Week 10 - Challenge 3 - Door Trim Lower with Engineering Features
DOOR TRIM LOWER WITH ENGINEERING FEATURES
Aim: To Create the Door trim lower component through the given Class-A surface.
Objectives:
• Creation of Tooling axis with appropriate draft angle.
• Creation of other surfaces (eg, B and C surfaces) for creating a solid component.
• Perform Draft analysis on Class A surface and Solid model hence created.
REFERENCE IMAGE:
Procedure for creation of Solid model:
MAIN REPORT:
Types of Surfaces and their importance for an Automotive Plastic Designer:
- Class A Surface: Class A is an aesthetic surface with the highest quality finish. Most Class A Surfaces for an Automotive Component are made using 'Autodesk-Alias' based on the final Concept-Sketch. All Class A surfaces should have 'Curvature-Continuity' which means the continuity between the surfaces should share the same boundary. It is taken as a reference by the Automotive Plastic Designer to create 'Class B' and 'Class C' Surfaces.
- Class B Surface: The Class B Surface resides below the Class A Surface at a certain thickness. It is created using Engineering Principles that consist of all the necessary features such as Ribs, Bosses, Snaps, etc. This surface isn't visible to the observer from the outside.
- Class C Surface: The Class C Surface is the surface created between the Class A and Class B surface to join them with each other.
Now, we will begin by checking the State of Connectivity for the Class A Surface and ensure that there are no gaps between the surfaces as all the surfaces should be joined well together with each other and shouldn't consist of any discontinuities between them.
Our Class A Surface:
Using the 'Boundary' Command' from the Operations Toolbar:
In this case, we have to click on the 'Boundary' command and then select the Class-A Surface. After that, we'll click on the 'Preview' button to highlight all the boundaries that are on the Class-A surface and check if there are any internal boundaries other than the outer edge boundaries.
In our case, there are two boundaries present on the Class-A Surface one of which is the Outer-Edge Boundary & the other is the Inner Hole-Boundary. Hence, we can conclude that all the surfaces are well connected.
PROCEDURE TO CREATE THE MAIN TOOLING AXIS:
There are two different methods that we can use to create the Main Tooling Axis for our Class A Surface. When we're trying to create our Main Tooling Axis we always have to focus on the direction in which we're going to create the Main Tooling Axis.
- Using a Vertex to create a line along the axis which allows us to view all the holes & exposes the maximum surface area of the Class A Surface.
- Using Inertia Method to find out the Center of Gravity and create a line along it.
INERTIA METHOD TO CREATE THE MAIN TOOLING AXIS:
This method may not work for every component but it was considered to be used for this component.
We'll click on the 'Measure Inertia' icon from the 'Measure Toolbar' as shown below:
We'll select our Class A Surface that will open up the 'Measure Inertia' dialogue box as shown below:
After that, we'll click on the 'Create Geometry' option in our Measure Inertia Window that'll open up the 'Creation of Geometry' window.
There we'll choose 'Non-Associative Geometry' and then click on 'Center of Gravity' to create the required C.G point as shown below:
Now, using the 'Line-Definition' command while choosing our Line-Type as 'Point-Direction' we'll create a line along the X-Axis as shown below:
Draft
The draft is the amount of taper for moulded or cast parts perpendicular to the parting. line. Draft angles are a design consideration that makes it much easier for a part to release cleanly from a mould. A draft angle is calculated as a degree measurement (or, less often, an inch or millimetre measurement) from the vertical axis of a mould, and it helps account for thermoplastic shrinkage, a practical reality of the injection moulding process for most materials.
Draft angles are generally a requirement of injection moulding design (though there are a select few soft materials, like nylon, that can get away with draft angles of zero). The draft should be a part of the design for manufacture, and all stakeholders and contributors should be aware of its need at the outset of the design process. This includes product designers, design engineers etc and this allows considerations for design requirements to be taken into account. Any draft is always better than no draft.
Importance of Draft:
By accounting for thermoplastic shrinkage during the cooling process, draft angles significantly reduce friction between the finished, cooled part and the side of the mould, Not only does this create a much easier release process, but it also offers several other benefits, depending on the design of the part which is as follows:
• Reduces the chance of damage to the part due to friction during the release.
• Reduces wear and tear and chances of damage to the mould.
• Ensures a uniform, smooth, unscratched finish when required.
• Ensures the integrity and uniformity of other surface finishes and textures.
• Reduces overall cooling time by lessening or eliminating the need for unconventional ejection setups.
• Most, if not all, of these benefits, offer either direct or indirect overall production cost reductions.
DRAFT ANALYSIS FOR THE CLASS A SURFACE
Before starting with a Draft Analysis Operation, we will go to the 'Customize View Parameters' option under the 'View Toolbar'. Then we will enter the 'Customize View Mode' where we will go under the 'Mesh' option and select 'Material' and press 'OK'.
To start the Draft Analysis in the 'Generative Surface Design Workbench', we will go to 'Insert' and then look for the option called 'Analysis'. Once found, we will go under that and click on 'Feature Draft Analysis. This will open the 'Draft Analysis' Dialogue box. There, we will ensure that under 'Mode' we have selected 'Quick Analysis', under 'Display' we will select 'Show or Hide the Color Scale' and then select '3 Degrees' as the permissible draft angle. Then, under 'Direction' we will choose the icon with the symbol of the compass on it which stands for 'Use the Compass to define the new current draft direction'.
