DESIGN OF NEW DIE HOLDER SYSTEM FOR REDUCING DIE EXCHANGE TIME ON 1000 TON HOT FORGING PRESS

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DESIGN OF NEW DIE HOLDER SYSTEM FOR REDUCING DIE EXCHANGE TIME ON 1000 TON HOT FORGING PRESS A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES OF MIDDLE EAST TECHNICAL UNIVERSITY
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DESIGN OF NEW DIE HOLDER SYSTEM FOR REDUCING DIE EXCHANGE TIME ON 1000 TON HOT FORGING PRESS A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES OF MIDDLE EAST TECHNICAL UNIVERSITY BY MUHAMMAD AHMAD SIDDIQUE IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN MECHANICAL ENGINEERING FEBRUARY 2015 Approval of the thesis: DESIGN OF NEW DIE HOLDER SYSTEM FOR REDUCING DIE EXCHANGE TIME ON 1000 TON HOT FORGING PRESS submitted by MUHAMMAD AHMAD SIDDIQUE in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering Department, Middle East Technical University by, Prof. Dr. Gülbin Dural Ünver Dean, Graduate School of Natural and Applied Sciences Prof. Dr. Tuna Balkan Head of the Department, Mechanical Engineering Prof. Dr. Mustafa İlhan Gökler Supervisor, Mechanical Engineering Department, METU Examining Committee Members: Prof. Dr. R. Orhan Yıldırım Mechanical Engineering Department, METU Prof. Dr. Mustafa İlhan Gökler Mechanical Engineering Department, METU Prof. Dr. Metin Akkök Mechanical Engineering Department, METU Prof. Dr. Haluk Darendeliler Mechanical Engineering Department, METU Özgür Cavbozar, M.Sc. Senior Expert Mech. Design Eng, ASELSAN Date: February 3rd, 2015 I hereby declare that all information in this document has been obtained and presented in accordance with academic rules and ethical conduct. I also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work. Name, Last name: Muhammad Ahmad SIDDIQUE Signature: iv ABSTRACT DESIGN OF NEW DIE HOLDER SYSTEM FOR REDUCING DIE EXCHANGE TIME ON 1000 TON HOT FORGING PRESS Siddique, Muhammad Ahmad M.S., Department of Mechanical Engineering Supervisor: Prof. Dr. Mustafa Ġlhan Gökler February 2015, 82 Pages In the forging industry, one of the main challenges is the reduction of setup change time which is non-productive time on the forging press. Long non-productive time reduces efficiency and affects profitability of the forging companies. In this thesis study, firstly setup change activities on the 1000 ton forging press of a forging company are observed and analyzed. With the help of these observations, it is seen that the new die holders with cassette holders and the new cassettes are required to reduce the setup change time radically. Different design versions of the new die holders have been studied. A new pair of die holders is designed and manufactured along with the new cassette holders and the new cassettes which hold the forging dies. The factors related to internal setup change operations, which are identified during the time and motion studies and root cause analysis, have been considered during design of the new die holder system. Several motion and time studies have been conducted to determine the average setup times for usage of new system. The average setup times for the new die holders and the previous die holders used in the particular forging company are compared and considerable reduction in setup time has been achieved. The time spent in mounting and aligning the die-cassette pairs on the die holders is significantly reduced during setup change by the help of the new die holder design. The motion and time study is concentrated on the internal setup change activities other than heating of the dies and cleaning of the forging press. By considering this way, 84% of reduction for the internal setup change time for the die holders with 2 die-sets and 62% of reduction for the internal setup change time for the die holders with 3 die-sets have been achieved on average. Keywords: Hot Forging, Die Exchange, Die Exchange Time, Die Holder v ÖZ 1000 TON SICAK DÖVME PRESĠNDE KALIP DEĞĠġTĠRME SÜRESĠNĠ AZALTMAK ÜZERE YENĠ BĠR KALIP TUTUCU