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

DOOR HANDLE WITH B SIDE FEATURES(RIBS AND SCREW BOSS):

Ribs are generally designed on the non-appearing surface of the plastic part, and its direction is as close as possible to the flow direction of plastic melt filling. Ribs should neither be too long nor too thick, otherwise, it will increase the difficulty of injection molding, causing problems such as voids and sink marks on the back.

Screw Boss are common structures on plastic parts in home appliances and interior and exterior of automobiles, mainly for positioning and fastening.

Aim:

To design the complete solid model of Door Handle and B-side Attachment features such as Ribs and Screw Boss with the help of Class A surface(input) by creating the tooling axis and analysing the draft angle.

Draft angle:

Draft angle (the degree of taper of the side wall of the mold or the angle of clearance designed to aid removal of a part from a mold) increase causes a linear decrease of the force required to remove a molded object from a mold. It is also used to avoid one of the plastic defects while casting is said to be a Drag lines.

Tooling Axis:

The tooling axis is a direction along which the core and cavity tends to move. Here the tooling axis is created in direction, which is normal to one of the Flat surface of the Door Handle.

Rules to be followed while designing the Ribs:

• Rib Thickness at the Tip is greater than or equal to 0.75mm
• Rib Height - Lesser than or equal to 5*t (where t is the Mould component)
• Rib Thickness - 0.4*t
• Rib Draft - 0.5 degrees
• Rib Fillet Radius - 0.25mm

Rules to be followed while designing the screw boss:

• 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 for fillets.

Draft Analysis of Class A surface:

The minimum draft angle for the design of plastic components is 3 degree.

Isometric view:

Front view:

Top view:

Side view:

Ribs and Screw Boss Creation:

Tree structure:

Draft Analysis of Final model:

Here the complete solid model is achieved the minimum draft angle of 3 degree.

Conclusion:

Thus the complete solid model of the Door Handle along with the attachment features such as Ribs and Screw Boss is formed from the Class A surface(input) and the analysed draft angle is 2.9 degree.