Cold Forging of an Hex M26 Nut

The scope of this study was to simulate the entire production process of a Hex M26 nut, manufactured on a four-station automatic press. The aim was to replicate the die filling routines at each station in order to evaluate and ultimately improve the quality of the part. The insertion of the nylon washer into the hex nut was also simulated in order to identify the most suitable die design that would guarantee a correct snap-fit.

Process of a Hex M26 nut

The simulation of the entire production process gave results that matched the actual production results very closely.  With this data as the starting point the engineering team was able to simulate changes that would streamline the cold forming process in order to match and go beyond the quality standards requested by the customer. The customer was ultimately able to produce a part free from some of the well known forming defects such as surface cracking and laps.

The Simulation Setup

Process of a Hex M26 nut

The die geometries of the four station process were created by the cold forming manufacturer DA-TOR Spa using 3-D AutoCAD Inventor and were then transferred into Transvalor ColdForm in the STEP file format. 

The starting slug was a 0.07 kilos CB4FF steel piece, whose characteristics were extracted from theColdForm FPD database. Different parameters were evaluated at each step of the production process with the results of each step being used as the starting condition for the next.

The Simulation Results

This original part was showing a series of surface defects and laps. The simulation carried out with ColdForm highlighted the reasons for the defects and the process step in which they arose. The modification of the third step eliminated these defects and enabled the realization of a part that met and went beyond the required quality standards. Furthermore, the analysis carried out with ColdForm allowed engineers to explore different configurations in order to achieve an optimal snap-fit between the nylon washer insert and the metal nut, eliminating the then current practice of manually adjusting the press to obtain the desired nut height.

From Mr. Giovanni Rocca's words at DA-TOR Spa:

"Applying ColdForm Simulation to all our "cold formed" parts currently in production will allow us to create a comprehensive database of the simulation results for each product family. We expect this to result in higher quality production, less machining, faster lead times and lower manufacturing costs in general"

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Raves

"Applying ColdForm Simulation to all our "cold formed" parts currently in production will allow us to create a comprehensive database of the simulation results for each product family. We expect this to result in higher quality production, less machining, faster lead times and lower manufacturing costs in general."

Giovanni Rocca
Managing Director,
DA-TOR S.p.A.

Hex M26 Nut Study