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Design and manufacture active surfaces to exact specifications

Precise CAD active surfaces result in enormous savings in the tryout phase


Active surfaces are the areas of the sheet metal die that come in direct contact with the sheet metal. There are active surfaces in all die components, such as the die, punch, blank holder and all small parts for trim and restriking operations.

When active surface designers account for realistic sheet metal thickness, thinning effects and reliefs in the CAD active surfaces, they save hundreds of hours in NC programming, machining and tryout.

Because of the supposedly large design effort, active surfaces are often fully designed for only one side of the sheet metal (e.g. for the die). Offset dimensions (= sheet metal thickness) are then factored into the NC programs for NC manufacturing. Often, stock allowances are also used in the NC programs to account for thinning effects and reliefs. Although this procedure quickly yields an initial result, it also requires an enormous amount of manual effort in the spotting presses and usually in additional iterations in tryout.

Tebis offers automated design functions for active surfaces. This enables designers to follow the exact procedure and generate die sets accounting for all known and simulated forming effects in the CAD model.

The conventional method:
Pressure surfaces (positive allowances) and reliefs (negative allowances) are not designed to meet exact specifications, but rather are milled in the active surfaces of the sheet metal die based on NC stock allowance attributes. The CAD surface (dotted surface) therefore does not correspond to the milled result (red surfaces).

The Tebis method:
Pressure surfaces (positive allowances) and reliefs (negative allowances), are designed precisely and with transition areas in the CAD design (green surfaces). The CAD model is produced on the milling machine. The milled die components and the CAD model are identical.


Automatically relieve and flatten radii for drawing operations

The die maker understands relief to mean the reduction of rounded areas in concave areas of the matrix, punch, blank holder and all small parts, so as to ensure that the sheet metal in these areas is only contacted by one side of the die on forming.

This effect is achieved in convex active surface areas by flattening the radii.

Modify your active surfaces in the CAD design wherever possible. This lets you stabilize your overall process from the drawing simulation to the tryout press. Changes in rounded areas in the CAD design are quickly and precisely implemented in the die through NC programs and can be modified in a controlled manner to promote a stable process.

Tebis automatically detects radii and roundings and reduces the radii in the rounded areas at the click of a button, thereby creating tangential transitions to the adjacent surfaces.

The user interactively performs graphical modifications to convex roundings in the active surfaces in real time. The Tebis user determines the degree of the change with the control arrow.


Automatically design pressure surfaces and reliefs for drawing operations

Pressure surfaces are required for large surface areas of the die in which the sheet metal must be held more securely during the drawing operation. Conversely, the sheet metal has greater freedom to stretch and expand when reliefs are designed within it, i.e. so that no pressure is exerted on the sheet metal.

Green areas remain unchanged. For red areas, Tebis automatically calculates positive and negative allowances. Areas shown in orange are transition areas.

The before and after differences are rendered visible with a comparison function and can be measured by the user.


Automatically generate outline surfaces for trim operations 

For designing lower trim steels, the Tebis active surface designer creates outline surfaces at the click of a button. These surfaces already include the cutting gap and reliefs, and a constant trim edge width. The calculated surfaces are then used for the solid design of the lower part of the die.

Tebis automatically calculates outline surfaces (light areas) with reliefs (dark areas) from 2D and 3D curves.

In the press, the sheet metal (green) is trimmed by the trim steel on the lower steel.

Tip: You can also use the Tebis automatic small-part process for designing your trim steels. 
 


Automatically design trim steels

Trim steels are among the small parts of a sheet metal die and can be designed and manufactured in a standardized and largely automated process. The Tebis automatic design process uses surface and solid geometry. It generates form and outline surfaces with offset and reliefs and cuts everything to exact solids with automatically generated extension and overrun surfaces.
The bores and fits required for securing the trim steel result from the assembly specification of the solid system. The cover surfaces needed to produce the trim steels by milling are created automatically.

The highly automated Tebis small-part process uses specifications from the solid design and the active surface design, enabling the user to easily generate precise and fully designed trim steels.

Bores and fits must first be closed to manufacture the trim steels on milling machines. Tebis automatically creates the cover surfaces.

 

Tebis uses bore features for all bores and fits, accessing the Tebis process library which is built up during process structuring. There are corresponding NC machining sequences for each bore feature, with information on tools and cutting data.


Compensating for press deflection

The upper sections of large-scale forming dies are subjected to gravitational forces that cause undesired defection of the die depending on the rigidity of the overall system. Tebis automatically and reliably compensates for this physical effect in the active surfaces. The Tebis morphing technology automatically morphs complex, free-form topologies to the specifications of an easily formulated morphing rule. See also Springback.

The die sags in the original state, with the result that the air gap to the punch is smaller in the center than around the outer area.

After compensation for press deflection, all surfaces have been changed minimally. The compensation is the greatest in the middle of the die, where the greatest deflection has been calculated.

 

Your benefits in the overall process

  • Fast and reliable NC programming: Exact active surfaces are the prerequisite for NC automation and simulation technologies
  • Fast track to the machine: Exact active surfaces are a prerequisite for the use of high-feed cutters (HFC)
  • Short manual try-out times: Finished die surfaces with no visible edges or transitions 

 


Customer feedback

Even if just one pressure area was overlooked in the process, the correction cost us up to 10,000 Euros. Today, for example, we install dies for doors that we previously had to rework directly in the press for roughly 160 hours.

Roland Schöbel, head of manufacturing, Wolfsburg die manufacturing, Volkswagen AG

Tebis has helped us improve our entire manufacturing process. We've become faster and more flexible, and manufacture more efficiently and reliably. All this thanks to the high consistency of the software, which no one else can offer in this form.

Björn Wind, Team leader for work preparation and NC manufacturing, Merima Präzisions-Werkzeugbau GmbH


White Paper

Challenges in Sheet Metal Draw Die Manufacturing: Perfect interaction between the virtual and real world

Tebis active surface preparation includes compensation of sheet metal thinning, incorporation of pressure surfaces and free design of negative radii. Specialized functions enable programming without virtual wall thicknesses, making visible edges and steps in the die surface disappear. Compensation for press deflection and die deformation can be simply integrated with corresponding overbending rules.
Find out more

Advances in sheet metal forming: End-to-end automation in the context of Industry 4.0

Tebis has developed functioning, software-supported processes specifically for die manufacturing. These processes enable the production of top-quality, class-A surfaces and automate manufacturing of small parts. Both processes verifiably reduce manufacturing costs, thanks to standardization and the integration of individualized knowledge of manufacturing.

Find out more



Are you interested in springback compensation and would you like us to contact you? Please click here 

 

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