- Email: [email protected]
Visualized press working and new feedback control for servo press
Available online at www.sciencedirect.com Available online at www.sciencedirect.com
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Procedia Manufacturing 00 (2018) 000–000 Available online Available onlineatatwww.sciencedirect.com www.sciencedirect.com Procedia Manufacturing 00 (2018) 000–000
ScienceDirect ScienceDirect
www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Manufacturing 15 (2018) 1033–1040 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia
17th International Conference on Metal Forming, Metal Forming 2018, 16-19 September 2018, 17th International Conference on MetalToyohashi, Forming, Metal Japan Forming 2018, 16-19 September 2018, Toyohashi, Japan
Visualized press working and new feedback control for servo press Visualized working new feedback control for2017, servo press Manufacturing press Engineering Societyand International Conference 2017, MESIC 28-30 June Vigo (Pontevedra), Spain Kazuhiro Ichikawa* Chikara Murata, Yuichi2017, Hashimoto, Hiroki Sunagawa, Chikara Murata, Yuichi Hashimoto, Hiroki Sunagawa, Kazuhiro Ichikawa*
Hoden Seimitsu Kako Kenkyusho Co., Ltd, 1-39-32 Komatsubara Zama-shi, Kanagawa, 252-0002, Japan Costing models capacity in Industry 4.0: Trade-off Hoden Seimitsufor Kako Kenkyusho Co., Ltd,optimization 1-39-32 Komatsubara Zama-shi, Kanagawa, 252-0002, Japan between used capacity and operational efficiency Abstract
Abstract a a,* b b A. Santana Afonso , A.screws Zanin , R. Wernke A 4-axes direct drive servo press which has ,a P. structure using ball as boosting press pressure mechanism, has made it A 4-axes direct drive servo press which has a structure using ball screws as boosting press pressure mechanism, it possible for high precision press forming, and furthermore has made it possible to visualize processing statehas bymade digital a University of Minho, 4800-058 Guimarães, Portugal possible for high precision press forming, and furthermore has made it possible to visualize processing state by digital information from the servo press [1]. However, all information of the processing state could not be visualized from only the servo b Unochapecó, 89809-000 Chapecó, SC, Brazil information from athe servo processing press [1]. However, all developed information the processing state could not are be visualized press. Therefore, certain system was inofwhich some additional sensors installed infrom the only moldthe in servo order press. Therefore, a certain processing wasinformation developed and in which additional sensors are installed in theare mold order to measure the other processing state, system and mold press some one are combined, then those information fed in back to to measure the other processing state, for andmuch moldhigher information andproduct press one are combined, then those information are fed back to the servo press. That made it possible precision processing. the servo press. That made it possible for much higher precision product processing. Abstract © 2018 The Authors. Published by Elsevier B.V. © 2018 2018 The The Authors. Published Elsevier B.V. © Authors. Published by by B.V. committee of the 17th International Conference on Metal Forming. Peer-review responsibility of Elsevier the scientific scientific Peer-review under responsibility of the committeeprocesses of the 17th International Conference Metal Forming. Under the under concept of "Industry production be pushed to be on increasingly interconnected, Peer-review under responsibility of the4.0", scientific committee of the 17thwill International Conference on Metal Forming.
information based on a real time basis and, necessarily, much more efficient. In this context, capacity optimization Keywords: Digital servo press; Visualization; Feedback goes beyond theservo traditional aim of capacity maximization, contributing also for organization’s profitability and value. Keywords: Digital press; Visualization; Feedback Indeed, lean management and continuous improvement approaches suggest capacity optimization instead of maximization. The study of capacity optimization and costing models is an important research topic that deserves 1. Introduction 1. Introduction contributions from both the practical and theoretical perspectives. This paper presents and discusses a mathematical model for capacity management on different costing models and TDABC). A generic model been Recent years, “IoT” has been based mentioned frequently. “IoT” stands(ABC for “Internet of Things” and means thehas network Recent years, “IoT” has been mentioned frequently. “IoT” stands for “Internet of Things” and means the network developed and it was used to analyze idle capacity and to design strategies towards the maximization of organization’s system in which multiple things are connected by internet and exchange their own information. In Germany, in order system in which multiple things are connected internetofand exchangeistheir own information. In Germany, inwhich order value. The trade-off capacity vsbyoperational efficiency highlighted and shown that capacity to decrease manufacturing costmaximization drastically, digitalization manufacturing is developed as it theisnational project to decrease manufacturing cost drastically, digitalization of manufacturing is developed as the national project which optimization might hide operational inefficiency. is called “Industrie 4.0”, and in this project all about manufacturing things are tried to be communicated to exchange © 2017 The Authors. Published by B.V. is called “Industrie 4.0”, in Elsevier thiseach project allThere about has manufacturing things attempt are triedtotoincorporate be communicated their own information andand control other. also been various the ideatoofexchange the “IoT” Peer-review under responsibility of theeach scientific committee of the Manufacturing Engineering Society International their own information and control other. There has also been various attempt to incorporate the ideaConference of the in press processing industry. However as the matter of fact, it is in the grope in the dark how to incorporate this “IoT” idea 2017. in press processing industry. However as the matter of fact, it is in the grope in the dark how to incorporate thisto idea at actual site. If the idea of incorporating the “IoT” technology into the production field is expressed, it comes 1) at actual site. If the idea of incorporating the “IoT” technology into the production field is expressed, it comes to 1) Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency
