How to Create a Cone with Skew (Oblique offset)

File Prefix: SKEW

Description: Skewed cone. Single piece with no intersection.

Dimensions:
Cone 600 mm long, 300 mm dameter at the base and 100 mm at the top. Skewed with a 250 mm offset in the X axis and 200 m in the Y-axis

Overview
The following defines the procedure to create a simple skewed cone in the vertical (Z) axis with an X and Y axis skew or oblique offset.
The example file/s are named SKEW1.GRD,SKEW2.GRD etc. showing the design at various stages as it develops. Use these files togther with the following procedure to understand the design procedure. You can download them here  - SKEW.ZIP. Unzip the files into your Sheet Lightning drectory (usually c:/sheet):

Procedure

1. Switch into a 3D view using the V3D command in the left hand designer menu. You should now be looking at the room in 3D. This procedure is defined to work with the default room size of 1000 long x 1400 wide x 500 high but for other sizes or units you may need to resize the room before commencing design (see the basics for setting the room size). We are now going to create the cone. To do so we must first create a 3D construction frame of the correct size. We then create the object and use the frame to fix the skew dimensions.
2. First create a vertical constructon line of the length of the cone (600 mm) as follows.
3. Select the CONSTRUCT command in the left hand menu. Page using the 'next'/'previous' paging command to find it.The command should highlight in the menu showing construction mode is on.
4. Now enable vertcal movement of the cursor as follows.
5. The X, Y and Z stabilisers should all currently be hightlighted in the left hand designers menu indicatng that the cursor is free to move in all axes. By dfault the cursor moves in the XY plane when all stabilisers are switched on. Switch the X stabiliser off in the left hand designer menu. This forces cursor to move in the YZ plane. It does not matter that the X position is negative, but if you wish to fix a more reasonable X position switch the X stabiliser back on, press the HOME key to get back to the origin, move the cursor to a reasonable X value position, press the left mouse button to switch modes, ten turn the X stabiliser off. You will ave to press the left button again to get back the cross cursor back when in the design are (see the basics)
6. With the cursor now moving in a vertical axis we can design a vertical construction line. Move the cross cursor in the design environment (see basics if you have an arrow cursor) to central position in the room - an exact position is not important.
7. Press the left hand mouse button. The cursor should now be rubber banding a new object centre line in the YZ plane.
8. Move across to the left hand menu and select the the AXES command (you may need to use the 'next'/'previous' paging commands to fnd it). The AXES command should both highlight. This means the next selection in the design area with cause the active center line to snap to the nearest aligned axis (X, Y or Z).
9. Move the cursor back into the design area (it should be the cross cursor - otherwise use the left hand mouse button to switch back modes - see the basics).
10. Move the cursor so that the rubber banded center line is aligned closest to the Z-axis.
11. Select with the right mouse button. The cross cursor movement should snap to the Z-axis. Movement is now restricted to this axis only.
12. At this point you can fix the length of the first object. The bottom of the screen shows the current length of the object center line. While the center line is active either press the F5 key or type a numeric key. An edit box will pop-up requesting the length of the object. Type in 600 to fix a length of 600mm.
13. Type in a length. Make sure the length you type is not too long for the current room size (see the basics for adjusting the room size). Having typed in the length the cursor is fixed at the point where the center line is the typed length on the Z-axis. You can retype the length by pressing numeric keys or pressing F5 again.
14. Having fixed the length press the right hand mouse button to select the point. The first construction line is created (see SKEW1.GRD) and the cursor is liberated. We now need to create construction lines for the X and Y skew, linked to the top of this vertical construction line.
15. Switch the X stabiliser back on to return to XY plane movement of the cursor.
16. Select the SNAP command. It should highlight to indicate that the next selection in the design area will snap the cursor to an object.
17. Move back into the design area, close to the vertical construction line and press the right hand mouse button.the cursor will snap to the line and move vertically as it slides along the line.
18. Push the cursor to the top end of the line and select. A new construction line is started (rubber banding), linked to the first at the top end.
19. Select the AXES command in the left hand menu. It should highlight to indicate that the next selection in the design area will snap the active line to the nearest axis (X, Y or Z).
20. Move close to the X-axis and select. The cursor will snap to the X-axis and be rstricted to slide along it.
21. Type is the X skew length of 250mm. As soon as you hit numeric keys (or the F5 key) and edit box will pop-up to accept te length. The cursor is nw fixed to a point on the X-axis with the axis construction line at the typed length.
22. Select to create the construction line (see SKEW2.GRD) and liberate the cursor.
23. Repeat the process from 16 but this time move the cursor near to the second construction line lying in the X-axis. Use the AXES command agan to align the new construction line with the Y-axis. Type in the length of 200mm and select to create the Y-axis construction line (see SKEW3.GRD).
24. Turn the X stabiliser off again to enable vertical plane movement.
25. Turn CONSTRUCT off in the designer menu. We are now going to create the cone object. At first only the vertical orientation of the cone is important. All location a sizing issues are handled after it has been initially created.
26. Move the cursor back into the design area and select to start rubber-banding the cone center line.
27. Use AXES to snap the cursor to the vertical Z-axis find a position above the first end and select to create it (see SKEW4.GRD). Don't worry about the location or actual position of the object at this tage. Next we set the top and bottom diameter.
28. Select SECTION in the left hand menu (use the 'next'/'previous' commands to find it), select CIRC and snap to the cone object (see setting sections and dimensions). Slide to the top end and select. Type is the diameter of 100 for the active end section (see SKEW5.GRD).
29. Do the same for the bottom but type in 300mm (see SKEW6.GRD) . Now to position the cone using the construction frame.
30. Select the DRAG command. Both the DRAG and SNAP command should highlight indicating the object you next snap to will be activated for movement by dragging.
31. Snap to the cone.
32. Slide to the top end and select. Movement of the cursor should now drag the object.
33. Select SNAP and snap to third construction line (the line lying in the X-axis).
34. Slide to the free unlinked end and select. The cone object is dropped with its top end at this point. You have positioned the top end (see SKEW7.GRD). Now for the bottom end.
35. Select the OBLIQUE command. The OBLIQUE and SNAP commands should both highlight to indicate that the next object you snap to will be 'obliquely' activated.
36. Snap to the cone object.
37. Slide to the bottom end and select to activate the object. Movement of the cursor now obliquely skews the cone.
38. Select SNAP and snap to the vertical construction line.
39. Slide to the bottom end and select to drop the cone base end at this point (see SKEW8.GRD).
40. This completes the design as seen in the design stage in file SKEW8.GRD in the download SKEW.ZIP. Unzip the files into the Sheet Lghtning directory (usually c:/sheet).
41. To see the cut results select the cutting and unfolding commands in the 'Compute' menu (see: obtaining design result).