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Simultaneous five-axis hard milling for highest precision

Final Report Summary - HARDPRECISION (Simultaneous five-axis hard milling for highest precision)

European tool and die making SMEs are facing a steady loss of competitiveness in their markets, since existing manufacturing technologies cannot fulfil the increasing demands on part quality. These companies are eagerly seeking for new technologies to enhance the economic production of high-quality tools and dies. The project HARDPRECISION aimed at developing a five-axis hard milling process for highest precision. The technology will be able to produce high-quality products in considerably less total throughput times.

The five axis hard milling process has to be understood as a highly complex process chain being influenced by many factors - starting with CAM and NC technology, the machine tool, tool and coating technology up to process and monitoring technologies and the final evaluation by in-machine measurement. The project encompassed the optimisation of a milling machine by applying light-weight parts and the enhancement of milling technology for high-hard materials. The investigations are concentrated on conventional and powder metallurgical high speed steels and the usage of coated solid carbide tools. These materials are typically used in tools for cold forging or injection moulding of highly abrasive materials. Moreover, a part measurement system capable of quality control within the machine tool is developed.

It can be said that the initial project idea of bringing together the complete process chain of hard milling in terms of knowledge, capacities and partners was a successful approach which has enlarged the total knowledge of this process for all partners. The dissemination of results has reached a large audience being present in many journals and conferences during the entire period and especially by being present with the machine tool and the developments at the Euromold fair 2007 in Frankfurt which is the by far most important fair for the tool and die making branch worldwide.

The growing loss of competitiveness of the European tool and die industry (where the end-users of the HARDPRECISION project are belonging to) can only be reversed by substantially reducing lead times and enhancing part quality simultaneously. This was the major basis for the introduction of the HARDPRECISION project. The basic idea can be seen in the following figure: the substitution of time-consuming finishing operations of the conventional process chain (EDM, grinding) with the much more productive hard milling process is a key issue.

Additionally, the hard milling technology is capable of substantially reducing or even eliminating manual finishing operations, eliminating idle times with unclamping, re-clamping and set-up operations. In a complete five axis hard milling process chain, the parts can be machined on one only machine tool, not on many machines as it is the case in the conventional process chain.

According to the performed work and the already described project achievements, some major key findings can be defined as the project outcome where special knowledge has been generated. These topics are described in the following including a short description of further exploitation and usage activities.

Enlarged knowledge of five axis hard milling technology
The enlarged knowledge of five axis hard milling technology specifies a better understanding of the hard milling process itself. With the parameters used and identified during the project work in combination with the applied tools enhancements regarding the attainable qualities can be achieved. The partners involved in this result can use the gained knowledge for their own production immediately (end-users), for their system developments (Jabro, ModuleWorks) and for advisory activities to help other companies with their hard turning processes (IPT, Hemtech).

Barrel tool technology
The milling technology based on a barrel tool geometry can considerably shorten manufacturing times. The technology can only be implemented succesfully, when tool geometry (Jabro), process technology (IPT) and milling strategy (ModuleWorks) work together as it is a highly complex manufacturing technology. The partners involved into this result can use the generated knowledge to create new products and services for their customers.

Optimised hard milling machine tool Hemtech will use the knowledge generated in regard to the machine tool components. This concerns the light weight spindle box as well as the evaluation of the dynamic behaviour or the machine. Hemtech will use the knowledge to enhance its existing machine tool.

Damped work piece clamping
The damped clamping device is a development of system 3R which has already proven its capability to enhance process stability in other projects. The developments within the HARDPRECISION project mainly aimed at understanding the interaction with a hydrostatic machine tool. The developments will be used to further enhance the products of system 3R.

Production of high precision milling tools
The milling tool precision has proven to be one of the weakest links in high precision hard milling. Production methods to enhance the precision and tighten the tolerances of the ball end mill shape therefore are of vital importance for the improvement of the overall process technology. Jabro will use the knowledge generated within the project to further enhance its products.

PVD coatings for milling hardened tool steel
PVD coatings considerably increase the abrasion resistance of milling tools. The developments within this project aim at an adaptation of such coatings to the needs of high hard milling and further developments to improve these coatings. The knowledge generated will be used by CemeCon to improve its existing and develop novel coatings for milling tools.

In-machine measuring methods and technologies
In-machine measurement methods make it possible to replace in many cases application of coordinate measuring machines by measurement of work pieces in working space of machine tools immediately after machining. Measured errors of work pieces can be analysed and applied for supervising and corrections of tools, machining processes and thermal dilatations of machines. It is supposed to offer these measuring technologies and the gained additional knowledge (RCMT) to all customers of high-precision Hemtech machines.

Knowledge of behaviour of acoustic emission signals in the field of hard milling
In the field of hard milling the measurement of acoustic emission signals is not established. The measurements taken in the project lead to a better understanding of the process of hard-milling. The aim is, to use this knowledge at Dittel to improve the strategies for process stability, detecting tool wear and tool breakage.

Optimised process chain and milling strategies for demonstrator parts
The sample parts defined in the HARDPRECISION project are taken from real parts of the end users. Finding a way to enhance the process chain for the manufacturing of these parts is a direct way towards a better competitiveness of the end users. The four companies will use the knowledge generated to ameliorate their production of the sample parts and comparable parts in the future.

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