Week 12- Final project

AIM : 

To create and assemble the Lower Door Trim Plastic component including all the Engineering features through the given Class-A surface with the thickness as per the master section. 

REPORT :

This Report demonstrates the design of an Automotive Plastic Component – Lower Door Trim (Plastic) with Engineering features. Heat Stakes, Locators, Dog House, Ribs,  Flanges, and Push pins are the Engineering features used for attaching different components ( Armrest, Map pocket, Bottle holder, lower Substrate ) with each other using industry principles i.e. Draft angles, Draft Analysis, Determining and implementing of Tooling axis, Coring axis, Class A, Class B, Class C surfaces, Manipulation, and Constraints in the product file. The component is designed using Surface Design and Solid Design techniques in CATIA V5.

OBJECTIVE :

• Conduct a Draft Analysis on the Class A surface for the Lower Door Trim Plastic for determining the appropriate Tooling Axis.
• Creation of other surfaces i.e. B & C Surface for creating a thick solid component (thickness must be as per the master section). 
• Performing the final Draft analysis for the inspection and checking if all the features are above the Nominal Drafting for the creation of the Solid Model.
• Creation of the engineering features i.e. Heat Stakes, Locators, Dog House, Ribs, Flanges, and Pushpins on the respective component and performing the draft analysis.
• In the conclusion creating a product file and assembling all the thickened components with engineering features and placing the Push pins.

THEORY :

The terms are briefly explained below:

( NOTE : All the figures mentioned below in theory are of Map Pocket and the engineering features of Lower Substrate )

         1) DRAFT :

The draft is an angular tapering given at the design stage to every Plastic Component that has to be manufactured. It is given in the direction of the Mold Movement. The Draft allows the parts to release easily from the mold without creating friction between the surface of the component and the core and cavity plates.

When a Plastic component cools down inside the mold, its natural tendency of it is to shrink and attach to the core or cavity half. The movement of the mold opening causes friction on the walls of the component as well as the core/cavity blocks. This reduces the life of the mold as well as the component itself. The component may also have a rough surface finish as well as a weak structure due to this. This problem can be solved by giving a draft to the component.

Most applications require minimum draft angles of around 0.5º to 1º however, 3º draft angles are widely accepted for cost-saving purposes. 7º Draft angles are given to textured surfaces like Instrument Panels. Minimum possible draft angles are given to screw bosses, ribs, and stiffeners due to their critical nature.

        2) DRAFT ANALYSIS :

Draft Analysis is a tool in CATIA that identifies the zones which deviate from the specified values of angles along a defined draft direction using color codes. Draft analysis is the first step performed after receiving the Class A of the component. Draft analysis should be passed in order to make the plastic component manufacturable. Acceptable draft angles are used as a range for draft analysis.

For Analyzing the Draft of the Class A Surface:-

1. Change View Mode Customization to Material mode
2. Go to INSERT ----> ANALYSIS ----> FEATURE DRAFT ANALYSIS.
3. Select the compass from the dialog box, and move the compass to the Tooling Axis.
4. Click on the surface to apply the color region on the component.
5. Change the range to 0º to 3º. Apply the settings as shown in Figure.
6. As shown the target area has a 0º draft angle which was the concerned face since it's a flat surface.
7. Thus, it passes the criteria of having a suitable draft and the Class A can be further designed into a solid plastic component and manufactured.

        3) TOOLING AXIS :

The tooling Axis is the direction in which the Mold opens and closes. Part Drafts are given along this axis. Identify faces that can potentially create problems while manufacturing. Surfaces at angles along a desired Tooling Axis. Extract a plain surface and create a point on its center for Axis system creation. In this case, X-axis can be a possible Tooling Axis Direction.

        4) MASTER SECTION :

Master sections are the guides for design requirements that decide the component packaging after technical (Styling, Concept, or Class-A) surfaces. The green lines in the below fig is the Master section.

        5) CLASS A SURFACE :

In automotive design, a class A surface is any of a set of freeform surfaces of high efficiency and quality. It is the visible aesthetic surface of any automotive component. Class A surface refers to those surfaces which are visible and abide by the physical meaning of a product. This classification is primarily used in the automotive and increasingly in the consumer goods industry. It is a requirement where aesthetics has a significant contribution. For this reason, the exterior of automobiles is deemed Class-A.

