Week 10 - Challenge 2- Attachment Feature Creation (Dog House)

Introduction:

CLASS-A SURFACE: the class-A surface is used in the automotive design industry. it describes the final production surface data for the aesthetic parts.

CLASS-B SURFACE: the class-B surface is the second surface that has a specific thickness from the class-A surface. this surface contains engineering aspects of a model. These must also be smooth and "error-free" but are not held to the standards that class A surfaces are.

CLASS-C SURFACE: The Class C finish allows more imperfections than Class A or B. Class C is often specified for interior surfaces not readily visible, surfaces that will be covered by another part when assembled, or surfaces.

Design methodology:

1. Insert the class A surface of the Bumper in CATIA software.

2. Determining the tooling axis for the Bumper

3. Draft analysis of Class- A

4. Creation of class B surface.

5. Creation of class c surface.

6. Use the publication option and publish the below

• Tooling Axis
• Class A, B, and C surface

7. Join the bumper class A, class B, and class c surfaces and ensure all the surfaces are closed.

8. Use the Close Surface feature to make a solid body from the surface.

9. Then Create the Dog House for the Door Trim considering the design rules mentioned in the video. Consider the thickness of the part to be 2.5 mm."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

10. finally, Perform the Draft analysis on the bumper plastic component.

Creation of Tolling axis:

To create the tooling axis first, we have to check the best suitable direction for tooling by using the compass. the y direction is suitable for creating the tolling axis because, in the y direction, most of the surfaces are clearing while performing draft analysis. Generally tooling axis is created using bisecting line method but here A line normal to the surface is created in the y direction and considered the tooling axis.

For checking whether our tooling axis is correct or not simply put the created tooling axis in normal view mode if our axis is correct then all the surfaces are visible

Draft analysis of Class- A

After creating a tooling axis we do the draft analysis. Before drafting we have to make sure that in the view mode, it is selected for the materials.

After selecting the feature draft analysis tool we drag the compass from its position to the tool axis. Then lock the compass. After that select anywhere on the component and it will give you the result.

We change the minimum draft for the component to 3°.

We can use the running point option to check the angle of the component.

Creating Class B Surface

Now offsetting the class A surface to 2.5mm. while offsetting some typical geometry has no offsets so we get patches in the surface.

we have cleared all the patches by extracting the method

Cretaing the C Surface.

To create the class C surface concerning the boundary of the class A surface, I used the sweep command. Initially, I extracted the boundary of the class A surface with tangent continuity, and I sweep the extracted boundary concerning the surface at 93deg (for draft angle) for 5mm to intersect properly with the class B surface. Once we sweep all the surface boundaries of class A, extrapolate the sweeped surfaces until both surfaces got intersected properly, and trim them to remove extended extrapolated surfaces to get a proper sweep boundary throughout the entire surface, including the centre hole of the door trim

Now trim or join the CLASS A AND C SURFACE

Now trim the above surface with CLASS B SURFACE

Creating a solid body by using a closed surface :

To create soild body firstly switch to part body work bench and use close surface command to soildify the surface body

So our part is created no we weill creaet B side feature that dog house on part body

Dog House Creation

Dog house is an engineering feature used in plastic trim design. Dog houses are used as supporting feature. Sometimes other engineering features like snaps; locators 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.

DESIGN CONSIDERATION FOR PLASTICS:

1.WALL THICKNESS:

Thick sections waste material and are simply uneconomic. So solid shapes that would do the job well in wood or metal must be transformed to a 'shell' form in plastics. This is done by hollowing out or 'coring' thick parts so you are left with a component which regardless of complexity is composed essentially of relatively thin walls joined by curves, angles, corners, ribs, steps and offsets. As far as possible, all these walls should be the same thickness. Wall thickness guide range is 0.75 mm to 3 mm for reinforced materials 0.5 mm to 5 mm for unreinforced materials.

WALL THICKNESS(W)=0.70*(NOMINAL THICKNESS OF PLASTIC MATERIAL)

2.CORNER RADII

Properly designed corners will make a big difference to the quality, strength and dimensional accuracy of a moulding. But there is another benefit too. Smooth curved corners help plastic flow in the mould by reducing pressure drops in the cavity and minimising flow-front break-up. Internal radii should be at least 0.5 and preferably 0.6 to 0.75 times the wall thickness.

CORNER RADII= (0.6-0.75) * (NOMINAL THICKNESS OF PLASTIC MATERIAL)

3.DRAFT ANGLE:

Tooling must be cleared for easy ejection of the component, from the core cavity. In order to clear tooling certain value of draft is given to the component. Minimum of 2-3deg is provides on all plastic components.

DRAFT ANGLE=2-3 DEGREE

4.FILLETS:

Fillet on the inner side = 0.25 * Thickness of the plastic material Fillet on the outer side = 1.25 * Thickness of the plastic material Fillet on the coring edges = 0.25 * Thickness of the plastic material Coring thickness = 0.40 * Thickness of the plastic material

so takinng all conseradations of desugn standards