Book Name: Sheetmetal User's Guide - Note this is taken off the web from Pro/Engineer

• Bend allowance-Set up the method to use to calculate the length (developed length) of flat sheet metal required to make a bend of a specific radius and angle. For the same bend, the developed length is different for different materials and thicknesses
  
• Fixed geometry-Set the default surface or edge which remains fixed when you bend or bend back the part.
  
• Default radius-Define the default radius that is used as an option when you create a bend or add walls.
  
• Flat state instances-Create, display or update flat state instances of a current part. Flat state instances are discussed in the chapter Manufacturing Preparation.
  
• Design rules-Create a set of design rules that are used to check sheet metal designs. Design rule checking is discussed in the chapter Manufacturing Preparation.

Bend Allowance
Bend Order Tables
Fixed Geometry
Default Radius

Bend Allowance

Use one of the following three methods to calculate the bend allowance:

• The system default equation
• One of the provided Pro/SHEETMETAL bend tables
• Pro/TABLE to create your own

If you want to use the formula equation only to calculate developed length, but you do not like the formula which is used by Pro/ENGINEER (see Y-factor) then you must create a bend table. The data in the table will be:

• FORMULA-Enter your equation for developed length.

• TABLE data-Enter a single thickness and radius combination that will never be encountered in your sheet metal parts, e.g., a 0.164 bend radius with material thickness of 5 inches!

Y-factor

If you do not assign a bend table to the part, Pro/ENGINEER uses the following equation to determine developed length:

where:

L-Developed length.

R-Inside bend radius.

Y-factor-A part constant defined by the location of the neutral bend line (see the following illustration). The default Y-factor is 0.5.

T-Material thickness.

-Bend angle (in degrees).

initial_bend_y_factor <value>

When you save a sheet metal part, the Y-factor value is stored with it. Use the Y-factor option in the Bend Allow menu to modify the Y-factor.

Enter Val Menu

• Enter-Enter a value, through the keyboard.

• 0.5000000-The default value.

• previous value-The previous value used (if any). For a new part, it is the initial_bend_y_factor, if defined in the configuration file.

1. Choose Set Up from the PART menu.

2. Choose Sheet Metal from the PART SETUP menu.

3. Choose Bend Allow from the SMT SETUP menu.

4. Choose Y-factor from the BEND ALLOW menu.

   If a bend table is currently assigned to the part, the system prompts you to confirm that you wish to discard it. Choose Confirm from the CONFIRMATION menu.

   The ENTER VAL menu appears.

5. Choose one of the options. The system completely regenerates the part, using the new value.

Note:

For stretched bends (see the following illustration) is negative, which makes the Y-factor negative too.

Negative Y-factor

For the same bend, the developed length is different for different materials and material thicknesses.

Bend tables can be read in at any time. Note, however, that once a part is associated with a bend table, its geometry depends on the table data. The bend table information is not stored with the part.

Every time the part is regenerated, it looks up the associated table for appropriate length values. If you modify a bend table, all parts associated with it are updated upon regeneration.

Pro/SHEETMETAL provides the following three bend tables for your use:

Table Name	Material	Y-Factor	K-Factor
TABLE1	Soft Brass and Copper	0.55	0.35
TABLE2	Hard Brass and Copper Soft Steel Aluminum	0.64	0.41
TABLE3	Hard Copper Bronze Cold Rolled Steel Spring Steel	0.71	0.45

The bend tables provided with Pro/SHEETMETAL are used with permission from Machinery's Handbook, 23rd Edition.

Note:

Bend Tables are applicable only for constant-radius bends. Bends with a varying radius (such as a cone have their developed length calculated using the Y-factor.

Bend tables are normalized for 90° bends. For other than 90° bends, Pro/ENGINEER takes those values and multiplies them by /90, where is the specific bend angle, in degrees.

The three Pro/SHEETMETAL bend tables use the following formula equation:

• FORMULA
  
  

(The Y-factor value for each table is shown above).

• TABLE-Developed length for specific radius and material thickness from Machinery Handbook, 23rd edition.

Note:

Since Pro/SHEETMETAL table data in the provided tables is the developed length, no CONVERSION statement is used.

• Part Bend Tbl-The bend table associated with the part is used for developed length calculations. If no table is currently assigned to the part, the Y-factor formula is used.

• Feat Bend Tbl-Specify a separate bend table to be used by the feature. Select one of the three supplied bend tables from the Data Files namelist menu, or choose Names and enter the name of the bend table file (including the path, if necessary).

Creating Bend Tables with Pro/TABLE

If you create your own library of bend tables, tell Pro/ENGINEER where to find them by using the configuration file option

pro_sheet_met_dir directory_<pathname>

Create your bend tables for 90° bends. For other than 90° bends, Pro/ENGINEER takes those values and multiplies them by /90, where is the specific bend angle, in degrees.

You do not have to insert a bend allowance value (A) in every cell in a bend allowance table. If you leave a particular cell blank, the system calculates a value for the exact combination of R (inside bend radius) and T (material thickness) that it represents by using the formula.