1. Introduction
* Corresponding author. Tel.: +81-46-240-1922; fax: +81-46-240-1925. * E-mail Corresponding Tel.: +81-46-240-1922; fax: +81-46-240-1925. address:author. [email protected] The cost of idle capacity is a fundamental information for companies and their management of extreme importance E-mail address: [email protected]
in modern©production systems. In general, it isB.V. defined as unused capacity or production potential and can be measured 2351-9789 2018 The Authors. Published by Elsevier 2351-9789 2018 Authors. Published Elsevier B.V.hours of the in several©ways: tons of production, available manufacturing, etc.Conference The management of the idle capacity Peer-review underThe responsibility of theby scientific committee 17th International on Metal Forming. Peer-review under responsibility thefax: scientific committee * Paulo Afonso. Tel.: +351 253 510of 761; +351 253 604 741 of the 17th International Conference on Metal Forming. E-mail address: [email protected]
2351-9789 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017. 2351-9789 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 17th International Conference on Metal Forming. 10.1016/j.promfg.2018.07.390
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Chikara Murata et al. / Procedia Manufacturing 15 (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018) 000–000
finding slight changes, 2) understanding the meanings of the changes, and 3) responding rapidly. When these three phrases are applied to the press processing, it becomes possible to realize how to incorporate “IoT” into the press processing. In other words, it is thought about a certain control system which prevents products from changing by external factors. First, “finding slight changes” means that material, mold, press machine, lubrication, environment can be cited as factor of the slight changes in the press processing. It has to be thought how or by what equipment these changes could be found. Then, “understanding the meanings of the changes” means that it needs to visualize processing state. In order to visualize the processing state, it is very important term to digitize the information, and the servo press could be a proper machine to be able to meet the term. Especially 4-axes direct drive servo press which was used in developing this “IoT” system, is the most advanced press machine in digitizing, and is proper to visualize. And “responding rapidly” means that currently when the changes during the production is found, the machine would be stopped manually and some warnings from the machine would be checked to correct the changes, however when more advanced system is considered, it need to construct another system in which the machine could correct the changes and keep going on the production without any stop. In this development, a new press processing system have been constructed and in this system each product is measured automatically, the product outline and factor of the external changes are visualized, signal is sent into the servo press to correct the changes, and the machine can compensate to proper processing term. 2. Construction of 4-axes direct drive servo press, mold and control system 2.1. Construction and characteristic of 4-axes direct drive servo press In order to find the slight changes, it is desirable for press machine to move accurately and to be digitizing behavior of the press machine. 4-axes direct drive servo press which was used in this development, uses ball screws to boost press pressure mechanism, and that make a big advantage in improving machine accuracy [2]. In addition to this advantage, in this 4-axes direct drive servo press as shown in Fig. 1, 4 ball screws and 4 servo motor are equipped and 4 linear scales are deployed to measure position of the slide [3]. Using the method of controlling each axis independently makes it possible to keep the slide parallel even if the load balance collapses by eccentric load generated from the mold and also keep high precision bottom dead position even in high press pressure [4, 5]. All the state the 4 motor are being controlled are digital information, and getting these information in real-time makes it possible to visualize mold dynamic behavior which has been impossible to see, or it has been difficult to see ever before [6]. (a)
(b) Specification
Press capacity: 200kN Stroke: 200mm Slide speed: 200mm / sec Bolster dimension: 600mm × 400mm Slide dimension: 600mm × 400mm
Fig. 1. (a) Machine picture; (b) machine structural drawing.
Chikara Murata et al. / Procedia Manufacturing 15 (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018) 000–000
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2.2. Mold structure It is progressive mold for plate forging that is used in experiment. 4 sensors are installed into a mold as monitoring; a linear sensor which measures material thickness, another linear sensor which measures product thickness after the forging, thermometer which measures mold temperature, and load sensor which measures load from the forging punch. Products are produced getting information from these sensors in real time during the processing in order to compare this information with the one from the servo press. Fig. 2 shows a cross sectional view of the mold installing sensors and a processed shape.
