Challenge Report

Week 9 challenge 2

Dog House Design:

Dog House:

It is a plastic attachment feature which is used to increase the height of a particular area where some other plastic feature like screw boss need to be mounted. It is designed such a way that it doesn’t produce sink marks at that region.

Its main application being mounting screw bosses at extreme heights. Dog houses becomes very useful when the screw bosses are perpendicular to the main tooling axis.

Design rules:

1. Dog house wall thickness at C should be 40% of main wall thickness T or less.
2. Height B should not exceed 6mm or less than 3mm
3. Overall dog house height should have a minimum of 6mm high.
4. Steel width : Height = 2 : 1 (preferred); 3 : 1 (accepted).
5. Width of dog house X should have minimum of 12mm.
6. Draft angle D of the walls of the dog house = 1.5^o

Tooling Axis:

In a separate geometric set “TOOLING AXIS”, create a point at the centre of a surface. Draw a line along y axis. Check if class A surface clears the surface.

If not create a sketch and 3d project the contour of the class A surface. Draw 2 lines parallel to the contour walls and draw a bisecting line by angle. Make all other lines as construction elements.

Do the draft analysis once again and make sure that most of the surfaces can clear the tooling axis.

Note: In the case of the door trim one surface of class A surface was not clearing the tooling axis. Even after multiple direction, the issue was persistent.

Publish the tooling axis once the final tooling axis is decided.

Class B creation:

Create a new geometric set “SURFACE DESIGN” under which we will be creating other geometric set “CLASS B”, “CLASS C”, “A+C”, “A+C+B”.

Defining in CLASS B, offset the whole class A for a thickness of 2.5mm. Give a distinct dark colour so that we can identify discontinuities in the surface.

For the simple discontinuities, create multiple extracts, extrapolate and trim. For complex ones, going for multi-section surface is the viable option.

Due to uneven surface, we need to extract the bottom surfaces separately, extrapolate and trim with the pocket wall. This will eliminate any irregularities in surface creation. For this we have to measure each fillet and measure them, in order to apply it at their respective places.

Trim each object individually to avoid any misstep or any mis-interpretation by the software. Join any separate entities which are present while troubleshooting the errors.

Note: Make the edges extrapolated beforehand to avoid errors while extrapolating in later stage of class B creation.

It is easy to work with separate geometric set in CLASS B, each for a particular part of the component. All the commands related to that particular part of the component will be grouped and it becomes easier to troubleshoot.

Class C creation:

This is the easier part in the creation of the plastic component. First define the geometric set CLASS C and decide which edges of Class A will be drafted with draft direction or reference surface.

The straight edges, which are almost parallel to the tooling axis, is ideal to be drafted along the tooling direction at 3^o. Choose the edges along the pocket section, as those are nearly parallel to the tooling axis.

Use multi-section surface to fix the discontinuous surfaces. Then sweep the remaining edges with reference surface at an angle of 87^o.

Extrapolate and trim the extreme ends of the 2 corners. Now join the class A and class C surfaces and put it in the geometric set A+C.

In a separate geo. set A+C+B, trim the extrapolated surface B and class A+C together.

Go to part workbench and activate the main part body. In the main part body, create a closed surface of the obtained surface. Conduct a draft analysis for the same along the tooling axis.

Creation of Dog House:

To create a dog house, we need the following inputs: main tooling axis, side-core/lifter axis and the position of the feature.

Create a new geometric set “DOG HOUSE DESIGN”. Extract the large panel and offset it to the given thickness of the component (2.5mm).

Place a point in the middle of the surface or in the position where we want to place the dog house. Create a plane parallel to the point, as the surface has some curvature and is not suitable to draw a sketch.

On that plane draw a centred rectangle of 12mm x 12mm. To make one end open, make that end a construction element.

Now extrude or sweep the surface with respect to the tooling axis for a height of 25mm. Also, extend it downward such that it crosses the part body.

Create a point at a height of 20 mm and create a line normal to the tooling axis. Extrude the line perpendicular to the tooling axis, such that it crosses the surface. Trim it with respect to the surface.

To close the top, create a point and a plane parallel to it and then draw a line along it. Extrude it normally. Trim it with the lateral wall.

Go to part design and create a new body. In that body, thicken that surface to 2mm. Now, draft the solid to 1.5^o. Give an edge fillet of 1mm all around the body except the ends.

For the thickness C and height B, use the same extrude and offset it. Calculate the distance from the bottom plane or top plane according to the design rules.

Create an offset of the top surface extrude to that distance. Enabling the surface of the lateral walls make an offset of distance B and trim them together. Give a minimal fillet of 0.5mm radius.

Now go to part workbench and use split to remove the inner mass of the body.

Creation of Lifter axis:

Using the existing point over the dog house, draw a line parallel to x axis. It will be used to lift the dog house.

The inside surface of the dog house should be drafted in order to be tooled out with respect to the lifter axis. Select the lateral faces to be drafted and the bottom face as the neutral element (with respect to lifter axis). The draft angle should be 1.5^o.

Note: Also consider the stepped surface to be drafted

Obtain a draft analysis of the dog house. After checking, create another point or use the existing point of the axis system to translate the dog house.

Before translating, copy and paste special the dog house body by creating a link. Now translate the new body to the desired destination (start point and finish point.)

Using Boolean operations, trim both the dog house bodies with the main part body and do the draft analysis with respect to the tooling axis.

FIND THE FOLLOWING FILES:

document: Challenge Report.docx

part file: CATPart.zip

images: Screenshots.zip