Week 9 - Attachment Feature Creation (Ribs & Screw Boss) - Challenge 1

Week 9 - Attachment Feature Creation (Ribs & Screw Boss) - Challenge 1

AIM

Create the rib for the Drill Handle considering the design rules mentioned in the video.

Create the Screw boss for the Drill Handle considering the design rules mentioned in the video.

Requirements

• A detailed report should be done explaining the draft analysis and the tooling axis creation.
• An explanation should be given on the way of creating the tooling axis, particularly the Bisecting method.
• Screenshots of the completed design in various orientations (Isometric, Front, Side, and Top View)
• CATpart should be submitted as an attachment

REPORT

Screw Bosses

Boss features are commonly found in injection molding designs. They are used to aid in the assembly of molded parts by providing a channel for a screw.

Ribs

Ribs are a feature in plastic injection molded parts. They are thin extensions that run perpendicular from a wall or plane. They are commonly used to provide additional support and strength to a part.

Tooling Axis

Tooling axis is a direction in which core and cavity opens and closes. Draft angle is provided with respect to the tooling axis. While creating mold component from Class-A surface, we need to decide the tooling direction. It can be decided by visual inspection, deciding complex surfaces and bisecting method.

Tooling Axis Creation- Bisecting Method

• First check for the discontinuity of the surface received by join or boundary command. Then visual observation is done to decide which direction will be more feasible to create component.
• Few surfaces are identified which can create concern over draft angle
• A reference point is created in center of the bottom surface. And Axis system is created at that point.
• Two different cross section profiles are formed using intersection with plane.
• For first profile in xy plane, Lines are drawn on the concerned boundary intersection profile. Then line is drawn bisectiong these two lines.
  
• For the second intersection profile in xy plane same procedure is followed.
  
• A bisecting line is created from the two lines created earlier with intersection profile. This bisecting line refered as Tooling axis line and this method is known as Bisecting method to create tooling axis.
  
  
  

Draft Analysis

To reduce the risk of damage to parts and tool while ejecting from mold a draft angle is provided to walls which are parallel to the tooling direction. It assists with releasing the part from mold.

To perform Draft analysis in Catia, Draft analysis feature is used. For that First tooling Direction decided. Then make sure material view mode is used. After opening the window, align the compass with the tooling axis by dragging it on the axis. Then click on the surface or the body on which draft analysis is need to perform. In the bottom black colour window provide the minimum draft angle and then match the body color with this color scale. Green indicated draft angle is more than minimum draft angle. If it is blue then it is between 0 to minimum draft angle. And red denotes it is less than zero. By this way we can identify the areas with draft angle less than minimum draft angle and work on that area by changing tooling axis angle.

In the 1st image minimum draft angle is kept 0.5 degrees specifically for the Ribs and screw bosses. And they are above the minimum draft angle.

In the 2nd image, mode is changed to full analysis, and draft angles are set at 0, 0.5 for ribs-screws, 3 degrees for solid body of Door Handle and negative. Class A has Positive draft and Class B and C has negative draft. In some patches Class A has draft between 0-3 degrees.

Procedure

• Check for Discontinuity. If any, join the surface. And Publish it as CLASS A surface
• Identify concern planes. Create line in every concern planes. From the these line create bisecting line ie. final Tooling axis.
• Perform Draft analysis on Class A surface in the Tooling Direction
• Create Class B surface by offseting Class A surface and join them by trimming. Fillet Edges. Or use fill by creating close profile.
  
• Create Class C surface by extracting boundary of class A surface and sweep it by minimum draft angle along the tooling direction.
  
• To create final closed surface body, join and trim all three surface together and finish by giving remaining fillets.
• Convert this surface body into Solid body by Close Surface Tool
  
• Create skech for Rib and extrude it in the direction of tooling axis. Provide thickness, fillet, draft as per design and attach to the body.
  
• Similar way create Screw boss and attach to body. Screw boss is designrd for M5 Screw.
  
• Perform Draft analysis again on the Solid body.

OUTPUT

3D Model Views

FRONT	SIDE
TOP	ISOMETRIC

Conclusion

Class A surface of Door Handle is successfully converted into solid body. And Rib and Screw Boss are created on Class B surface.