Press Brake Bend Allowance Chart. Discover ideas about Welding Gear. Bending Technology. What others are saying. Sheet Metal Bending Process Sheet metal bending is the process by which force is applied to a piece of thin metal, to make it bend. This is the beginning process of making items as small as brackets or as large as chassis. Bend Radii & Minimum Bend Sizes Bend Radii & Minimum Bend Sizes. It is most economical to use a single bend radius throughout the design, but if necessary, you can utilize multiple radii. Use this document to choose values that are both manufacturable and meet your needs. Calculate unfold size with bend allowance chart. Bend forming 0°L=A+B-0.43T, T=Thickness, Deduction=0.43T. The deduction is 1.8 times the steel plate thickness and 1.6 times the aluminum plate. For plate under 2mm, K-factor is 0.432, R=plate thickness, unfold size can accurate to 0.05. PDF On Jul 4, 2007, Achilles Vairis and others published Bend Allowance Constants For Use In Sheet Metal Forming. Few sources for bend allowance data i ncluding sheet metal suppliers. Title: H&HBend Guide Author: DLeaman Subject: H&HBend Guide Created Date: 1/7/2003 2:06:16 PM.
Bend Allowance and Bend Deduction Value You can specify an explicit bend allowance or bend deduction for any sheet metal bend by entering the value when you create the bend. By definition, the bend allowance is the arc length of the bend as measured along the neutral axis of the material.
| SpaceClaim Online Help |
Bend deduction table
Bend deduction tables are used to calculate flat pattern layouts. The tables are based on the Bend Deduction (BD) formula, which calculates the flat line length to produce a specific bend angle.
BD = 2 X OSSB - BA
Where:
- BD is Bend Deduction
- BA is the Bend Allowance that equals the arc length of the bend along the neutral line. The neutral line is the radius where the material transitions from compressive stress (inside) to tensile stress (outside)
- OSSB is the Outside Set Back. Depending on the bend angle, SpaceClaim uses two different definitions of OSSB as explained below.
For bend angles less than 90-degrees, OSSB is measured from the beginning of the bend to the Outside Mold LineA straight line, arc, or spline drawn in Sketch mode or on a layout plane. Lines have length but no area. When you pull a sketch into 3D with the Pull tool, lines become edges., which is the intersection of the planar faces. See the image below.
OSSB = Tan(A/2) X (BR + T) Hence BD = 2 X Tan(A/2) X (BR + T) - BA Where:
|
For bend angles greater than, or equal to, 90-degrees, the OSSB is measured from the beginning of the bend to a plane tangent to the outside bend face. This means that the OSSB is the same as the outside radius of the bend. See the image below.
OSSB = BR + T Hence BD = 2 X (BR + T) - BA Where:
|
NOTE:
- If a bend table is not assigned to a part, the Bend Allowance is calculated from the default K-factor found in the Sheet Metal options.
- If a bend table is assigned to a part, the Bend Allowance is obtained from the table and the assigned bend table file must specify tables for all possible combinations of part thickness and Vee Die width.
- If some bends in the part use Vee Die and other bends in the part do Not, the assigned bend table file must specify a table with no Vee Die Width entry.
- If you enter values in the Properties panelArea of the user interface that displays editable details about the selected object(s). This panel is initially displayed on the lower left side of the screen, but can be moved. for a Bend Allowance or Bend Deduction, it will override the values obtained from the bend table or computed using K-factorParameter of bends in a sheet metal part used to calculate the bend radius. K-factor is a percentage of the metal thickness and depends on factors such as the material and type of bending operation. Relates to the depth of the neutral axis; a line within the sheet where the length does not change when the sheet is bent. The inside of the bend is under compression, the outside is under tension, and the neutral axis occurs somewhere between the midpoint of the material (K-factor=0.50) and a point closer to the inside of the bend (K-factor=0.25)..
- You can set the bend deduction to a negative value to correctly represent the corresponding bend allowance.