        6) CLASS B SURFACE :

Class B surfaces are Engineering Surfaces that are invisible to the eyes or often on the back side of the Class A surfaces. It is mainly the thickness of the component or Class A. These surfaces need to be designed as per the Class A surface i.e., the continuity, thickness of the component, functionality, etc should be maintained. These surfaces include the main engineering features such as Screw bosses, Ribs, Snaps, Stiffeners, and fixations. B surfaces also do not contain any aesthetic styling content and textures since it is not visible to the eyes.

The pink colored surface is the Class A surface, and the Grey colored surface is the Class B surface.

        7) CLASS C SURFACE : 

Class C surfaces are connectors between Class A and B surfaces. This surface connects both A and B surfaces along the Tooling Axis. It contains the draft as per the design. It is basically the thickened surface between both A and B surfaces.

The pink colored surface is the Class A surface, the Grey colored surface is the Class B surface & the yellow colored surface is the Class C surface.

          8) DOG HOUSE :

The dog house is an engineering feature used in the plastic trim design. Dog houses are used as supporting features. Sometimes other engineering features like snaps, locators, Screw bosses, etc. are mounded on them to increase their strength. Dog houses are subjected to draft analysis to prevent breakage of the component during ejection from mould cavity. Dog house and other engineering components are built on B-surface.

          9) LOCATORS :

Locators are mainly used to Arrest the Degrees of Freedom of the Plastic Component. Usually, there are 2-way and 4-way Locators. It also supports the Position of Plastic Component While Assembly or Joining of Components. A 2-way locating pin restricts motion along 1 axis (or 2 degrees of Freedom), like a round pin in a slot. Likewise, a 4-way pin restricts 4 degrees of freedom along 2 axes. A round locating pin located concentrically in a hole is a common application of a 4-way pin and helps to further secure the piece. A 4-way means you prevent movement at 2 axes (+X, -X, +Y, and -Y) on the plane. Generally, you have a cylindrical push pin on the fixture and a circular hole at the workpiece part.

          10) HEAT STAKES :

Manufacturing operations currently use many different combinations of attachment methods to keep components together.  Common fasteners such as bolts, screws, and rivets can be used to form permanent attachments, but there are attachment methods that don’t require secondary hardware.  One of those methods is heat staking, which doesn’t require additional fasteners. Heat staking also known as Thermoplastic staking is the process of joining two Plastic Components together.

          11) FLANGES :

A flange is a protruded ridge, lip, or external or internal rim that increases strength. A flange allows for easy attachment and transfer of contact force with another object. They help with stabilizing and guiding the movements of a machine

          12) PUSH PINS :

The heart of the device is a straight pin topped with a flat or mushroomed head. Pushing this pin into the fastener body (in this case dog house) spreads out a set of segments or legs. Spreading them locks the fastener in place. Over the years, vehicle manufacturers have adopted push pins as inexpensive alternatives to traditional screws.

Here as you can see push pin is attached to the dog house.

METHODOLOGY :

                         Here the operations are done stepwise for better understanding and an easy yet effective process. The Steps are as follows ;

    STEP 01 : Correcting the Class A surface in case of any patches and creating a tooling axis on the Class A surface.

    STEP 02 : Class B surface.

    STEP 03 : Class C surface.

    STEP 04 : Closed and thickened components. 

    STEP 05 : Draft analysis on all the created components.

    STEP 06 : Heat Stakes with supporting ribs on the appropriate component.

    STEP 07 : Locators on the appropriate component.

    STEP 08 : Dog Houses on the appropriate component. 

    STEP 09 : Creation of Flanges for assembly.

    STEP 10 : Assembling all the created components in a product file and constraining the push pins. 

OPERATIONS :

STEP 01 : Correcting the Class A surface in case of any patches and creating a tooling axis on the Class A surface.

               

       A.  Arm Rest : 

 Given Class A surface of Arm rest.

• Here in the given Arm rest there is some error, this error is corrected by extracting, extrapolating, and joining the surfaces.
• After creating a proper Class A surface, the Tooling axis is created. 

 

       B.  Map Pocket : 

 Given Class A surface of Map Pocket.

• Here the given Map Pocket is proper (no errors).
• The Tooling axis is created. 

 

       C.  Bottle Holder : 

 Given Class A surface of the Bottle Holder.

• Here the given Bottle Holder is proper (no errors).
• The Tooling axis is created. 

       D.  Lower Substrate :

 Given Class A surface of the Lower Substrate.