Product cut Scrap cut
Half cut
Forming
φ8 hole punching
(b) Pilot and φ7.6 hole punching
(a)
Material: SPCC
Mold Layout Sensor detecting the load of punch
Sensor detecting the metal mold temperature
Sensor detecting product thickness
Unit: mm
Sensor detecting material thickness
Fig. 2. (a) Cross sectional view of mold installing sensors; (b) processed shape.
The most important quality item in the plate forging is thickness accuracy after the forging. As one of the factor which changes the thickness accuracy after the forging, variation of the material thickness can be cited. However when the material is purchased there is limit to management dimensions, therefore in order to have the product meet required specifications which is higher precision than the material accuracy, it needs to get this required specifications during press processing. The linear sensor has been installed, which measures the product dimension after forging, and this sensor measures the thickness of all products. If the thickness is out of the required dimension, bottom dead position will be corrected automatically, and thus the product thickness is controlled within the allowable value. However the factor the thickness after forging changes is not only the material thickness. For example, a punch temperature rises as the processing goes on. As the punch temperature rises, the punch gets longer slightly. Therefore the punch pushes more than ever under the same bottom dead position and the product thickness will get thinner. In this experiment mold, thermometer is installed in order to monitor this temperature change. Also lubrication state can be cited as another factor the product dimension changes. Material liquidity depends on the lubrication and that may changes the product thickness. If the lubrication is insufficient, the material will not transform easily, and the load on the punch will get higher. In order to measure this load on the punch alone, load cell is installed in the mold. This load cell can monitor both compressive and tensile load, therefore it can also monitor state the punch bites the material. However, how accurate these information from the sensors are depends
Chikara Murata et al. / Procedia Manufacturing 15 (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018) 000–000
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on performance of the servo press which puts the mold in motion. Therefore it needs to monitor linking information from the mold to one from the press machine. The important point in the press machine is that repeatability of bottom dead position, state of the slide inclination by reaction load from the mold, and the load which the servo press receives is needed to be monitored at the same time. In other words, in order to find the slight changes, the servo press accuracy have to be very high, the processing system have to be that information from the press machine are sent in real time, and product state is judged from the press information linking to the mold one. The slight changes measured from the inside mold would be much more trustworthy by multiple information in which the press one and the mold one are combined in this way. 2.3. Control system In this experimental control system, a computer C1 was equipped to take in the information of the slide position and the load from the servo press and the one from sensor installed in the mold, and it was attempted to visualize the information by equipping the function which shows the information from the C1 in real time. The servo press keeps moving by command from its own control system, and sends 4 position data from each linear scale and 4 servo motor torque data into the C1 every single shot. And the information from the sensor installed in the mold is sent into the C1. The C1 outputs these information in real time by display device. In this experiment, a control system was built and in the system the C1 checks whether the average of every 100 products dimension during continuous production is within ±0.005 mm from the specified range, and when the average dimension is out of the specified range, the C1 commands 0.005 mm bottom dead position compensation to the servo press. (a) (b) Communication with press machine
Servo Press
Bottom dead position
Display
Motor torque Material thickness
Communication with mold
Product thickness
C1 (Computer)
Forming load
Mold
Mold temperature Communication with outside Server cloud
Production quantity
Fig. 3. (a) Structural drawing of control system; (b) data outputted from C1.
3. Experimental result 3.1. Processing mechanism found from the sensor data The data of 1000 products in the continuous production by the mold which have been said in the preceding paragraph was analyzed. Firstly, Fig. 4 (a) shows correlation between material thickness and product one after processing. This graph shows that the material thickness do not have a big changes. Though it has several μm differences, it is guessed that it is measurement error, or the material surface characteristics at the measurement point and influence of thickness of lubricating oil film. Anyway there is not the big change in the material thickness. While, it can be seen the product thickness obviously get thinner as the production increases. This cause can be seen from Fig. 4 (b) which shows correlation between the product thickness and the mold temperature. It can be seen that along with the production increases, the mold temperature rises, and the product thickness gets thinner. Especially there is a rapid temperature change until the production reaches around 800 from the start, and there is a big change
Chikara Murata et al. / Procedia Manufacturing 15 (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018) 000–000
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in the product thickness as with the mold temperature. When the continuous production goes furthermore, the mold temperature saturates, and it is guessed that the mold temperature has less influence on the product thickness. (a) (b) 1.22
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Fig. 4. (a) Correlation between material thickness and product one after processing; (b) correlation between product thickness and mold temperature (No automatic bottom dead position correction).
