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Monitoring of process and tool status in forging process by using bolt type piezo-sensor
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Procedia Manufacturing 00 (2018) 000–000 Available online atatwww.sciencedirect.com Available www.sciencedirect.com Procedia online Manufacturing 00 (2018) 000–000
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www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Manufacturing 15 (2018) 542–549 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
Monitoring of process and tool status in forging process by using
MonitoringEngineering of process and tool status in forging process by28-30 using Manufacturing Society Conference 2017, MESIC 2017, June bolt International type(Pontevedra), piezo-sensor 2017, Vigo Spain bolt type piezo-sensor Soo-Young Kim*, Akifumi Ebina, Asuka Sano, Satoshi Kubota Costing models forKim*, capacity optimization in Industry 4.0: Trade-off Soo-Young Akifumi Ebina, Asuka Sano, Satoshi Kubota Yamanaka Eng, Co., 2-11-2 Osaku, Sakura, Chiba, 285-0802 Japan between Yamanaka used Eng, capacity andSakura, operational efficiency Co., 2-11-2 Osaku, Chiba, 285-0802 Japan Abstract A. Santanaa, P. Afonsoa,*, A. Zaninb, R. Wernkeb Abstract a The objective of this study is to introduce the new possibility of sensing technology University of Minho, 4800-058 Guimarães, Portugal based on the bolt type piezo-sensor to The objective of this is to and introduce thethe new possibility ofChapecó, sensing technology on the bolt type piezo-sensor to monitor the status of study workpiece tools bUnochapecó, in forging process. In order toBrazil validatebased the effectiveness of proposed sensing 89809-000 SC, monitor the the status workpiece and and toolsdesignated in the forging process.system In order to applied validateinto theaeffectiveness proposed sensing technology, boltof type piezo-sensor measurement were typical closedofforging die-set used technology, the bolt type piezo-sensor and designated measurement werethe applied into piezo-sensor a typical closed forging die-set used for the manufacturing of precision automotive part. The locations tosystem implement bolt type were selected carefully for the manufacturing of based precision The locations to implement the bolt type piezo-sensor selected carefully by the design engineers on automotive their designpart. know-how to obtain the necessary information to satisfy were the desired purpose of Abstract by the design engineers based their designresults know-how obtain thechange necessary information to satisfy desired purpose of process monitoring. From the on measurement of thetobolt force during one forging cycle, the it was found that the process results of the to bolt force change during behaviors one forging cycle, and it was found the proposedmonitoring. monitoring From systemthe canmeasurement provide useful information understand the detailed of die-set tools in thethat closed proposed monitoring can provide useful informationprocesses to understand behaviors die-set and tools in the closed Under the conceptsystem of "Industry 4.0", production willthebedetailed pushed to be of increasingly interconnected, die forging process. die forging process. information based on a real time basis and, necessarily, much more efficient. In this context, capacity optimization © 2018 The Authors. Published by of Elsevier B.V.maximization, contributing also for organization’s profitability and value. goes beyond the traditional aim capacity © 2018 2018 The The Authors. Published by Elsevier B.V. B.V. © Authors. Publishedand by Elsevier Peer-review under responsibility of the scientific committee ofthe the17th 17th International Conference onMetal Metal Forming. instead of Indeed, lean management continuous improvement approaches suggest capacity optimization Peer-review under responsibility of the scientific committee of International Conference on Forming. Peer-review under responsibility of the scientific committee the 17thmodels International Metal Forming. maximization. The study of capacity optimization andofcosting is anConference important on research topic that deserves
Keywords: Bolt type piezo-sensor; Process monitoring; Tool status monitoring; Forging process; Closed-die forging contributions from both the practical and theoretical perspectives. This paper presents and discusses a mathematical Keywords: Bolt type piezo-sensor; Process monitoring; Tool status monitoring; Forging process; Closed-die forging model for capacity management based on different costing models (ABC and TDABC). A generic model has been developed and it was used to analyze idle capacity and to design strategies towards the maximization of organization’s 1. Introduction value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity 1. Introduction optimization might hide operational inefficiency. The sensing technology has been focused in these days as one of the key technologies for new trend of © 2017 Authors. Published by Elsevier B.V. The The sensing technology hasas been (Internet focused in days as one of the technologies for trend the of manufacturing such of these Things) or Industrie4.0 [1].key How to visualize andnew quantify Peer-review underindustries responsibility of theIoT scientific committee of the Manufacturing Engineering Society International Conference manufacturing industries such as IoT (Internet of Things) or Industrie4.0 [1]. How to visualize and quantify the process status to detect the abnormal behavior efficiently during the process has been an important issue for the shop 2017. process status toindetect the abnormal behavior efficiently the process has been an important for the shop floor engineers manufacturing industry. Especially in during the forging industries, the monitoring andissue management of floor engineers in manufacturing industry. Especially in the forging industries, the monitoring and management of Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency
1. Introduction
