Challenge

Week 12- Final project

MMathi Selvan8 Jun 2023

AIM :- To create a CAD model for door trim panel's parts by considering the given inputs of class A surface along with master section by following the design rules followed in OEM and tier1 companies.

Objectives :-

To create individual tooling axis for the parts and perform draft analysis on the class A surface
To create the class B and class C surfaces from the given class A surface
To form a solid geometry by combining all the surfaces
To decide an attachment strategy for the part and create engineering features in reference from the master section provided
To perform draft analysis on the solid part model with all engineering features
To assemble all the components togehter to obtain the final trim

Given Data :-

Class A Surface for Door Trim Panel -

As we know in automotive industry there are complex products that we have to design but this is not possible with simple sketches for that we need Class A Surface.

The A-surface or the styling surface is first checked for any gaps and other issues in its surfaces. This Surface acts as the input surface so any correction to be done should be with approval from the styling team or done by them. A- perfect surface is the one when a boundary is created, the lines are only on the edges of a component and its holes or cutouts as shown below.

The door trim panel is created by follwing steps

Check given Class A surafces for any modification.
Segregate given surafces into separate part body namely Lower Substrate , Arm Rest , Map Pocket , Bottle Holder.
Work individually on each part.
Perform Draft analysis on class A surafce.
Creation of class B and Class C surafce.
Craete a closed body
Follwed same procedure to craete all parts .
Then create attachement features for all parts.
Then do Draft analysis on final parts and then constrain them for assembly.

Arm rest design

In the front of the car, a central armrest, which commonly folds away based on user preference, will also often include a storage compartment and sometimes even cup holders. Some also provide the location for controls for non-essential functions of the vehicle, such as climate control or window motors.

For the Arm rest design the input class a surface provided is

we have found a small discontinuity in the arm rest which is repairable

by using extrtact and trim command

EXTRACT

TRIM

REPAIRED SURFACE

Tooling axis creation:

Extract the surface from the class A where the surface is entirely visible and easy for the manufacturing by viewing the surface in different orientations

Now create a point at the middle At 0 coordinates and create a line in point and direction method and the create line is our main tooling axis

We are creating the line in the Z direction as most part of the body are visible in this direction

Performing Draft analysis

It clears most of the area but as you can see the arm rest some areas are not claearing because of their their shape so we need another tooling axis to clear the sides

we call it as the side core axis

Generating of the class B surface

For the class B surface generation refer to the master section provided to measure the thickness of the plastic component then offset the class A surface to an extend of 2.5 mm thickness beneath the class A surface

Extrapolate then class b edges to an extent to form the proper trim with the class a & C join

Generating the class C surface:

For the class C surface generation we use the class A surface as an reference and follow the draft with respect to the reference surface and the main tooling axis

Generating the final close surface:

After creating the class B and the class C surfaces join the class A and the class C surfaces and trim the resultant with the class B surface then the resultant surface is the final closed surfaces

The Class B should intersect the surface of the joined surface

Then make the B surface trim with the class A & C join

It is the close surface of the plastic componenet with a thickness of 2.5mm

Then create a new body and use the solid body feature to create the solid surface body out of it

Draft analysis of the final solid body :

After generating the final closed body perform the draft analysis with a draft angle of 2.98 ~3 degrees

And examine whether all the required surfaces are clearing the draft with respect to the main tooling axis of any draft applied surfaces can’t be able to clear the draft analysis write a report mentioned what might be the reason for the surfaces not clear in the draft analysis and suggest the appropriate solution if else

Lower substract:

In case of the door lower substract after examining the provided input surface we can able to detect a projection or an extension so we don’t need it for any further so, create a line and split the unnecessary surface

Tooling axis creation:

Extract the surface from the class A where the surface is entirely visible and easy for the manufacturing by viewing the surface in different orientations

Now create a point at the middle At 0 coordinates and create a line in point and direction method and the create line is our main tooling axis

Draft analysis of the class A surface:

Perform the draft analysis on the class A surface to check whether all the surface are clearing the draft of 3 degrees with respect the tooling axis we create then continue with the model or if you notice any flaws notice them with the class A team to rectify or else continue with the class B surface creation

The class A surface is com[pletely clearing the draft analysis of the 3 degrees with respect to the tooling axis created

Creation of class B surface:

In case of the lower substract offset the class A surface to a value of 2.5 mm beneath the class A surface then extrapolate the class B surface which would help to make the final trim with the class A and C combined surface

Creation of class C surface :

When the surface of the class C is parallel to the tooling axis then make use of the sweep with respect to the draft Direction to an angle of 3 degrees and the surface need to be outside the class A surface when seen from the normal direction with respect to the main tooling axis. And if the class C surface which need to create is perpendicular to the tooling axis then make the sweep with the reference surface With 90 degrees

