Unfolding rules

 

 

Links/Videos:

 

This command allows to define or select sheet metal unfolding rules. In this case, the preferred radii for the current thickness are automatically proposed during the sheet metal creation and also all the associated unfolding parameters.

 

Creation stages / Use:

 

Click the icon or select Sheet Metal > Unfolding Rules... from the drop-down menu.

 

  1. Select an unbending method.

  2. Indicate the position of the neutral fiber (K factor) and any additional losses if applicable (correction).

  3. Validate the unfolding rules with the button.

 

Available Options:

 

The Predefined Rules option allows you to use the rules defined in the Unfolding Rules document (bend tables).

These Predefined rules can be of two types: Document (selection of a single rule) or Parameter (selection of Unfolding rules parameter or Switch unfolding rules parameter). Parameter allows to drive  the rule with a family document or according to a material.

 

By checking Imposed Bend Tool, the bend tool to apply is defined no matter the internal radius defined in the design (in the "standard" case, the bend tool is selected based on the associated bend radius).

 

 

  • You can rapidly define the unfolding rules by selecting an unfolding rules document in the project tree then by moving it to your part document by holding the left mouse button, and releasing the button to make the connection between the two documents.

  • The Analyze sheet metal contextual command summarizes applied unfolding rules on the sheet metal (by taking in account the thickness).

 

 

  • If the Imposed bending tool option is checked, the thickness used to create the sheet metal is not yet known, TopSolid doesn't check if the selected tool is compatible with this thickness. The user must be careful of this.

Imposing the bending tool at that time means that you do not have to do it when creating the flattening (you can therefore only make this choice when creating the flattening), which is interesting if you wish, for example, to automatically generate the unfolds via the multiple flattening command.

  • To force the global bending tool during the unfolding operation, you have to edit the sheet metal inclusion operation and use the unfolding tools section of the dialog. Only available tools for the current thickness are proposed.

  • You can also force locally the tool with the unfolding process command in the unfolding document.

 

 

Modifications / Additional information:

 

All sheet shaping processes deform the material. These distortions cause the material to elongate or contract.

 

There are two main modes for calculating losses in bends:

 

  • Calculations by neutral fiber:

The sheet metal length is considered as constant at the neutral fiber. But the neural fiber position changes along the thickness regarding materials or bend characteristics.

 

Under the neutral fiber, the material is compressed, on the neutral fiber it is stretched.

 

The most elementary method is to provide the neutral fiber to be applied (K factor, position of the neutral fiber) directly, but there are also other methods for calculating this coefficient depending on the material, thickness and bend radius (DIN6935).

 

Another option is also to store these coefficients in tables based on material, thickness, bend radius and bending tool used.

 

 

Characteristic lengths in a neutral fiber calculation

 

  • Loss calculations on draft:

The length of the unfolded sheet is assimilated to the internal or external face lengths that are extended to eliminate bends.

There are three types of calculations: internal, external or tangent dimension.

Internal dimension

Loss calculation on draft for internal dimension:

External dimension

Loss calculation on draft for external dimension:

Tangent dimension (internal or external)

Loss calculation on draft for external tangent dimension: