Door Trim Lower

INTRODUCTION OF DOOR TRIM LOWER

Next to the dashboard, the door trims are the interior parts that contain the most controls and decorative parts. As such, there is a necessity for balancing gap between parts, as well as an overall sense of unity between the numerous parts.

Materials used for Door Trim Lower

1) Acrylonitrile Butadiene Styrene (ABS)

The acrylonitrile in ABS plastic provides chemical and thermal stability, while the butadiene adds toughness and strength. The styrene gives the finished polymer a nice, glossy finish. ABS has a low melting point, which enables its easy use in the injection moulding process.

Mechanical Properties of ABS

Elongation at Break	10 - 50 %
Elongation at Yield	1.7 - 6 %
Flexibility (Flexural Modulus)	1.6 - 2.4 GPa
Hardness Shore D	100
Stiffness (Flexural Modulus)	1.6 - 2.4 GPa
Strength at Break (Tensile)	29.8 - 43 MPa
Strength at Yield (Tensile)	29.6 - 48 MPa
Toughness (Notched Izod Impact at Room Temperature)	200 - 215 J/m
Toughness at Low Temperature (Notched Izod Impact at Low Temperature)	20 - 160 J/m
Young Modulus	1.79 - 3.2 GPa

2) Polypropylene (PP)

Polypropylene (PP) is a tough, rigid, and crystalline thermoplastic. It is made from propene (or propylene) monomer. This linear hydrocarbon resin is the lightest polymer among all commodity plastics.

Mechanical Properties

PROPERTY	UNIT	VALUE / RANGE
Tensile Strength, Yield	MPa	31 - 45
Tensile Strength, Break	MPa	18 - 22
Elongation, Yield	%	10 - 12
Elongation, Break	%	50 - 145
Tensile Modulus	MPa	1950
Flexural Strength, Yield	MPa
Flexural Modulus	MPa	1350 - 1800
Compressive Strength	MPa
Izod Notched	J/m (kJ/m2)	35 - 60 (3.0 - 6.5)
Izod Unnotched	J/m

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.

Overview:
Initially, we need to offset the given Door trim lower class A surface in the inner direction to the required thickness (here the thickness is 2.5mm). After that, we need to close the patches on the offset surface of the Door trim lower, the patches are formed due to the fillets on the Class A surface. Once all the patches are closed properly join them together to make a proper class B surface and now sweep the boundary of the class A surface to trim with the class B surface to make a closed body. By using the closed body command in the Prat workbench we can get the solid body from the closed surface of the Door trim lower. Now, again went back to the surface workbench to perform the 'Draft analysis' for the solid body.

Class A Surface-

Class A Surface is the asthetic sutface that is created through scaning of clay model. This Class a Surface is a input CAD model for part design.

Class B surface-

Class B surface is created in a certain distance according to the thickness of the part. Class B Surface contain all engineering component.

Class C Surface-

Class c Surface joins the Class A & Class B Surfaces.

The steps involved in creation of this project are:

1. Bringing the class A surface of the Door trim lower in Catia v5 software.

2. Determining the tooling axis for the Door trim lower.

3. Creation of class B surface.

4. Creation of class C surface.

5. Joining all the class A, class B and class C surfaces of the Door trim lower.

6. Building closed surface after joining all the surfaces.

7. Draft analysis on the Door trim lower.

METHODOLOGY:

In this model we have focused on the following things:

• Tooling axis
• Draft analysis
• Class-B surface
• Class-C surface
• Making a solid model from surface.

Following tools were used to reach the final step:

• Trim
• Extrapolate
• Offset
• Split
• Multiple-Extract
• Multi-section surface
• Boundary
• Sweep
• Join
• Close (part design)

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.

Procedure

Below is the class A surface which was incorporated in the Catia V5 work bench to work upon.

Tooling axis & Draft Analysis: The direction in which the mold or core and cavity opens is the tooling axis.

To create the tooling axis, I extracted a surface from class A and created a point in the middle of the surface by using the point command and created a line at that point through the x-axis. Now, I performed a draft analysis check from that line whether the created tooling axis is in the correct position or not. If, in the draft analysis check the surface highlighted with green colour on both sides of the surface the tooling axis is in the correct position and direction.

CLASS B SURFACE:

To create the class B surface, offset the class A surface inside as per our thickness requirement ( 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.

PATCH-1

Repaired Patch-1

Patch-2

Repaired Patch-2

After Fillin Patches Class B Surface

CLASS C SURFACE:

To create the class C surface concerning the boundary of the class A surface, I used the sweep command. Initially, I extracted the boundary of the class A surface with tangent continuity, and I sweep the extracted boundary concerning the surface at 90deg (for reference Surface) for 5mm 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 intersected 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 lower.

Class C Surface

Now, join both class A and sweep boundary to get the complete class C surface.

Now, unhide the class B and class C surfaces. Check whether all the sides of class B and Class C surfaces are intersecting properly with each other, to get a closed surface by trimming class B and class C surfaces. If the class B and class C sides are not intersected properly, we need to extrapolate the sides of the class B surface which are not intersecting with the class C surface. Now, check class B and class C surface boundaries whether all the sides are intersecting or not with each other. Once the surfaces are intersecting properly trim them together to get a closed surface.

In the above-given image, the sides are not intersected properly. I extrapolated the surfaces which are not properly intersected with each other like above.

The below-given image represents the sides which are extrapolated until the surfaces are intersected.

CLOSED SURFACE

Trim

PART BODY:

To create the solid part body from the closed surface, I used the closed surface command in the part workbench.

DRAFT ANALYSIS:

After creating a solid body from the closed surface I performed a draft analysis on it, to check the draft angle of the solid body.

Conclusion

1. Class A, Class B and Class C surfaces are created following standards of automotive industry using Catia V5 software.

2. Draft analysis was performed on the Door Trim Lower and it was observed that draft was under permissible limit for the manufacturing of the component using injection moulding process.