At this point it has to be investigated that this is really the cause by the mold temperature. Firstly, whether accuracy of bottom dead position is uneven or not, is doubted. In order to investigate this suspicion, bottom dead position data at each corner of the slide from the linear scale are visualized along with the production increases, and that is shown in Fig. 5. This graph shows that although there is 3 μm difference at right front side of the slide from the command value 41.750 mm, it can be seen that it is about 1 μm in the repeatability of the bottom dead position along with the production increases. Therefore, it can be judged accuracy of bottom dead position is not the cause. In this way plate forging processing is greatly influenced in the quality by the slight changes such as the temperature. It is impossible to produce stable products by responding manually for this slight changes all the time. In this model mold, a function has been equipped to be able to measure the product thickness, and compensate the bottom dead position according to the change of the product thickness. Correction term is when the average of 100 product thickness is more than 5 μm from the setting based thickness, the bottom dead position is corrected automatically. 41.755
41.755 41.754
Press slide keeps parallel in high precision and repeatability of the bottom dead position is within ±1μm.
41.753
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Right back side
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Fig. 5. Command value to 4-axes of slide and fluctuation of actual measurement value (No automatic bottom dead position correction).
Chikara Murata et al. / Procedia Manufacturing 15 (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018) 000–000
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The state of the bottom dead position correction can be seen from correlation between the product thickness and the mold temperature in the Fig. 6 (a). At about 600 production which the product thickness begins to get thinner along with the mold temperature rises, first correction occurs in order that the product become thicker. After that, at about 900 production second correction occurs in order that the product become thinner conversely. In this way, the product thickness is controlled to minimize the difference from the setting based thickness all the time. Fig. 6 (b) shows how the press machine moves when these correction occurs. This graph shows the product thickness and the actual measurement data from the linear scale equipped at 4 corner of the slide. It can be seen that the bottom dead position changes at 600 and 900 production and the product thickness changes along with the positon changes. Variation is about 5μm and that means very high precision control is performed. (b) 29
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When bottom dead position is corrected, product thickness changes. 23 1000
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400 600 Product quantity
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Fig. 6. (a) Correlation between mold temperature and product one after processing; (b) correlation between 4-axes bottom dead position data and the product thickness (Automatic bottom dead position correction).
In this model mold, a sensor which measures the load at a punch for forming process is also equipped. Fig. 7 shows a correlation between the product thickness and the punch load. Although at the beginning of this experiment. It has been guessed that the punch load would have a tendency to rise along with the product thickness got thinner, this could not be seen from this model mold. This is because the indicated change in load is small for the actual change in the product thickness, which is about 5 μm, therefore it is possible to say we did not chose the proper specification sensor. However, it is thought that the load sensor also can make it possible to see the state of lubrication and unexpected load to the punch, therefore it is required sensor to see the slight changes.
Chikara Murata et al. / Procedia Manufacturing (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018)15000–000
0.91
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-1.5 Punch load -2
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0.87 Product dimension changes about 5μm though, change of punch load is not shown.
0.86
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Fig. 7. Correlation between punch load and product thickness (No automatic bottom dead position correction).
In this way, it may be a big transformation in the press processing that have made it possible to see the processing state and various changes in real time. It is desirable that these data also could be used for production management which has not been introduced for this time, and also could be used for maintenance and preventive actions of machine and mold, and evolution of the visualization could make it possible to get in the short term what technician have got experienced for the long time. 4. Conclusions A certain press processing system has been developed which feeds back the data from the sensor installed in the mold of the servo press by using a 4-axes direct drive servo press. 1) Dimension after forming could be kept within an accuracy of ±0.005 mm using the system developed for the plate forging processing. 2) This system made it possible to visualize slight changes in the press processing and predict abnormality. 3) A certain press processing system has been developed a closed loop control press processing system which feedback the information after the processing, from conventional open loop control system the machine just moves the mold. References [1] C. Murata, J. Endou, S. Futamura, Development of direct drive digital servo press, (Steel Grips-Journal and related materials-) 2, Supplement 10th Metal Forming 2004, (2004) 371–374. [2] C. Murata, T. Machira, S. Futamura, J. Endou, Intelligent control system for direct drive digital servo press, Proceeding of the 5th International Conference on Intelligent PROCEEDING AND Manufacturing of Materials, IPMM 05 (2005) CD-ROM. [3] K. Hasegawa, J. Endou, A. Inada, N. Kawachi, Effect of control of press with eccentric force, Steel Research International, Special Edition: 13th Metal Forming, 81-9 (2010) 690–693. [4] C. Murata, T. Machida, S. Futamura, J. Endou, A proposal “progressive stair die working”, (Development of direct drive digital servo press, 2nd report), Advanced Technology of Plasticity, (2005) 181–182.
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[5] K. Ichikawa, C. Murata, T. Takahashi, Nonsimultaneouse press forming using 4-axes direct drive digital servo press, Procedia Engineering, Proceedings of the 11th International Conference on Technology of Plasticity, (2014) CD-ROM. [6] C. Murata, T. Machida, S. Futamura, J. Endou, Development of direct drive digital servo press, Supplement (Proceedings of Metal Forming 2004), Steel Grips 2 (2004) 371–374.