• Here the given Lower Substrate is proper (no errors).
• The Tooling axis is created.

STEP 02 : Class B surface.

       A.  Arm Rest : 

• Offset the Class-A surface, Offset length is 2.5 mm according to the master section.
• Here are some patches which are not offset as required, these patches must be filled properly with their respective dimensions.
• There are 2 patches (shown in below figs.).

• For creating a proper Class B surface, extract all the vertical and horizontal surfaces, extrapolate them with proper length, trim them, and give an edge fillet as per the class a surface and offset 2.5. 
• Using the multi-section surface the other patch can be cleared. 
• Here we have the Class B surface of Arm Rest. 

       B.  Map Pocket :

• Offset the Class-A surface, Offset length is 2.5 mm according to the master section.
• Here is a patch (as shown in Fig below) that is not offset as required, this patch must be filled properly with the respective dimensions.

• For creating a proper Class B surface, use spline and extract the surface boundary for creating a curve and a guide curve. 
• Using the multi-section surface the patch can be cleared. 
• Here we have the Class B surface of Map pocket. 

       C.  Bottle Holder :

• Offset the Class-A surface, Offset length is 2.5 mm according to the master section.
• Here there were no patches so the offset surface will be the Class B surface.

       D.  Lower Substrate :

• Offset the Class-A surface, Offset length is 2.5 mm according to the master section.
• Here there were no patches so the offset surface will be the Class B surface.

    STEP 03 : Class C surface.

• Using the Boundary feature and the surface edges of Class A Surface, create boundaries on the edges.
• The sweep option is carried on the boundary lines to create a draft length extension (5mm) and draft angle (87°) or (3°). Here instead of taking 90°, we have to take 87° or 3° because of some inclination and for trimming with the Class B surface.  

       A.  Arm Rest : 

       B.  Map Pocket :

       C.  Bottle Holder :

       D.  Lower Substrate :

    STEP 04 : Closed and thickened components. 

• After creating the C surface using Sweep Operation, the Class A surface and the sweep surface are joined with each other (as Class C surface can be manipulated accordingly, hence Class A surface is joined with Class C ) in order to create a joined surface for trim. 
• Now trim the joined surface with the Class B surface.
• Here we have the Final component which is closed and thickened. 

       A.  Arm Rest : 

       B.  Map Pocket :

       C.  Bottle Holder :

       D.  Lower Substrate :

     STEP 05 : Draft analysis on all the created components.

       A.  Arm Rest : 

       B.  Map Pocket :

       C.  Bottle Holder :

       D.  Lower Substrate :

                                         Closed and thickened Lower Door trim

    STEP 06 : Heat Stakes with supporting ribs on the appropriate component.

• All the other components are being attached to the Lower Substrate, Hence Heat stakes must be created on the Lower Substrate.
• For Creating the heat stakes with supporting ribs, the dimensions should be referred with the master section. 
• Unhide the Master Section 04 and with reference draw the sketch.
• Plot a point for sketching between the lines of the master section and create a reference plane on it. 
• Firstly draw a sketch of the circular portion and the supporting ribs using the Position Sketch and reference plane.
• Created a solid Body in the part Design by using the commands Pad and thickness option (only while creating supporting ribs) with appropriate dimensions.
• Now give the Draft and fillet as required.

• Here 1 Heat stake is created with a closed body but more must be created.
• For creating more Heat stakes, draw a parallel curve and use the point and plane repetition command for creating multiple points with required spacing.
• Copy the created locator and paste it with a special link as many times it is required.
• Now translate it to the point which is created using the point and plane repetition command.
• Create a body where these Heat stakes can be assembled and union trim this body with the main Lower door trim body. 
• Hence final Heat stakes are obtained. 

• In total there are 13 Heat stakes created, from that 4 are for Arm rest, 5 are for Bottle holder, and 4 are for Map pocket.
• The dimension of the arm rest heat stakes is different than other heat stakes as per the master section.
• Hence final Heat stakes with supporting ribs are obtained.  

    STEP 07 : Locators on the appropriate component.

• All the other components are being attached to the Lower Substrate, Hence Locators must be created on the Lower Substrate.
• Locators are created similarly to the heat stakes only the sketch will be different.
• Draw a sketch for the locators using the Position Sketch and reference plane just keep the height a little more than the heat stake as per the design rules.
• The remaining procedure is the same as heat stakes. Hence final locators are obtained.

