Extended modules > Creo Elements/Direct Sheet Metal > Creo Elements/Direct Sheet Metal customization > Bends, hems, offsets, and reliefs
  
Bends, hems, offsets, and reliefs
This chapter discusses the following topics:
The Bend Processes
The Hem Process
The Offset Process
Bend and Corner Relief Tools
The Bend Processes
The "demoshop" supports the following bend processes:
Air Bending
Bend Forming
Bend Folding
3 Point Bending
Roll Bending (for bends that have an angle greater than 180 degrees)
Cone Bending
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Refer to Graphical help for tools and processes for details on each of these processes.
Every bend process must have at least a :RADIUS column or a :CONE_ANGLE column. The other columns are optional. In the case of air-bending, the :RADIUS is calculated dynamically according to the actual material and bend-angle values.
The :DYNAMIC-COLUMN statement is used for the dynamic calculation of the context-dependent bend radius. The dynamic column remains empty until it is filled at runtime through the associated formula (held in a different column). Note that multiple columns can be included in the same :DYNAMIC-COLUMN statement.
If you do not specify an allowance table or a specific allowance formula, Creo Elements/Direct Sheet Metal defaults to the allowance formula specified in the shop table entry :ALLOWANCE_FORMULA.
For further details see:
Adding a Bend or Corner Relief Tool
Deleting a Bend or Corner Relief Tool
Bend Allowance Calculation
Adding a Bend Tool
To add a bend tool to a shop definition, you need to extend the relevant bend process table:
air_bending
bend_forming
bend_folding
3pnt_bending
or one of your own (custom) bend process tables.
For example, if you want to add a bend tool for the bend forming process, you need to add the new bend tool specification to the "Bend Forming" table. This table is shown below. Either use the Technology Database Browser (see The Technology Database Browser) or edit this table manually.
(sha-define-shop-table "bend_forming" :TABLE-TITLE "Bend Forming" :COLUMNS ( :RADIUS :ANGLE :ALLOWANCE_TABLE :PREFERENCE :MAX_THICK :ADVICE) :COLUMN-NAMES ( "Rad" "Ang" "Allow Tab" "Pref" "Max Thick" "Advice") :UNITS ( :MM :DEG nil nil :MM nil) :CONTENTS( (0.40 90 "bend_form_allow" :PREF 1.6 "-") (0.40 30 "bend_form_allow" :PREF 1.6 "-") (0.40 45 "bend_form_allow" :PREF 1.6 "-") (0.40 60 "bend_form_allow" :PREF 1.6 "-") (0.60 90 "bend_form_allow" :PREF 1.6 "-") (0.80 90 "bend_form_allow" :NONPREF 1.8 "-") (1.60 90 "bend_form_allow" :NONPREF 1.9 "-") (2.40 90 "bend_form_allow" :NONPREF 2.6 "-") ) :DISPLAY (:RADIUS :ANGLE :PREFERENCE :ADVICE) :KEY (:RADIUS :ANGLE) :FLAT-TEXT ("Bend form R={1} A={2} {3}" :RADIUS :ANGLE :UPDOWN) :HELP "sha_bnd_form" )
Under :CONTENTS, add a line which specifies your additional bend tool. For the "demoshop", each bend tool specification consists of entries for the following columns:
:RADIUS
Tool radius.
:ANGLE
Tool angle.
:ALLOWANCE_TABLE
Reference to the appropriate allowance table
:PREFERENCE
Preference status: ":PREF" for preferred tools or ":NONPREF" for non-preferred tools.
:MAX_THICK
The maximum material thickness for which the tool is designed.
:ADVICE
Creo Elements/Direct Sheet Metal fills this column according to checks against :MAX_THICK, :ANGLE (and :MIN_THICK, if existing).
The following line is an example of an additional bend tool specification.
(0.50 45 "bend_form_allow" ":PREF" 2.0 "-")
The bend radius of this new bend tool is 0.50 mm. Its bend angle is 45 degrees. Its associated allowance table is named "bend_form_allow". It is a preferred bend tool. The new bend tool is designed for a maximum material thickness of 2 mm. At runtime, the "-" entry for the :ADVICE column is dynamically replaced by the tool check result when this tool is listed in the tool selection table.
