Sliver Doctor

Overview

The Sliver Doctor utility was written to assist the designer in locating and correcting characteristics on their bodies.

Activation

Enter into command line

   (load "sliver_doc") 

Or add this line to your customization file.

Loading this file will create a button in the toolbox.

Description

Solid bodies designed in both Solid Designer and ME30 are being leveraged from site to site with greater and greater frequency. This, plus the general complexity of todays parts, makes managing the quality and precision of solid bodies very important. A large number of different designers may modify a solid body over it's life and because of this long life it is more and more common for designers to run into sliver faces, skew faces and micro edges in their parts. These characteristics are defined as

• Sliver Face: An unintentional, very small face.
• Skew Face: A face with a normal direction that is unintentionally not perfectly square with the XYZ coordinate system.
• Micro Edge: An edge of a face that is unintentionally very small.

All of these characteristics at times can be undesirable and because Creo Elements/Direct Modeling has only limited zoom capabilities it may be terribly difficult to locate these characteristics on a body. The Sliver Doctor utility was written to assist the designer in locating and correcting characteristics on their bodies.

NOTE: Bodies with these characteristics are not typically corrupt. The body checker will most likely not report any of these characteristics.

Symptoms

If a body has the characteristics noted above the designer may encounter any number of the following symptoms.

• Seemingly simple machining operations fail for no apparent reason or with an error that relates to numerical precision.
• Extra edges appear on a body that are not removed with the merge command.
• Difficulty blending seemingly clean edges.
• Errors or failure when attempting to convert files to other file formats such as IGES or STL.
• Microscopic errors appearing on bodies exported to other systems

Causes

There are many ways to cause the characteristics noted above. Some causes include:

• Rotating a body or workplane some multiple of ninety degrees in space will cause skew faces. Using a skew face as a machining reference for some other "square" geometry can cause sliver faces.
• Inputting round numbers instead of the actual measured values (6.00 instead of a measured 6.00000000000012). Measurement should be captured into the calculator for re-entry.
• Improper use of Catch during tool creation. Catching 2D instead of a 3D vertex.

Sliver Doctor User Guide

The utility is comprised of two main parts. The first is the Entity Definition section. It is here that the user will define the part to check, the characteristic to check for, and to what resolution. The second section is where the user will define what process to do on the entity. The user can show all entities that meet the specified requirements or the user can select each entity off a table and process each individually.

Working

To check for Sliver Faces, Skew Faces or Micro Edges in a Body

1. Click Part and select the body to be evaluated. The default will be the active part.
2. Select one of the three characteristics that will be evaluated: Sliver Faces, Micro Edges or Skew Faces.
3. Click Max Value if you wish to change the default value. The Max Value is the maximum value that will be searched on. (i.e. all faces with a larger area than the Max Value will not be found in the search)
   
   Go to Step 4 to identify all entities or Step 5 to identify and operate on a single entity
   
   
4. To highlight all of the entities that met your search requirements Click Highlight All. This is the quickest way to display the search results and will give you a good indication of the magnitude of the problem. Refine the Max Value and rerun if desired.
5. Click Entity to bring up a table of all entities that met your requirements. Click the entity that you would like to operate on and click Apply.

Due to resource limitations, the time required to bring up the entity table will be excessive if the number of qualifying entities exceeds 150. In cases where a large number of entities will be selected it is recommended that you use the Highlight All feature (Step 4).

Depending on whether you are operating on a Sliver Face, Micro Edge or Skew Face, when a single entity has been specified the appropriate process buttons will be enabled for your use. These process buttons are as follows.

Highlight:

If the entity is a face then it will be colored red and the vertices of the face will be highlighted. If the entity is an edge then just the vertices will be highlighted.

Label:

Will place an arrow and label pointing to the center of the entity.

Delete (Sliver Faces and Skew Faces Only):

Will conduct the standard remove face command from the Modify 3D menu on the entity selected. Due to limitations with this command the success rate with this command is poor.

Square (Sliver Faces and Skew Faces Only):

Not yet Implemented

Notes

1. If you are searching for Skew faces and you get the message "Greater than half the faces are skew. Part alignment is recommended". This is indicating that the majority of the part's faces are skew and rather than trying to square each face, it may be easier to square the body.
2. If the label "EDGE-" is applied to the end of the leader line pointing to a face then the system was not able to locate and label the center of the face so it labeled one of the edges of the face instead.
3. Sliver Faces and Micro Edges are more severe than Skew faces. If your part has a large number of Skew faces this utility will point them out. You should make note of where they are and potentially how they might have gotten there so you can possibly prevent them in the future but no matter how careful you are you will run into Skew faces. Skew faces are not a corruption and should not have any adverse effects on your design but it is possible that they will lead to Sliver faces. Skew faces are hard if not impossible to completely remove and are probably not worth attempting to remove unless they have a relatively large skew or are in a critical area.

Removing Sliver Faces that don't respond to the Sliver Doctor Delete command

Due to limitations with the Remove_faces command you will find that the Delete option in Sliver Doctor will have poor results. The biggest advantage of Sliver Doctor is in identifying where and how large the Sliver face is. Once the Sliver Doctor has located the Sliver face you may need to deal with it manually.

There are a number of ways you might manually remove a Sliver face. If there are a number of Sliver faces that comprise a defect, you may find it possible that the Modify 3d-Delete option will work if you use a Box Select to capture all of the faces that make up the defect.

A Sliver face is also commonly dealt with the same way that a corruption would be using a machining operation. You can machine away the entire Sliver face and reconstruct the area. This is not a desirable process but if the Sliver face is preventing the processing of the body then it may be necessary.

Restrictions

The Square command for Skew faces will not perfectly square a face. Due to limitation with the Move command, which is the command used in the process, it is common that the skew in a direction will be reduced down to 1E-32 or something similar and still not be perfectly square. While this may not completely square a face it will minimize the skew and hopefully reduce the likelihood of Sliver faces being created.