Week 9 - Attachment Feature Creation (Ribs & Screw Boss) - Challenge 1

RIBS AND SCREW BOSS CHALLENGE 1

AIM :

• Create the rib for the Drill Handle considering the design rules.
• Create the Screw boss for the Drill Handle considering the design rules.

DRAFT ANALYSIS OF CLASS A SURFACE

TOOLING AXIS :

Tooling axis is the direction in which the core and cavity opens and closes. In order to construct the Class B and Class C surfaces, it is crucial to determine the tooling axis from a Class A surface since this axis serves as a reference line for the draft angle.

In this challenge, the tooling axis is discovered by just sketching a line perpendicular to the surface as shown below.

BISECTING METHOD :

• It's a method of finding tooling axis. In order to find the tooling axis we need to under find the better tooling direction by analysing the body.
• Finding tooling axis should be in a manner which will reduce the manufacturing cost, like wise there will be some better tooling direction which can avoid the use of side core.
• If we get the better tooling direction as Z axis. Firstly find the tooling direction in X and Y axis if there are inclined surface to be considered this is achieved by intersection solid and bisecting method.
• After finding both the tooling axis in X and Y direction, bisect it to find the main tooling axis.

DRAFT ANALYSIS :

In order to recognise that our drafted component is at an angle that is higher than the typical draft angle, which is about 3 degrees, draft analysis is employed. Draft analysis is done using a tool in Catia called "Feature draft analysis." When you click on this tool, the window below will appear.

• In the mode section, there are two modes: the Quick analysis mode and the Full analysis mode. In this challenge, quick analysis mode is being used to visualise draft analysis.
• First, a tool named "Compass" from the direction category is used to define new draft direction. The direction of the draft is determined by positioning that compass above the tooling axis.
• Then by just clicking over the surface or the component we can visualize the colour corresponding to the angle as set in the draft analysis.
• There is an another tool which is used to find angles at running points. The tool is under display category, in that by selecting the tool named "Analyses under the running point" there by moving the cursor over the component gives the draft angle at that particular point on the component.
• There is an another tool to change the draft direction of the compass, which is under direction category next to the compass tool.

PROCEDURE

• Tooling axis is found as explained in the theory section.
• By Feature draft analysis tool the draft analysis of the class A surface is done initially to know whether our find class A is acceptable or not. And the given class A is acceptable.
• Then nextly creating class B surface just by offseting class A by 2.5 mm.
• The class B will have some gaps on the surface and those gaps are cleared by multi sections surface command.
• After solving those gaps in class B, class C surface is created, then trimmed the unneessary portions to get the exact bumper design.
• By using close surface command in the part design the surface body is converted to part body.
• Then the draft analysis of that particular part body is performed.

In the given class A surface some of the areas are highlighted in blue colour which means in those areas the angle is almost equal to zero. So that areas should be reworked to make a draft angle greater than 3 degrees.

DRAFT ANALYSIS OF CLOSED BODY

DRAFT ANALYSIS OF RIBS AND SCREW BOSS

The Ribs and Screw bosses are provided with 0.5 degree of draft angle. The draft analysis for the same is done and got the result as shown.

Even though the draft angle is given 0.5 degree, in the draft analysis it's highlighted in red, that's because of some of the areas do not achieve 0.5 degree w.r.t the tooling axis. The minimum draft angle is changed to around 0.49 degree, then the whole part get highlighted in green colour.

RIB ROOT ANALYSIS

Rib root analysis is done and got a thickness of about 2*1.343 = 2.6 mm which is less than the 30% of the wall thickness of the plastic component. The thickness of the component is given is 2.5 mm.

ISOMETRIC VIEW

FRONT VIEW

LEFT END VIEW

RIGHT END VIEW

TOP VIEW