Deleting a Bend Tool
To delete a bend tool from the selection table of a shop definition file, either use the Technology Database Browser (see The Technology Database Browser for an example) or use one of the following manual methods:
Delete the tool specification line from the associated bend process tool table in the shop definition file.
Comment out the tool specification line by placing a semicolon (;) in front of it. The advantage of this method is that you can retain existing bend tool definitions for future use and/or for use in other shop definition files.
For example, if you want to exclude the 2.4 mm bend tool from the bend tool selection table, place a semicolon in front of the associated tool specification line. The resulting line in the :CONTENTS section of the "Bend Forming" table is shown below.
;(2.40 90 "bend_form_allow" :NONPREF 2.6 "-")
Radius Formula for Air Bending Tools
The bend radius of air bending tools is calculated by means of a special formula included in the sha_demoshop_func.lsp file. The bend radius produced by air bending tools depends mainly on the die width. A radius amounting to 15% of the die width is a good approximation.
The resulting bend radius will be equal to the piston radius only if the bend radius is smaller than the bend piston radius. A customized formula has been introduced to account for this dependency and to allow more accurate or even completely different bend radius calculations.
An example of such a function named air_bend_rad is specified in the sha_demoshop_func.lsp file. This function is called implicitly by the following bend-generating commands when these are set to air bending:
ADD_SHEET
ADD_PROFILE
NEW_PROFILE
ADD_LIP
The air_bend_rad function uses the following parameters:
Input
tool_id
Tool key property list. The following syntax applies: (:shopname <shopname> :tabname <tablename> :rowkey <property list with tool key columns>)
For example:
(:SHOPNAME "demoshop" :TABNAME "air_bending" :ROWKEY (:DIE_WIDTH 20.0 :PISTON_RAD 1.6 :PISTON_ANG 0.78539816339744828))
sheet_material
Material property list. The following syntax applies: (:shopname <shopname> :tabname <tablename> :rowkey <property list with tool key columns>)
For example:
(:SHOPNAME "demoshop" :TABNAME "sheet_metals" :ROWKEY (:MATERIAL "UST 1203" :THICK 1.25))
sheet_thickness
Material thickness (mm).
bend_angle
Angle of bend (degrees). 0 implies "no bend".
Return
property list: ( :radius ; [mm] must, = nil if tool invalid
:error-type violation-type ; optional, e.g. :dfm_warning
:error-message <message string> ) ; optional
The optional return properties can be used to flag an error which may have been detected during the allowance calculation. The error feedback to the user consists of:
a headline string which is displayed as the headline in the error popup box,
an error type defining the error severity level and thus the color of the error popup box,
a more detailed string describing the error condition.
The error type should be one of the types specified in the *sha-severity* list in the sha_demoshop_func.lsp file or your working copy of this file; for instance:
DFM_rule_violation
Each defined error type is mapped to one of the three severity level colors:
:low = yellow
:medium = orange
:high = red
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You can customize these severity level mappings as required by your organization. See the
sha_demoshop_func.lsp file for examples.
The Hem Process
The hem process supported by the "demoshop" requires a :HEM_DIST column to specify the hem distance. The other columns are optional.
If you do not specify an allowance table or a specific allowance formula, Creo Elements/Direct Sheet Metal defaults to the allowance formula specified in the shop table entry :HEM_FORMULA. If this entry cannot be found, the :ALLOWANCE_FORMULA entry for regular bends will be used instead.
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By default, the :HEM_FORMULA is not used in the sha_demoshop.lsp file.
For further details see:
Adding a Hem Tool
Deleting a Hem Tool
Hem Allowance Calculation
Adding a Hem Tool
To add a hem tool to a shop definition file, you need to add the new bend tool specification to the "Hems" table. Either use the Technology Database Browser (see The Technology Database Browser) or edit this table manually. The relevant section of this table is shown below.
