Die / Tool simulation
QForm can show die stress on the surface of the die and internally in both 2D and 3D tool simulations.
A tool simulation can be run where the user can see the following properties in the tool:
- Effective stress and strain
- Mean stress
- Radial stress and strain
- Axial stress and strain
- Hoop stress and strain
- Shearing stress and strain
- Volumetric strain
- Distortion due to forming load
- Radial and axial displacement
- Die wear factor
It is useful to see the effective stress values in your tools to be sure that you are within the yield strength of your tool steel. If you exceed the yield strength of your die steel you will encounter localized plastic deformation in those areas of your dies that will quickly lead to failure. Elevated values of effective stress should be avoided.
Example of die stress simulation benefits
In the following example a forge die for a gear with finish-forged teeth for a PTO Application was cracking after around 400 parts. Improvement was needed for production quantities.
Close up of die crack
Simulation showed local elevated levels of stress where the die was cracking
The problem is solved by separating the die into two parts with the use of an insert so that the die can move freely eliminating the high stress in this area.
It is very easy to see the effects of a shrink ring on both 2D and 3D tool simulations.
The dimensions and fit of the shrink ring can be easily adjusted to find the optimal values.
Effective stress without shrink fitting
Effective stress with shrink fitting
QForm can show a relative die wear factor across the surface of the die. This will graphically show the areas on the die with the most wear and the areas on the die with the least wear.
Die wear factor on die surface
Example of die wear simulation
In this cold headed bolt, the original design yielded a defect free trimmed bolt in four stations.
However the top die cut the workpiece in the third station creating a lap that was later trimmed off.
This created uneven die wear factors on the top and bottom dies
Maximum die wear factor of 20.78 on the top die and 2.8 on the bottom die.
This means that the top die would wear out almost ten times faster than the bottom die.
The design was modified to have more even material flow in three stations
Now there are more even values of die wear on the top and bottom dies (7.28 and 9.9) and the die set will last much longer.
QForm can show die deflection based on the forging loads applied through the workpiece in both 2D and 3D simulations. This allows the user to see where the forces are greatest within the tooling. A magnification factor can be applied to make the deflection more visible.
die deflection in 3D tooling
In 2D tool simulations the inverse profile of the deflection can be exported to CAD so you can build your dies to compensate for the deflection. For instance in the following forging sequence:
A tool simulation of the end of stroke showed that the die deflection was greatest at the center of the die.
The inverse of the die deflection was exported to cad and the forging with the new die showed much more even deflection that was well within the design tolerances.
QForm version 7 can perform coupled simulations that simulate the die and the tool together and show their influence on each other. QForm 7 can perform coupled mechanical as well as coupled thermal simulations. In the following example you can see the advantages of a coupled mechanical simulation.
This forging was run with and without a coupled mechanical simulation.
Non-coupled simulation Coupled simulation
You can see the difference in the flash. In coupled mechanical simulation, the die deflects during the forge stroke so that there is more volume for the workpiece to fill. Therefore the flash does not extend out as far in the coupled mechanical simulation.