CHAPTER 3: COMMANDS
CHAPTER 3: COMMANDS
Before beginning the tolerance application in Pro/ENGINEER, an assembly model must be loaded and all necessary points and planes must be defined. Modeling elements are located using assembly datum points, so there must be an assembly datum point wherever a datum reference frame, feature datum, joint, or specification endpoint will be located. Each assembly datum point must be created separately (i.e. not as a group).
To initiate the TI/TOL 2D assembly tolerance modeler select Info from the ASSEMBLY menu window. Select TOLERANCE from the Info menu window and TOL-2D from the TOLERANCE window. The TOL-2D menu provides access to all TI/TOL 2D options. The TOL-2D menu is shown below:
The Project, Quit Window, and Change Window commands in the Pro/Engineer main menu cannot be accessed while running the TI/TOL 2D application. The Done/Return option under the TOL-2D main menu must be selected before using these commands.
The menu tree for TI/TOL 2D is shown in Figure 3-1.
Figure 3-1. TI/TOL 2D menu tree.
A detailed description of each command available in TI/TOL 2D will now be presented. The commands will be presented in descending order as they appear in the TOL-2D main menu.
Before executing TOL-2D commands, a two-dimensional reference plane must be identified, as well as a plane perpendicular to it. In addition, the size of the symbols that are used in defining the tolerance model may be set. These parameters are set by selecting Display from the TOL-2D menu.
From the DISPLAY menu select 2D Ref Plane. Prompts in the message window will ask you to identify the location of the reference plane, and then to identify a plane that is perpendicular to the reference plane. The reference plane must be defined as an assembly reference plane, identified with an ADTM symbol. The perpendicular plane can be any plane in the assembly that is perpendicular to the assembly reference plane.
There are different methods of selecting elements in the model. These are contained within the GET SELECT menu which pops up every time you are asked to select an element.
The default selection method is Pick, which allows the user to directly identify a model element by clicking on it with the mouse. Assembly points must be selected by clicking on the APNT symbol next to the point. Other parts of the assembly can be picked directly. Query Sel allows the user to select hidden elements, or one of several elements that overlap each other. The Sel By Menu option queries through selected elements by name. Tolerance elements are named in the order in which they were created. The Done Sel option indicates the end of a selection sequence and closes the GET SELECT window. The Quit Sel option ignores the selection sequence that was just made and closes the GET SELECT window.
Tolerance symbol size may be changed by selecting Symbol Size from the DISPLAY menu. The default setting is 2.0.
Selecting Done/Return from the DISPLAY menu indicates that the display has been properly defined and closes the DISPLAY window.
Note: The Disp Settings option of the DISPLAY menu is not available in this version of TI/TOL 2D.
Datum Reference Frames
Datum reference frames are points that are defined on each part from which all measurements on that part are made. Each unique part has its own unique datum reference frame, or DRF. To create datum reference frames, select Datums from the TOL-2D main menu.
Continue by selecting Create from the DATUMS menu and Datum Ref Fr from the CREATE menu.
There are two types of datum reference frames -- rectangular and cylindrical. If the part is manufactured by turning on a lathe or similar process, then Cylindrical should be selected. In most other cases Rectangular should be selected as the DRF type. As noted earlier, a DRF must be defined for each unique part in the assembly model. The location of the DRF must be specified by following the prompts in the message window.
The DRF requires an axis definition. The cylindrical DRF's axis is automatically defined when the DRF location is picked. The rectangular DRF requires the user to define a feature surface that establishes the DRF direction. The user then picks the part that is associated with the rectangular DRF.
After a DRF has been created, the appropriate symbol appears on the assembly drawing in the specified location.
Any necessary feature datums can also be created from the DATUMS menu. Feature datums specify controlled dimensions that can be used in defining datum paths from kinematic joints to associated DRF's. Feature Datums are created by selecting Create from the DATUMS menu and Feature Datum from the CREATE menu.
