Week 9 - Project_1 - Door Trim Lower with Engineering Features

AIM

To Create the Door Trim Lower Plastic component through the given Class-A surface. Also, to create heat staking and locators considering all the design rules.

INTRODUCTION

Door Trim

Door panels serve as an interface between the interior of the car and the inner workings of the door, and between vehicle occupants and the door. They are expected to meet a variety of design specifications regarding safety, aesthetics, and functionality.

Heat staking

Heat staking also known as thermoplastic staking is the process of joining two dissimilar materials together. In heat staking we use local heating and cooling to raise the temperature of plastic components and allow plastic reforming to be carried out. This reforming can be used in a wide variety of applications.

Heat staking can be performed using wide range of thermoplastic materials including polypropylene, ABS, polycarbonate and many others. The integrity of a thermal staked assembly depends greatly upon the geometric relationship between the boss and the thermal tip.

The heat staking tip is brought into contact with the thermoplastic part to be reformed. The heating tip is then heated by direct electrical heating within the tip for a short period of time. The heated tip softens the plastic material and forms the melted plastic into the shape of the tip.

In addition, heat staking has many benefits. However, this depends upon the application, benefits include:

• Heat staking enables similar and dissimilar materials to be joined.
• Local heating ensures that there is no damage to adjacent materials.
• There are many heat stake shapes available through custom designed tools.
• No mechanical vibration.
• Very simple design guidelines are required for success.

Although proving extremely beneficial for many, heat staking has its drawbacks:

• If formers are too cold, they will strain the stake causing stress, which may also impact breakages leading to failure.
• Temperature control is difficult to achieve with large multiple staking applications.
• The number of posts heat staked at one time is limited by the configuration design of the parts being assembled.

LOCATORS

Locating pins are the rib like structures on the B surface which are used to position the child part with parent part while assembling. These locators were placed in the multiple location on the part depending upon the degrees of freedoms which needs to be arrested. They were classified as two-way locators and four-way locators.

OBJECTIVE

• Create Tooling axis for the given CLASS -A surface.
• Create the CLASS B and C surfaces of door trim using the given CLASS-A surface.
• Create final surface model and convert it into solid body using close surface command in the part design workbench.
• Create Locators and Heat stakes on the B side of the door trim part body.
• Perform draft analysis for both Class-A surface and Final part body.

Design Methodology

Class-A surface means visible surface. It gives the aesthetic of the component which is created by the styling team and gives to the part design engineer to create the part with all engineering aspects.

Given CLASS-A surface

Tooling axis creation

• Check the best possible tooling direction by manually adjusting the compass.
• By analysing it is found that y axis as tooling direction would clear all the faces.
• Now extract any surface and create a mid-point on it.
• Since all the faces of the given surfaces have draft angle more than 3 degrees, I have chosen the normal to the surface method to create the tooling axis.

Draft analysis of class-A surface

CLASS-B surface creation

Class-B surface means thickness of a part it is not visible and is inside part. In other words, Class-B surface is a surface below a certain thickness from the class-A surface. This is the surface that contains engineering aspects of a model.

• Create offset surface of CLASS-A about 2.5mm inward direction.

• Check for the discontinuity and rework on the offset surface using extract, multi-extract, multi sections surface.
• Join the surfaces and ensure the final CLASS-B surface created has no gaps.

CLASS-C surface creation

Surface that joins class-A and class-B surfaces is class-C surface. Class C is often specified for interior surfaces not readily visible, surfaces that will be covered by another part when assembled

• Create the sweep surfaces with reference to surface and tooling axis by multi extracting the CLASS-A boundary

Creating the Final surface

• For creating the Finals door trim surface, join the CLASS-A and CLASS-C surface together.
• Then Extrapolate the B surface little bit outward direction to make sure that there would not be any gap when trimming with joined surface.
• Then trim the extrapolated CLASS-B surface with Join surface (CLASS-A and CLASS-C)
• Ensure the final surface has no gaps using the boundary command.

Creating engineering features on the B surface

1) Locators creation

Locators are used when assembling sub parts and are very useful engineering feature for easy way of locating the position of the parts to be assembled

I have created two 4-way locators and one 2-way locator for the given door trim design.

Design procedure

• Create positioned sketch and make required iso-constrained sketch.

• Pad the sketch profile with reference to the tooling axis. Locator’s height should be more than that of heat stakes.
• Create chamfer of 3*45 degree on the to face for the easy entry of the locators to the holes.
• Draft angle 0.5 degree is given to all the faces.
• 0.25 mm edge fillets are given to all the edges.
• Finally, using union trim Boolean operation, trim the locators with the door trim body part.

2) Heat stakes creation

Heat staking method is commonly used in OEM to assemble door trims, instrument panels etc.

The below image shows a simple animation of heat staking process.

Heat stake Design procedure

• Using positioned sketch, create sketch of the heat stake profile.

• Pad it with reference to the tooling axis.
• Heat stake height should be lesser than the height of locators provided.
• Thickness should be 40% of the component main thickness to avoid sink marks on the A surface.
• Provide draft angle of 0.5 degrees on both inside and outside walls of the heat stake.
• There should be minimum 50 mm gaps between each heat stakes.
• Create more heat stakes by special copying option and translate it to desired points.
• Then union trim them with door trim part body to get the final component.

DRAFT ANALYSIS

The Draft Analysis is a command enables you to detect if the part you drafted will be easily removed. This type of analysis is performed based on colour ranges identifying zones on the analysed element where the deviation from the draft direction at any point, corresponds to specified values.

Draft analysis is done after determining the tooling axis, draft analysis is used to check whether the minimum draft (3 degrees) is maintained or not.

• Procedure for performing the draft analysis are as follows
• Change the view mode of the component to be in customized parameter mode and then select the shading mode as materials.
• Then open the featured draft analysis tool from the insert menu.
• Then click on use the compass to define the current drafting direction and then drag and align the compass on the Tooling axis.
• Then lock the draft direction and perform draft analysis by clicking on the component.