The illustration Developed Length of Material and Y-factorshows variables associated with a bend. The illustration Pro/TABLE Bend Table is an example of a bend table. It shows the layout and data that needs to be provided to Pro/ENGINEER for it to correctly unbend a sheet metal part.

The following table, Bend Table Format shows the Pro/TABLE format. Enter the appropriate data in the columns.

Note:

Enter the words FORMULA, END FORMULA, CONVERSION, END CONVERSION, START MATERIALS, END MATERIALS and TABLE exactly as shown.

An explanation of the data for Pro/TABLE follows.

Formula Equation

• L-Developed straight length of stock.

• R-Inside radius of the bend.

• T-Thickness of the material.

• ANGLE-Bend Angle (in degrees).

• The formula must be the first equation in the table.

• The formula must begin with the descriptor FORMULA, in the first column.
  • If the equation is a simple one, then it can be written in the second column on the same line as the descriptor, as in these examples:

  FORMULA L = (0.55*T) + (PI*R)/2.0

  FORMULA L = (ANGLE*PI/180)*(R+T/2)

  • If the formula is more complex and/or contains some logic statements, then the FORMULA descriptor must precede the actual formula on its own line and the formula must be concluded by the descriptor END FORMULA, again on its own line and in the first column. See the example below:

  FORMULA

  IF (R/T) < 1.10 | (R/T) > 1.83

  L = (PI*R*T)/2.0

  ELSE

  L = (PI/2)*(R + (T*0.35))

  END FORMULA

  In a multi-statement formula like this, you can enter the statements in columns other than the column one. When Pro/ENGINEER verifies the table, it moves the statements into the first column. (If you edit the table from within a session, Pro/ENGINEER verifies the table as soon as you exit/quit the editor; if you edit the table outside a session, Pro/ENGINEER verifies the table when you apply it to a sheet metal part.)

Conversion Equation

L = 2*(T + R) - A

Note:

L must never be negative.

The variables you can use in a conversion equation are:

• L-Developed straight length of stock.

• R-Inside radius of the bend.

• T-Thickness of the material.

• ANGLE-Bend Angle (in degrees).

• A-Bend allowance value contained in the table data section.

• Only use a conversion equation when the developed length L is not equal to your table values A.

• The conversion must begin with the descriptor CONVERSION, in the first column.
  • If the equation is a simple one, then it can be written in the second column on the same line as the descriptor, as in this example:

  CONVERSION L = 2*(T +R) - A

  • If the formula is more complex and/or contains some logic statements, then the CONVERSION descriptor must precede the actual formula on its own line and the formula must be concluded by the descriptor END CONVERSION, again on its own line and in the first column.

    Example of Determining a Conversion Equation
    
    

1. Bend a known length of flat stock to the 90° L-shape as shown in the above illustration.

2. Add the measurements X and Y and subtract the original flat stock length from this sum.

3. Apply this deduction value to determine the developed length for models with common material type, inside bend radius, and material thickness.

Material Data

Follow these rules when you enter and create materials in a bend table:

• Enter the material list immediately after the conversion equation. It must begin with the descriptor START MATERIALS, in the first column.

• The material names must be entered in uppercase, one per line, in the first column.

• The material list must end with the descriptor END MATERIALS, on a separate line, in the first column. (See the illustration in Example of Bend Table Data.)

If you subsequently try to apply another bend table to the part, by choosing Set from the Bend Tab menu, the system again checks to see if the table lists the assigned material. If it does not, the system rejects the command, and issues the above error message.

Table Data

For bend radii and material thicknesses between the values in adjacent cells, a linear interpolation is used.

Note that the values in the bend tables are independent of the model units. They do not change if you change the model units. For example, you originally create a sheet metal part with the model units set to inches. The sheet metal thickness is 0.25 and the bend radius is 0.5. The system looks up the bend table to find the developed length at the ordinates (0.25, 0.5). If you change the model units to centimeters and keep the model the same size, the thickness of the sheet metal becomes 0.625 and the bend radius 1.270. The system looks up the table to find the developed length at the ordinates (0.625, 1.270).

• Define-The Define Btable menu appears to enable you to create a new bend table, edit or show an existing bend table.

• Set-The Set Btable menu appears to enable you to apply a selected bend table to a part or remove the bend table from the part.

• Outside a Pro/ENGINEER session enter:

[protab]

...or...

• Inside a Pro/ENGINEER session:

  Choose Define from the BEND TAB menu.

1. Choose Define from the BEND TAB menu.

2. Choose Create from the DEF BTAB menu. Enter the name of the bend table.

   A Pro/TABLE window displays with an outline table in it.

3. Enter the data into the empty table

   ...or...

   Select File, then Read from the Pro/TABLE pulldown menu to use another bend table as a baseline.

   A dialog box appears and prompts you to enter the full name of the file. After you enter the filename, the system reads in the file from disk and writes it over the current file in session. You can then edit the file.