* Corresponding author. Tel.: +81-43-498-3492; fax: +81-43-481-5100. * E-mail Corresponding Tel.: +81-43-498-3492; fax: +81-43-481-5100. 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 Peer-review underThe responsibility of theby scientific committee 17th International on Metal Forming. in several©ways: tons of production, available manufacturing, etc.Conference The management of the idle capacity 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.2018.07.275
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Soo-Young Kim et al. / Procedia Manufacturing 15 (2018) 542–549 Author name / Procedia Manufacturing 00 (2018) 000–000
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tool status is one of most important issues in quality control and productivity of forging process. In general, the abnormal behaviors of forging tools are closely related with the quality trouble of forged product since the tools including dies and punches are directly contacted with the workpiece during forging process. Also in terms of productivity, it is not difficult to image the serious decrease of production efficiency in forging process caused by the abrupt termination of process due to unexpected tool failure. Most usual method applied to confirm the tool status is the visual inspection during the process maintenance occurred periodically in the mass production. It is a traditional and effective method to detect any abnormality of forging tools but still it is difficult to determine the adequate period for inspection and to evaluate the inspection result quantitatively. Several practical monitoring solutions for parts forming machines have been developed and introduced already as referred in the publication by Faulhaber et al. [2]. In these solutions, the forming load in each forging stand were measured by implementing piezo-electrical pressure sensor to the inside parts of forming machine. The abnormal status of process could be detected by recognizing the change of forming load comparing with the normal status. Also, various sensors and monitoring systems have been widely applied in the sheet metal forming and stamping industries. In general forging processes using the press machines, the quality control of product and management of tool status are still based on human senses and skills such as visual observation. In the present study, new possibility of sensing technology to monitor the status of forging process and tools was proposed. The main objective of the investigation is to evaluate and validate the effectiveness of proposed sensing technology in the practical forging process. A typical closed die forging die-set was re-designed to have a monitoring ability using the bolt type piezo-sensors. Several test measurements were carried out to analyze the tool status during the forging process. Designated measurement system
Bolt type piezo-sensor
Touch panel interface
(Front view)
Active/Deactivate switch
Wire type linear sensor
(Rear view)
Channel box
Signal processing unit
Fig. 1. Exterior of bolt type piezo-sensor and designated measurement system used in this study. Process monitoring Warning
Bolt Force
Warning
Designated Measurement System Cur. Ref. Dif.
Bolt type load sensor
Stop Time or Stroke
Feed-back control
Fig. 2. Typical concept of process monitoring in forging process using bolt type piezo-sensor.
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2. Sensor and measurement system The sensor used in the current study is a bolt type piezo-sensor based on the “Sensoric Fastener” technology proposed by Groche and Brenneis in Technical University of Darmstadt [3]. Fig. 1 shows the exterior of bolt type piezo-sensor and measurement system used in this study. The bolt type load sensor “PiezoBolt” is a piezo-electric load sensor developed by ConSenses GmbH [4] and can be applied to the conventional mass-production environment of manufacturing processes easily by replacing the existing bolt in assembly structure to the bolt type piezo-sensor. It provides highly reliable and sensitive sensing environment to measure the change of local bolt force in the repeated manufacturing process. The designated measurement system “ProductionSenses” can measure the signals from 8 different bolt sensors simultaneously. The signals can be synchronized based on the reference signal obtained from the wire-type linear sensor measuring the distance between upper and lower die plates. Fig. 2 explains the concept of process monitoring presented in this study. The bolt type piezo-sensor is applied to the die-set and tools for the forging process. Adequate location of bolt replacement is chosen carefully considering the purpose of measurement and the abnormal behaviors that want to be detected during the process. The force follow-up ability between the bolt force change and the major loading component related with monitoring parameter is the most important factor in this choice. In the manufacturing process, the measured sensor signal is compared with reference signal obtained during the normal process status. Then, the abnormal status can be detected easily by just analyzing the difference between two signals. If any feed-back control scheme is applied to the measurement chain, adequate process control to avoid any abnormal status becomes possible with relatively simple modifications of manufacturing facility. The typical abnormal patterns according to various defect types are depicted in Fig. 3. The defects directly related with forming load such as under-filling can be detected by applying the bolt type piezosensor to the place receiving the forming load. Unbalance of process such as eccentricity of product or unrequired thrust force can be recognized from the change of balance between the signals from multiple bolt sensors distributed circumferential direction. Also, the indication of seizer defect and fatigue failure, which are two representative tool failure patterns in cold forging process, can be visualized by detecting the abnormal increase of knock-out force during ejection of workpiece and the shock reaction force occurring at crack generation, respectively.