ScienceDirect ScienceDirect
Procedia Manufacturing 00 (2018) 000–000 Available online Available onlineatatwww.sciencedirect.com www.sciencedirect.com Procedia Manufacturing 00 (2018) 000–000
ScienceDirect ScienceDirect
www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Manufacturing 15 (2018) 1033–1040 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia
17th International Conference on Metal Forming, Metal Forming 2018, 16-19 September 2018, 17th International Conference on MetalToyohashi, Forming, Metal Japan Forming 2018, 16-19 September 2018, Toyohashi, Japan
Visualized press working and new feedback control for servo press Visualized working new feedback control for2017, servo press Manufacturing press Engineering Societyand International Conference 2017, MESIC 28-30 June Vigo (Pontevedra), Spain Kazuhiro Ichikawa* Chikara Murata, Yuichi2017, Hashimoto, Hiroki Sunagawa, Chikara Murata, Yuichi Hashimoto, Hiroki Sunagawa, Kazuhiro Ichikawa*
Hoden Seimitsu Kako Kenkyusho Co., Ltd, 1-39-32 Komatsubara Zama-shi, Kanagawa, 252-0002, Japan Costing models capacity in Industry 4.0: Trade-off Hoden Seimitsufor Kako Kenkyusho Co., Ltd,optimization 1-39-32 Komatsubara Zama-shi, Kanagawa, 252-0002, Japan between used capacity and operational efficiency Abstract
Abstract a a,* b b A. Santana Afonso , A.screws Zanin , R. Wernke A 4-axes direct drive servo press which has ,a P. structure using ball as boosting press pressure mechanism, has made it A 4-axes direct drive servo press which has a structure using ball screws as boosting press pressure mechanism, it possible for high precision press forming, and furthermore has made it possible to visualize processing statehas bymade digital a University of Minho, 4800-058 Guimarães, Portugal possible for high precision press forming, and furthermore has made it possible to visualize processing state by digital information from the servo press [1]. However, all information of the processing state could not be visualized from only the servo b Unochapecó, 89809-000 Chapecó, SC, Brazil information from athe servo processing press [1]. However, all developed information the processing state could not are be visualized press. Therefore, certain system was inofwhich some additional sensors installed infrom the only moldthe in servo order press. Therefore, a certain processing wasinformation developed and in which additional sensors are installed in theare mold order to measure the other processing state, system and mold press some one are combined, then those information fed in back to to measure the other processing state, for andmuch moldhigher information andproduct press one are combined, then those information are fed back to the servo press. That made it possible precision processing. the servo press. That made it possible for much higher precision product processing. Abstract © 2018 The Authors. Published by Elsevier B.V. © 2018 2018 The The Authors. Published Elsevier B.V. © Authors. Published by by B.V. committee of the 17th International Conference on Metal Forming. Peer-review responsibility of Elsevier the scientific scientific Peer-review under responsibility of the committeeprocesses of the 17th International Conference Metal Forming. Under the under concept of "Industry production be pushed to be on increasingly interconnected, Peer-review under responsibility of the4.0", scientific committee of the 17thwill International Conference on Metal Forming.
information based on a real time basis and, necessarily, much more efficient. In this context, capacity optimization Keywords: Digital servo press; Visualization; Feedback goes beyond theservo traditional aim of capacity maximization, contributing also for organization’s profitability and value. Keywords: Digital press; Visualization; Feedback Indeed, lean management and continuous improvement approaches suggest capacity optimization instead of maximization. The study of capacity optimization and costing models is an important research topic that deserves 1. Introduction 1. Introduction contributions from both the practical and theoretical perspectives. This paper presents and discusses a mathematical model for capacity management on different costing models and TDABC). A generic model been Recent years, “IoT” has been based mentioned frequently. “IoT” stands(ABC for “Internet of Things” and means thehas network Recent years, “IoT” has been mentioned frequently. “IoT” stands for “Internet of Things” and means the network developed and it was used to analyze idle capacity and to design strategies towards the maximization of organization’s system in which multiple things are connected by internet and exchange their own information. In Germany, in order system in which multiple things are connected internetofand exchangeistheir own information. In Germany, inwhich order value. The trade-off capacity vsbyoperational efficiency highlighted and shown that capacity to decrease manufacturing costmaximization drastically, digitalization manufacturing is developed as it theisnational project to decrease manufacturing cost drastically, digitalization of manufacturing is developed as the national project which optimization might hide operational inefficiency. is called “Industrie 4.0”, and in this project all about manufacturing things are tried to be communicated to exchange © 2017 The Authors. Published by B.V. is called “Industrie 4.0”, in Elsevier thiseach project allThere about has manufacturing things attempt are triedtotoincorporate be communicated their own information andand control other. also been various the ideatoofexchange the “IoT” Peer-review under responsibility of theeach scientific committee of the Manufacturing Engineering Society International their own information and control other. There has also been various attempt to incorporate the ideaConference of the in press processing industry. However as the matter of fact, it is in the grope in the dark how to incorporate this “IoT” idea 2017. in press processing industry. However as the matter of fact, it is in the grope in the dark how to incorporate thisto idea at actual site. If the idea of incorporating the “IoT” technology into the production field is expressed, it comes 1) at actual site. If the idea of incorporating the “IoT” technology into the production field is expressed, it comes to 1) Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency
