Week 9 - Project_1 - Door Trim Lower with Engineering Features
Aim: To Create Door Trim Lower with Engineering Features through the given Class-A surface.
Objectives:
• Creation of Tooling axis with appropriate draft angle.
• Creation of other surfaces (B and C surfaces) for creating a solid component.
• Perform Draft analysis on Class A surface and Solid model hence created.
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.
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. By analysing the component the most easily ejectable direction is somewhere close to the Z direction,(might be inclined to it) so we have made a sketch on the Y direction to create a tooling axis.
Draft Analysis of solid part
Same steps are followed to get the draft analysis 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 0.4 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.
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 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 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.
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 to see 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.
SOLID PART BODY:
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:
CREATING THE RIB
Ribs are thin wall protrusions that extend perpendicularly from a wall or plane. They are usually found in clusters offering support to a plane that would have otherwise been too thick, but can also be stand-alone support for a single wall. They are commonly used to provide additional support and strength to a part. Thickness and location are essential to rib design.
Next, the profile is extruded, to find the height,h=Wall thickness * 5
=2.5*5
= 12.5 mm
Therefore, the height is 12.5 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 0.25 mm.
RIB:
CREATION OF SCREW BOSS
To create the screw boss, 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 screw boss, I created the ribs for supporting purposes. To create the ribs, I draw a sketch and padded it to 15mm 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 screw boss.
CREATING THE DOGHOUSE
The dog house is an engineering feature used in the plastic trim design. Dog houses are used as a supporting feature. Sometimes other engineering features like snaps; locators, etc. are mounded on them to increase their strength. The doghouse is created by following the design rules. The nominal wall thickness guide range is from 0.75 mm to 3 mm for reinforced materials and 0.5 mm to 5 mm for unreinforced materials.
WALL THICKNESS (W) = 0.70 (NOMINAL THICKNESS OF PLASTIC MATERIAL)
This process is usually done by Thicken surface command.The fillets and the draft are given as per the design rules. An important thing while designing a doghouse is to maintain 40% less thickness than the wall thickness (T) at the area of the intersection to avoid sink marks. So, a C shape is formed at the intersection.
This can be made using the split command to remove the solid at the intersection.
Draft Analysis
VIEWS
ISOMETRIC VIEW
TOP VIEW
FRONT VIEW
LEFT SIDE VIEW
RIGHT SIDE VIEW