KO pin Stroke
S1
OK NG
S1 Crack generation
Stroke of KO pin
Bolt force
S1
OK NG
Tool failures Detection of impact load by crack generation
Seizure / frictional defect Increase of friction force
Bolt force
S2
Bolt fore2 Bolt force1
Eccentricity / unbalance Change of load balance
OK NG
Stroke
Fig. 3. Several patterns of bolt force change with respect to various abnormal behaviors occurred in forging process.
3. Experimental conditions In the present study, these sensors and measurement system was applied to the closed-die forging process to monitor the status of tools and die-set during the forging process. Fig. 4 shows the image of closed-die forging process applied in this study since the real process details cannot be opened in public because it contains the confidential information. Initial blank
Closed-die forging equipment
Product
Fig. 4. Image of closed forging die-set and typical forging product.
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Synchronizing pin Timing of synchronization Failure of synchronizing pin [PB08-05] Ring type monitoring device Elastic deformation of tool Crack generation Ring type monitoring device [PB08-06 ~ PB08-07]
Front Front [PB12-05]
[PB12-01 ~ PB12-04]
M42 bolt Balance of die-closing force
Die spacer bolts Balance of die-closing force KO force monitoring
[PB12-06 ~ PB12-09]
[PB08-01 ~ PB08-04]
Guideposts & Sub-guideposts Irregular motion of die-set Prediction of seizure defect
Fig. 5. Locations of bolt type piezo-sensors implemented in closed forging die-set used in this study. Table 1. Major specifications of bolt type piezo-sensors used in this study. Code
Serial No.
Bolt size
Length (mm)
Piezoelectric coefficient (pC/N)
Implemented position
PB08-01
PB08YxK6
M8
42
4.883
Sub-guidepost (Back side 1)
PB08-02
PB08YxA17
M8
42
7.313
Sub-guidepost (Back side 2)
PB08-03
PB08YxK4
M8
42
5.295
Sub-guidepost (Front side 1)
PB08-04
PB08YxK5
M8
42
5.894
Sub-guidepost (Front side 2)
PB08-05
PB08YxAx006 M8
55
7.276
Synchronizing pin
PB08-06
PB08YxAx008 M8
55
7.276
Ring type monitoring device (Upper)
PB08-07
PB08YxAx007 M8
55
8.057
Ring type monitoring device (Lower)
PB12-01
PB12YxAx026 M12
75
3.870
Die spacer (Upper 1)
PB12-02
PB12YxAx027 M12
75
3.197
Die spacer (Upper 2)
PB12-03
PB12YxAx024 M12
75
3.115
Die spacer (Lower 1)
PB12-04
PB12YxAx025 M12
75
1.994
Die spacer (Lower 2)
PB12-05
PB12YxAx030 M12
110
2.704
M42 bolt
PB12-06
PB12YxAx009 M12
65
2.719
Guidepost (Back side 1)
PB12-07
PB12YxAx010 M12
65
2.725
Guidepost (Back side 2)
PB12-08
PB12YxAx011 M12
65
2.078
Guidepost (Front side 1)
PB12-09
PB12YxAx012 M12
65
2.851
Guidepost (Front side 2)
The location of sensors and the major objective of monitoring in each sensor are explained in Fig. 5. Four sensors (PB12-01 ~ PB12-04) were applied to the inside of the die spacers in upper and lower closed-dies to visualize the behaviors related with the closing die force and forming load. Also, for the same purpose, another additional sensor (PB12-05) was implemented to the inside of M42 bolt located at the bottom die plate. To understand the behavior of sub-guideposts during the forming process, four M8 size bolt sensors (PB08-01 ~ PB08-04) were applied to two sub-guideposts located at the front and back sides. On the other hand, four M12 size bolt sensors (PB12-06 ~ PB1209) were implemented to the guideposts located at the front and back sides to detect the defects such as seizure or abnormal deflection. To monitor the status of synchronization between upper and lower closing die plates, a M8
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sized bolt sensor (PB08-05) was applied to the synchronizing pin. Finally, two ring type monitoring devices implementing M8 sized bolt sensor (PB08-06 and PB08-07) were applied to the outside of upper and lower dies, respectively, to monitor any abnormal behavior of product and tools such as under-fill of workpiece or crack generation of tool. The concept of ring type monitoring device is referred in the publication [5]. The signals measured from the ring type monitoring device clearly shows the abnormal curve patterns caused by the impulsive load pattern generated due to the crack generation. The detailed specifications of sensors used in this study are listed in Table 1. Each sensor has its own piezoelectric coefficient obtained from calibration test carried out individually. Table 2. Test forging conditions applied in experiment.
