Coin Holder Design and Draft Analysis using CATIA V5.

AIM: To create the Coin Holder Plastic component through the given Class-A surface. To begin with, the tooling axis for the given Class-A Surface should be created meeting the requirements of the draft angle and at the end perform the Draft analysis on the model.

Take the Thickness of the component to be 2.5 mm

OBJECTIVES:

• To ensure proper tree structure is followed.
• Geometrical sets should have a proper name based on the sketches present inside of them.
• All the sketches should be created under the geometrical set.
• Use of the Close Surface feature to make a solid body from the surface.
• To publish the Tooling Axis Class A, B and C Surface.

THEORY:

• Draft Analysis:

Draft analysis helps to detect if your drafted part is easily removable from the mould (in case of plastic component) or die (in case of sheet metal). All plastic components will have a minimum draft of 0.5 to 3deg. And for automotive sheet metal parts, the draft will be 7deg or more. If a mould wall is perpendicular to the part ejection, there is ample friction or interference between the mould and the part which will not allow one to release from the other. This is why design engineers give a minimum draft to the part.

In CATIA V5 the feature draft analysis dialogue box looks like this:

1. Mode:

• The mode option let you choose between quick analysis and full analysis mode.
• In quick mode, there are 3 ranges blue, red and green colours. In the case of the plastic component, we will set the draft angle as 3°.

2. Display:

• The first box is to open and close the colour scale dialogue box.
• The second box is the analysis under the running point when activating the checkbOx and moving the pointer over the surface. This option enables you to perform local analysis. Arrows are displayed under the pointer, identifying the normal to the surface at the pointer location (green arrow), the draft direction (red arrow), and the tangent (blue arrow). As you move the pointer over the surface, the display is dynamically updated. Furthermore, circles are displayed indicating the plane is tangent to the surface at this point. The displayed value indicates the angle between the draft direction and the tangent to the surface at the current point.
• Click the No Highlight Representations button to set the display option of highlight effect sources as 'on/off. When checked 'On" the surfaces are selected but they will not be seen in the specification tree.
• Click the Light Effect button and the colours of the analyzed elements react to the light source.

3. Direction:

• The first check box is the locked direction icon which is used to lock the direction of the compass after selecting the specified direction.
• Click on the compass icon to specify the new pulling direction to remove the part.
• Click the Inverse button to automatically reverse the draft direction. When several elements are selected for analysis, the draft direction is inverted for each element when the button is clicked.

• Tooling Direction:

The Tooling Direction is the direction that the mould pulls apart. The mould is built into two separate pieces. You have a Cavity side and you have the Core side. The Core pulls apart from the Cavity and that's the Dyeline or the Tooling Direction. There are different methods to find out the tooling direction. Here we are using bisecting method to find out the tooling direction. We can use any method the ultimate aim is to reduce the cost of manufacturing by reducing the complicity in manufacturing the component.

• Class A: Class A surface is the term mainly used in the automotive design industry. It describes the final production surface data for the aesthetic parts of the car.
• Class B: Class B surface is the second surface which is not visible normally. These must be smooth and "error-free" as well, but not held to the standards that class A surfaces.
• Class C: Class C surfaces are the backside surfaces that can have tool marks, flash and other imperfections without hurting appearance function etc.

PROCEDURE:

• Step 1: Importing the Coin Holder File and Check Class A Surface design file:

After receiving the Class A of the Coin Holder check for the connectivity of all surfaces on it. Use Join operation, boundary operation and disassemble. The check is over if any discontinuities do not arise. Delete the operations after the check.

Figure1: Join Operation for checking connectivity.

Figure2: Boundary Operation for checking connectivity.

• Step 2: Determine Tooling Axis and Side Core Axis:

• Extract the base surface of the Coin Holder and place a point in between the Surface > Point definition select surface > Distance = 0mm and place an Axis system on that point.

Figure3: Creating a point on the Base Surface.