Final surface formation:

Now join the class A surface with the class C surface and trim the class B surface with the join A and C surface

Solid surface body formation:

Now go to the part work bench and use the solid surface feature to create the solid surface body

Draft analysis of the solid body:

Preform the draft analysis on the solid body with a draft angle of 3 degrees and see the results

Map pocket design:

Map pocket is the sub element situated right at the hub of the lower substract of the door trim panel . The processs illustrated is same as the prevous components first, we need to check the boundary of the given input surface whether there might have any open patches or else protrude the input surface as the required class A surface

The provided input surface is

Tooling axis creation:

In case of the map pocket the we extract the surface in the Y direction orientation and use the point - direction to generte the tooling axis of the map pocket

Draft analysis of the class A surface:

Once the tooling axis is create analyze the draft for the class A surface with a draft angle of 3 degrees

Class B surface creation:.

Now step forward to create the class B surface deploy the 2.5mm offset of the class A surface to generate the class B surface beneath the class A surface

Extrapolate the class B surface edges to form the perfect trim with the class A & C join

Class C surface creation:

Now create the class C surfcae which is an intermediate surface between the class A and the class B surface generally like a fill between the two surfaces created with the help of the sweep feature with a draft of 3 degrees

along the tooling axis direction and with a draft of 90 degrees along the reference surfcae sweep

Final surface creation:

Once all the surfaces are created that is the class B and the class C surfacesthen join the class A & class C surfcaes and trim the join surface with the class B surfaceto form the final closed surface

solid body creation:

Go to the part workbench and use the close surface feature to form the solid body out from the close surface body and perform the draft analysis

Draft analysis of the solid body:

Now perform the draft analysis with a draft angle of 3 degrees on the solid body

The results obtained are

Bottle holder design:

The input surface provide for the bottle holder is

Check for the open patches if exists , here in case of the bottle holder the oe particular surface is creating a problem in the further solid body creation . So ,here we use the join command and use the sub elements to remove feature to remove the particular surface from te input one and use the multisection feature to complete the class A required surface

Tooling axis creation:

In the case of the bottle holder use the flat surface and extract the surface and create a point at the 0 coordinates and use the point - direction to create the tooling axis

Draft analysis of the class A surface:

Perform the draft analysis of the class A surface with a draft angle of 3 degrees the result obtained is

Class B surface creation:

Now offset the class B surface to 2.5mm following the master section beneath the class a surface and extrapolate the class b edges to an extent to form the proper ytrim with the class A and C join Choose the correct direction for offsetting the surface

Class c surface creation:

Now create the class C surface with the aid of the class a surface and the sweep feature along the draft direction and the reference surface parameters . So provide adraft of 3 degrees along the draft direction making the direction of the draft as the main tooling axis and 90 degrees draft with rreespect to the reference surface

Final surface creation :

Once all the surfaces are created that is the class B and the class c surfaces join the class C surface with the classs A surface and trim the joined surface with the class b surface

Solid surface creation:

Once the closed surfae is created then go to the part workbench and use the solid surface feature to generate the solid body out of it

Draft analysis of the solid surfcae body:

perform then draft analysis of the solid body with a draft angle of 3 degrees

The obtained results are the

Once all the solid bodies of the components are generated we need to move onto the B sifde attachment features

The B side attachment features may include the

Dog house
Ribs
Screw bosses
Flanges
Snap fits
Heat stakes

Lower substract attachment features:

Based on the master sections provided for the for the input surface of the lower substrate it indicates theat the heat stakes are positioed on the surface

Following the master section wee need to create the heat stakes on the lower substract B side

Heat stakes :

Process for heat stakes assembly:

In thermal staking, also referred to as “heading or riveting”, the controlled flow of the molten plastic is used to capture or retain another component, usually of a different material.Thermal staking provides an alternative to welding when the two parts consist of dissimilar materials which cannot be welded or when simple mechanical retention of one part relative to another is adequate .

The most commonly used application involves the attachment of metal to plastic. A hole in the metal part receives a pre-molded plastic boss. The thermal tip contacts the boss and creates localized heat. As the boss melts, the light pressure from the horn forms a head to a shape determined by the horn tip configuration. When the heat is terminated, the plastic material solidifies and the dissimilar materials are fastened together.

So taking the references from the master section here we need to make a note of that whenever we take the reference from the master section the referenced elrement should be isolated from the master section

so start working on the heat stakes creation and provide the support it with ribs on the four sides to add additional strength to the heat stake

Design parameters:

Height we need to follow the master section
Draft provided on the outer and the inner face with an angle of 0.5 degrees

Pad the sketch with a height represent in the master section taking reference as the tooling axis direction

Now apply the draft of 0.5 degrees on both inner and outer edges.