1. Introduction
* Corresponding author. Tel.: +81-46-240-1922; fax: +81-46-240-1925. * E-mail Corresponding Tel.: +81-46-240-1922; fax: +81-46-240-1925. address:author. [email protected] The cost of idle capacity is a fundamental information for companies and their management of extreme importance E-mail address: [email protected]
in modern©production systems. In general, it isB.V. defined as unused capacity or production potential and can be measured 2351-9789 2018 The Authors. Published by Elsevier 2351-9789 2018 Authors. Published Elsevier B.V.hours of the in several©ways: tons of production, available manufacturing, etc.Conference The management of the idle capacity Peer-review underThe responsibility of theby scientific committee 17th International on Metal Forming. Peer-review under responsibility thefax: scientific committee * Paulo Afonso. Tel.: +351 253 510of 761; +351 253 604 741 of the 17th International Conference on Metal Forming. E-mail address: [email protected]
2351-9789 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017. 2351-9789 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 17th International Conference on Metal Forming. 10.1016/j.promfg.2018.07.390
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Chikara Murata et al. / Procedia Manufacturing 15 (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018) 000–000
finding slight changes, 2) understanding the meanings of the changes, and 3) responding rapidly. When these three phrases are applied to the press processing, it becomes possible to realize how to incorporate “IoT” into the press processing. In other words, it is thought about a certain control system which prevents products from changing by external factors. First, “finding slight changes” means that material, mold, press machine, lubrication, environment can be cited as factor of the slight changes in the press processing. It has to be thought how or by what equipment these changes could be found. Then, “understanding the meanings of the changes” means that it needs to visualize processing state. In order to visualize the processing state, it is very important term to digitize the information, and the servo press could be a proper machine to be able to meet the term. Especially 4-axes direct drive servo press which was used in developing this “IoT” system, is the most advanced press machine in digitizing, and is proper to visualize. And “responding rapidly” means that currently when the changes during the production is found, the machine would be stopped manually and some warnings from the machine would be checked to correct the changes, however when more advanced system is considered, it need to construct another system in which the machine could correct the changes and keep going on the production without any stop. In this development, a new press processing system have been constructed and in this system each product is measured automatically, the product outline and factor of the external changes are visualized, signal is sent into the servo press to correct the changes, and the machine can compensate to proper processing term. 2. Construction of 4-axes direct drive servo press, mold and control system 2.1. Construction and characteristic of 4-axes direct drive servo press In order to find the slight changes, it is desirable for press machine to move accurately and to be digitizing behavior of the press machine. 4-axes direct drive servo press which was used in this development, uses ball screws to boost press pressure mechanism, and that make a big advantage in improving machine accuracy [2]. In addition to this advantage, in this 4-axes direct drive servo press as shown in Fig. 1, 4 ball screws and 4 servo motor are equipped and 4 linear scales are deployed to measure position of the slide [3]. Using the method of controlling each axis independently makes it possible to keep the slide parallel even if the load balance collapses by eccentric load generated from the mold and also keep high precision bottom dead position even in high press pressure [4, 5]. All the state the 4 motor are being controlled are digital information, and getting these information in real-time makes it possible to visualize mold dynamic behavior which has been impossible to see, or it has been difficult to see ever before [6]. (a)
(b) Specification
Press capacity: 200kN Stroke: 200mm Slide speed: 200mm / sec Bolster dimension: 600mm × 400mm Slide dimension: 600mm × 400mm
Fig. 1. (a) Machine picture; (b) machine structural drawing.
Chikara Murata et al. / Procedia Manufacturing 15 (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018) 000–000
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2.2. Mold structure It is progressive mold for plate forging that is used in experiment. 4 sensors are installed into a mold as monitoring; a linear sensor which measures material thickness, another linear sensor which measures product thickness after the forging, thermometer which measures mold temperature, and load sensor which measures load from the forging punch. Products are produced getting information from these sensors in real time during the processing in order to compare this information with the one from the servo press. Fig. 2 shows a cross sectional view of the mold installing sensors and a processed shape.
Product cut Scrap cut
Half cut
Forming
φ8 hole punching
(b) Pilot and φ7.6 hole punching
(a)
Material: SPCC
Mold Layout Sensor detecting the load of punch
Sensor detecting the metal mold temperature
Sensor detecting product thickness
Unit: mm
Sensor detecting material thickness
Fig. 2. (a) Cross sectional view of mold installing sensors; (b) processed shape.
