Week 8 - Challenge 5 - Core & Cavity Design
OBJECTIVE:
1) Create the Core and cavity blocks for the switch bezel designed
THEORY:
The draft analysis helps to detect if your drafted part is easily removable from the mold or die. All plastic components will have a minimum draft of 0.5 to 3deg. And for automotive sheet metal parts, the draft will be 7deg or more. If a mold wall is perpendicular to the part ejection, there is an ample friction or interference between the mold and the part which will not allow one to release from the other. This is why design engineers give a minimum draft to the part.
The Tooling Direction is basically the direction that the mold pulls apart. The mold is built in two separate pieces, basically. You have a Cavity side and you have the Core side. The Core pulls apart from the Cavity and that's the Dyeline or the Tooling Direction. There are different methods to find out the tooling direction. Here we are using bisecting method to find out tooling direction. We can use any method the ultimate aim is to reduce the cost of manufacturing by reducing the complicity in manufacturing the component.
PROCEDURE:
The procedure is divided into two parts first creating the tooling axis then performing the draft analysis.
Creating tooling axis :-
1) The first thing to do is finding out the possible tooling direction by visually checking the part. Rotate the part in all directions and find out the most suitable direction for tooling. Here in case of Switch Bezel viewing from Z direction, we can clear the face in tooling.
2) Then we create a point on the surface of the part, we can create the point anywhere on the surface but usually, we take CG point or take a point near to the center. On this point, we put a new axis system.
3) Then we are finding out the tooling axis in Y direction. For that intersect command is used to get the boundary in Y direction or YZ plane. We use the Bisceting method here
4) Extending the drafted face using a point-to-point line command. Then using bisecting line command bisect both extended lines to get the tooling axis in Y direction.
5) Since in X direction there is only one wall to create tooling axis, bisecting method wont work here. We make an axis in a way it clear the draft in X direction.
6) After creating the tooling axis along X and Y direction bisect both the lines and create the actual tooling axis.
Steps to do draft analysis:
1) Use Generative shape Design, Open Feature draft analysis option from Insert > Analysis > Feature draft analysis.
2) A new window pops up by default it will be in quick analysis mode. Change the range to 3deg.
3) Next you have to position the compass on the tooling axis by dragging the compass from the top right corner of the working area. The W axis of the compass should be inline with the axis.
4) Then you have to define the compass by click on the compass icon on the draft analysis window. Then lock the position of the compass by clicking the lock icon.
5) After that select the surface and the whole surface will show a color range. Here the Switch Bezel surface is fully in green color, which means all faces are having a minimum draft angle and it’s good for manufacturing. If any face is showing blue or red color we have to work on that face to give a good draft.
Creation Of Class B Surface :-
B Surface is the inner side of the component, where A surface is the outer and visible side.
1) For the creation of the B surface we will Extract the flat surface in the A surface using Extract tool.
2) Untrim the extracted flat surfaces.
3) Then Extrapolate the extracted parts.
4) Trim the surfaces and remain only the wanted surfaces and offset it with the thickness of 2.5mm
6) Add fillets as in the A surface.
Creation Of Class C Surface :-
C surface is the thickness side of a part which joins the A surface and B surface.
1) First creat the boundary line of the A surface. As the switch bezel is having a curvy boundary we create boundary as two parts
Create boundary at backside
Create boundary on front side.
2) Then using the Sweep command make the side surface with draft.
3)In Sweep using the Line option. For Subtype select "With draft direction"
4) For Guide Curve1 Show the Boundary of A surface.
5) Draft direction show the Tooling Axis.
6) For Angle give 3 degree.
7) Join both sweep parts and make the Class C surface
8) Then use trim option to trim the unnecessary surface. And join A,B and C surface to form a Closed surface.
9) Go to Part Workbench and make a solid part with the closed surface.
Screenshots of the solid model with the proper color code of the draft angle in various orientations (Isometric, Front, Side, and Top View)
Creation of Core And Cavity Blocks :-
Core Block creation :-
1) Core is the bulge out part, From the switch bezel surface we have, we will take B surface and extrapolate its boundaries.
2) The we make a sketch in the XY plane, which cuts the b surface as a perfect rectangle and the closed surface should be in the middle.
3) Now extrude the rectangular line.
4) Now Trim it in a way that the upper part of the extract is taken and rest is deleted.
5) Fill the upper gap using Fill surface tool
6) Now Join all parts and make a single closed part.
7) Now go to Part Design and make a solid out of the closed surface
8) This is the Core Block, We can see the part design in Core as a small depression of 2.5mm which is the thickness of the part.
Cavity Block Creation :-
1) Cavity is the part having depression of the core in it, From the switch bezel surface we have, we will take B surface and extrapolate its boundaries.
2) The we make a sketch in the XY plane, which cuts the b surface as a perfect rectangle and the closed surface should be in the middle.
3) Now extrude the rectangular line.
4) Now Trim it in a way that the lower part of the extrude is taken and rest is deleted.
5) Fill the lower gap using Fill surface tool
6) Now Join all parts and make a single closed part.
7) Now go to Part Design and make a solid out of the closed surface
