Shells are parametric features used for cast and molded parts. Material from the part interior is removed, leaving a hollow cavity. Changes to the dimensions of either the part or the shell automatically resize both.
To define a shell, you specify one or more part faces to remove from one or more bodies, leaving the remaining faces for shell walls. You set the thickness of the shell wall and indicate the direction relative to the current part face. If no faces are specified for removal, the shell creates a hollow part.
It is a good practice to specify a uniform wall thickness, because uniform wall thickness helps prevent distortion during manufacture and cooling. If necessary, specific walls can have a different thickness.
In a precise solution, each point of the original surface has a corresponding point on the offset surface. The distance between the two points is equal to the specified thickness. An approximate solution enables Autodesk Inventor LT to deviate from the specified distance in an attempt to find an acceptable solution.
You can control where the deviation is allowed to occur, as well as the accuracy of the approximation. Keep in mind that the more accurate the approximation, the longer it takes to compute. Approximate solutions are provided only when a precise solution does not exist and when an approximate solution can be found. If approximate solutions are not acceptable, you can turn off this option .
Each time approximation is used, the tolerance of the deviation is reported upon selecting OK.
Because shells remove material from the entire part, features added to a part after the shell is applied is not shelled. For example, if you sketch and extrude a solid feature on a shell wall, the extrusion is not shelled.
To make sure that all features are included in a shell feature, use one of the following methods:
On the 3D Model tab, Modify panel, click Shell to remove material from a part interior, creating a cavity with walls of a specified thickness. By default, Autodesk Inventor LT provides a precise shelling solution. When a precise solution does not exist, Autodesk Inventor LT attempts an approximation.
Removes material from a part interior, creating a hollow cavity with walls of a specified thickness. Selected faces can be removed to form a shell opening.
Thickness Specifies the thickness to be applied uniformly to shell walls. Part surfaces not selected for removal become shell walls. To use the thickness value in a parameter table, highlight the value in the box, and then right-click to cut, copy, paste, or delete it.
When no precise solution exists, allows a deviation from the specified thickness while computing the shell feature. A precise solution creates a shell where each point on the original surface has a corresponding point on the shell surface. The distance between these two points is the specified thickness.
Select whether to allow an approximate solution, and then click the arrow to select the deviation type from the list. Click a command to choose a computation option.
Mean deviation is divided to fall both above and below the specified thickness.
Never too thin preserves minimum thickness. The deviation must fall above the specified thickness.
Never too thick preserves maximum thickness. The deviation must fall below the specified thickness.
You can override the default thickness to apply a unique thickness to selected walls. Click in the row to activate, then select faces.
Displays the number of selected faces to which the new thickness applies.
Sets new thickness for selected faces.
Deleting a row resets the shell walls to the default thickness.