Drawing a 3D Offsetbox


Draw 3D offset boxes around fittings and pipes with rolling offsets.

Drawing a 3D offsetbox is easy provided you know the offsetbox dimensions in the East, North, and Up directions. Here’s how to use SpoolFab to draw the offsetbox shown in the sketch below.

Let’s assume that your North arrow points up and to the right. Start a new drawing in the lower middle part of the page. Draw a piece of 10 inch pipe pointing straight up. To the top end of the pipe, add an Odd Angle Elbow. The roll direction of the elbow does not matter for now. In the dialog, click Don’t know Angle.

Bearing in mind that North is up and to the right, fill in the Define New Direction dialog as shown. The new direction has components 14 West, 12 South, and 14 up. Enter these as -14 East, -12 North, and 14 Up. <cf>

Click Update. The components are normalized to unit vector and the elbow angle is found to be 52.79 degrees. <cf>

Click OK and place a dimension of 40 inches for the vertical pipe. This includes the fitting dimension of the 52.79 degree elbow.

Add a piece of pipe to the upper end of the elbow.

Draw an odd angle elbow on to the end of the pipe. Do not worry about the direction for now. Be sure to click on Don’t know Angle.

We know the new direction is West. Since we will be normalizing the vectors, we just need to delete the North and Up components and make sure the East component is negative. Then click Update. <cf>

Clicking Update makes it clear the new direction is West <cf>

Click OK, then place the diagonal dimension, but don’t enter its value. Click Don’t know yet.

SpoolFab “knows” that the offsetbox has the proportions 14 x 12 x 14 but still needs a dimension. The best way to supply this is to dimension one of the three components. Select Dimension, Offsetbox (or use the shortcut key, F7). The cursor changes to a different arrow. Click on the middle of the East-West component of the offsetbox.

Position the dimension, then enter its value as 14 inches as shown below.

You can now place dimensions for the other two components of the offsetbox. You do not need to enter dimensions for them because they are already defined. Don’t worry if the diagonal pipe disappears, just press F4 to update the screen. The result is shown below.

To hide an offsetbox corner, select Tools, Offsetbox, Hide Corner. Then click on the corner(s) you want to hide.

To label an angle in an offsetbox, select Tools, Offsetbox, Label Angle. Then click on the three corners of the offsetbox that define the angle to be labeled. An arc indicates the angle and a note indicating its magnitude appears in red. Use the arrow keys to place the angle label precisely. This label is simply a note, so it can be repositioned and made larger or smaller.