SĠSTEMĠ GELĠġTĠRĠLMESĠ ĠÇĠN TASARIM Siddique, Muhammad Ahmad Yüksek Lisans, Makina Mühendisligi Bölümü Tez Yöneticisi: Prof. Dr. Mustafa Ġlhan Gökler ġubat 2015, 82 Sayfa Dövme sanayiinde en büyük zorluklardan birisi, üretim dıģı kayıp zamana yol açan kalıp sistemi değiģtirme süresinin kısaltılmasıdır. Üretim dıģı kayıp zamanın uzun olması verimliliği düģürmekte ve dövme firmalarının karlılığını etkilemektedir. Bu tez çalıģmasında ilk olarak bir dövme firmasındaki 1000 tonluk dövme presi üzerindeki kalıp sistemi değiģtirme eylemleri gözlemlenmiģ ve analiz edilmiģtir. Bu gözlemlerin yardımı ile kalıp sistemi değiģtirme süresinin temelden azaltılması için kaset tutuculu yeni kalıp tutuculara ve yeni kasetlere ihtiyaç olduğu görülmüģtür. Yeni kalıp tutucuların değiģik tasarım alternatifleri üzerinde çalıģılmıģtır. Yeni bir set kalıp tutucu yeni kaset tutucularla birlikte tasarlanmıģ ve üretilmiģtir. Gözlemler sırasında tespit edilen tüm kalıp sistemi değiģtirme ile ilgili etmenler ve kök neden analizleri, yeni kalıp tutucu sistemi tasarımında dikkate alınmıģtır. Yeni sistemin kullanımı sırasındaki ortalama kalıp sistemi değiģitirme sürelerini belirlemek üzere birçok hareket-zaman analizi çalıģması yapılmıģtır. Ortalama kalıp sistemi değiģtirme süreleri bir dövme firmasındaki mevcut kalıp tutucular ve yeni kalıp tutucular için karģılaģtırılmıģ ve kalıp sistemi değiģtirme sürelerinde kayda değer bir azalma sağlanmıģtır. Yeni kalıp tutucusu tasarımı ile kalıp-kaset çiftlerinin kalıp tutuculara bağlanması ve hizalanması sırasında harcanan zaman önemli bir Ģekilde düģürülmüģtür. Hareket-zaman analizi, kalıp sistemi değiģtirme eylemlerinden kalıpların ısıtılması ve dövme presinin temizlenmesi aģamaları dıģında olan ve pres üzerinde uygulanan eylemlere odaklanmıģtır. Bu Ģekilde düģünüldüğünde, kalıp sistemi değiģtirme sürelerinde ortalama olarak 2 kalıplı sistemlerde %84, 3 kalıplı sistemlerde %62 oranında bir azalma elde edilmiģtir. Anahtar Kelimeler: Sıcak Dövme, Kalıp DeğiĢtirme, Kalıp DeğiĢtirme Zamanı, Kalıp Tutucusu vi To my family, vii ACKNOWLEDGEMENTS I would like to express my sincere gratitude and appreciation to Professor Dr. Mustafa Ġlhan Gökler for his valuable guidance, advice, criticism and systematic supervision throughout this thesis study. Thank you for providing me with the vision and direction at times when mine was blurriest. This thesis would not have been possible without the support of AKSAN Steel Forging Company. I thank Mr. Cevat Kömürcü, Mrs. Tülay Kömürcü, Mrs. Tülin Özkan, Mr. Yakup EriĢkin, Mr. Rahmi Türkmen, Mr. Budak Erdağlı, Mr. Ġsmail Burak Çetin and Mrs. Gözde Erdoğan from AKSAN Steel Forging Company Ankara. I thank you all for your technical support regarding forging processes, access to the machines and design facilities, your valuable time and resources. During the thesis related project works at AKSAN, I have found all of the participating members as more than colleagues but rather a family like team. I wish you all the best in your future endeavors. Furthermore, I would like to extend my thanks to METU - BILTIR Research & Application Center for providing me with their facilities and resources in support of this thesis. I am forever thankful to my parents Muhammad Siddique and Fouzia Siddique for their never ending moral support, love and patience during my studies. I would also like to thank my brothers Dr. Nasir Siddique, Mr. Azhar Siddique and Dr. Talal Siddique for their encouragement and valuable advice during my graduate education and stay in Turkey. Finally, I would like to thank my very talented colleagues Meriç Uçan, Remzi Çöl, Sevgi Saraç Karadeniz, BaĢak GüneĢ Orhan, Kamil Özden, Tuğra Erol and Özhan Geçgel for their invaluable support and assistance. viii TABLE OF CONTENTS ABSTRACT...v ÖZ...vi ACKNOWLEDGMENTS...viii TABLE OF CONTENTS...ix LIST OF TABLES...xi LIST OF FIGURES...xiii CHAPTERS 1. INTRODUCTION Forging Classification of Forging by temperature Classification of Forging by type of machine used Classification of Forging by type