When you choose Part from the Geometry Repair Tools dialog box, the Tool list displays the following methods for repairing entire parts:
Stitch 
If a part is imported as a group of disconnected faces, you can stitch the resulting small gaps. Similarly, you can stitch the resulting gaps after you remove small faces or small slivers from a part. You can perform stitching as a global operation during which Abaqus/CAE stitches all gaps in the part, or you can pick the edges that you want to stitch, stitch edges with gaps smaller than a user-specified tolerance, or use both of these options. You should perform a global stitching operation for your entire part for small gaps only, and this process can be lengthy. For more information, see “What is stitching?,” Section 66.3. You can use the Query toolset to highlight any free edges. For more information, see “Using the geometry diagnostic tools,” Section 68.2.4.
Repair face normals 
You can repair the face normals of shell and solid imported parts, and you can perform these repairs on either manifold parts (parts in which every edge is shared by only one or two faces) and non-manifold parts. The tool has different uses for solid and shell parts.
Solid
In rare cases the Query toolset reports that the volume of an imported solid part is negative because the face normals indicate it was inside out in the CAD system from which it originated. The Repair face normals tool will flip the normals and turn the solid right side out.
Shell
An imported shell part can contain faces that have normals pointing in opposite directions. The Repair face normals tool will align all the normals on a shell part. If the face normals are already aligned, this tool will flip all the normals so that they remain aligned but point in the opposite direction.
Note: The element normal orientation, which is specified using the Element Normal assignment in the Property module, specifies the relative element normal with respect to the geometry normal. These element normals will be updated using the new geometry normals after the Repair face normals operation.
When you perform repairs of non-manifold shell parts, you cannot align the normals for all of the faces in the part in a single operation; you must select faces individually to flip the direction of their normals. You can perform a query using the Shell element normals option from the Query dialog box to assess the orientation of the face normals before you repair your shell part.
Convert to analytical 
Abaqus/CAE tries to change the internal definition of edges, faces, and cells into a simpler form that can be represented analytically. For example, a face that is nearly planar will be converted to an equation that represents the plane. Converting to an analytical representation usually provides the following advantages:
Processing of the part is faster.
The converted entity is available during feature operations. For example, the extrude operation requires a planar face and a linear edge.
The geometry is improved.
If you subsequently need to stitch the part, the stitching operation is more likely to be successful.
Convert to precise 
Abaqus/CAE offers two methods to convert entities to precise geometry:
If you choose Tighten Gaps, Abaqus/CAE attempts to improve the precision of the faces, edges, and vertices in your model. This method is faster but does not perform a full computation of the geometry.
If you choose Recompute Geometry, Abaqus/CAE tries to change neighboring entities so that their geometry matches exactly. Recomputing geometry usually results in precise geometry; however, this operation can be lengthy and increases the complexity of the imported part, which means that processing of the part is slower. Moreover, if the part contains many complex surfaces, converting to a precise representation is likely to fail. If possible, you should return to the CAD application that generated the original file and increase the precision.