Week 8 - Challenge 1 - Draft Analysis on a Fan Cover
INPUT: Automotive Class-A surface, obtained from Autodesk Alias.
OBJECTIVE: Create Tooling axis for the given surface and carry out Draft analysis to meet the required minimum draft angle for plastic injection molding.
Tooling Axis: It is the axis/line created by the plastic part designer so that the moving mold core and fixed mold cavity are clamped and retracted along this particular line in an injection molding machine.
Draft angle: It is the angle given to the plastic part along the surfaces of the mold core/cavity walls, so that easy ejection of the part is made possible at the end of the cycle.
The general minimum draft angle followed across the Automotive industry is 3 degrees for Class-B surfaces and 0.5 degrees for B- Side Engineering features. Anything below these values are difficult to manufacture without defects in the palstic part.
Draft Analysis: It is the process carried out to analyse and to ensure that the direction of tool clamping and declamping in a injection molding machine occurs along the created axis by the Designer, called as "Tooling axis", there by ensuring the draft angles along various planes across the geometry of the part meets the minimum manufacturing criteria.
Steps to create Tooling axis:
1. Initial step is to visualise the given input surface carefully so that all the surfaces clears during tooling at one go. While doing this, generally holes, large surfaces with less contours and flat land surfaces are preferred.
2. There are 3 Axis in a 3D part. i.e., X,Y and Z and 3 planes, XY, XZ and YZ. Next step is to "Intersect" the axis on the surface along the 2 planes mentioned above leaving the axis along which the tooling axis will be created. As it can be seen in below screenshots, the intersects are the white lines running across the length and width of the surface along XZ and YZ planes.
3. Next step is to create the lines using the drop down option stating "Point to Point" across the intersects created along the points where the surfaces creates problem for clearing the tool.
4. Next step is to create the line between the lines created earlier using "BISECTING" method.
In this method of creating the Bisecting line, there has be of two lines and a point. The resulting line is the mean of the two lines initially created and it passes along the point selected/created/. The lines created may not be parallel, have same angles on opposite sides and also bisecting lines with different direction along two non parallel or different planes of the initial two lines can also be created. But the primary focus is on the lines laying on same plane is used extensively. The point along which the resulting bisecting line passes can be selected if present or can be created seperately using various options, but "midpoint" option is preferred, so that the resulting point will be the mid point between the points at the extreme ends of the initial lines created.
5. After creating the bisecting lines across the two of the planes mentioned above, the final Line has to be created using the same bisecting method using the lines created which will be the final TOOLING AXIS for the plastic part. The Blue line is the tooling axis in the below image.
DRAFT ANALYSIS:
Steps to be followed for draft analysis:
1. Initially View mode selection is selected for Material mode.
2. It is made sure that the workbench is "Generative Shape Design". Select the "Feature Draft Analysis" under the drop down menu in "Analysis" inside "Insert" option.
3. Select the "compass" option in the "Direction" and drag the compass, so that the "W" axis in the compass is inline with the Tooling axis. Lock the Compass on to the Tooling axis, using the lock symbol.
4. Next is to click on the part/surface on which the analysis is carried out.
5. The colour scale variant can be changed as per the needs.
Green colour represents, the draft angle meets minimum requirement and can be cleared.
Red colour indicates the surfaces can't be cleared for the given minimum draft angle (3 degrees)
Blue colour indicates the surface has negative draft angle.
The surface is cleared for 3 degrees, but fails for 10 degrees, which represents, it needs to be reduced.
If the tooling direction is reversed, the below is the result, which shows the whole part has negative draft angle.
Below is the screenshot of various orientations of the tooling cleared surface.
CONCLUSION: Draft analysis has been carried out on the CLASS-A surface and is cleared along all the surfaces as per the industry standard for further processes in an injection molding machine.