Splitting, thinning and wrinkling checks: It goes without saying that the primary purpose of the forming simulation step is to check how the material behaves prior to machining of any tool steel.

The results produced in the forming simulation step illustrate very clearly the calculated areas of material yielding (splitting), amounts of necking (thinning or changes in thickness) and areas of material compression (wrinkles and folds). The Forming Limit Diagram (FLD) is key to analyzing this data as it plots each element’s strain (in major and minor axis) on a graph and compares it to the material’s limits to determine if any of these defects will be present. With this information in hand, countermeasures and adjustments are made to the die face design and then the forming simulation is re-run, until each defect is removed or an acceptable result is achieved.

Die face data export
Once all the problems have been ironed out of the draw process and an acceptable “draw panel” has been produced in the virtual environment, the die face data that was used in the simulation can be export as CAD (igs, stl or any other format) for use when designing a complete tool and creating NC cutter paths. Basically, the die face data can be used in any other CAD/CAM package for use in an actual tool build.

Blank shape development
There are many cases where it is not possible to simply blank the material to the shape estimated in the first step (blank shape estimate), form it and end up with a perfect result. If the part needs to be drawn then wiped down for example, then some trimming occurs aftering drawing and needs to be developed so that after the wipe down, the trim length is correct. With the simulation software, this can all be done in a virtual environment. After the draw simulation step is complete, the “virtual draw panel” can be virtually “laser trimmed” then wiped or flanged down. The virtual laser trim shape can then be adjusted until the final trim line is developed to the correct shape. This means when the time comes to develop an actual trim die, a very accurate starting point is available, which rarely needs further adjustment meaning the time and cost to build a real trim die, is drastically reduced.

Multiple stage forming
If a part cannot be formed in a single stage then each subsequent stage can be simulated and checked too. It is simply a matter of taking the result from the previous stage and feeding it into the next. The previous stage results may include a draw, a trim, a hole pierce or any other operation, all of which gets carried over into the next stage’s simulation.

Pierce hole roundness checks
You may have realised already that a simulation of a hole pierced in a blank, then formed can be performed. This gives an accurate simulation of whether a hole can be safely pierced in a blank stage then drawn, without losing it’s roundness or desired position (usually determined by the quality specification of the final part). Conversly, such a simulation may show that an unimportant hole will go “egg shaped” after forming but if acceptable, it can remain as a hole pierced in the blank, as opposed to piercing it last when maybe a cam unit or otherwise would be required.

Springback check
A springback check can be performed after any stage. For example, after the first draw stage or after the final stage. The end result is not just a number on paper of the amount of springback, but a full 3D CAD model of the part in the sprung back state (and can be exported in any CAD format). This means it is very easy to use this data to counteract the spring back or decide whether the amount of springback is acceptable or not.

This ends the two part comment on the capabilities of forming simulation.