Door Trim Panel design

DESING OF DOOR TRIM PANNEL

Objective

With the input of class A surfaces and master sections, the plastic door trim parts are to be developed following industry standard design guideline using Catia V5 software.

Introduction

Door Trim is an interior component attached to the inner side of the door. This product does more than merely improve the appearance of the vehicle interior. Rather, it is a vital module component that creates a more comfortable interior by providing a variety of accoutrements and functions.

Design Methodology

For this project we need to design four parts of the door trim using the master sections provided, namely

1. Door Arm Rest
2. Lower Substrate
3. Bottle Holder
4. Maap Pocket

Terms and definitions

Class A surface

This is the styling surface which provides the aesthetic features of a component. A designer starts the component design from a class A surface.

Class B surface

Class B surface is obtained by offsetting the class A surface by the component thickness value. This B surface contains all the engineering features of the component.

Class C surface

Class C surface is created along the tooling direction of the component and connects the class A and class B surfaces.

Draft Angle

Sheet metal and plastic parts that are made by forming, casting, pressing or even molding, require a draft angle at their side walls. Draft angles are the degree of taper that is incorporated into the side wall and cores of the die cast tool to aid in the removal of a part. Primarily, they function to reduce the friction between the part and the tool as it is ejected. Without draft angles, parts can be stripped, dented, or get stuck in the tool.

Draft angles are measured from the Tooling axis of the part. For mould designs where one metal mould component make direct contact with another, a minimum of 3° draft is required to ensure that the mould can separate properly.

Draft Analysis

Draft analysis measures the draft angle on multiple surfaces of a part along the tooling axis to check if the surfaces have the minimum required draft angle for it to be moulded properly.

Tooling Axis

Tooling axis is the direction in which the 2 halves of a mould (core and cavity) opens or closes, or the direction in which the part is released from the mould.

Parting Line

A ‘parting line’ is the line of separation on the plastic part where the two halves of the plastic injection mold meet. The line actually indicates the parting ‘plane’ that passes through the part. Within more basic plastic part design plans this plane can be a simple, flat surface, but it is often a complex form that traces the perimeter of the part around the various features that make up the part’s outer ‘silhouette’.

Ribs

Ribs are thin wall-like structures that add support and rigidity to injection moulded parts. They are thinner than primary walls and are used to support these walls, as well as bosses, by running perpendicular to these structures. Ribs are often used to replace thick wall sections to avoid sink marks, warp, and voids.

Dog House

Dog house is an engineering feature used in plastic trim design. These are used as supporting feature and other engineering features such as bosses, locators etc are mounted on them to increase their strength. Dog houses require a slider for moulding and are subjected to draft analysis along the slider axis to prevent breakage during ejection from mould cavity.

Heat Staking using heat stakes

Heat staking technology is quite simple in concept. Whenever two or more components need to be attached to one another, and at least one is made of a thermoplastic, a combination of heat and pressure can be used to reform the plastic to the many shapes or profiles to retain or join the parts together.

This creates a solid, hardware-free bond that uses the plastic’s inherent strength to keep the finished assembly together.

4 way

4 way locators restrict 4 degrees of freedom along 2 axes of an object.

Design Process

• For all the parts the class A surface is checked for surface abnormalities, if found ok then the plastic component design is started else the class A surface is sent back to the product design team for correcting it
• Tooling and slide core axis (if required) is created for each of the part and draft analysis of the class A surface is done
• The class B surface is then created by offsetting the class A surface by the component thickness value which is measured from the master sections that are provided
• C surface is then created by extracting the edges of the class A surfaces and sweeping them wrt of the tooling axis or the refernce surfaces
• The A, B and C surfaces are then trimmed and joined to create a closed body
• Flanges and other attachment features are then design on the closed body following the master sections
• Draft analysis is then done on the final body along their respective tooling axis to check the draft provided in the surfaces for proper removal of the part from the moulds
• Once all the part design are finalized they are assembled along the Push Pins which are situated right abive the Dog House roof on the Lower Substrate

Input

Class A surfaces

Master sketches

Door Arm Rest

Class A surface draft analysis along tooling axis

Class A surface draft analysis along side core axis

Class B surface (offset - 2.5mm)

Class C surface

Closed Body

Flanges on the door arm rest for attachment with the lower substrate

Door Arm Rest final body draft analysis along tooling axis

Door Arm Rest final body draft analysis along slider axis

Lower Substrate

Draft analysis of class A surface

Class B surface (Offset of 2.5mm)

Class C surface

Closed Body

Body with attachment features

The 4 way locators, ribs and dog houses were created using design guidelines, while the heat stakes are created using the master sketch

Design rules for Rib creation (and 4 way locators)

• Draft – minimum of 0.5° per side
• Thickness – generally 40% of wall thickness
• Thickness of Tip – minimum of 0.75mm
• Radii – maximum of 0.25

Measurements taken for this design

Draft angle: 0.5degree

Thickness: 1mm

Height: 30mm

Fillet Radius: 0.1mm

Dog House design and guidelines

Draft analysis of final body along tooling axis

Draft analysis of dog house inner surfaces along lifter axis

Maap Pocket

Draft analysis of class A surface

Class B surface (offset of 2.5mm)

Class C surface

Closed body

Flanges for attachment with lower substrate

Draft analysis of closed body along tooling axis

Bottle Holder

Draft analysis of class A surface

Class B surface (offset 2.5mm)

Class C surface

Closed body

Flanges of lower substrate heat stakes and 4 way locators

Draft analysis of final body

Assembly

Entire Door Trim assembly

Door arm rest flanges and heat stakes

Door arm rest and Maap pocket flanges with heat stakes

Bottle holder flanges with heat stakes and 4 way locator

Assembly of Push pin and dog house on lower substrate

Rendered Images

Door Arm Rest

Lower Substrate

Maap Pocket

Bottle Holder

Assembly

Door arm rest flanges and lower substrate heat stakes

Door arm rest & maap pocket flanges and lower substrate heat stakes

Bottle holder flange and lower substrate 4 way locator

Dog house and push pin assembly

Door Trim

Conclusion

Thus, the Door Trim was successfully designed from the given inputs and following industry standard design guidelines.