To use a sheet metal bend table to calculate unfolded lengths
Copy a CSV file to the SpaceClaim LibraryYou can select from the Materials Library in the Properties panel and add them to your Local Materials./Bends folder or into a SpaceClaim Support File directory.
Set the bend table for a sheet metal component by selecting the component in the Structure treeDisplay in the Structure panel that shows you each of the objects in your design. You can expand or collapse the nodes of the tree to view the objects. You can rename objects, create, modify, replace, and delete objects, as well as work with components. and selecting the bend table from the Bend Table property.
All values may then be obtained from the bend table instead of being calculated. Any values not obtained from the bend table may result in an error when you unfold the design. You can clear the sheet metal bend table assignment from a component by selecting the blank value from the Bend Table property drop-down.
The table below shows a simple bend table as it would appear in a spreadsheet editor. Keywords are shown in bold. Angle Values are measured from the flat.
When you unfold a sheet metal design, the thickness, inner bend radius, and angle from the design are used to determine the value in the selected table.
Once you select a bend table, you can edit the Vee Die Width property in the Properties panelArea of the user interface that displays editable details about the selected object(s). This panel is initially displayed on the lower left side of the screen, but can be moved.. Vee die width sets the width of the tooling that produces the bend.
Comma-separated value file
Bend table files are stored as comma-separated value (CSV) files, which can be edited. The file below shows the same data as in the previous table, but as it appears when stored in the comma-separated value file.
Tables can have two types of data. In the example above, the data type is DataTypeCompensation, which is the default. The table below is an example where data type is set to DataTypeRadius.
In this table, each combination of Thickness and VeeDieWidth represents a table that provides the actual radius based on tool radius and angle. In the example above the green cells are the tool radius, blue cells are the angle, and pink cells are the actual radius applied to the geometry.
The radius table only affects bend creation. Once the bend is created the actual (table lookup) radius is stored in the bend. You can change the value later or disconnect the table without affecting the bend.
When a radius table is applied, Bend creation changes slightly. In the Sheet Metal Options panel, Die width is a dropdown list. The Bend radius text box label is changed to Tool radius and the input dynamically changes to a dropdown list if the following conditions are met.
- One or more edges of a sheet metal part are selected
- The selected edge is in a part that references a bend table file
- The bend table file contains a table that matches the part's thickness and selected vee die width
Keyword description parameters for bend tables
| Keyword | Description | Parameters |
|---|---|---|
Version,<version-number> | Specifies the file format version. | The file format version number is provided. The current version is 3.00. Versions 1.00 and 2.00 are also supported. |
Type,<type-name> | The type of data contained in the file. | A single string representing the type of data contained in the tables. Supported values are file format version dependent.
|
Units,<units-type> | The default units are used for numeric values which do not have units provided explicitly. | Must be in, mm, or cm. |
Thickness,<value> | Begins a bend table definition. | A single parameter specifying the thickness for which the bend deductions in the table are defined. |
VeeDieWidth,<value> | Optional. Specifies an optional tooling parameter, allowing multiple sets of bend deduction values for a given thickness. Must occur after a Thickness keyword. | A single parameter specifying the width of the die tool. |
DataType, <datatype-name> | Optional. Specifies whether bend radii will be specified manually or obtained from a Bend Table. Inputs in the Bend tool switch to dropdown lists of values contained in the table. | Two types are supported in Version 3.0.
