Challenge

Week 11 - Project - A pillar Design with Master Section

SSumit Digar7 May 2023

1) AIM :-

Create the A pillar plastic part from the given Class A surface, considering the design rules using master section and perform the draft analysis.

2) INTRODUCTION :-

A. DOG HOUSE :-

Dog house is an engineering feature used in plastic design. Dog houses are used as support feature. Sometimes other engineering features like snaps, locators, screw bosses are mounted on them to increase their strength.

Dog houses are subjected to draft analysis to prevent breakage of the component during ejection from the mould cavity. Dog house and oher engineering components are built on the B-surface.

Part I - Closed Surface from Class A Surface:

Material suggestion:

Polybutylene terepthalate (PBT):

good chemical resistance and bearing and wear properties.

Acrylonitrile Butadiene Styrene (ABS):

good balance of impact, heat, chemical and abrasion resistance, dimensional stablity, tensile strength, surface hardness, rigidity and electrical characteristics.

Tooling Axis:

Core and Cavity Tooling axis:

When a plastic body is created in a molding, the core is moved with respect to the cavity in a linear path. The joining line of core and cavity is called the tooling axis, The plastic component is poured and ejected respectively to hat axis of the core and cavity motion.For, this above challenge to be satisified, the discussed tooling axis must be created for the product, keeping the motion of core and cavity in mind.

Slider Tooling axis:

Here the slider tooling axis is used to show the motion of the slider to create the dog houses.

Steps in Catia to add tooling axis:

Here, the master section given has specific tooling axis, the tooling axis must be created by using the reverse approach.
Using Bisecting method the tooling axis of the given dog house in the master section can be achieved.
To use bisection method, we should have two lines which must intersect at a point somewhere.
To create these lines the drafted sides of the given dog houses must be used to extract the points.
Now, isolate the points that have been extracted and give coordinates to them.
Draw the lines using either side of the dog house points that have been extracted.
Now using the bisection option, use the two lines and a point created in-between at two of the four points that lies closely next to each other, create a line.
In a seprate geometrical set, make the drawn line and its operation under the name "Tooling Axis".

Tooling axis 1

Slider Tooling axis:

Class A Surface:

Starting with the Class A as the input, and required output as the plastic component, we should consider the following:
The Surface A is the asthetic part of the given component. Hence, changes made over Class A Surface should be avoided.
Draft Angle must be on the Class C Surface.

Steps in Catia to import Class A Surface as neutral file (STP, IGS):

Using open option in the catia file menu, the class A Surface file is opened from either IGS, STP or CatPart.
If it is in IGS format, the surface A must be joined using distance propagation.

Class A Surface snippet:

Draft Analysis:

When the final componet is created, the drafting analysis done to ensure the draft angles are given to the surface C is within the standard range of 3 degree. By giving this angle, the plastic component is protected from damage while it is ejected. The colour order of GBR in the order of Green, Blue or Red.

if the draft shows green colour, then the draft angle is clearing the 3 degree angle.
If the blue colour is highlighted, then the draft is somewhere between 0 and 3. This area must be studied to make its value close to the 3 degree clearance.
if the red colour is highlighted, then the draft is below 0 degree, this colour seperates the core from the cavity or slider.

Draft Analysis to the engineering feature, must also be checked.

Here, the dog house is the only feature that is made, so the outer draft of 1.5 degree and inner draft of 0.5 degree, should also be studied by changing the green value and the tooling axis with slider axis at necessary positions respectively.

Steps in Catia to Drafting Analysis:

Add material using the view option to let the draft analysis to run.
Select the surface or final part body to make it highlighted in the feature tree.
Use the analysis in the insert option in the CATIA's menu bar, to find the Feature draft analysis.
Now after selecting the option, two pop window will be displayed, where:
One has the colour coding, where we must define the colors in the order of GBR (Green, Blue, Red) respectively and set the angle value to be 2.9 for Green, 0 for Blue, and less than 0 as Red.
Other pop up has several tools for draft analysis, Now from the right most corner of the screen, drag the direction compass and place it on the tooling axis, where the resulting compass aligns with the tooling axis. Now after it gets aligns, lock the compass position using Compass Lock tool.
To view the draft analysis, select the Surface or final closed body. By choosing it as mentioned, the analysis produces the color coding over the parts where the draft condition/angle satisfies as we mentioned.

Draft Analysis - Class A Surface:

Draft Analysis - Closed Body clearing by Class A Side:

Drafting Analysis - Closed Body with Engineering Features clearing by tooling axis :

Drafting Analysis - Closed Body with Engineering features clearing by slider axis:

Class B Surface:

The Class B surface is the other side of Class A surface of the plastic component and where the portion sits on the core.

Make Class B as the sacrificing portion of the component at the core, we ensure the ejector pins motion to push the finished component out of the mold to fall on Class B, again saving Class A from the stress from ejector pins.

Steps in Catia to Create Class B Surface:

From the given master section by using the measure tool, the thickness of the given model is identified as 2.5mm.
Now use the offset option to offset the Class A Surface.
There are some places where the offset fails to add the surface.
Use the sweep command with reference surface, by sellecting the profile and guide curvce, to recreate the surface lost.
Now use the join command, to join the surface created.
Now the Class B surface is created successfully.

Class B Surface :

Class C Surface:

The Class C surface is the in between portion of Class A and Class B, where the volume is added or in other words, plastic thickness is given here.
The Class C Surface is given the draft angle of 3.
To make the component to be easily ejected from the mold, it requires 3 degree draft angle.

Steps in Catia to create Class C Surface:

Use the Class A surface as the reference and extract the boundaries individually on every sides where the curvature changes using boundary tool with tangent continuity.
Now use the "swept tool" and "with draft directions" to extrude the boundaries and tooling axis as the guidelines and with draft angle as 3 degrees in outward direction.
Now use the extrapolate tool to intersect the swept extrudes by selecting the unintersected edges of the swept extrudes to intersect with adjacent swept extrudes.
Use the trim to join the swept surfaces.
Save it in a separate geometrical set.

Class C Surface :

Final Trim:

The resulting surface being formed after joining the Class A, B and C as per the above spoken features specific to the surfaces respectively is done in Final trim.
This showcases the cavity's and core's design of how the mold should be created.

Steps in Catia to create joined Class A, B and C Surface (closed):

Use the join command to join the Class C surfaces of boundary and hole swept extrudes with Class A.
Use the trim command to trim the extended edges of the class C with Class B.

Final Trim :

Solid Body:

Solid body is the part body created after calling the closed surface command on the Final trim surface.

Steps in Catia to create Closed part body:

Use the closed body tool in part design to create the part body.
Run Draft analysis using feature draft analysis from tools, and selecting the part.

Solid Body from Class A Side:

Solid Body snippet from Class B Side:

Part - II: Engineering Features - Dog House:

Explanation: Dog House is a supportive feature that is used to hold screw bosses, snap fits or locators, where the mentioned features required a vertical clearance to combine with another plastic material.

Design consideration of the Dog House: