Continuing the series of articles dedicated to “The cold forging process at ETMA”, after addressing the what this process is about and its main technological aspects, we requested a brief article from Miguel Queirós, an engineer that works as a sales technician at ETMA, regarding “Tool Design and Manufacture through the Cold Forging Process”.
TOOL DESIGN AND MANUFACTURE THROUGH THE COLD FORGING PROCESS
ETMA’s strategy in developing and manufacturing its own tools, through the most varied production processes, has enabled the company to follow the market evolution in terms of quality requirements and meeting deadlines.
At ETMA, the design of tools through the cold forging process has a well-defined and established sequential procedure, with the following stages described below.
Stage 1 – Pre-project (project analysis, part analysis)
Technical drawing of the part
The first stage for the development of any tool is always to analyse the requirements and final specifications that the client intends for the manufacture of the part. Therefore, the tool design needs to take into account the characteristics of the materials and the process to produce the part and compare them to the expected final functionality. The pre-project is a good practice that consists in performing a pre-analysis to establish the general stages or the flow of operations, and defining the general architecture of the tool.
The next step is testing the pre-project, which will be analysed in detail regarding the sequence of operations, shape changes and impacts on the material. In general, the metal alloys suffer hardening by mechanical labour. Since cold forging is a process in which the material may receive many requests from this point of view, it is important to verify if the transformations are within the ductility parameters of the material used. This analysis is applied to every transformation, from its initial form (wire) to the final form of the part.
There is a limit for the ratio between the initial and the final diameter. That ratio has a maximum value that cannot be exceeded, otherwise, the allowed ductility for the material is exceeded and, consequently, cracks appear in the material. This analysis aims to establish if a certain reduction can be done in only one step or if two or more steps are needed. This is the action that determines the architecture of the tool, in terms of the number of necessary stations.
After checking the main function of the tool (forming), secondary functions are verified (transport of the material, extraction, lubrication), which need to be integrated. Possible incompatibilities regarding the main function are analysed and, if they exist, they need to be resolved.
Lastly, final dimensions and tolerances the tool will produce are determined. In cases of single station processes, this step is immediate, since the final dimensions/tolerances are those established. In multi station processes, the sequence of successive steps needs to be established to ensure the final dimensions and tolerances of the part.
The pre-project stage is also essential to ensure the quality of the production process. The most important and representative dimensional and geometric characteristics for the production process are identified, thus defining a preliminary control plan. Therefore, quality assurance is included in the process starting with its design.
Stage 2 – Design and Manufacture
In this stage, the tool is developed taking into account the details of the parts that comprise it. The necessary technical drawings for the manufacture of the tool parts and components are performed. Even though the project is prepared in a 3D modelling software, the 2D drawings are still necessary information for the manufacture in the machine.
Tool manufacturing drawing
Then, the manufacture of the tool is started, with several production stages, such as milling, hardening, wire erosion and grinding, assembly and first tests. The materials used are mainly steels for the tool and hard metal of several degrees.
Stage 3 – Testing
When forging tools, the first tool test is performed in the machine, where the first parts are produced, called FOT – First of Tool. At this stage, the tool is considered as almost complete, but can still be improved in some functional aspects.
This stage focuses on the final details of the tool. It consists in performing the necessary adjustments in terms of dimensions or other small details that are preventing the full functionality of the tool. The goal is to ensure that the tool produces perfect parts, based on the production rate foreseen in the estimate. These “100% parts”, which fully meet the client and ETMA requirements are called “initial samples”.
This final stage is essential to achieve the necessary precision and for the tool to be in full production conditions, ready to manufacture series parts with total safety and quality.
After completing the tool, the tool goes through rigorous tests to ensure that it meets the manufacture and process specifications of the part. This includes a validation of resistance and durability (Run @ Rate), as well as functionality tests to ensure that, during the production process, the tool can perform its job efficiently and safely.
In the following article, we will conclude the topic of the cold forging process at ETMA, with an approach to the different applications and examples of parts obtained through this production process.
In the meantime, if you are interested in learning more and, eventually, talking to us about a project, please do not hesitate to contact us.
