event of maintenance or repairs, the strategic placement of fir tree clips enables easier access to the wiring harness and associated components. By considering the serviceability aspect during the design phase, we facilitate efficient troubleshooting and maintenance procedures, minimizing vehicle downtime and enhancing overall customer satisfaction.

 

By thoughtfully placing the fir tree clips on the backdoor's inner panel, we achieve a well-organized, secure, and visually appealing wiring harness installation. This attention to detail not only ensures the proper functioning of the connected components but also contributes to the overall quality and refinement of the vehicle's electrical system.

 

Now, We have placed the required fir tree clips, connectors and clamps at appropriate locations in the Assembly Workbench as shown below:

 

In CATIA V5, when designing a wiring harness, clicking on the Geometrical Bundle and then selecting the wiring harness routing file is a crucial step in associating the logical design with the physical representation of the harness. This process, known as "binding," establishes a link between the logical definition of the harness and its 3D geometric routing. Let's delve into the details of why this step is necessary and what it accomplishes.

 

1. Logical to Physical Mapping:

The wiring harness routing file, created in the Electrical Harness Assembly (EHA) workbench, represents the logical definition of the harness. It contains information about the wires, cables, connectors, and other components that make up the harness.

The Geometrical Bundle, on the other hand, represents the physical 3D routing of the harness within the vehicle's geometry. It defines the path and shape of the harness as it navigates through the vehicle's structure.

By clicking on the Geometrical Bundle and selecting the wiring harness routing file, we establish a mapping between the logical definition and the physical representation. This mapping ensures that the logical components are correctly associated with their corresponding geometric counterparts.

 

2. Synchronization and Consistency:

The binding process synchronizes the logical and physical aspects of the harness design. Any changes made to the logical definition in the harness routing file will be reflected in the Geometrical Bundle, and vice versa.

This synchronization ensures consistency between the logical and physical representations of the harness. It allows for seamless updates and modifications throughout the design process, reducing the risk of discrepancies and errors.

 

3. Enabling Routing and Path Definition:

Once the binding is established, the Geometrical Bundle becomes aware of the logical components defined in the harness routing file. This enables us to route the harness in 3D space, defining its path and shape within the vehicle's geometry.

The Geometrical Bundle provides tools and functionalities specifically designed for harness routing, such as the ability to create segments, add branches, define clip and clamp locations, and perform interference checks.

By binding the logical definition to the Geometrical Bundle, we unlock these routing capabilities and can proceed with defining the physical layout of the harness.

 

Now, let's discuss the significance of clicking on the Multibranchable option after binding the harness routing file to the Geometrical Bundle.

1. Handling Multiple Branches:

In complex wiring harnesses, it is common to have multiple branches or sub-harnesses that diverge from the main harness trunk. These branches may serve different components or systems within the vehicle.

The Multibranchable option allows us to create and manage these multiple branches within the Geometrical Bundle. It enables us to define branch points, specify branch properties, and route each branch independently.

 

2. Flexibility and Modularity:

By activating the Multibranchable option, we introduce flexibility and modularity into the harness design. Each branch can be treated as a separate entity, with its own set of wires, cables, and connectors.

This modular approach facilitates the design of complex harnesses, as it allows for the independent development and modification of each branch. Changes made to one branch do not necessarily impact the entire harness, promoting efficiency and reducing the risk of unintended consequences.

 

3. Realistic Representation:

The Multibranchable option enables us to create a more realistic representation of the wiring harness in 3D space. By defining multiple branches, we can accurately capture the harness's structure and organization within the vehicle.

This realistic representation aids in visualizing the harness layout, identifying potential routing challenges, and optimizing the overall packaging of the electrical system.

 

4. Manufacturing and Assembly Considerations:

The Multibranchable option also has implications for manufacturing and assembly processes. By clearly defining and organizing the branches within the harness, we provide clear instructions and guidance for the production team.

Each branch can be manufactured and assembled separately, allowing for parallel processing and potentially reducing overall production time. The modular nature of the branches also simplifies troubleshooting and maintenance tasks.

In summary, clicking on the Geometrical Bundle and selecting the wiring harness routing file in CATIA V5 establishes a crucial link between the logical definition and the physical representation of the harness. This binding process ensures synchronization, and consistency, and enables the routing and path definition of the harness within the vehicle's geometry.

Furthermore, activating the Multibranchable option allows for the creation and management of multiple branches within the harness, introducing flexibility, modularity, and a more realistic representation of the harness structure. It facilitates the design of complex harnesses, promotes efficiency in the design process, and provides clear guidance for manufacturing and assembly.

 

 

Applied Corrugated Tubes as Protective Coverings:

Protective coverings will be applied to specified segments of the wiring harness bundles to ensure optimal performance and protection within the backdoor assembly. Two types of corrugated(COT) tubes have been selected for this application. The first type features a 5mm inner diameter and a 6.5mm outer diameter, while the second type has a 10mm inner diameter and a 12.5mm outer diameter.

The wiring harness routing has been meticulously designed to accommodate the specific requirements of the backdoor assembly. The placement of the COT tubes has been strategically determined to provide maximum protection for the wiring harness while maintaining ease of installation and serviceability.

The selection of COT tube dimensions has been based on a thorough analysis of the wiring harness requirements, taking into account factors such as wire gauge, current capacity, and environmental conditions. The 5mm inner diameter COT tube will be utilized for smaller gauge wires and lower current applications, while the 10mm inner diameter COT tube will be employed for larger gauge wires and higher current applications.

 

The use of COT tubes in this backdoor wiring harness design provides several advantages, including enhanced abrasion resistance, improved flexibility, and increased durability. These attributes ensure that the wiring harness will maintain its integrity and performance throughout the intended service life of the vehicle, even under demanding operating conditions.

 

WIRING HARNESS FLATTENING OPERATION:

The next step involves transitioning the complete wiring harness assembly into a two-dimensional representation. This will be achieved within the 'Electrical Harness Flattening' workbench by defining a set of parameters to govern the flattening process.

Then, we're going to use the 'Extract' option present under the 'Flatten' Toolbar. 

The flattening process will be guided by the selection of a target plane within the design environment. Subsequently, a single, representative bundle segment will be chosen. Utilizing the 'Select All Branches' function, all electrically continuous segments within the harness will be automatically identified and included in the flattening operation.

 

The flattened wiring harness assembly will be documented in a drawing utilizing the A0 ISO paper size (1189mm x 841mm) in landscape orientation. A first-angle standard projection will be employed to ensure a clear and consistent representation of the assembly.

 

 

DRAWING FOR OUR FLATTENED WIRING HARNESS ASSEMBLY: