Week 8 - Challenge 4 - Coin Holder Design
Coin Holder Design
Aim: To create the Coin Holder Plastic 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.
The image below shows the given class A surface for which a solid model is to be created.
Surface Inspection:
Firstly, the given surface is inspected for its quality/continuity such that no gaps are present in it thus clearing our way to go ahead with tooling axis creation.
If at all irregularities/ gaps are present on the surface it is looked after using various tools/commands available in CATIA V5. As we can see in the image below there are no gaps in the given surface.
Tooling Axis creation:
It is defined as the direction in which the mould/core and cavity open. Selection of the direction of the tooling axis depends on the ease at which components can be easily ejected.
Hence the given surface is inspected for the tooling axis directions in standard X, Y & Z directions and accordingly best direction suited for the component is chosen. In this case, the flat bottom face (bin) is chosen and the line perpendicular to the surface passing through its centre of gravity is created.
As per the observation, three walls of the bin are not having any draft angle ie they are perpendicular to the bin surface. Hence they will fail in the draft analysis. So we will consider the created line as our tooling axis.
Draft Analysis of components
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
Every part which is manufactured from a press tool or injection moulding process requires some positive draft on the faces which are parallel to the tooling direction. If we don't give a draft (Zero Draft) or give negative drafts on these faces it will stick to the mould surface and when the mould is in motion it will destroy the surface thus reducing its surface finish. Thus Draft Analysis command enables us to detect if the part we have drafted can be easily removed or not. It also gives insights into the critical zones, so that appropriate changes in the design can be made if needed.
To perform draft analysis on the given CLASS A surface following steps are followed:
Firstly, in the View mode toolbar Customize view is selected and in that, the material option is selected as shown below.
Compass is dragged onto the component and aligned with the tooling axis and the draft analysis is visible after clicking anywhere on the surface of the component.
As we know minimum draft angle for the faces of the plastic component should be 3degrees. 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 0 and the RED bar shows the negative draft angle. As it can be seen in the draft analysis of the class A surface some faces are green and some are red hence the surface has not cleared the draft analysis. Hence the styling department (Class A designer) needs to be communicated to give the required draft angle on the faces required.
3D Views of Class A surface with draft analysis.
Draft Analysis of Solid Model
Same steps are followed to get the draft analysis of the solid part as followed 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 0 and the RED bar shows the negative draft angle. As it can be seen in the draft analysis of the solid component some faces are green and some are red hence the part body has not cleared the draft analysis.
3D Views of the part model with draft analysis
FILE REVIWED BY ABHISHEK