(sha-define-shop-table "hems" :TABLE-TITLE "Hems" :COLUMNS ( :HEM_DIST :PREFERENCE :ALLOWANCE_TABLE :MAX_THICK :ADVICE) :COLUMN-NAMES ("Dist" "Pref" "Allow Table" "Max Thick" "Advice") :UNITS ( :mm nil nil :mm nil) :CONTENTS ( (0.88 :PREF "hem_allow" 1.6 "-") (1.00 :PREF "hem_allow" 2.0 "-") (1.25 :PREF "hem_allow" 2.5 "-") (1.50 :PREF "hem_allow" 3.0 "-") (0.01 :NONPREF "hem_allow" 1.0 "-") (1.60 :NONPREF "hem_allow" 3.2 "-") (2.00 :NONPREF "hem_allow" 4.0 "-") (3.00 :NONPREF "hem_allow" 6.0 "-") )
Under :CONTENTS, add the line which specifies your additional hem tool. For the "demoshop", each hem tool specification consists of entries for the following columns:
:HEM_DIST
The tool dimension defining the hem distance (= 2 * inner bend radius).
:PREFERENCE
Preference status: ":PREF" for preferred tools or ":NONPREF" for non-preferred tools.
:ALLOWANCE_TABLE
Reference to the appropriate allowance table.
:ADVICE
Creo Elements/Direct Sheet Metal fills this column according to checks against :MAX_THICK, (and :MIN_THICK, if existing).
:FLAT-TEXT
Same as in "The Bend Process".
Except for the :HEM_DIST entry, all entries are optional.
The following line is an example of an additional hem tool specification.
(2.00 ":PREF" "hem_allow" "-")
The hem distance produced by this new hem tool is 2.00 mm. It is a preferred tool. Its associated allowance table is named "hem_allow". The "-" entry is the default entry for the :ADVICE column. At runtime, the "-" entry for the :ADVICE column is dynamically replaced by the hem tool check result.
Deleting a Hem Tool
To delete a hem tool from the selection table of a shop definition file, either use the Technology Database Browser (see The Technology Database Browser) or use one of the following manual methods:
Delete the tool specification line from the associated hem tool table in the shop definition file.
Comment out the tool specification line by placing a semicolon (;) in front of it. The advantage of this method is that you can retain existing hem tool definitions for future use and/or for use in other shop definition files.
For example, if you want to exclude the 0.88 mm hem tool from the hem tool selection table, place a semicolon in front of the associated tool specification line. The resulting line in the :CONTENTS section of the "Hems" table is shown below.
;(0.88 :PREF "hem_allow" 1.6 "-")
The Offset Process
The offset process supported by the "demoshop" requires the :OFFSET_HEIGHT column to specify the offset distance. The other columns are optional.
If you do not specify an allowance table or a specific allowance formula, Creo Elements/Direct Sheet Metal defaults to the allowance formula specified in the shop table entry :OFFSET_FORMULA. If this entry cannot be found, the allowance will be calculated according to the allowance formula for regular bends specified by the :ALLOWANCE_FORMULA entry.
For further details see:
Adding an Offset Tool
Deleting an Offset Tool
Offset Allowance Calculation
Adding an Offset Tool
To add an offset tool to a shop definition file, you need to add the new bend tool specification to the "Offsets" table. Either use the Technology Database Browser (see The Technology Database Browser) or edit this table manually. The relevant section of this table is shown below.
(sha-define-shop-table "offsets" :TABLE-TITLE "Offsets" :COLUMNS ( :OFFSET_HEIGHT :PREFERENCE :ALLOWANCE_TABLE :MAX_THICK :ADVICE) :COLUMN-NAMES ("Height" "Pref" "Allowance" "Max Thick" "Advice") :UNITS ( :mm nil nil :mm nil) :CONTENTS ( (1.0 :PREF "offset_allow" 1.0 "-") (2.0 :PREF "offset_allow" 2.0 "-") (3.0 :PREF "offset_allow" 3.5 "-") (4.0 :PREF "offset_allow" 4.5 "-") )
Under :CONTENTS, add the line which specifies your additional offset tool. For the "demoshop", each hem tool specification consists of entries for the following columns:
:OFFSET_HEIGHT
The tool dimension defining the offset height.