• With the observation of the Class A Surface, the above which we have created is in the centre of the model and covers major of the parts of the Class A Surface. So we will carry on with the centre point and make a Tooling Axis for the model on the point we have made.

Figure4: The required Tooling Axis for the Coin Holder.

As this model is a little complicated while production we will be requiring a Side Core for this component, hence we will have to make a Side Core Axis.

• The best possible position for the Side Core Axis will be along with the hole in Class A Surface, so let's take the boundary of the hole.

Figure5: Taking the boundary of the hole section in the Coin Holder.

• Now we will fill the boundary of the hole and create a Surface, on the centre of the Surface we will create a point.

Figure6: Taking the boundary of the hole section in the Coin Holder.

• From this point, we have Created the Surface of the hole part let's make a line which will be our Side Core Axis.

Figure7: The required Side Core Axis for the Coin Holder.

• Now that we have the Tooling Axis and the Side Core Axis, let's publish the Tooling Axis, Side Core Axis and the Class A Surface of the Coin Holder.

Figure8: Publication of the Tooling Axis, Side Core Axis and the Coin Holder.

• Step 3: Draft Analysis of Class A Surface:

• Change View Mode Customization to the Material mode for the Draft Analysis.

Figure9: Material Mode.

• Go to INSERT > ANALYSIS > FEATURE DRAFT ANALYSIS and move the compass to the Tooling Axis. Change the range to 3°. Apply the settings as shown in Figure.

Figure10: Draft Analysis tools Coin Holder.

The Draft Analysis of the Class A Surface of the Coin Holder is shown below, if I see the model from the top or bottom along with the Tooling Axis then it has no Negative Draft.

Figure11: Screenshot of Draft Analysis of Class A Surface of the Coin Holder.

• But if I examine the model from other views I can see the model has some Negative Drafts along the Tooling Axis.

Figure12: Screenshot of Draft Analysis of Class A Surface of the Coin Holder showing the Negative Drafts.

So to eliminate this we have Created the Side Core Axis, but for that also there should be a minimum of 3° draft angle on all the negative sides of this model.

• So when I briefly examined the model and used to running point tool to check the surface draft value, I observed that the sides have 0° or -° from the tooling axis.

Figure13: Screenshot of Negative Drafts when measured with the running point tool.

As we can see, these red surfaces are almost or equal to 0°. Now, this is an issue because it will not compete with the recommended classifications of a plastic part manufacturer. If the surfaces are at 0° the plastic part won't eject put easily at the end due to contraction after the cooling process. To tackle this problem there are mainly two solutions which I have come to know. One way is to create a secondary and tertiary side core tooling axis to overcome this problem, but the overall point is to manufacture the product with fewer expenses. So what I would recommend to the Class A surface engineer is to give some draft angles on these sides up to 3° on the negative sides.

Step 4: Class B Surface:

Now we need to create a B Surface which will be similar to the A surface at an offset value of 2.5mm.

• First, we will start by creating the Side Walls for this we will Extract the walls of the Coin Holder; Untrim, Extrapolate, Trim and Offset to a distance of 2.5mm. We will also give the required Fillet values to the walls.

Figure14: Final look of the Side Walls after the above operations.

• Now let's make the Base we require, let's Extract all the 5 base parts that we require from the Class A surface Untrim them, Extrapolate them, Trim all 5 bases together and at last Offset them at a distance of 2.5mm.

Figure15: Final look of the 5 base surface after the above operations.

• Now let's make the Top Surface we require, let's Multiplextract the Top Surface of the Class A surface Extrapolate and at last Offset them at a distance of 2.5mm.

Figure16: Final look of the Top Surface after the above operations.

• Now that we have created the Side Walls, Base and Top Surface for the B Surface, let's Trim them together and get an initial trim output for the B Surface. First, let's trim the Side Walls and the Base.

Figure17: Final look after the trim of Side Walls and Base.

