Week 9 - Attachment Feature Creation - Challenge 2

Attachment Feature Creation : DOG HOUSE

AIM :

• To Create the Door Trim Component from the given Class-A surface.
• To Create the Tooling axis for the given Class-A Surface meeting the requirements of the draft angle.
• To perform the Draft analysis on the model. 
• To Create the B Side Feature in the component by following the design rules.

INTRODUCTION :

DOG HOUSE

         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. Dog house and other engineering components are built on B-surface.

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

DESCRIPTION:

1. CREATING TOOLING AXIS -

                      The Tooling Direction is basically the direction that the mold pulls a part. The mold is built in two separate pieces, basically. You have a Cavity side and you have the Core side. The Core pulls apart from the Cavity and that's the Dye line or the Tooling Direction.

• Open the given CAT part file.
• Check for gaps between surfaces for that click on join and then preview.
• If theres any gap between the surfaces join them with a maximum tolerance of 0.003 mm.
• Extract the boundary and dissemble the boundary.
• Find the correct tooling axis where the material don't interfere with the tooling axis and all the elements can be created.
• Intersect the yz plane with respect to the class A surface.
• Hide the class A surface and create point to point lines on the suspected drafts.
• Create bisecting line with the two lines and point to create a tooling axis.
• BISECTING LINES were used to get the exact medium from the two sides so that maximum positive draft angle can be achieved. 
• The tooling axis is created for the component.

2. DRAFT ANALYSIS

          The Draft Analysis command enables you to detect if the part you drafted will be easily removed. This type of analysis is performed based on color ranges identifying zones on the analyzed element where the deviation from the draft direction at any point, corresponds to specified values.

• Before going to drat analysis go to customized view parameter >under mesh >check material and then click ok.
• Now for draft analyses go to insert » analysis » feature draft analysis.
• Use the compasss to define the draft direction.
• In the colour scale change the draft angle to 3 degree.
• The component changes to green in indication of passing draft angle.
• Use running point to check the angle on the component.
• The draft analysis is complete.

 Draft Analysis of Class A Surface :

 Draft Analysis of  Close Body :

3. CREATING CLASS B SURFACE

• Extract the surfaces from the class A using multiple extract and untrim them.
• Use Extrapolate to make sure that all the untrims are properly intersected to trim and offset the surfaces to 2.5 mm to create the thickness.
• Trim the extra surfaces using trim command.
• Insert them into new geometrical set and name it with respective part names.
• Apply fillets to the model after creating the entire surface.
• If the edges are outside the fillet value will be added to the thickness of the component and if the edges are inside, the fillet value will be subtracted from the thickness of the component, for instance the thickness of the component Is 2.5mm the fillet value is 15mm so the outside portion value should be 17.5mm and inner eges should be filleted 12.5mm to get uniform thickness.
• Perform trims one at a time so that it will be clear to understand.

4. CREATING CLASS C SURFACE

• Extract the boundary from the class A surface using boundary command.
• Using disassemble tool to divide the boundary as the boundary contains domains.
• Use sweep command > choose profile type line > subtype as with draft direction > choose guide curve and draft direction > draft angle as 3 degree > preview.
• After getting sweep then trim the output with class B surface to get final output.
• Now open part design workbench and using close body surface create a solid of the component.

5. PUBLICATION

• Publication is done to the component to make it visible and navigate easily.
• To publish the component go to tools > publications and then select the tooling axis and the class A surface.
• A separate tree structure is formed under the main part.

Tree Stucture :

6. B SIDE FEATURES CREATION

        DOG HOUSE CREATION

• Design Principle for Dog House Creation

        

 

CONCLUSION:

• The Tooling axis and the SolidCAT part with B side feature is created from the given Class A Surface and Draft Analysis is Performed.
• Creation of the B Side Feature (DOG HOUSES ) in the component are done.