of die set used Classification of Forging by workpiece material Forging practice in AKSAN Steel Forging Problem Statement and Previous attempt for the solutions Scope of the Thesis LITERATURE SURVEY Setup time Single Minute Exchange of Dies (SMED) Quick Change Over (QCO) Locating Principle (3-2-1) The 5S Technique OBSERVATIONS AND STUDY OF SETUP CHANGE ACTIVITIES ON 1000 TON FORGING PRESS Previous study related to setup change Motion and Time Study analyses Root cause analysis Conclusion of observations and study of setup change on the 1000 ton forging press ix 4. PROPOSED METHOD AND SOLUTIONS Currently manufactured parts on 1000 ton press in AKSAN Development of the new die holder system and cassettes Version-1 of the new die holder Version-2 of the new die holder Version-3 of the new die holder Version-4 of the new die holder Components of the new die holder assembly MANUFACTURING AND TESTING OF THE NEW DIE HOLDER Manufacturing and assembling of the die holder components Comparison of setup change times for the previous and new die holders CONCLUSIONS Discussion of results Recommendations for future studies...77 REFERENCES...79 APPENDICES A. OUTER DIMENSIONS OF THE PRODUCTS FORGED BY AKSAN STEEL FORGING x LIST OF TABLES TABLES Table 1.1 Initial data of time study of a typical part on 1000 ton forging press in AKSAN Table 3.1 Problems and solutions in setup change of 1000 ton forging press in the previous study [11] Table 3.2 Time study of setup change for Part-A, Part-B and Part-C requiring 2 die pairs...27 Table 3.3 Time study of setup change for Part-D, Part-E and Part-F requiring 3 die pairs...28 Table 3.4 Time study of setup change for Part-G, Part-H and Part-I requiring 4 die pairs...29 Table 3.5 Average setup change times...30 Table 4.1 Distribution of Non-Circular Part Geometries according to x-dimension (width) [9]...37 Table 4.2 Distribution of Non-Circular Part Geometries according to y-dimension (length) [9]...38 Table 4.3 Distribution of Circular Part Geometries according to diameter, Ø [9]...38 Table 4.4 Distribution of Circular and Non-Circular Part Geometries according to z- dimension (height) [9]...38 Table 4.5 Components of the new die holder assembly...50 Table 4.6 Materials used for major components of the new die holder assembly...61 Table 5.1 Time Study of setup change for Parts A, B and C requiring 2 die-sets in the new die holder...69 Table 5.2 Time Study of setup change for Parts D, E and F requiring 3 die-sets in the new die holder...70 Table 5.3 Time Study of setup change for Part E on the 1000 ton hot forging press by experienced and inexperienced operators using the new die holder...71 xi Table 5.4 Comparison of average values of total setup change times for parts requiring two die-sets and three die-sets during setup change for previous and new die holders...72 Table 5.5 Comparison of internal setup change times for Parts A, B and C requiring 2 die-sets using previous and the new die holders...72 Table 5.6 Comparison of internal setup change times for Parts D, E and F requiring 3 die-sets using previous and new die holders...73 Table 5.7 Comparison of average values of total internal setup change times for parts requiring two die-sets and three die-sets during setup change for previous and new die holders...73 Table A.1 The outer dimensions of the products forged by 1000 Ton Press during 2013 and 2014 in Aksan Steel Forging Company...81 xii LIST OF FIGURES FIGURES Figure 1.1 Stages in closed die forging of a connecting rod [1]...4 Figure 2.1 Single-Minute Setup (SMED): Conceptual Stage and Practical Techniques [14] Figure 2.2 Available degree of freedom of rectangular block [16]...12 Figure 2.3 Principle of locating a part by method [17]...13 Figure 2.4 The 5S cycle [18]...16 Figure 3.1 Slip problem due to horizontal misalignment [11]...17 Figure 3.2 Planar forms suggested to eliminate rotational misalignment [11]...20 Figure 3.3 Conventional cassette design currently used for mounting the dies by using shoes and bolts in die housing [11]...21 Figure 