Designing the inner panel of an automotive back door

Objective

To model the inner panel of the back door of a car using catia V5 with necessary embosses and reinforcements

Introduction

Back door is the rear most part of a car. It is a critical component to design and model because it has to be strong enough for sustain the rear crash.

The car back door consists of the following parts

• Outer panel
• Inner panel
• Hinge reinforcement
• Gas stay reinforcement
• Latch reinforcement
• Wiper motor reinforcement

The hood modeling involves 2 stages

• Modeling of the individual parts
• Assembling of the parts

Designing

Outer panel is a class A surface where aesthetics is mainly concentrated because only these surfaces are visible but here we design only the inner panel of the back door

figure 1: inner panel

The inner panel is designed based on the outer panel as the inner panel should provide necessary strength to the outer panel, embosses are added wherever necessary. Embosses are done via deep drawing operation therefore a minimum draft angle of 7 degree must be provided to perform the deep drawing operation smoothly.

Generally, inner and outer panel are made of 0.75 mm thick. Reinforcements are given a thickness of 1.5mm. Adding more reinforcements improves the strength but it also increases the cost.

Some of the commands used in generative shape design are offset, split, extrude, extract,extrapolate, sweep, project, trim, shape fillet, edge fillet, boundary, parallel curve, smooth curve, symmetry, join,healing, thicken etc.

Reinforcements

The reinforcements are added to strengthen the parts, the reinforcements used here are gas stay reinforcement, hinge reinforcement, latch reinforcement, side reinforcement, wiper reinforcement

figure 2: gas stay reinforcement

Gas stay reinforcement is used for fixing the gas stay which is placed on necessity of ergonomics and is used for aiding the motion of the back door with an ease.

figure 3: hinge stay reinforcement

Hinge reinforcement is to enable the open and close motion of the hood. It is a reinforcement part which also increases the strength of the hood. It has two parts one part mounted to the roof and other one is mounted to the back door.

figure 4: wiper reinforcement

Wiper motor reinforcement is used as seat for the wiper motor and is used to assemble the wiper motor with back door

figure 5: side reinforcement

Side reinforcement is used for supporting the side of inner panel which provides additional strength to the back door

Assembly

The modelled parts are imported one after the other and the constraints like fix, offset, coincidence, symmetry (with mirroring the part) are used to assemble the parts where it is to be placed.

Figure 5: inner panel

Inner panel is the first part that is imported and is fixed, as the primary parts are to be fixed

Figure 6: gas stay reinforcement is imported and assembled

Figure 7: gas stay reinforcement is mirrored

Gas stay reinforcement is then imported and the respective planes of the gas stay and the inner panel are selected and the offset distance is set as zero. and is mirrored.

Figure 8: hinge reinforcement is imported and assembled

Figure 9: hinge reinforcement is mirrored

Hinge reinforcement is then imported and mated with inner panel of the back door and it is mirrored

Figure 9: latch reinforcement is assembled

Latch and striker is then imported respective planes of the latch and the inner panel are selected and the offset distance is set as zero.

Figure 10: side reinforcement is assembled

Figure 11: side reinforcement is mirrored

Figure 12: wiper motor reinforcement is imported and assembled

side reinforcement is assebled to the planes of the back door and is mirrored

Figure 13: assembled inner panel of back door

the above figure shows the assembled back door with necessary reinforcements