The most important quality item in the plate forging is thickness accuracy after the forging. As one of the factor which changes the thickness accuracy after the forging, variation of the material thickness can be cited. However when the material is purchased there is limit to management dimensions, therefore in order to have the product meet required specifications which is higher precision than the material accuracy, it needs to get this required specifications during press processing. The linear sensor has been installed, which measures the product dimension after forging, and this sensor measures the thickness of all products. If the thickness is out of the required dimension, bottom dead position will be corrected automatically, and thus the product thickness is controlled within the allowable value. However the factor the thickness after forging changes is not only the material thickness. For example, a punch temperature rises as the processing goes on. As the punch temperature rises, the punch gets longer slightly. Therefore the punch pushes more than ever under the same bottom dead position and the product thickness will get thinner. In this experiment mold, thermometer is installed in order to monitor this temperature change. Also lubrication state can be cited as another factor the product dimension changes. Material liquidity depends on the lubrication and that may changes the product thickness. If the lubrication is insufficient, the material will not transform easily, and the load on the punch will get higher. In order to measure this load on the punch alone, load cell is installed in the mold. This load cell can monitor both compressive and tensile load, therefore it can also monitor state the punch bites the material. However, how accurate these information from the sensors are depends
Chikara Murata et al. / Procedia Manufacturing 15 (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018) 000–000
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on performance of the servo press which puts the mold in motion. Therefore it needs to monitor linking information from the mold to one from the press machine. The important point in the press machine is that repeatability of bottom dead position, state of the slide inclination by reaction load from the mold, and the load which the servo press receives is needed to be monitored at the same time. In other words, in order to find the slight changes, the servo press accuracy have to be very high, the processing system have to be that information from the press machine are sent in real time, and product state is judged from the press information linking to the mold one. The slight changes measured from the inside mold would be much more trustworthy by multiple information in which the press one and the mold one are combined in this way. 2.3. Control system In this experimental control system, a computer C1 was equipped to take in the information of the slide position and the load from the servo press and the one from sensor installed in the mold, and it was attempted to visualize the information by equipping the function which shows the information from the C1 in real time. The servo press keeps moving by command from its own control system, and sends 4 position data from each linear scale and 4 servo motor torque data into the C1 every single shot. And the information from the sensor installed in the mold is sent into the C1. The C1 outputs these information in real time by display device. In this experiment, a control system was built and in the system the C1 checks whether the average of every 100 products dimension during continuous production is within ±0.005 mm from the specified range, and when the average dimension is out of the specified range, the C1 commands 0.005 mm bottom dead position compensation to the servo press. (a) (b) Communication with press machine
Servo Press
Bottom dead position
Display
Motor torque Material thickness
Communication with mold
Product thickness
C1 (Computer)
Forming load
Mold
Mold temperature Communication with outside Server cloud
Production quantity
Fig. 3. (a) Structural drawing of control system; (b) data outputted from C1.
3. Experimental result 3.1. Processing mechanism found from the sensor data The data of 1000 products in the continuous production by the mold which have been said in the preceding paragraph was analyzed. Firstly, Fig. 4 (a) shows correlation between material thickness and product one after processing. This graph shows that the material thickness do not have a big changes. Though it has several μm differences, it is guessed that it is measurement error, or the material surface characteristics at the measurement point and influence of thickness of lubricating oil film. Anyway there is not the big change in the material thickness. While, it can be seen the product thickness obviously get thinner as the production increases. This cause can be seen from Fig. 4 (b) which shows correlation between the product thickness and the mold temperature. It can be seen that along with the production increases, the mold temperature rises, and the product thickness gets thinner. Especially there is a rapid temperature change until the production reaches around 800 from the start, and there is a big change
Chikara Murata et al. / Procedia Manufacturing 15 (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018) 000–000
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in the product thickness as with the mold temperature. When the continuous production goes furthermore, the mold temperature saturates, and it is guessed that the mold temperature has less influence on the product thickness. (a) (b) 1.22
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Fig. 4. (a) Correlation between material thickness and product one after processing; (b) correlation between product thickness and mold temperature (No automatic bottom dead position correction).
At this point it has to be investigated that this is really the cause by the mold temperature. Firstly, whether accuracy of bottom dead position is uneven or not, is doubted. In order to investigate this suspicion, bottom dead position data at each corner of the slide from the linear scale are visualized along with the production increases, and that is shown in Fig. 5. This graph shows that although there is 3 μm difference at right front side of the slide from the command value 41.750 mm, it can be seen that it is about 1 μm in the repeatability of the bottom dead position along with the production increases. Therefore, it can be judged accuracy of bottom dead position is not the cause. In this way plate forging processing is greatly influenced in the quality by the slight changes such as the temperature. It is impossible to produce stable products by responding manually for this slight changes all the time. In this model mold, a function has been equipped to be able to measure the product thickness, and compensate the bottom dead position according to the change of the product thickness. Correction term is when the average of 100 product thickness is more than 5 μm from the setting based thickness, the bottom dead position is corrected automatically. 41.755
41.755 41.754
Press slide keeps parallel in high precision and repeatability of the bottom dead position is within ±1μm.