:PREFERENCE
Preference status: ":PREF" for preferred tools or ":NONPREF" for non-preferred tools.
:ALLOWANCE_TABLE
Reference to the appropriate allowance table.
:ADVICE
Creo Elements/Direct Sheet Metal fills this column according to checks against :MAX_THICK and :MIN_THICK (if these exist).
:FLAT-TEXT
Same as in "The Bend Process".
Except for the :OFFSET_HEIGHT entry, all entries are optional.
The following line is an example of an additional offset tool specification.
(2.5 :NONPREF "offset_allow" 2.0 "-")
The offset distance produced by this new hem tool is 2.5 mm. It is a non-preferred tool. Its associated allowance table is named "offset_allow". It is designed for a maximum material thickness of 2 mm. The "-" entry is the default entry for the :ADVICE column. At runtime, the "-" entry for the :ADVICE column is dynamically replaced by the offset tool check result.
Deleting an Offset Tool
To delete an offset tool from the selection table of a shop definition file, either use the Technology Database Browser (see The Technology Database Browser) or use one of the following manual methods:
Delete the tool specification line from the associated offset tool table in the shop definition file.
Comment out the tool specification line by placing a semicolon (;) in front of it. The advantage of this method is that you can retain existing offset tool definitions for future use and/or for use in other shop definition files.
For example, if you want to exclude the 4 mm offset tool from the offset tool selection table, place a semicolon in front of the associated tool specification line. The resulting line in the :CONTENTS section of the "Offsets" table is shown below.
;(4.0 :PREF "offset_allow" 4.5 "-")
Bend and Corner Relief Tools
The demoshop.lsp file supplied with Creo Elements/Direct Sheet Metal includes a number of predefined tools for bend and corner reliefs. Each of these tools is marked by one of the following entries specifying the type of relief it is designed for:
:USABLE-AS-RECTANGULAR-RELIEF
for rectangular bend reliefs
:USABLE-AS-ROUND-RELIEF
for round bend reliefs
:USABLE-AS-CORNER-RELIEF
for corner reliefs
For example, the sqr_sharp table in the demoshop.lsp file includes the following entry:
:USABLE-AS-CORNER-RELIEF :LENGTH
This line classifies the "square sharp" tools as suitable for corner reliefs. :LENGTH specifies the tool table column containing the relevant relief dimension.
For further details see:
Adding a Bend or Corner Relief Tool
Using an Existing Punch Tool as a Bend or Corner Relief Tool
Deleting a Bend or Corner Relief Tool
Adding a Bend or Corner Relief Tool
To add a bend or corner relief tool to a shop definition, you need to add the new relief tool specification to the associated bend relief or corner relief table. Either use the Technology Database Browser (see The Technology Database Browser) or edit the underlying TDB table manually.
Using an Existing Punch Tool as a Bend or Corner Relief Tool
Alternatively, to use an existing punch tool as a bend or corner relief tool, you need to manually extend the relevant punch tool table by adding the applicable USABLE-AS-... statement to the end of the associated tool definition table. Please note that this statement must also specify the tool table column containing the relevant relief dimensions, for example :VERT or :LENGTH.
For example, if you want to add the "Oblong" punch tool to the selection list of relief tools, add the following line to the obl table in your shop definition file:
:USABLE-AS-ROUND-RELIEF :VERT
This line implies that the :VERT column provides the dimensions for the round relief tool.
Deleting a Bend or Corner Relief Tool
To delete a bend or corner relief tool from the selection table of a shop definition file, either use the Technology Database Browser (see The Technology Database Browser) or use one of the following manual methods:
You can delete a bend or corner relief tool from the selection table of a shop definition file in one of two ways:
Delete the tool specification line from the associated relief tool table in the shop definition file.
Comment out the tool specification line by placing a semicolon (;) in front of it. The advantage of this method is that you can retain existing relief tool definitions for future use and/or for use in other shop definition files.
For example, if you want to exclude the "Square Corner Relief" tool from corner relief operations, place a semicolon in front of the associated line in the sqr_corner_relief table. The resulting line in this table is shown below.
:USABLE-AS-CORNER-RELIEF :LENGTH