Challenge

Week 9 - Project 1 - Door Trim Lower with Engineering Features

NNaresh Kumar28 Nov 2022

AIM

Create the Door Trim Lower Plastic component through the given Class-A surface with Heat Stakes and the locators considering the design rules and perform Draft analysis.

METARIAL SELECTION:

ABS

WHY THIS MATERIAL IS USED:

ABS has a low melting point which enable its easy use in the injection moulding process and 3D printing .It also has high tensile strength and is very resistance to physical impacts and chemical corrosion,which allow the finished plastic to withstand heavy use and adverse environmental condition.
High dimensional stability (mechanically strong and stable over time).
High surface brightness and excellent surface aspect.

THEORY

CLASS A SURFACE: Class A surface is a surface made by the designer specially in automotive design which is the aesthetic part of a body and is given as an input to the plastic designer to work on it.

CLASS B SURFACE: It is a surface which comes below the class A surface with a particular thickness. This surface contains engineering features of a model.

CLASS C SURFACE: It is the surface which joins class A with class b surface.

TOOLING AXIS: Tooling axis is the direction in which the core and cavity opens. If we are using proper tooling axis, we can avoid adding side cores thus the cost of manufacturing the component can be reduced.

It is defined as the direction in which the mould/core and cavity open. Selection of the direction of the tooling axis depends on the ease at which components can be easily ejected.

Generally tooling axis is decided from the natural axis of the design, that is, tooling axis is analysed with the x, y and z axis of the system. If the axis doesn’t clear the draft analysis, the next step is to look for the surface in which the drafting axis can be created in such a way that the axis is normal to the surface taken.

DRAFT ANALYSIS: From draft analysis, we can verify draft angles, examine the angle changes within a face, as well as locate parting lines, injection and ejection surfaces in parts.

It is an important feature in Catia which helps the user to analyse the draft on various surfaces. The draft analysis toolbar provides two modes for analysis of the draft, first is the quick analysis which basically has three colours (green, red, and blue) for analysing on the other hand other option is the full analysis mode which enables a few more details into the draft and is used in the complex components.

DOG HOUSE

Dog house is an engineering feature used in plastic design. Dog houses are used as support feature. Sometimes other engineering features like snaps, locators, screw bosses are mounted on them to increase their strength.

Dog houses are subjected to draft analysis to prevent breakage of the component during ejection from the mould cavity. Dog house and oher engineering components are built on the B-surface.

LOCATORS: It is a feature which is used to arrest the degrees of freedom for the components being assembled.

FUNCTIONALITY:

constraining DOF
Acting as an element/guide dor assembling

TYPES OF LOCATOR:

Two way & Four way locator

length of locator 22mm

(datum) - support
(4way) - support
(2way) - support

>2-3mm of heat stake

HEAT STAKES: 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.

Advantages of heat stakes are:

Simplification of machinery.
Reduced cost of machinery.
Multiple fastening points.
Allows higher density of welds compared to hot air cold form or ultrasonic welding.

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 side core axis for the dog house
Create Dog house on the B surface by considering the design rules.
Perform draft analysis for both Class-A surface and Final part body.

PROCEDURE

Creation Of Class A Surface

Class A surface is obtained as the input.
Join all the surfaces to obtain Class A surface if different surfaces are given as input and ensure no gap is present between any surfaces. Thus, Class A surface is obtained and publish it. Here, the provided surface is completely joined and can be taken as class A surface.
For the file provided, there is a projection which is found out to be not the part of real class A surface, so that surface is splitted from main class A surface.
Publish class A surface.

Creation Of Tooling Axis

Tooling axis here created is by selecting one of the natural axes as it clears the draft.
Here, tooling axis is created by extracting one of the surfaces for creating a point and a new axis is created at that point.
So, a flat face is extracted and created a point at its centre. Axis is also created at that point.
Now, line is created using line tool and giving line type as point-direction and selected the point and direction for creating tooling axis. Tooling axis is created along y direction.
Publish Tooling axis.

Draft Analysis Of Class A surface

Draft analysis is performed over Class A surface and every surface is obtained as clearing.

Surfaces obtained are all green in color, which means that the surfaces are clearing the draft analysis.

Creation Of Class B Surface

Now, Class B surface has to be created. For this, multiple extract is used to extract surface in a single operation. Surfaces obtained are the offsetted for 2.5mm.
Small filleted portions are avoided from extract and other surfaces are extracted. Small fillets are avoided as when they are offsetted to 2.5mm, fillets cannot be automatically formed in CATIA.
Similarly, other surfaces are extracted avoiding the fillets and offsetted, extrapolated and trimmed with the main surface to get proper B class surface.
Fillets are measured from the Class A surfaces and appropriate fillets are provided for Class B surface by adding or subtracting the thickness of the component to obtain correct thickness everywhere.
Publish class B surface.

Creation Of Class C Surface

Now class C surface has to be created and it is created from the boundaries obtained from the Class A surface. This boundary is provided as the input curve for sweep command. Using sweep command, class C surface is created.
Appropriate sweep is the provided considering the flash and considering manufacturing procedures. Surfaces are extrapolated if necessary.
Publish class C surface.

Creation Of Closed Surface

Now Class A surface and Class C surface is joined.(A&C JOIN)

Now Class B surface is also trimmed with the obtained surface to get the closed surface. (FINAL TRIM)

The closed surface then obtained moved to part design and close surface tool is used to obtain the part.

DRAFT ANALYSIS OF FINAL TRIM OF ABC JOINT:

Class A Surfaces obtained are all green in color, which means that the surfaces are clearing the draft analysis. The faces that are obtained in red will be clearing in core side, as the draft direction is reversed, those red faces will be turned to green which means those surfaces are also clearing draft analysis.

Creation Of Heat Stakes

Sketch for heat stakes is drawn and it is padded.
Proper drafts are given for the clearing of the surfaces.
Fillets are also provided.

Heat stakes are created and it is copied and pasted on part body. It is then transferred using point to point option to the desired position.

Creation Of Locators

Sketch for the locators is created using position sketch.
It is then padded and drafts are provided.
Proper chamfer and fillets are given to the locators.

TWO WAY LOCATOR

FOUR WAY LOCATOR

Creation Of Ribs

Sketch for the rib is drawn and it is padded.
The padded ribs are given the proper draft and fillet.

DOG HOUSE Creation

Dog houses are designed to avoid SINK MARK created on the CLASS-A surface by screw bosses and to solve the length issues when giving screw bosses which need to be assembled to other components.
It is also useful when perpendicular screw bosses are required on the part to the tooling direction.

C thickness should be 40% of the main wall thickness T
Minimum width of the dog house is 12 mm.
Height of B should be 3-6 mm
Minimum draft for the do house is 1.5 degree to die draw.

Lifter - Internal cutter (cutout)
slider- outernal cutter (cutout)
60mm max height of doghouse [3.0-6.0]

draft angles as 3degree or less than 3degree.we can use 1.5degree as a nominal degree of outer face of dof house
inner draft angle of dog house should be 0.5degree

sink marks between 3-6mm height