Week 8 - Challenge 1 - Base Bracket Design

Objective:

The objective of this challenge is to create Class B and C Surface from the given Class A Surface by choosing the right tooling axis and keeping the manufacturability of the plastic product in mind. The thickness of the material taken here is 2.5mm.

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Material selection:

Choosing ABS as the material for Base bracket would provide the following advantages:

• High rigidity
• Good impact resistance, even at low temperatures
• Good insulating properties
• Good weldability
• Good abrasion and strain resistance
• High dimensional stability
• High surface brightness
• Excellent surface aspect

Tooling Axis:

When a plastic body is created in a molding, the cavity and the core is moved respectively to one another. The plastic component is poured and ejected respectively to that axis of the core and cavity motion. This axis is called as "tooling axis". For the challenge to be satisfied, the discussed tooling axis must be created for the product, keeping the motion of core and cavity in mind.

Steps in Catia to add tooling axis:

1. An visual analysis by us to be undertaken at every axis plane of X,Y and Z to comeup with the suitable plane that holds all the features of the surface A.
2. Here the X and Y axis, doesn't suit the above requirement, hence moving to Z-plane we preserve majority of the details given to surface A.
3. At first we must create a geometrical set, where it should be renamed as the "Tooling axis".
4. To Fix Z axis as the tooling axis, we must construct line to represent it.
5. For the line creation, we can use the hole present in surface A as the reference and using the point option, we must include a point in the centre of the hole.
6. Now to draw a line, use the line-direction command, where the previously created point as the starting end, we must extend it on both the sides for a considerable distance, with Z-axis as the direction.
7. Now to comfortably view the final tool axis, we must publish it separetly using publish command in the tools option in CATIA.

Tooling axis snippet:

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Class A Surface:

Starting with the Class A as the input, and required output as the plastic component, we should consider the following rules:

• The Surface A being the aesthetic part of the plastic component, whatever surface creater after that must not alter the original surface A.
• The Draft angle must be on the surface B and C.

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

Use the open option in the catia to open the file if the class A file is given in above formats, instead for part file from CATIA.

If the file file is in IGS format, the surface A will be in patches, so join it before proceeding to other steps.

Surface A snippet:

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Drafting Analysis:

When the final component created, the drafting analysis done to ensure the draft angle given to the surface C is within the standard range of 3 degree. By keeping this angle, the part produced are safer to be ejected by the ejector pins, without being damaged. The color order of GBR (i.e., Green, Blue, Red) discusses whether the draft angle is safer in limits,

if it is green, then the draft is within 3 degree

if it is blue, then the draft is not less than 0 and not more than 3 degree.

if it is red, then the draft is less than 0.

Steps in Catia to Drafting Analysis:

1. Add material using the view option to let the draft analysis to run.
2. Select the surface or final part body to make it highlighted in the feature tree.
3. Use the analysis in the insert option in the CATIA's menu bar, to find the Feature draft analaysis.
4. 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 compas positon 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.

Drafting analysis snippets:

1. Class A Surface analysis:

2. Closed Surface / Final part analysis:

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Class B Surface:

The Class B surface is the othe 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:

1. Study the Class A surface features by using vernier measure tool to distinguish between the flat and curved surface, by the symbol appears next to it.
2. Extract the flat ones by using extract command and leaving behind the curved unselected.
3. Now offset the extracts by using the thickness value 2.5 as the offset and now use the untrim command to derive the untrimmed surfaces from the offset.
4. Due to the lack of intersection, we must use extrapolate tool by point continuity to make them intersect with each others respectively.
5. Now trim the required parts and save in separate geomentric sketch.
6. Give the fillets to the intersecting corners as per the Surface A but, following the Fillet offset rule, where the bulging upward fillets value must be reduced by thickness and vice versa for the bulding downward fillet.

Now the Class B surface is created sucessfully.

Class B Surface snippet:

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Class C Surface:

The Class C surface is the inbetween portion of Class A and Class B, where the volume is added or in other words, plastic thichkness is given here.

The Class C Surface is given the draft angle of 3 degree, to make the component to easily ejected from the mold.

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 the surface A with thickness more than intersecting the surface B.

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.

Now do the same approach of swepting the holes by taking the reference as the boundary using boundary tool with same dimensions, with only change giving the draft inwards to the surface A.

Save it in a seperate geometrical set.

Class C Surface snippet:

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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 extendend edges of the class C with Class B.

Final Trim snippet:

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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 snippet:

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