Like datum reference frames, a feature datum can be either rectangular or cylindrical, depending on the part to which it is applied. The steps required to define feature datums are the same as those required to define datum reference frames, as outlined previously. If Rectangular is selected as the feature datum type, the message window will prompt the user for the location of the feature datum as well as for a sliding plane that defines the direction of the feature datum. If Cylindrical is selected as the feature datum type, the message window will only prompt for the location of the feature datum. The feature datum will then be applied at the specified location and the appropriate symbol will appear.
Both datum reference frames and feature datums can be modified by selecting Modify from the DATUMS menu. The features that can be modified are displayed in the DATUM MOD menu.
To modify the degrees of freedom of a datum, the user selects Deg of Freedom from the DATUM MOD menu. The message window will prompt the user to select the datum to modify. A SELECT FILE menu and a MODIFY DOF window will then pop up. The List option of the SELECT FILE menu is automatically selected in order to display all of the degrees of freedom of the specified datum in the MODIFY DOF window. The user can toggle a degree of freedom by selecting it from the MODIFY DOF window. The Done Select command in the SELECT FILE menu can be selected to return to the DATUM MOD menu.
To modify the name of a datum, the user selects Name from the DATUM MOD menu. The message window will prompt the user to select the datum to modify and will ask for a new name.
Note: The Location and Axis options in the DATUM MOD menu are not available in this version of TI/TOL 2D.
To begin identifying the contact points between parts select Joints from the TOL-2D main menu and Create from the JOINTS menu.
The information required to define a joint includes the kinematic joint type, a global location, the two parts that are in contact, and the joint's location relative to the DRF of each part (i.e. the path back to each part DRF). The kinematic joint type can be selected from the JOINT TYPE sub-menu that pops up after selecting Create.
After selecting the desired joint type, the user must pick the location of the kinematic joint. The message window may also prompt the user to select a feature surface that defines the sliding plane for the joint. A sliding plane must be defined for all joint types except revolute joints. The user must then locate the kinematic joint by defining a path to the DRF of each part associated with the joint. The Query Sel or Sel by Menu options in the GET SELECT pop up menu allows the user to select the proper feature datums and DRF's required for the datum paths. Each contact point and datum reference path back to the DRF should be carefully identified in order to create a kinematically and geometrically correct model.
Joints can also be modified by selecting Modify from the JOINTS menu. A JOINT MOD menu will pop up that displays the joint features that can be modified.
The procedure for modifying the degree of freedom of a joint or the name of a joint is the same as that outlined for datums.
Note: The Location and Axis options in the JOINT MOD menu are not available in this version of TI/TOL 2D.
Specifications are similar to feature controls, with the exception that design specifications apply to the assembly rather than individual parts. Design specifications can be applied by selecting Specifications from the TOL-2D main menu and Create from the SPEC menu. The SPEC TYPE menu displays the types of specifications available in TI/TOL.
The loop specifications are summarized as follows: Dependent Angle specifies the relative angle between two mating parts; Dependent Length specifies the kinematic length between two parts; Parallelism specifies the angle between two parts; Orientation specifies an acceptable bandwidth for the relative orientation of two planes on two separate parts; Position specifies a point's horizontal and vertical position relative to another point; and Gap specifies the resultant clearance between two part surfaces. Dependent Angle and Dependent Length differ from the other specifications in that they are for closed loops and must be applied after the closed loop has been created. The other specifications can be applied before the loops have been created.
Note: The Runout and Concentricity options of the SPEC TYPE menu are not available on this version of TI/TOL 2D.
The following procedures can be followed for specifying design specifications after selecting the appropriate specification type from the SPEC TYPE menu.
The two vectors must share a common vertex. The tolerance is specified after the second vector has been selected. The tolerance applied is a plus and a minus angular tolerance. The nominal angle used in the analysis is the inside angle formed by the two vectors (i.e. the angle less than 180[[ring]]).
The dependent angle specification will appear at the vertex of the two vectors.
The dependent length specification will be appear on the specified vector.
Parallelism or Orientation
The specification symbol will appear between the two reference locations.
The position specification will be applied to the model.
The gap specification will appear between the two reference points.
Like other model elements, specifications can be modified. An applied specification tolerance can be modified by selecting Modify from the SPEC menu and Value from the SPEC MOD menu.
