Week 9 - Project - A pillar Design with Master Section

Introduction:

CLASS-A SURFACE: a surface made by the designer which is given as an input to the plastic modeler to work on. It is an aesthetic surface and the outermost surface.

CLASS-B SURFACE: a surface below a certain thickness from the class-A surface is a class-B surface. This is the surface that contains engineering aspects of a model.

CLASS-C SURFACE: a surface that joins class-A and class-B surfaces is a class-C surface.

Tooling axis: the direction in which the mold opens or the core cavity opens. By providing a tooling axis to the component we can perform the draft analysis of the component.

Design procedure:

• Checking Class A input for imperfections.
• Ensure that the class A surface has no gaps and no discontinuities of the surfaces using the boundary command. 

Tooling axis Creation

In injection molding, the Class A surface is first analyzed to determine the axis or tooling direction that separates the molds. Tooling direction is critical for plastic product design because it determines mold direction

DOG HOUSE: It is an engineering feature used in the plastic trim design. It is used as a supporting feature. By using dog house, we can support the other engineering features like heat stakes, screw boss, and locators to locate them at a certain height where we cannot violate the design rules for the features. By using a doghouse, we can avoid sink marks on the class A surface.

 

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

The height of  ( B ) should be between 3.0 – 6.0 mm 

MASTER SECTION:

Master sections are the guides for design requirements that decide the component packaging after technical (Styling, Concept, or Class-A) surfaces. Creating this master section should need 5 to 6 years of experience. This helps you to decide the feasibility, clearance, packaging, and fixation strategy before working it on a 3D.

We have a master section

Creation Of Tooling Axis

• The tooling axis is created by selecting one of the natural axes as it clears the draft. 
• Here, the 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 center. Axis is also created at that point
• Now, the line is created using the 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 the x direction

Creation Of Class A Surface

• Class A surface is obtained as the input.
• Join all the surfaces to obtain Class A surface if different surfaces are given as input and ensure no gap is present between any surfaces. Thus, Class A surface is obtained and published. Here, the provided surface is completely joined and can be taken as a class A surface.

Creation Of Class B Surface

• In this component Creation of the class B surface first, we have to offset the entire model by 2.5mm inward some of the surfaces give offset error and ask for offset without these subelements click okay and work on the incomplete surfaces by using the multi-section surface command, sweep and different commands used to complete the class B surface.

Creation Of Class C Surface

• We first extract the edges from the Class A surface with the help of the multi-extract or boundary command which we create the path for a sweep for class C.like this, we have to create all separate sweeps and join them together. once all the sweeps are joined together we create a class c surface.

Creation Of Doghouse

• Doghouses are created by following the design rules.
• For this, the sketch is created from the master section provided.
• It is then made into a closed body and is made into a part model.
• Shell operation is performed to get a hollow structure and then coring is done in order to avoid sink marks on the class A surface.
• Drafts are given for the surfaces as per design rules and proper fillets are also provided.
• As per the given master section, ribs and supporting features are also added to the doghouse.
• Then, the doghouse is added to the main body.

All the sketches used are iso-constraint.

Tree Structure

Surface Part

Solid Part

Isometric

Front

Left

Right

Top

Bottom

A detailed report on draft analysis and the tooling axis creation. 

DRAFT ANALYSIS

• For molded or cast parts, the draft angle is the amount of taper perpendicular to the parting line. It is measurable in degrees. Because plastic shrinks and sticks on molding surfaces as it cools, we draft the walls of the plastic part so that it ejects or breaks free from the molding surfaces more easily and without dragging. To reduce the risk of damage to the parts and ensure ejection, a functional injection molding part must have drafts on both the cavity and core sides

Nominal values for Draft angles 

• 3 Degrees is a nominal draft angle
• 5 Degrees can also be manufactured. Increasing the manufacturing cost
• 7 Degrees is considered for Textured surface parts

Importance of Draft in injection molding

• Reduces the possibility of part damage due to friction during the release
• Reduces mold wear and tear
• Ensures a uniform, smooth, unscratched finish
• Ensures the integrity and uniformity of other surface finishes and textures
• Reduces overall cooling time by reducing or eliminating the need for unusual ejection setups

Steps followed for Draft Analysis

• The created part must be changed to the material mode in the display frame
• Compass is enabled and placed in the direction of the Tooling Axis
• The lock command is then used to fix the compass along the tooling axis
• Colour codes are classified and Draft angle is applied
• Running point analysis is used to display permissible draft angle

In Class A surface draft analysis we can see that the whole surface is green so we can say that the tooling axis that we have created is correct as well as the component can be easily ejected.

Draft Analysis of B- Side features

The obtained part is a draft analysis to check for the correctness of obtained model by following the draft analysis procedure mentioned above.

Side core has to be created for the doghouse to get ejected. So, a side core axis is also created for checking the draft analysis of the component.

A minimum of 0.5-degree draft is provided and the B side engineering features are analyzed using the side core axis. The green color is obtained in the draft analysis, which indicates that the draft provided all are in the correct direction.

As we have given a draft angle of 0.5 deg to the B-side features like locators and heat stakes. so we are going to check the draft analysis by giving it 0.49 deg. We will give a draft angle of 0.49 and we will check the draft analysis of B-side features along the side-core axis and the normal tooling axis. We will check the inside features of the B side by side-core tooling axis. And outer surfaces by normal tooling axis. 

Dog House Analysis along Side Core Axis

Dog House Analysis along main Tooling Axis

 

So we can say that by the side core axis we will eject the doghouse easily and by the main tooling axis, we will eject our main component.

CONCLUSION

• Created Tooling axis
• Created Class B and Class C surface from provided Class A surface.
• Created solid part out of surface modeling.
• Created engineering features from the master section provided.
• Draft analysis of Class A surface and final part is also done.