| Electric screw press is a newly general Die-forging equipment, the most important advantage of electric screw press is exact energy control which ensures high process reliability and repeatability. This technology is highly suitable for precision die forging and has been widely used for forging various types of materials, credited to the press ram which has no fixed dead point. Some key technologies of numerical control electric screw press about control and test are researched in this paper, including the digital heavy-duty motor driving technology, a dedicated numerical control system, testing technologies of effective press energy and actual press force, etc..The digital heavy duty mechanical driving technology based on AC servo system is the key to the numerical electric screw presses. This paper researched the permanent magnet synchronous motor driven system based on flux vector control technology and the AC induction motor driven system based on direct torque control technology, both of them are applied to the numerical electric screw press and the experimental results showed that the above problems were solved well. Then comparison of the DTC AC induction motor drive with corresponding permanent magnet synchronous motor drive showed that for the J58K-315 electric screw press prototype, the former attains a higher maximum speed (786 r/min) within a shorter (1.13 s) during a 250 mm stroke and undergoes smaller motor temperature rising (42.0℃) after running for 2 hour at a 12 min-1 strike frequency than the latter does (751 r/min within 1.19 s, and 50.6℃rise). Moreover, the DTC AC induction motor drive, with no need of a tachometer or position encoder to feed back the speed or position of the motor shaft, enjoys increased reliability in a strong-shock work environment.High-secure and dedicated numerical control system of electric screw presses is needed for its special processing conditions and harsh environment. This paper describes the design of a numerical control system with programmable logical controller as the core and industry used touch screen as the human machine interface which based on open system idea and modular programming methods. The system achieved high performance, such as exact energy control from 10% to 100% ensuring high process reliability and repeatability, convenient to adjust stroke and return exactly, programmable forging can preset stroke energy of each step, etc.. Also, the system has a friendly interactive interface and some fault diagnosis ability. In a word, the operator only has to enter the required power and the stroke for the process, the controller then computes all the relevant data and makes the above mentions fulfilled reliably. Effective press energy testing is the key to proving the design and manufacture of electric screw presses which is whether qualified or not. This paper applied copper cylinder upsetting method to checking the effective energy of electric screw presses, and the testing principle of copper cylinder upsetting has been put forward according to electric screw presses, such as testing process, rules and calculations, etc.. Then, testing standards of the corresponding type of equipment according to each kind of nominal press force have been carried out. At last, the experimental results show that the J58K series of electric screw presses are qualified well and have a very high efficiency.To protect the screw press equipment from the damage of overloading, the best way is to install load gauge indicator which monitoring press force of every strike. This paper presented a load gauge indicator used in numerical electric screw presses. The strain gauge bridge excited by dual constant-current source to increase the performance and precisions; The control circuit adopted many chips with serial interface and so that the structure is compact and volume is small; Digital potentiometers were applied in the circuit of strain gauge bridge and amplification to make the bridge auto keep balance and amplify gain adjust digitized. The experimental results show that the measurement is accurate and stable, and the load gauge indicator has been an important component of the J58K series numerical electric screw presses.The research work above in this paper has been all tested in practical applications, the project "Auto parts precision forging technology and key equipment development and application" won the first prize of scientific and technological progress by Hubei Province in 2008, "a kind of compacting and limiting device about slipped disc spring of screw press flywheel" was patented, the software version V1.0 and V2.0 of J58K series numerical electric screw presses have been achieved computer software copyright. The results of research in this paper guided and all applied to J58K series numerical screw presses developed by our laboratory, achieved the commercialization of products and marketing work of nominal press force from 1600kN to 25000kN. The research of this paper will provide a theoretical basis and practical experience for the future domestic research and development of heavy-duty electric screw presses.
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