Now create the ribs for the additional support .

Ribs provides a mean of strength and stiffness to the molded component without increasing the overall wall thickness

Ribs basically facilitates:

Locating and arresting the components of an assembly
Providing alignment in mating parts
Acts as a guides or stops in mechanisms

Design parameters:

Draft: 0.5 Degree per side (minimum) and maximum upto 1.5 degrees
Thickness of ribs: 40 to 50% of wall thickness
Height: ≤ 5 times the wall thickness
Spacing (for more than 1 rib): 3:1- steel height/width ratio (maximum). h/w =3 or2(preferred) where h is the height of the rib and w is the space between two ribs.
Minimum thickness at the tip: 0.75mm
Rib fillet Radius: 0.25mm max or 0.125*thickness of the component
Rib root thickness should not be more than 30% of the wall thickness.

Now pad the sketch and apply the draft analysis with reference to the tooling axis

The result of the draft analysis are

Heat stake:

Apply the fillets of 0.25 mm minimum on all the sharp edges and also you can apply chamfer for the tip of the ribs and apply the boolean operation of unoin trim to combine tyhe ribs with the heat stake

So we need to position the heat stakes all over the component following the distance between the two hewat stakes is 50-100 mm

Another attachment feature we create is 4 way locator as when there is a need of more heat stakes but because of the design rule if the distance is not sufficient enough tio create the another heat stake then we create theb locators and the height of the locator mush be higher than the heat stakes

Locators:

Locators are used to locating the position of the mating part while assembling.
The design rule for the locator is mostly the same as the rib but the height of the locator should be more than the heat stakes at a min of 5mm.
The locator also constrains the movement of the mating part.
The gap between Flange and the locator should range between 0.5mm and 1 mm.
There are two types of locators.

1. 2-Way Locator.

2. 4-Way Locator.

The design rules follows the same as in case of ribs foloowed by some changes the sketch is

The height should be greater than the heat stake and providev a draft of 0.5 degrees selecting the neutral elament as the sketch plane and the pulling direction is the main tooling axis

The final attachment of the 4 way locator by applying a minimum fillet of 0.25 mm on all the sharp corneres and at the top apply thenchamfer of length and angle of 3 mm and 45 degrees

The draft analysis of the component is

3. Dog house creation:

DOGHOUSE- Doghouse is an engineering feature used in the plastic trim design which helps to remove sink marks formed on Class-A surface while creating attachment feature on Class-B surface. Doghouse is a supporting feature, other features like locators, heat stakes, pushpins are mounted on top of doghouse for fixing and assembly purpose. Doghouses are subjected to draft analysis to prevent breakage of the component during ejection from the mould.

Design rules for Dog house creation

C" is where the doghouse contacts the backside of the surface

Doghouse wall thickness at the intersection of the part wall ( C ) should be 40% or less than the main wall stock ( T ).

The height of ( B ) should be between 3.0 – 6.0 mm

At first extract a surface and create a point on the surface center using Tooling axis as reference create a plane with respect to the point created

With the plane created use positioned sketch to draw the layout for the dog house iam using centered triangle to draw a 30x20 rectangle

Then usig the layout create a sweep on 3deg with reference to the tooling axis

Then create a closed surface

Give a shell of 2.5mm

Give drafts on the inside wall

Give fillets to clear the sharp edges

Use the booolean operation to remove the component from the dog house and apply the draft of 0.5degrees on the walls of the coring

Rib cage:

For provoding the additional support for the dog house we create a rib cage with two ribs of 1 mm thickness and providing a draft of 0.5 deg with respect to the side core tpooling axisb

At the top surfcae provide a cutout to provide the room for the pushclip to positrion it in the top of the dog house

SO on the lower substract we need to provide upto 2 dog house maintaining that there might not be any engineeering feature with in a direction of the slider movement upto

We use the translate option from point to point translation to copy and paste the dog houses atb arious locations and use the rotate option to change the direction of the opening for the slider

These are the 2 dog housess along with their slider axis

B side attachments on the Door arm rest:

Flanges are the joining features that help to assemble different components. The mastersection was used to make flanges. After creating one flange point to point translation is used to translate the flanges. We need to provide a draft of 0.5 degrees for the flanges . The gap between flanges should be 50-100 mm. Boolean operations were used to add attachment features into closed body

Design:

In case of te door arm rest we need to folow the master section provided for the flange creation

The thickness of the flange is equal to the thickness of the plastic component that is 2.5 mm

The draft provided is 0.5 deg

Apply requierd fillets on all the sharp edges

The sketches taking the references from the master section are