3.4 Height adjustment plates [11]...22 Figure 3.5 Use of fastening plates to fill the gap between shoes and cassettes...22 Figure 3.6 Marking for correct orientation of cassettes [11]...23 Figure 3.7 Proper positioning of the cassettes on die holder [11]...24 Figure 3.8 Sequence of setup change operations...26 Figure 3.9 Fishbone diagram for the causes of long setup time on the 1000 ton forging press...31 Figure 3.10 Sheet metal plates used between cassettes for intuitive adjustment...35 Figure 4.1 Die holder with dovetail form (Version-1)...40 Figure 4.2 Dovetail cassettes, cassette holder, and back supporting module (Version- 2)...41 Figure 4.3 Demonstration model of the Version Figure 4.4 Cassette holder with T-channels (For Version-3)...43 Figure 4.5 A view of the multiple quick acting hydraulic clamps used on the die holder (Version-3)...44 Figure 4.6 A view of the cassettes, cassette holder with T-channels, side T-slots and back support module (Version-3)...45 xiii Figure 4.7 A view of the quick acting clamp (Power Screw) on the die holder...46 Figure 4.8 A view of the wedge clamps on the die holder...46 Figure 4.9 A view of the final die holder design (Version-4)...48 Figure 4.10 A view of the mounting or dismounting the die holder assembly from anvil adapter...49 Figure 4.11 A view of the anvil adapter...51 Figure 4.12 Side rail for guiding die holder on anvil adapter Figure 4.13 A view of the lower die holder...52 Figure 4.14 A view of the back support module...52 Figure 4.15 A view of the cassette holder...53 Figure 4.16 Views of the cassettes...53 Figure 4.17 A view of the upsetting die...54 Figure 4.18 A view of the shoe for clamping cassettes...54 Figure 4.19 A view of the guide pin...55 Figure 4.20 Guide pin bushing...55 Figure 4.21 Plate for locking guide pin on lower die holder...55 Figure 4.22 Top closing flange for guide pin bushing...56 Figure 4.23 Lower die holder assembly...56 Figure 4.24 Bronze insert...57 Figure 4.25 Bushing for bronze insert...57 Figure 4.26 Top closing flange for bronze insert bushing...58 Figure 4.27 Solid model of the upper die holder...58 Figure 4.28 Upper die holder (rear view)...59 Figure 4.29 Back cover plate under bronze insert bushing...59 Figure 4.30 Solid model of the upper die holder assembly...60 Figure 4.31 Solid model of the die holders complete assembly...60 Figure 5.1 A view of the die holders...63 Figure 5.2 A view of the housing for bronze insert and the bronze insert...64 Figure 5.3 A view of the bronze insert fitted inside housing...64 Figure 5.4 A view of the guide pin bushings...65 Figure 5.5 A view of the guide pins...65 xiv Figure 5.6 A view of the cassette holders...66 Figure 5.7 A view of the fully assembled lower die holder...66 Figure 5.8 A view of the fully assembled upper die holder (rear view)...67 Figure 5.9 A view of the die holders assembled on the forging press...67 Figure 5.10 Die holders fully assembled with upper and lower die-cassette pairs on the 1000 ton hot forging press for production...68 xv CHAPTER 1 INTRODUCTION 1.1 Forging Forging is a metal forming process in which the workpiece is plastically deformed into desired shape by application of compressive forces using various dies and tooling [1]. As a result of this process, grain structure and material properties of the parts are greatly improved. Forged products are among the strongest manufactured parts when compared to other metal products [2]. Forging can be classified into four different category sets: 1. Classification of Forging by temperature as hot, cold and semi-hot (warm) forging 2. Classification of Forging by machine used as hammer, press forging, etc. 3. Classification of Forging by die-set used as open-die forging and closed-die forging 4. Classification of Forging by workpiece material as steel forging, aluminium forging, etc Classification of Forging by temperature Hot forging is the plastic deformation of the metal workpiece at a temperature above its recrystallization temperature such that strain hardening of the metal