    STEP 08 : Dog Houses on the appropriate component. 

• All the other components are being attached to the Lower Substrate, Hence Dog Houses must be created on the Lower Substrate.
• Extract a surface and create a point as well as a reference plane where the dog house must be created.
• Draw a sketch for the Dog House using the Position Sketch.
• Use pad command on both sides with appropriate dimensions and shell it with 2.5 mm
• Draft the outer walls with 1.5°. 
• A reference drawing of the dog house is given below.

• Now Draw a line on the base of the dog house and extrude it. This extruded surface will help us in creating the ribs of the dog house 
• Offset the line with 20 mm upside and give thickness of 1.5 mm. 
• Draw a sketch on the created rib as per the reference fig dimensions and gibe thickness.
• Extract and extrapolate the front surface of the dog house and split it.
• Give draft to the created ribs and union trim it with the Lower door trim main body.

• Draw a sketch (as per reference fig above) on the top surface for creating the Push pin slots and pocket it with 3 mm. 

• Now for creating the core offset the extracted surface with a 3 mm upside.
• Extract the 3 side surfaces of the dog house and offset them with 1 mm inside.
• Trim the surface with each other as shown in fig below.

• Split the trimmed surface with the main body.
• Give edge fillet as per the design rules. Hence Dog House is created.

• Now for creating the second Dog house, All the steps will be same till the push-pin slot.
• After the creation of the push pin slot, create a line on the point which was created for the dog house creation.
• Rotate the dog house with respect to the created line at 45° and then create the core in order to get the proper core shape inside the dog house.
• Hence the second Dog house is also created. 

    STEP 09 : Creation of Flanges for assembly.

• Flanges must be created separately on the arm rest, map pocket, and on Bottle holder as per the heat stakes.
• For creating a flange extract the vertical and horizontal surface, extrapolate the vertical surface with some specific height, offset the horizontal surface according to the master section, and trim them. 
• After triming offset the extrapolated vertical surface and trim it with the trimmed surface.

 

• Now offset the horizontal surface, extrapolate it, and trim it with the trimmed surface. Ruff flange is ready as shown in the fig below,

• Give thickness to the flange surface as 2.5 mm, as per the mastersection.
• Now create a vertical line, extrude it with proper dimensions, and offset it on both sides as per the requirement.
• Split this offset surface with the thickened surface.

• The Flange is ready now for the counterbore. For creating the counterbore extract the heat stake circular surface and offset it with 0.5 mm outside as per the design rules. 
• Split the offset surface with the created flange, Give edge fillets as per required.
• Hence the final flange is ready.

• Now for creating multiple flanges use the same method as above or copy the flange body and paste it with link.
• Translate them as per the requirement.
• In the end create a body for every closed component and assemble every flange in it.
• By using the boolean operation add the created body with the main Body.
• Hence the flanges are ready.

Here in total 15 Flanges are created 13 for the heat stakes and 2 for the locator.

    STEP 10 : Assembling all the created components in a product file and constraining the push pins. 

• All the above operations were done in the Generative shape design and Part design, Further process of assembling must be done in the Product file.
• Go to FILE ----> NEW ----> PRODUCT (in the right bottom side dialog box).
• A product file is created, Add all the Parts ( i.e. Arm Rest, Map Pocket, Bottle Holder, Lower Substrate and add the Push Pin part 2 times as there are 2 Dog houses ) with the existing component option.
• Now create a point on the upper edges of the dog house as well as on the lower vertical cylindrical shape of the push pins.
• Create an axis on the same point which was created earlier. (shown in figs. below)

 

• For assembling the push pin with the dog house, Double click on the product file which will activate the product file and all the commands will be visible. 
• Now Constraint the push pin points with the Dog house points using Coincidence constraint.
• Similarly, Constraint the push pin created axis with the Dog house created axis using Coincidence constraint.
• The push pin will be upside down, for rotating it keep the compass on the pushpin point and hold the compass top point and rotate it as required.
• Hence the Assembly is done.

CONCLUSION :

The Design and Assembly of the Automotive Plastic Component – Lower Door Trim with engineering feature from Class A is completed using concepts of Draft angle, Draft Analysis for Class A & Final enclosed surface, Tooling Axis creation & Implementation, Class B & Class C creation, and Assembling in the Product file. All this work is done in the CATIA Software.