ANOTHER METHOD TO CREATE THE MAIN TOOLING AXIS:
Now, to create our Main Tooling Axis using the first method, we'll choose a vertex as shown in the image below to create a line using the 'Line-Definition' command while choosing our Line-Type as 'Point-Direction' where our direction will be towards the X-Axis.
It is evident from the above image that the Draft-Analysis on our Class A Surface was successful for the degree of 3 degrees.
Hence, we can see that the Draft Analysis was successful along both the Tooling Axes and hence either one of them can be used as our Main-Tooling Axis.
PROCEDURE TO CREATE THE CLASS B SURFACE:
To create the class B surface, offset the class A surface inside as per our thickness requirement (here the thickness is 2.5mm, so I offset the class A to 2.5mm inside). Once the offset is created, we can observe some patches on the offset surface by taking the boundary for the offset surface, those patches are formed due to the fillets on the class A surface. We need to cover those patches with the help of the multi-section surfaces command by extracting the patch boundaries. Once all the patches on the offset are covered properly join all the patches with the offset surface, to get the replicated surface of the class A surface.
CLASS C SURFACE:
I used the sweep command to create the class C surface concerning the boundary of the class A surface. Initially, I extracted the boundary of the class A surface with tangent continuity, and I sweep the extracted boundary concerning the surface at 93deg (for draft angle) for 4mm to intersect properly with the class B surface. Once we sweep all the surface boundaries of class A, extrapolate the sweeped surfaces until both surfaces got intersect properly, and trim them to remove extended extrapolated surfaces to get a proper sweep boundary throughout the entire surface, including the centre hole of the door trim. Now, join both class A and sweep boundary to get the complete class C surface.
PART BODY:
To create the solid part body from the closed surface, I used the closed surface command in the part workbench.
Draft Analysis of Solid Model
Same steps are followed to get the draft analysis of the solid part as in Class A Surface
As we know minimum draft angle for the faces of the plastic component should be 3 degrees. So the value of 2.9 degrees (considering tolerance) is provided in the Draft analysis colour mode window Inside the colour scale, the GREEN bar shows the draft angle of 2.9 or above 2.9 degrees. The blue bar shows below 2.9 degrees draft angle the other limit being and the RED bar shows the negative draft angle. As shown in the image below all the top faces and side faces of the component are green, while the bottom faces are red. The line of demarcation between the green and red faces is the parting line which divides the core and cavity halves. The solid model has cleared the draft analysis successfully as shown in the image below.
PROCEDURE TO ADD ENGINEERING FEATURES:
1. LOCATORS
2. HEAT STAKES WITH GUSSETS
USE OF LOCATORS: Any workpiece has 12 degrees of freedom for movement in space that consists of 6 Axial and 6 Radial Degrees of Freedom. All 12 degrees of freedom must be restricted to ensure proper referencing of a workpiece. These 6 Axial Degrees of Freedom permit Straight-Line Movement in both directions along the 3-principle axis shown as X, Y & Z. The Radial Degrees of Freedom permit Rotational Movement, in both Clockwise & Counterclockwise radial directions around the same three axes.
We have two objectives when assembling the child component with the parent component:
1. Accurately position the part at the desired coordinates.
2. Restrict all degrees of freedom except the one direction in which it'll fix so that the part cannot move.
CREATION OF LOCATORS:
To create the locators, I created a sketch on the body. After creating the sketch, I pad it 20mm in height and thicken it to 1.3mm and I drafted it with 0.5deg in the direction of the tooling axis. I gave 5mm of chamfer with 45deg of inclination and after I gave a fillet of 0.25mm radius.
4-way locator:
Next, the profile is extruded, to find the height,h=Wall thickness * 8
=2.5*8
= 20 mm
Therefore, the height is 20 mm
The extruded surface is thickened,
Thickness,w=0.4*t
=0.4 2.5
=1mm
Therefore, the thickness of the rib is 1 mm
The draft is applied to the sides of the ribs. As per the design rule, the ideal draft angle is 0.5 deg
Then fillet is applied to the faces of the rib. As per the design rule, the fillet can be 0.3 mm.
SOLID BODY
DRAFT ANALYSIS
CREATION OF HEAT STAKES:
To create the heat stakes, I draw a sketch on the surface. After the creation of the sketch, I pad it to 18mm height and I gave a draft angle of 0.5deg on both sides (inside and outside) and then I gave a fillet with a 0.25mm radius. After creating the heat stake, I created the ribs for supporting purposes. To create the ribs, I draw a sketch and padded it to 12mm in height and 1mm in thickness. After padding the ribs, I drafted 0.5deg in the tooling asix direction and filleted it with a 0.25mm radius. Finally, I union trim the ribs with a heat stake to remove the ribs, which are present inside the heat stakes.
DRAFT
The draft is applied to the sides of the ribs. As per the design rule, the ideal draft angle is 0.5 deg
Then fillet is applied to the faces of the rib. As per the design rule, the fillet can be 0.25 mm.
DRAFT ANALYSIS ON THE ENGINEERING FEATURES:
3D VIEWS OF THE FINAL PART WITH PROPER COLOR CODE OF THE DRAFT ANGLE
