Week 9 - Attachment Feature Creation - Challenge 2

Screw Boss & Doghouse Feature for Coin Holder

Aim : The main objective is to create Screw Boss and Doghouse feature for coin holder. Here, we will use a coin holder plastic component as input.

On draft analysis along already created tooling axis, it is readable that the side walls are perfectly parallel and has zero degree draft along tooling direction. So, CAS team can be informed and requested to provide little tilt at those surfaces.

Lets move forward and create screw boss in one corner for a flat surface where the component would need some fastener.

Extract the surface and create a sketch as shown where the boss is required. The thickness of wall should follow the rule of 0.4*thickness of base.

Use pad feature onto the profile and give required draft of 0.5 degree. Consider the height to diametre ratio equal to 3:1

Now as the height is more, the component needs some surround support and for that create ribs.

Keep thickness of supprot ribs equal to 0.4 times the base thickness. Draft angle as usual 0.5 degree. Assemble and trim the bodies to the main body and give fillet of 0.25mm radius.

Draft analysis shows green surface, so the created boss feature is manufacturable.

Lets create a doghouse in another corner and will add the same screw boss on top of it. So create a suitable sketch profile.

Create surface by extrusion of the profile. By taking offsets, create a closed body for doghouse as shown below. Dont forget to follow the rules.

Doghouse wall thickness at the intersection of the part wall ( C ) should be 40% or less than the main wall stock ( T ).

Height of ( B ) should be between 3.0 – 6.0 mm

Solidify the closed surface in part workbench. Give draft of 0.5 degree along tooling axis to outer walls.

Also, as we can see the inner walls of doghouse will need a side tooling axis for creation. So create one tooling axis by rotating the existing one to 89.5 degrees and give draft of 1 deree to all inner wallls. We are taking 89.5 derees and 1 degree of draft, so that from the base we get clearance and also top wall of doghouse as shown.

Assemble the body with main body and give fillet of 0.25 mm radius.

Copy and paste the screw boss and translate it on top of the doghouse.

On taking intersection of doghouse, and analysing the root thickness, following are the results. So this design will not create any sink mark.

For draft analysis, we can see the features are perfectly created and shows green surface for 0.5 degree draft value.

For, inner walls of doghouse, align the compass along side tooling axis and we can see all green surfaces inside. That means the part is manufacturable perfectly.

Tree Structure