Project 2

CAR BACK DOOR WIRING HARNESS DESIGN- PROJECT 2

AIM

To route the Wiring harness on the given car body back door and prepare a flattened view drawing in CATIA V5.

INTRODUCTION

A wire harness, also commonly referred to as a wiring harness, is an exterior sheath used to cover some types of electronic wires. Generally, wiring harnesses are made of thermoplastic or thermoset materials that can help protect the cables from the environment.

Automobiles today come with some great features. Their design, though, calls for deft wiring considerations. An automotive wiring harness is an assembly of wires, connectors, and other electrical parts. You use it in a vehicle for the transmission of signals.

Design of Wire Harness

The design of the harness comprising the interconnected mesh of wires is crucial. Select the important components like connectors, fuses, and sensors. Ensure their reliability.

Study the schematic circuit diagram. Divide the entire vehicle into detachable parts like chassis, body, and engine. Then design the wiring harness that suits the requirements. Ensure that it fits the customer's requirements, shape, and size of the vehicle. Chalk out electrical routing in a way that reduces complexity and uses minimal space.

There are three types of engine wire harnesses based on the vehicle part you are looking at. The engine wire harness is a set of wires, connectors, and terminals to relay the signal to and from the engine. It also communicates messages from all sensors within the engine.

The body wiring harness routes electrical and electronic bits of information. It’s what keeps the major components of the automobile working. The body wiring takes care of power windows, lighting, and other accessories. And then, you need a chassis wiring harness for connecting the components.

Door Wiring Harness

In the case of car doors, as the door of the automobile opens and closes, the wires bend. If you use the car every day, the door will open and close many times. In the case of the Back door, the trunk could be opened and close many times in daily life. The backdoor wiring harness was mainly introduced to connect the brake lights, number plate lights, rear wiper motor, and defogger connections. The harness routing should be maintained properly with all the supporting components like clips, clamps with proper protective covers, and rubber grommets.

OBJECTIVE

• Define all the mechanical connectors electrically and save them in the Catalogue.
• Place required Connecters on the Back door CAD data.
• Place Fir Tree clips at the required position by following the packaging rules.
• Create the Wiring Harness Routing with all the electrically defined connectors and mounting equipment.
• Create branching points at required locations to create sub-branches and connect to various connectors in the geometrical bundle.
• Apply Protection coverings as required.
• Create Wiring harness flattening for the final geometrical bundle.
• Using the drafting workbench, create a drawing sheet with the flattened wiring harness.

DESIGN METHODOLOGY

Some important packaging rules and best practices to be considered during wire harness routing and placing of the clips and clamps are as follows

• The distance between two clamps on a straight branch should be a maximum of 200mm.
• The minimum branch length should be 50mm.
• The minimum distance between the clip and the nearest branching point should be 25mm.
• The minimum distance between two straight connection points should be 200mm.
• The minimum distance between two breakout points should be 50mm.
• To limit the number of branches from a single branch point to 4.
• Enough clip clamps shall be provided to ensure positive clearance with surroundings and the safety of the wiring harness.
• Fir tree clips and other clips can be added to the Geometric bundle as they are electrically defined and are part of the Wire harness routing and should be provided with the Wire bundle package.
• Enough slack should be provided to the wiring harness which helps not to get damaged during the opening and closing of the Back Door.
• Easy manufacturing, installation, removal, and maintenance have to be considered while designing the wire harness.
• The wire routing should be done keeping in mind the cost-effectiveness of the bundle package.
• To avoid the harness routing and clipping in blind zones of the operator during the assembly and the service.
• Provide proper slack at end connectors so that there will be no tension on the wire bundle.
• To avoid sharp edges on the sheet metal parts and if it is not possible then provide protection parts to prevent damage of the wire bundle.
• Routing through small structural holes and openings shall be avoided. To minimize chaffing and handling of the wiring harness during installation.
• To provide separate branch points for separate connectors to ensure Poka-Yoke.
• The bend ratio for all the bundle segments is considered to be 1.4

STEP 1: download the Back Door CAD data from the given source.

STEP 2: Creating the context assembly

Context assembly is nothing but the product file which contains the back door 3D-CAD data and the back door geometrical bundle. Here the geometrical bundle product contains all the connectors and clips which are electrically defined for the assembly.

• Create a new product file and rename it as Back door harness assembly context.

• Now add the back door CAD data into the context assembly and also create the geometrical bundle product file inside the context assembly.