workpiece is avoided. This temperature is about 1200 C in case of steels. It is easier to achieve large plastic deformation due to high temperatures involved. However, costly heating requirements, extensive scale formation due to oxidation, low dimensional accuracy and large tolerances required for further machining are the key disadvantages of the process. Cold forging is the plastic deformation of metal at the room temperature. Precise geometries with low tolerances can be achieved during this process. Heating and material costs are saved. However the stresses developed on the dies are high in cold 1 forging due to low temperatures involved. As a result, limited geometries and volumes can be cold forged [3]. Semi-hot forging process exists between the closer tolerance and more costly cold forging process and the lower precision hot forging process. It helps to forge parts of steel alloys with close tolerances that were not possible by cold forging. The components formed are close to final shapes and have good finish compared to those formed by hot forging previously [4]. Another advantage is the reduction of flow stress and hence the forging force required compared to cold forging process [3] Classification of Forging by type of machine used Hammers operate by converting the potential energy of the ram into kinetic energy. They are energy restricted machines that work at high speeds. The short process time reduces the cooling of a hot forging part. Low cooling rates thus permit the forming of intricate profiles, especially those with thin and deep recesses. To reach the final shape, many consecutive blows may be made in the same die [1]. Mechanical presses are crank or eccentric type machines that are stroke restricted. This implies that their speed is greatest at the center of the stroke and zero at the end of the stroke. A large flywheel connected to an electric motor generates the energy required by the mechanical press. A clutch engages the flywheel to an eccentric shaft. A connecting rod translates the rotary motion into a reciprocating linear motion. The force available at a time depends on the position of the stroke and becomes extremely high at the end of the stroke. Hence, setup should be made carefully to prevent damage to the dies and tooling. There are numerous advantages of using mechanical presses over other forging machines such as high production rates, easy automation, less operator training required and high precision production of forging parts. Screw presses generate their energy from a flywheel and are therefore energy restricted machines. A large vertical screw transmits the force, and the ram comes to a halt when the flywheel energy has been dissipated. If the dies do not close at the end of the cycle, the operation is repeated until the forging is completed. Screw presses are used for 2 various open-die and closed-die forging operations. They are suitable particularly for small production quantities, especially thin parts with high precision, such as turbine blades. Hydraulic presses operate at constant speeds and are load restricted. They stop if the load required exceeds their capacity. Large amounts of energy can be transmitted to a workpiece by a constant load throughout a stroke - the speed of which can be controlled. Because forging in a hydraulic press takes longer than in the other types of forging machines, the workpiece may cool rapidly unless the dies are heated. Compared with the mechanical presses, hydraulic presses are slower and involve higher initial costs, but they require less maintenance [5] Classification of Forging by type of die set used Open-die forging involves plastic deformation of the workpiece billet between two flat plates to reduce its thickness [6]. The process is called open-die forging because the workpiece is not confined laterally by impression dies. This process is generally used to upset the initial billet or to gradually shape the starting billet into the desired
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