Challenge

Master Section Development

SSwarochi Aemula10 Jun 2021

OBJECTIVE:

Creating the B-Pillar Master Section development through the given Class-A surface. To begin with, the tooling axis for the given Class-A Surface is created to meet the requirements of the draft angle and at the end perform the Draft analysis on the model.

Creating the Dog Houses, Ribs, and the locators considering the design rules

The Thickness of the component is obtained from the Master section

INTRODUCTION:

Draft:

A draft angle is a slant that is applied to each side of most features of an injection molded part. In other words Draft is providing tapers on the product features such as walls ribs posts and bosses that lie parallel to the direction of the release from the mold part ejection
The nominal draft is 3mm for plastic components and for automotive sheet metal components is 7mm

Tooling axis :

It is defined as the direction in which the molds opens or core and cavity, with the help of tooling axis created along x and Y axes are used for creating the Main Tooling axis by using the bisecting method

Master Section:

The master section helps us to decide the feasibility clearance, the packaging and the fixation strategy of a component before working in 3D. on the other hand master section gives us the thickness of the component

DOG HOUSES:

Helps to avoid sink marks
solves the length issues(ex: screw bosses can be formed at 100mm form B-surface)
always design houses perpendicular to the tooling axis

DOG HOUSE DESIGN CONSIDERATIONS:

"C" is where the doghouse contacts the backside of the surface
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

RIBS:

Ribs are a feature in plastic injection molded parts. They are thin extensions that run perpendicular to a wall or plane. They are commonly used to provide additional support and strength to a part.
These provide economical stiffness and strength in the molded parts without increasing the overall wall thickness
Facilitate locating and arresting of components of an assembly
provide alignment in mating parts

RIB DESIGN CONSIDERATIONS/RULES:

Thickness
Height
Location
Quantity
Manufacturability

Thick ribs often cause sink marks and inturn create cosmetic problems on the opposite surface of the wall to which they are attached
highly glossy, critical surfaces require thinner ribs
if the wall thickness is less than 1mm the rib thickness should be equal to the wall thickness
very thin ribs can be difficult to fill
Measure the base thickness of the rib at the tangent of radius if radii are molded in

The larger the area of the base of the rib the more retained heat which results in sink formation

PROCEDURE:

Connectivity of Class A surface:

The first and foremost thing to do is to check for the connectivity of the surfaces this is to ensure that there are no gaps between the surfaces if gaps are present then it should be resolved.

This can be done visually or by creating boundaries, if their gaps are present they are graphically represented by green lines. If not while performing boundary command it shows an error.

Creation of Dummy axis :

This is a normal line which we construct by analyzing the best possible direction(X/Y/Z axis) for the draft for the part, this axis is only for reference and is not used for Tooling Axis

Creation of Tooling Axis for Class A surface:

Taking the dummy axis as a reference, intersect the class A surface along the different axis (XY/YZ/ZX ) Check for the possible places where the part might face difficulties while ejecting the component from the mold.

Lines are drawn at the places where the part boundary has difficulties

Later the Tooling axis in one direction (let’s say X) is obtained by bisecting the lines drawn in the above process

In the same way, the other axis is also checked and then the Tooling axis in another direction(let’s say Y) is drawn

Now both Tooling axes are bisected and the final Tooling direction is obtained which is further used for all draft analysis axis and later unto developing Class C and Class B surfaces.

In this model, the tooling axis is taken from the Master sections provided, at the intersection of the Master sections

Publication:

The publication is used for easy access to published components. These will come in handy while modeling (we are not required to search the entire tree structure for a particular operation)

DRAFT ANALYSIS:

Click the Inset—Analysis -- (Feature) Draft Analysis icon

If material is not on There will be a warning message is shown and then we need to select the material

The Draft Analysis dialog box is displayed. It gives information on the display (color scale), the draft direction and the direction values

FLANGE CREATION ACCORDING TO THE MASTER SECTIONS TO CLASS A:

Considering the master sections provided the flange dimensions are taken later class A is modified i.e., Modified class A with flanges(Master section)

The final Class A is obtained by trimming Class A with master sections

DEVELOPMENT OF CLASS B SURFACE:

Class B surface is created by extracting each wall and untrimmed walls extrapolating the walls and then trimming the extra surfaces and offsetting it to a certain value based upon the thickness of the component where it is 2 mm as obtained from the master section. The offset surface will be the B-Surface