Week 9 - Project 1 - Door Trim Lower with Engineering Features

Report -

3-2-1 Principle:
Locating Process: In order to completely specify the position in space of a three-dimensional object (such as the cube that’s shown), we refer to six coordinates with total 12 degrees of freedom.

1. Translational position along the X-axis
2. Translational position along the Y-axis
3. Translational position along the Z-axis
4. Rotational position about the X-axis
5. Rotational position about the Y-axis
6. Rotational position about the Z-axis

These six coordinates are known as the six degrees of freedom of a three-dimensional object. As the double-headed arrows indicate, the translational and rotational positions can vary in either direction with respect to each of the three axes. To completely prevent movement, all six degrees of freedom must be restricted.

Locators -

A 2-way locating pin restricts motion along 1 axis (or 2 degrees of Freedom), like a round pin in a slot. Likewise, a 4-way pin restricts 4 degrees of freedom along 2 axes. A round locating pin located concentrically in a hole is a common application of a 4-way pin, and helps to further secure the piece.

Heat staking:
Heat Staking is a pulsed-heat process to join two or more parts out of which one at least is made of plastic. The process is to deform the plastic material using heat and force at a set process time. The bond is made by partially de-forming the plastic part in order to fix the other. Heat Staking makes it easy to bond metal to plastic and is commonly used in high volume/low cost applications such as automotive, IT and consumer appliances.

Shaping Plastic Using Heat and Pressure:
The plastic is deformed by heating it to a temperature above the glass transition temperature. Super-heated air or a thermode is used for this. Pressure is then applied to create the stake. After the stake has been formed, the plastic should be cooled down again below the glass transition temperature. Cooling is performed under constant pressure to ensure good fixation of the parts. Compressed air can be applied for cooling when a thermode is used. Heat is used to facilitate the creation of the stake. Heat control is critical, especially for glass-filled plastics which often have a process window of less than 10 degrees Celsius. When the temperature is too high, the glass fibres come out of the plastic which leads to a rough surface and adhesion to the thermode. If the temperature is too low, the plastic will crack due to cold deformation.

Heat staking Benefits:

1. Similar and dissimilar materials may be joined: metal to metal, plastic to plastic, metal to plastic
2. Accurate control operating within a small process window
3. Local heating resulting in no damage to surrounding materials
4. Processing of glass-filled materials
5. No mechanical vibration
6. Many heat-stake shapes possible through custom designed tools

Draft analysis -

Draft analysis is important here to check the feasibility of manufacturing the component. A safe draft angle of 3 degrees is provided so that the surface of the component upon shrinking does not stick to the core surface. Upon cooling within few seconds, it is the tendency of the plastic moulded component to shrink towards the core surface. This can cause diffculty to remove the final component or can even damage the surface of the component and core.

Creation of tooling axis -

There are generally four methods of creating tooling axis to check whether the component will clear the draft analysis test.

1. Along axis direction (X,Y,Z)

2. Normal to face part

3. Trial and error compass

4. Bisecting line method

Here, Trial and error compass is used to plot the main tooling axis. First the direction where major percentage of component is visible is the direction in which tooling axis is created through centroid of the component. Then the compass is adjusted by changing its angle to get the most suitable angle where the whole or majority of component is clearing the draft angle requirement. Compass is locked and the line is drawn through centroid in the compass direction. This is the main tooling axis.

Class A surface -

Class A surface is clearing the draft angle required i.e 3 degrees.

Class B surface -

Class B surface is clearing the draft angle requirement of 3 degrees.

B side features i.e Locators and Heat stakes -

B side festures are clearing the draft angle requirement of 0.5 degrees.

Isometric view -

Front view -

Side view -

Top view -