• Define the geometrical bundle product file electrically using the geometrical bundle command.

STEP 3: Add the required suitable Connectors from the Connectors Catalogue.

Connectors selected for the cack door harness assembly are as follows

Catalog creation:

STEP 4: Place fir tree clips in the required locations to ensure proper harness routing throughout the Assembly.

• Ensure no fouling of the harness to the back door sheet metal components.
• Enough clamps shall be provided to ensure positive clearance with the surroundings and the safety of the wiring harness. The distance between two clamps/clips on a straight branch should be a maximum of 200mm. However, clamping requirements should be decided based on the harness bending and mounting arrangements.

STEP 5: Wiring Harness Routing

• Add branch points at a minimum of 25mm distance from clips and clamps to create new sub-branches connecting various connectors.
• The minimum length of the bundle should be 50mm.
• Now, the car tailgate assembly is ready for the bundle routing.
• We have activated the Geometrical bundle product file from the context assembly to create new multi-branches.
• First, we have started bundle routing from the interconnection connector to the nearest Mounting clip available and continue to add multibranchabe bundles to achieve the required harness bundle. The main bundle harness diameter is considered 15mm.
• Now create a branch point to route the sub-bundle to the Top mount brake light connector. Fir tree clips are added in between the branch point and top mount brake light connector to ensure proper and safe routing. The bundle diameter s considered to be 15 mm
• Add branch point to create bundle connection towards the defogger connector
• Now add a branch point for creating a sub-bundle connection for the Wiper motor and number plate connectors.
• Add sub-bundle segments with a bundle diameter of 15 mm.

• Add a clip on the sheet metal in between the main harness bundle and number plate connector connections. This will improve the routing and prevent the bundle from unwanted fouling with sheet metal components.

STEP 6: Applying Protective Cover

After bundle routing, we have to add a protective covering to the harness bundle so that it will get protected from damage.

• The harness bundle should be protected with a flexible rubber cover at the interconnection region where it is a critical place and subjected to opening and closing of the door. There are more possibilities to damage the wiring harness if no proper protection coverage is provided.

• Corrugated conduits and protective hoses with various properties, from heat resistance through abrasion protection and impact strength to noise reduction, protect valuable cables against all unfavorable external influences.
• Slit COT tubes are provided for protecting the harness from physical and other environmental damages that can occur in the long run.
• Start or End Extremities at the Connector bundle entry side should be given a gap of 30mm

• The selection of corrugated tubes is mainly driven by the wiring harness bundle diameter and temperature resistance requirements.

Geometrical Bundle after applying COT tubes

STEP 7: ELECTRICAL CONTINUITY CHECK

We need to ensure that the entire bundle is fully connected.

• Go to edit and then click on the search command.
• Go to advanced
• Select workbench as electrical, type as bundle segment, and attribute as Fully connected
• The select result should be TRUE or FALSE and then click search to see the connectivity analysis result
• For now, we will select "TRUE" and search for results. All the bundle segments are highlighted and found showing that all the bundle segments are electrically connected.

Step 8: WIRING HARNESS FLATTENING

The wiring harness Bundle packaging process is done. Now we need to convert the geometrical bundle into a flattened wiring harness in the Electrical Harness Flattening Workbench.

• To create the Flattened Harness, we need to create a new product file and switch it into the electrical harness flattening workbench.
• Now we need to define the Harness Flattening Parameters, save it in the same folder with all other files of the back door harness project and then Extract the geometric bundle from the wiring harness context product file.
• Then select all the branches and flatten the entire Geometric bundle.
• The bundles can be rotated and rolled with a proper radius in order to fit the drawing sheet.

Final Flattened Harness:

STEP 9: FLATTENED HARNESS VIEW IN THE DRAWING SHEET

Create a Drawing File for the flattened harness product.

First, we need to make sure that in the flattened parameter settings bundles and protective coverings have different graphical representations which are

Bundle Segments – Single-line representation

Protective coverings – Double line representation.

• Create a new drawing file in the drafting workbench

• Insert the flattened harness product into the drawing sheet using the view option and selecting the front view command.
• Modify the drawing sheet view with the required parameters.

Final Back Door Flattened Harness Drawing

Conclusion

CAR back door wiring harness assembly has been successfully completed considering all the packaging rules and industry standards, Wiring harness flattening and Flattened view drawing preparations are also done using CATIA v5 software.