Week 9 - Attachment Feature Creation - Challenge 2

Boss and Dog House Design

Objective: To create the Boss and the Dog House for the Centre Console Coin Holder considering the design rules.

Introduction:

Boss:

Bosses are small cylindrical elements in a design. They are used for accepting screws or other fastening components. Essentially, they are locating, mounting and assembly devices built into the design of the part and if not accepting screws, will attach to the mating part of another component of the design.

Dog House:

Dog house is an engineering feature used in plastic trim design. Dog houses are used as supporting features. Sometimes other engineering features like snaps, locators etc. are mounted on them to increase their strength.

Dog houses are subjected to draft analysis to prevent breakage of the component during ejection from mould cavity.

Tooling Axis:

Tooling axis is the direction in which the mold or core and cavity opens.

Draft:

Draft is the angle in which the part is tapered to allow it to release. As the part cools, it tends to shrink to the core side of the mold. Draft is required on all parts in the direction of mold movement in order to allow parts to release or eject from the mold properly.

Most parts or applications require a minimum of 0.5 to 1 degree, however 3 degree is widely accepted as normal.

General guidelines for Boss and Dog House:

Procedure:

Creation of Tooling Axis:

Bisecting line method:

First of all, we have to analyse manually or visually to see which direction is the most appropriate for tooling axis. After analysing we found that Z-direction seems easy to be tooled. So, we use the bisecting line method to create the tooling axis. For that we extract the base and create a point on the surface at 00 mm. After that we create an axis system on the same point and intersect the YZ plane with Class A Surface. Here we found that the walls are at 0 degree to the normal which will be very difficult to manufacture as the plastic part would not eject at the end due to contraction after the cooling process is completed.

So, we have to contact with the styling team to give a minimum draft to the surface. But here, we will proceed with the same Class A Surface. So, for that we create a line on a point that was created earlier using point and direction option giving the extract as a direction which means the line is normal to the surface. This is our main tooling axis.

Note: After creating the tooling axis, the class b, class and then final component was created.

Screw Boss creation:

First of all, we have to create an extract and then create a sketch on it.

After that, we pad it and then do draft on both sides.

For giving support to the boss, we have to create ribs. So, we create a sketch on it.

Then we pad it and then do draft.

Then we add the screw boss to the main body and then do union trim of the ribs with the boss.

After that we apply fillet.

Dog House creation:

First of all, we create a sketch for the dog house.

And then create a sweep providing the draft of 1.5 degree.

Then the sweep was thickened.

Then we have to create the side core tooling axis and then provide the draft of 0.5 degree.

The inside portion have been filleted 1 mm.

Now for the lower portion ‘C’ part the surfaces are offset to 1 mm inside and 4 mm upside and they are trimmed off.

And then the part is split.

The lower portion is also drafted 0.5 degree and then fillet is provided.

The outer edge is also filleted to 3 mm.

Then the dog house is added to the main body.

After that the screw boss is translated and kept on the top.

Draft Analysis of the Boss and the Dog House:

First of all, we should change the view to the Customize View parameters and then select the material mode and then Ok. After that we will open draft analysis command and then click on the compass icon and then align the compass of the window with the tooling axis earlier created and then lock the draft direction. After that click on the surface and see that the surface is within permissible limit of the draft value.

Tree structure:

Conclusion:

The Boss and the Dog House are created for the Centre Console Coin Holder considering the design rules.