|
AngleValues,<value>,… | Defines the columns of the bend deduction table. NoteAnnotation placed on a design, drawing sheet, or 3D markup. Notes contain text or symbols that you insert and can be connected to geometry by a note leader. the extra empty cell to aid in table alignment. Here you can download the free lecture Notes of Solid Waste Management Pdf Notes – SWM Pdf Notes materials with multiple file links to download. Solid Waste Management Notes Pdf – SWM Notes Pdf book starts with the topics Waste Collection, From Low and Medium-Rise apartments, Landfill Technique, Types of Landfill, Landfills for commingled MSW.Solid Waste Management Pdf Notes – SWM Pdf NotesPlease find the download links of Solid Waste Management which are listed below:Complete NotesUnit 3Unit 4Unit 5 Solid Waste Management Notes Pdf – SWM Notes PdfNote:- These notes are according to the R09 Syllabus book of JNTU. Types of waste pdf. In R13 and R15,8-units of R09 syllabus are combined into 5-units in R13 and R15 syllabus. The values defined by the table are associated with the preceding Thickness and VeeDieWidth keywords. | A list of angles, specified in degrees. |
Radius,<radius>, <deduction-value>,… | Defines the body of the bend deduction table. Individual deduction values may be omitted. The total number of deduction values provided cannot exceed the number of values provided above for the AngleValues keyword. | The first parameter (radius) provides the inner bend radius for the table row. The following parameters all provide the deduction values for each combination of angle and radius. |
| KFactorFallback <True/False> | Controls what happens when an invalid VeeDieWidth is encountered. | True: K-Factor is used False: The Bend fails. This is the default. |
© Copyright 2014 SpaceClaim Corporation. All rights reserved.
Typical Sheet Metal Bending Process
Sheet metal bending process can be briefly jotted down as:
- Developed sheet metal size is obtained from drawing.
- Developed sized sheet metal is cut out from large sheet by punching operation.
- Bending brake is used to bend the sheet metal piece to the required shape and angle.
Bending Allowance Calculation
Bending allowance is the input for calculating developed sheet metal size. How? See the snap below:
If you have a sheet metal bending product (as shown in above picture) with two legs of length “X' and “Y' and you unbend it, you will see that total length of the unbend sheet will NOT X + Y rather, the length will be X + Y + BA. Where, BA is bending allowance.
The formula for calculating sheet metal bending allowance is (Please refer to the above picture):
BA= Bend Angle * (Π/180)* (R+ K factor* T)……Eqn.1
Where,
BA is Bend allowance.
Bend Angle represents the angle to which sheet metal has bend (here it is 90 degree).
R is inner bend radius.
K factor= t/T……….Eqn.2
So, if you got K factor value now, you can easily calculate bending allowance.
Calculating K factor
There are standard charts available with sheet metal design handbook for calculating K factor (ideally it should be 0.5). But the most accurate way to find out K factor is reverse engineering of a small but same sheet metal sample piece. Procedure is as below:
- Now by referring Fig.1 and Fig.2 we can write:
Aluminum Bend Allowance Chart Pdf
X= X’ – (tan (A’/2))*(T+R)….Eqn.3
Y=Y’- (tan (A’/2))*(T+R)……Eqn.4
Since, all the items of right hand sides of the Eqn.3 and Eqn.4 are known so we can get the values of X and Y of the sample.
- We also know the developed length of the sample (P).
- By doing P – (X+Y), we can get the bend allowance (BA) for the sample.
- Now, use Eqn.1 and you will get K factor. This K factor will be same for the actual product.
- Use this K factor value to calculate bending allowance for main product.
Bend Allowance Formulas
Conclusion
For getting accurate output of sheet metal bending process you need to calculate accurate sheet metal developed length. And for calculating accurate sheet metal developed length you need to accurately calculate sheet metal bending allowance and for bending allowance calculation you need to have accurate K factor value. The procedure discussed in this sheet metal design guide is the simplest way to calculate bend allowance with accepted accuracy.
Related Reading
Bend Deduction Chart
- Creating die and punch for sheet metal parts using pro engineer: Pro Engineer is developed in such a way that the feature operations in ProE are actually similar to real life manufacturing operations. Form feature in Pro Engineer is identical to the real life sheet metal forming operations (where components are produced by sheet metal punch and Die press tools.
- Overview of Sheet Metal Design using Pro Engineer: Pro engineer is considered to be the leading software for sheet metal design. Like surfacing of catia, sheet metal design module of pro engineer is the unique selling feature of the software