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

Attachment Feature Creation

(Ribs & Screw Boss)

Aim:

Create the Screw boss for the Drill Handle considering the design rules mentioned in the video.

General Guidelines for Bosses:

• Draft - 0.5 degrees on the walls of boss
• Thickness - Typically 40%* of the nominal wall at the base.
• Height to Diameter Ratio - 3:1
• Radii - 0.25mm maximum radii.

Objectives:

• A detailed report should be done explaining the draft analysis and the tooling axis creation.
• An explanation should be given on the way of creating the tooling axis, particularly the Bisecting method.

REPORT:

RIBS:

They increase the stiffness and strength without increasing overall wall thickness of the model which is not desired. They also facilitate as Locator and arrest components of an assembly. Providing alignment in mating parts and acting as stopper or guides for mechanisms.

TOOLING AXIS: 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 Dyeline or the Tooling Direction. Again, depending upon where you're working at, you may have a different name for it. So, when you go in and you create that Tooling Direction, you want to make sure that whatever you create is going to be used as a reference to design your data up against. So, when you add in your ribs, maybe some pockets, walls, whatever that may be, bosses, the walls are going to be drafted based off of the Tooling Direction. It's to make sure that the Core can pull apart from the Cavity, nice and clean.

Creation of tooling axis.

• Tooling axis here created is by selecting one of the natural axes as it clears the draft.
• Here, tooling axis is created by extracting one of the surfaces for creating a point and a new axis is created at that point.
• So, a flat face is extracted and created a point at its centre. Axis is also created at that point.

• Now, line is created using line tool and giving line type as point-direction and selected the point and direction for creating tooling axis and tooling axis is created along z direction.

Draft Analysis Of Class A surface

Draft analysis is performed over Class A surface and every surface is obtained as clearing.

Creation Of Class B Surface

• Now, Class B surface has to be created. For this, multiple extract is used to extract surface in a single operation. Surfaces obtained are the offsetted for 2.5mm.
• The Unfilled areas have to be filled with multisection surface and join them two.

• Check the B surface by boundary command to make sure there is no gap in the surface.

Creation Of Class C Surface

• Now class C surface has to be created and it is created from the boundaries obtained from the Class A surface. This boundary is provided as the input curve for sweep command. Using sweep command, class C surface is created.
• Appropriate sweep is the provided considering the flash and considering manufacturing procedures. Surfaces are extrapolated if necessary.
• Publish class C surface.

• Closed surface command is performed with the help of part workbench and later the draft analysis is performed.

Rib Designing

• First, the base surface where the rib has to be created is extracted using the Extract command. A positioned sketch is created and the profile for the rib is drawn.
• Next, the profile is extruded, to find the height, h=Wall thickness * 5

=2.5*5

= 12.5 mm

• The extruded surface is thickened,

Thickness, w=0.4*t

=0.4*2.5

=1mm

• Then the thickened surface is performed union trim option with the closed surface to trim of the extra elements.

• Perform draft command to give draft for the ribs. And give fillets as 0.25mm for avoiding sink marks.

Screw Boss Designing

• Extract the face which is needed screw boss. Draw a sketch according to the design parameters of the screw boss. That is for a M6 screw the the inner hole should be 5.2mm and the outer wall calculation is

0.6*t= 2.5*.6 = 1.5 per side.

So the outer wall dimension will be 5.2+3= 8.2mm

• Pad the sketch to a height of 15mm as per 3:1 ratio.

• Give draft to the outer and inner walls. Give fillets as .25mm. And Add the Boss part to the main part body.

Draft Analysis Of the Closed Body