4. Choose Save or Exit. The system writes the bend table out to disk, in the current directory.

How To Edit a Bend Table

1. Choose Define from the BEND TAB menu.

2. Choose Edit from the DEF BTAB menu.

3. Choose the bend table from the TBL NAMES namelist menu, which lists all the bend tables that were ever applied to the part or were created when that part was the one currently in session.

   A Pro/TABLE window displays with the selected table in it.

4. Edit the file.

5. Choose Save or Exit. The system writes the bend table out to disk, in the current directory.

1. Choose Set Up from the PART menu.

2. Choose Sheet Metal from the PART SETUP menu.

3. Choose Bend Allow from the SMT SETUP menu.

4. Choose Bend Table from the BEND ALLOW menu.

5. Choose Set from the BEND TAB menu.

6. Choose Apply from the SET BTAB menu.

7. Choose Confirm from the CONFIRMATION menu.

8. Select one of the three supplied bend tables (TABLE1, TABLE2 or TABLE3) from the DATA FILES namelist menu

   ...or...

   Choose Names and enter the name of a bend table file (including the path, if necessary).

• Choose Remove from the SET BTAB menu

  ...or...

• Choose Y-factor from the BEND ALLOW menu.

Bend Order Tables

Note:

You cannot create or edit a bend order table on a completely unfolded model.

• Clear-Delete an existing bend order table.

• Show/Edit-The Show/Edit menu appears.

• Info-Display the bend order table on the screen and write it to a .bot file.

• Next-In response to the prompt, select a plane that is to remain fixed. The highlighted bends in the current sequence are bent back. Proceed to the next sequence.

• Skip-Skip the specified number of bending sequences.

• Add Bend-Add additional bend to the bending sequence. If you select a bend that is currently being used in a later sequence, you have the option to move it to the current sequence. You cannot select a bend that has already been bent back in a previous sequence.

• Delete Bend-Remove bend from the current bending sequence. Use this if you plan to use the bend in a later sequence.

• Insert-Insert a bending sequence after the previous bending sequence.

• Done-Save all the bending sequences.

• Quit-Quit editing or creating a bend order table without saving the changes.

How To Create a Bend Order Table

1. With a model in the bent condition, choose Sheet Metal from the PART SETUP menu.

2. Choose Bend Order from the SMT SETUP menu.

3. Choose Show/Edit from the BEND ORDER menu. The
   GET SELECT menu appears.

4. In response to the system prompt, select a plane or edge to remain fixed while the model is completely unbent. The model is completely unfolded.

5. The Add Bend option in the SHOW/EDIT menu is enabled. The GET SELECT menu appears and you are prompted to select the bends for the first sequence. You can select any bend, and any number of bends in any order.

6. When you have finished adding bends to the current sequence, and you want to start another sequence, choose Next from the SHOW/EDIT menu. The bends in the current sequence are now highlighted in magenta.

7. In response to the prompt, select a plane which is to remain fixed. The highlighted bends are then bent back.

8. The Add Bend option in the SHOW/EDIT menu is re-enabled and the GET SELECT menu re-appears. You are now starting a new sequence.

9. Repeat Steps 6 through 8 until the whole part is bent back.

10. Choose Done from the SHOW/EDIT menu. The system creates the bend order table.

How To Edit a Bend Order Table

1. With a model in the folded condition, choose Sheet Metal from the PART SETUP menu, then Bend Order from the SMT SETUP menu.

2. Choose Show/Edit from the BEND ORDER menu.

3. In response to the system prompt, select a plane or edge to remain fixed while the model is completely unbent. The model is then completely unfolded.

4. Bend geometry included in the first bending sequence highlights in magenta. Choose an option from the SHOW/EDIT menu.

5. Select the bend(s) you want to edit.

How To Delete a Bend Order Table

1. With the model in the folded condition, choose Sheet Metal from the PART SETUP menu.

2. Choose Bend Order from the SMT SETUP menu.

3. Choose Clear from the BEND ORDER menu.

Fixed Geometry

Use the Fixed Geom menu found under the Smt Setup menu to do the following:

• Select (default)-Bring up the Get Select menu. Select a surface or edge to be used as the default fixed geometry.

• Show-Highlight the existing default fixed geometry.

• Clear-Clear the default fixed geometry.

• Done/Return-Return to the previous menu.

1. Choose Sheet Metal from the PART SETUP menu.

2. Choose Fixed Geom from the SMT SETUP menu.

3. Choose an option to proceed.

4. Choose Done/Return when you finish accessing the default fixed geometry.

Default Radius

Use the Sel Radius menu found under the Smt Setup menu to do the following:

• Thickness-The default bending radius is equal to the thickness of the sheet.

• Enter Value-Enter a random value.

• From Table-If a bend table is assigned to the part, the From Table menu appears with a listing of all the radii in the table. Choose one of the values.

• 0.031250

• 0.46875

• 0.25000

• 0.281250

• 0.312500

1. Choose Sheet Metal from the PART SETUP menu.

2. Choose Default Rad from the SMT SETUP menu.

3. Choose an option to proceed.