Developing the right fastening solution involves engineering challenges: defining the forming sequence, reducing production costs, respecting the desired geometry and weight, improving product performance, preserving tooling, etc.
Digital simulation is therefore required upstream of production in order to analyze and optimize your process and the final product. It also reduces development time and costs of testing and production.
Simulation helps master all stages of the manufacturing process for fasteners, from wire drawing to shearing, cold forming, then rolling of threads to heat treatment.
The use of phosphatized steel reduces wear on tools and dies. The phosphatized surface of the wire can be taken into consideration during data setup.
Phosphatizing feature available in COLDFORM®
Upstream of cold forming operations, the wire is drawn to form coils of the required diameter. Generally, the drawn wire then undergoes a heat treatment called spheroidization annealing. If this heat treatment is not applied, the plastic deformation induced by wire drawing should be taken into account in the simulation. COLDFORM® can initialize the fields along an axis or a radius. This feature allows the initial plastic deformation along the radius of the billet to be defined.
Application for unannealed wire before forming:
Left: Initialization of the plastic deformation
Right: Comparison of the tonnage obtained by forming a pre-drawn and annealed wire
The second step of the process that can be simulated is the shearing of the metal wire necessary for the manufacture of small billets.
Our software measures the necessary shear force according to the thickness of the wire, the material, the parameters of the machine, etc.
The sheared surface is accurately predicted using the adaptive remeshing technique.
Billet shearing simulation. Courtesy of Hatebur.
The striking range is then developed to ensure at each stage a good distribution of the material, the absence of defects and well-balanced striking forces. The steps are defined in COLDFORM® and different types of results can be analyzed:
This example shows a forging sequence for the manufacture of a screw, carried out by the Miguel Altuna Institute (Spain). The process was broken down into 5 steps on COLDFORM®:
The first three stages were the subject of a 2D simulation (axisymmetric revolution part) and the last two stages were simulated in 3D
Modeling of all stages of the forging sequence
The deformation, stresses, temperature, etc. can be analyzed for each step of the sequence.
Torx hex head screw forging sequence. Real part vs. Simulation of metal flow and mechanical properties at every stage.
Courtesy of Miguel Altuna Institute Spain
COLDFORM® also simulates the creation of threads around the screw. The contact algorithm and the temporal integration diagram make the simulation of the threading totally predictive: the software models the actual kinematics applied to the chaser and highlights the internal and external stresses.
Modeling of the increase in equivalent stresses during threading
Courtesy of the Miguel Altuna Institute
By using a cutting plane, it is possible to anticipate the areas of underfill on the screw thread.
Highlighting of under-filled areas on the thread
The fasteners must guarantee an excellent level of resistance since they are often used in areas with high tensile stress. To achieve the desired metallurgical and mechanical properties, manufacturers apply heat treatment such as heating, quenching and tempering.
Following your cold forming simulation on COLDFORM®, this operation can be simulated with our SIMHEAT® software.
The blue meshing corresponds to the increment of the last forming step. The part in gray corresponds to the springback increment. The displacement due to springback is therefore easily visualized.
Multi-view display of a given case