Week 8 - Challenge 2 - Switch Bezel Design

Aim :

To create the Switch Bezel plastic component through the given class A surface and create the required Tooling axis and perform the Draft analysis on the model.

Objective :

• First, create the required correct Tooling axis and perform the Draft analysis on the given class A surface.
• Create the class-B surface and class-C surface by using the surface modeling tools.
• And make the closed surface of class-A, class-B, and Class-C a single solid body.
• And perform the Draft analysis on the solid model.

Theory :

Tooling Axis :

Class-A surface is first analyzed to create the tooling axis or tooling direction that molds pull apart in injection molding. Tooling direction is important for plastic product design as it decides the direction for mold separation.

Steps followed for the creation of the tooling axis :

• The reference point is first created on the extracted surface.
• A new axis system is deployed to plot clearance lines.
• The X-direction and Y-direction along the class-A were used to create the tooling axis.
• Two clearing lines were bisected to form the tooling axis.
• The graphic properties of the tooling axis were changed before publishing.

Draft Analysis :

The Draft angle is the amount of taper for molded or cast parts perpendicular to the parting line. It can be measured in degrees. A functional part for injection molding has to have drafts facing both cavity and core sides to reduce the risk of damage to the parts and ensure ejection. And also important is to overcome the vacuum forces by letting air in between the metal and the plastic for the part to release properly. Adding maintaining a decent cosmetic finish.

The draft should be a part of the design for manufacturing and the plastic products Designer should be aware of its need at the outset of the design process. This allows considerations for design requirements to be taken into account.

Design Consideration

• Class – A surface should be aesthetically smooth and good.
• Class – B surface should have all the supporting features like ribs.
• The parting Line should coincide with the B surface since flashing couldn’t affect the aesthetic of Class – A.
• Class – C surface should also pass the draft analysis

Nominal values for Draft angle :

• 3 Degrees is the nominal Draft angle.
• 7 Degrees for a textured surface.
• A minimum of 0.5 Degrees can be manufactured with special tools. But it will increase the manufacturing cost.

Tooling axis creation :

• Considering the Ejection from the cavity of the mold after manufacturing the interior trim (switch bezel) must have the nominal 3-degree draft angle.
• Hence the tooling direction is created by considering the above factor and bisecting method is used.
• The base surface of class – A was extracted and a point at the center is created and an axis system was inserted to the point with the current feature disabled.
• Then, using project intersection along yz plane is created and the two inclined lines were drawn inside the positioned sketch.
• Then bisecting lines with the two inclined lines were drawn.
• Now the same procedure is done along the xz plane but on one side we don’t have inclined lines so the center point is used to extrude a line along the z-direction and gave a measurement of 5 degrees (Tentatively).
• With these two lines from sketches 1 and 2, the bisecting line is created and published as Tooling Axis(tooling direction).

Class B Surface Creation

• For creating the class-B surface the required surface except the offset surface has been extracted and then untrimmed all the surfaces.
• Then all the surfaces have been extrapolated to get intersections between them.
• Since the thickness of the Switch bezel is 2.5mm the B-Surface was offset to 2.5 mm and the required trim operations must be carried out.
• Finally, the required corners have been filleted to 12.5mm (15mm-2.5mm). [ 15mm - fillet value of the A-surface, 2.5mm – Thickness of the component ]

Creation Of Class-C Surface

• The required outer edges of the A-Surface were extracted using Multiple Extract. Then for avoiding the patches the curve is smoothened using the Curve Smooth option.
• Then by using the sweep command the surface was created.
• Then by using extrapolate command the edges were intersected between the surface corners which eases the trimming operation.
• Now the required portion of the C – the surface was trimmed out.

Tree Structure

Creation of Closed Surface

• Now the class – A and Class- C surfaces were joined together by removing the gaps in-between them with the help of extrapolation(tangent continuity) and Trim surface.
• Then the exact surface of the Switch bezel was trimmed from the above-resulted trim surface with the class-B surface.
• Then, by defining the part body by using the Closed Surface command in Part Design, the component's solid body is created.

Isometric

Front

Back

Right

Left

Top

Bottom

Procedure For Draft Analysis

• First the class – A surface is checked before creating the Class –B&C surface and finally the solid body must be analyzed. Both can be done by following the below procedures.
• By changing the view mode to custom view parameters – Material mode then the feature draft analysis is enabled.
• Then the compass was activated and placed with the tooling axis by dragging the red pointer and then locked it.
• Then, by selecting the quick analysis mode, the nominal value will be 3 degrees and checked for the component's draft angle.
• The green color area shows that it satisfies the 3-degree draft angle. If not satisfied then by using the Running point tool the area is measured and then altered to get a successful draft for the created tooling direction.

Draft Analysis on Given Class A Surface

From the given class A surface, After analyzing it we can see that one of the walls is a red(0 deg) draft, and the remaining surfaces are green which means they are satisfying the draft angle analysis. So for that one wall, we will ask the class A designer to modify the design accordingly.

Draft Analysis On Final Closed Surface

As we have discussed in Class A analysis One of its walls shows a red surface in the analysis and the other surfaces are green it's showing similar output for Class A in the final component.

When the angle given is 3 deg. We can see that Class C is Completely RED. Class B is BLUE. So we can Modify the angle to 2.9 deg.

Bottom View

When we make the angle 2.9 Deg we will see some difference in the draft analysis. In these images, we can see that the Class C surface is green.

Conclusion :

Hence the Switch Bezel plastic component through the given class A surface and created the required Tooling axis and performed the Draft analysis on the model and also for the solid model. so this Draft analysis feature is very useful to check the Draft angle and can check whether this part makes any problem while manufacturing that product. And the nominal Drafting angle is 3 Degree so we need to design the part with a minimum of 3 Degree has the Draft.