• Let's use the above trim and Trim it with the Top Surface.

Figure18: Final look after the trim of Side Walls, Base and Top Surface.

• To complete the B Surface, we need to create one more surface i.e. the Outer Flange; for this, we will Multiplextract the Outer Flange, Extrapolate, Trim, Split and Offset them at a distance of 2.5mm to get the final required surface.

Figure19: Final look of the Outer Flange after the above operations.

• To Complete the B Surface, we need to Trim the Outer Flanges with the Trim that we have created for the Side Walls, Base and Top Surface. Also, we will provide the Fillet Values to them so that we will have the Final B Surface that we need.

Figure20: Final look of the B Surface.

• Step 5: Class C Surface:

• To create a Class C Surface, first, Multiple Extract the boundaries and the Top Surface and the Boundaries of the Hole and the Side Surface of the Hole of the Class A Surface.

Figure21: The Boundary and Surface of the Top Surface and Hole part of the Class A Surface created by Multiple Extract.

• Now we will use the Sweep option to create the required surface. To perform this operation, Go to the Toolbar > Sweep > Profile type > Line > Subtype: With Reference Surface > Guide curve 1- (select the extracted boundaries) the in Reference Surface (select the extracted surface) angle and length as 90° and 4mm respectively and click ok.

Figure22: Sweep operation on the boundary and surface of Class A Surface.

• This is the Class C Surface we need to create the final Coin Holder Surface.

Figure23:Final Class C Surface after the Sweep operation.

• Step 6: Creation of Final Coin Holder Surface and Close Surface Body:

• After the creation of Class A, Class B and Class C Surfaces, we need to join Class A and Class C surface to form a new surface. Then trim the joined surface with Class B surface to form the Final Coin Holder Surface.

Figure24: The Final Coin Holder Surface after the above operations.

• Now that we have the required surface we can make a Solid Body out of it. To make a solid body we will go to the Part Design section over there we will use the Close Surface tool to make a Solid Body.

Figure25: The Solid Body made with the Close Surface operation inside Part Design.

• Step 7: Draft Analysis of the Coin Holder :

• Change View Mode Customization to the Material mode for the Draft Analysis.

Figure26: Material Mode.

• Go to INSERT > ANALYSIS > FEATURE DRAFT ANALYSIS and move the compass to the Tooling Axis. Change the range to 3°. Apply the settings as shown in Figure 26.

Figure27: Draft Analysis tools Coin Holder Body.

• The Draft Analysis of the Coin Holder is shown below the Component is safe.

Figure28: Screenshot of Draft Analysis of the Coin Holder Body.

• Terms asked to Mention:

• Tree Structure:

Figure29: Screenshots of Tree Structure of Coin Holder.

• Publications:

Figure30: Screenshot of Publications made.

• Screenshots of the model with the proper colour code of the draft angle in various orientations (Isometric, Front, Side, and Top View):

Figure31: Model in Various Views.

RESULT:

• The Draft Analysis of the Class A Surface of the Coin Holder is shown below the Component is safe.

Figure32: Result of Draft Analysis of Class A Surface of the Coin Holder.

• The Creation of the Class B Surface.

Figure33: Final Result of the Class B Surface.

• The Creation of the Class C Surface.

Figure34: Final Result of the Class C Surface.

• Creation of Final Coin Holder Surface and Close Surface Body.

Figure35: Final Result of the Coin Holder Surface.

Figure36: Final Result of the Coin Holder Body made by Close Surface.

• The Coin Holder Body has passed the Draft analysis test as the draft values of the Coin Holder are less than 3° and the Holder is safe for production.

Figure37: Result of Draft Analysis of Coin Holder Body.

CONCLUSION:

1. Class A, Class B and Class C surfaces are created following standards of the automotive industry using Catia V5 software.

2. Draft Analysis was performed on the Coin Holder and it was observed that the draft was under the permissible limit for the manufacturing of the component using the injection moulding process.