The specification tolerance value can be modified by following the prompts in the message window.
The modified specification value will be written to the tolerance model database.
Note: The Label Loc option of the SPEC MOD menu is not available on this version of TI/TOL 2D.
Loops relate the parts, contact joints and DRF paths in an assembly. To create a loop on an assembly select Loops from the TOL-2D main menu and Create from the LOOP menu.
The three options available in TI/TOL 2D, as shown in the LOOP TYPE menu, are Autoloop, Open, and Closed. The processes required for each method of loop generation are as follows:
The Autoloop command completely automates the loop generation process. This command is especially helpful with loops that are difficult or tedious to create.
The system will now automatically generate the optimum vector loop with the datums and joints that were created in the assembly.
The open loop will be generated for the selected specification.
The closed loop will be generated through the selected joints.
Generated loops can be modified by selecting Modify from the LOOP menu. The three options available for loop modification are shown in the VECTOR DESC menu.
The Vector Names command allows specific names to be assigned to vectors in a loop.
The system will highlight all of the vectors in the loop in turn until it returns to the first vector that was highlighted.
The Vector Tol command allows the user to modify the dimensional tolerance assigned to a vector in a loop.
The message window will display when the tolerance change has been successfully completed.
The Equiv Vect command allows the user to equivalence vectors whose variations are not independent.
The message window will display when the vectors have been equivalenced successfully.
Geometric tolerances allow the engineer to incorporate machine variations into the tolerance analysis. The eleven geometric tolerances available in TI/TOL 2D are accessed by selecting Geometric Tol from the TOL-2D main menu and Create from the GEOM TOL menu.
All geometric tolerances require a bandwidth or diameter to be entered. An example with the Flatness geometric tolerance option follows:
The specified geometric tolerance will be applied at the joint and the symbol associated with flatness will be added to the model (see Figure 3-2).
Figure 3-2. Flatness Geometric Tolerance on Joint 3.
For certain combinations of joint type and geometric tolerance, a characteristic length of surface contact must also be specified. An example with Straightness applied at a planar joint follows:
Select the part associated with the geometric tolerance.
The geometric tolerance will be applied at the specified joint.
Geometric Tolerance Modification
Geometric tolerances can be modified by selecting Modify from the GEOM TOL menu. The modification options are displayed in the GEOM MOD menu.
To modify the tolerance applied to a specific geometric tolerance, select Tolerance from the GEOM MOD menu and follow the prompts in the message window.
The new tolerance will be applied to the specified geometric tolerance.
Note: The Location and Label Pos options of the GEOM MOD menu are not available in this version of TI/TOL 2D.
Any elements used in a tolerance model can be deleted with the Delete command in the TOL-2D main menu.
After selecting the Delete option from the TOL-2D menu, the GET SELECT menu will pop up and the message window will prompt for the entity to delete.
Deleting a loop can be done by picking any vector in the loop. A loop cannot be deleted if it has a dependent specification associated with it.
Be very careful that you don't delete DRF's, feature datums, or joints out from "under" other modeling elements. For example, joint paths use datums and DRF's to define their location on the part. If one of those datums or DRF's is deleted after the joint is created, the datum path is no longer valid. If the joint is not deleted and re-created, an invalid assembly will be the result. Analysis results will be faulty at best. At worst, no analysis can be performed on the model. In general, when deleting modeling elements, all elements newer than it that use that element in their own definition should also be deleted.
After all of the necessary modeling elements have been applied to the assembly, the model can be analyzed by selecting Analyze from the TOL-2D main menu.
Refer to the TI/TOL 2D Analyzer Manual for more information about this option.
EXITING TI/TOL 2D
To exit the TI/TOL 2D environment, select Done/Return from the TOL-2D main menu.
Modeler: Title | Overview | Modeling | Commands
Analyzer: Title | Overview | Analysis | Allocation | Interface
Modeler: Title | Overview | Modeling | Commands
Analyzer: Title & TOC| Overview | Analysis | Allocation | Interface
Verification: Title | Overview
Modeler: Title | Overview | Modeling | Commands | Building a Tolerance Model
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