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Right back side
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Fig. 5. Command value to 4-axes of slide and fluctuation of actual measurement value (No automatic bottom dead position correction).
Chikara Murata et al. / Procedia Manufacturing 15 (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018) 000–000
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The state of the bottom dead position correction can be seen from correlation between the product thickness and the mold temperature in the Fig. 6 (a). At about 600 production which the product thickness begins to get thinner along with the mold temperature rises, first correction occurs in order that the product become thicker. After that, at about 900 production second correction occurs in order that the product become thinner conversely. In this way, the product thickness is controlled to minimize the difference from the setting based thickness all the time. Fig. 6 (b) shows how the press machine moves when these correction occurs. This graph shows the product thickness and the actual measurement data from the linear scale equipped at 4 corner of the slide. It can be seen that the bottom dead position changes at 600 and 900 production and the product thickness changes along with the positon changes. Variation is about 5μm and that means very high precision control is performed. (b) 29
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41.73
When bottom dead position is corrected, product thickness changes. 23 1000
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400 600 Product quantity
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Fig. 6. (a) Correlation between mold temperature and product one after processing; (b) correlation between 4-axes bottom dead position data and the product thickness (Automatic bottom dead position correction).
In this model mold, a sensor which measures the load at a punch for forming process is also equipped. Fig. 7 shows a correlation between the product thickness and the punch load. Although at the beginning of this experiment. It has been guessed that the punch load would have a tendency to rise along with the product thickness got thinner, this could not be seen from this model mold. This is because the indicated change in load is small for the actual change in the product thickness, which is about 5 μm, therefore it is possible to say we did not chose the proper specification sensor. However, it is thought that the load sensor also can make it possible to see the state of lubrication and unexpected load to the punch, therefore it is required sensor to see the slight changes.
Chikara Murata et al. / Procedia Manufacturing (2018) 1033–1040 Author name / Procedia Manufacturing 00 (2018)15000–000
0.91
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-1.5 Punch load -2
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-3
0.87 Product dimension changes about 5μm though, change of punch load is not shown.
0.86
0.85
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600 Product quantity
800
-3.5
-4 1000
Fig. 7. Correlation between punch load and product thickness (No automatic bottom dead position correction).
In this way, it may be a big transformation in the press processing that have made it possible to see the processing state and various changes in real time. It is desirable that these data also could be used for production management which has not been introduced for this time, and also could be used for maintenance and preventive actions of machine and mold, and evolution of the visualization could make it possible to get in the short term what technician have got experienced for the long time. 4. Conclusions A certain press processing system has been developed which feeds back the data from the sensor installed in the mold of the servo press by using a 4-axes direct drive servo press. 1) Dimension after forming could be kept within an accuracy of ±0.005 mm using the system developed for the plate forging processing. 2) This system made it possible to visualize slight changes in the press processing and predict abnormality. 3) A certain press processing system has been developed a closed loop control press processing system which feedback the information after the processing, from conventional open loop control system the machine just moves the mold. References [1] C. Murata, J. Endou, S. Futamura, Development of direct drive digital servo press, (Steel Grips-Journal and related materials-) 2, Supplement 10th Metal Forming 2004, (2004) 371–374. [2] C. Murata, T. Machira, S. Futamura, J. Endou, Intelligent control system for direct drive digital servo press, Proceeding of the 5th International Conference on Intelligent PROCEEDING AND Manufacturing of Materials, IPMM 05 (2005) CD-ROM. [3] K. Hasegawa, J. Endou, A. Inada, N. Kawachi, Effect of control of press with eccentric force, Steel Research International, Special Edition: 13th Metal Forming, 81-9 (2010) 690–693. [4] C. Murata, T. Machida, S. Futamura, J. Endou, A proposal “progressive stair die working”, (Development of direct drive digital servo press, 2nd report), Advanced Technology of Plasticity, (2005) 181–182.
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[5] K. Ichikawa, C. Murata, T. Takahashi, Nonsimultaneouse press forming using 4-axes direct drive digital servo press, Procedia Engineering, Proceedings of the 11th International Conference on Technology of Plasticity, (2014) CD-ROM. [6] C. Murata, T. Machida, S. Futamura, J. Endou, Development of direct drive digital servo press, Supplement (Proceedings of Metal Forming 2004), Steel Grips 2 (2004) 371–374.