Synchronizing pin
Ring type monitoring device
Guidepost
Subguidepost
Wire type linear sensor
Fig. 6. Exterior of closed forging die-set.
Condition name
Forging condition
Channel combination*
N
Normal-1
Normal
Pattern 1
30
Normal-2
Normal
Pattern 2
30
Normal-3
Normal
Pattern 3
5
Irregular-A
(A) Blank temperature: RT
Pattern 2
3
Irregular-B
(B) Blank length: 1.3% shorter
Pattern 2
3
* Channel combinations Pattern 1: PB12-03, PB12-05, PB08-03, PB08-04, PB12-08, PB12-09, PB08-05, PB08-07 Pattern 2: PB12-01, PB12-02, PB12-03, PB12-04, PB08-06, PB08-07 Pattern 3: PB08-01, PB08-02, PB08-03, PB08-04, PB12-06, PB12-07, PB12-08, PB12-09
The developed die-set for the current closed-die forging process and the measurement system used for the experiment are depicted in Fig. 6. Due to the limitation in the number of channels (maximum 8) of the measurement system, several experiments were planned as listed in Table. 2. Three types of channel combination were applied in the experiments. The channel combination pattern 1 is using 8 bolt sensors selected from entire measurement locations to confirm the overall response. The channel combination pattern 2 is composed of 6 sensors selected from the die spacers and the ring type monitoring devices located at upper and lower dies. In the channel combination patterns 3, the sensors implemented at the sub and guideposts are monitored. The measurements were carried out under normal process condition (N = 30 for channel patterns 1 and 2, N = 5 for channel pattern 3). To confirm the detect ability of monitoring system, additional forging try was carried out under two irregular process conditions descripted below (N = 3 per each condition): • Condition (A): Initial temperature of blank is changed to room temperature (200 0C in normal condition) • Condition (B): Length of blank becomes 1.3% shorter comparing with normal condition The sampling rate was 1 kHz for all measurement conditions and the stroke range for data measurement was set to 150 mm from the bottom dead center of the press machine. The stroke of press was measured using the wire type linear sensor as shown in Fig. 1. 4. Result The changes of bolt force in the upper and lower die spacers are shown in Fig. 7. The average and min/max curves obtained from measured data of 30 forging shots are plotted in each graph. The measured results show that all sensors in this location undergo the compressive force during the process. It clearly shows the compressive load from the hydraulic equipment for closing upper and lower dies. The maximum compressive force appeared at the bottom dead center of the press machine. Based on the average data, the maximum compressive forces of sensors are -3.6 and -5.3 kN in the upper die spacer and -4.2 and -4.3 kN in the lower die spacer, respectively. The deviation of the measured data is ranged from 11% to 20%. The information obtained from these results can be useful to understand the variation of total die closing force and the local balance of loading status in upper and lower dies.
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The bolt force change of ring type monitoring devices is shown in Fig. 8. As same as the previous figure, three curves (average, minimum, and maximum) are plotted using the measured data of 30 forging shots in each graph. The deviation between minimum and maximum data is small comparing with the deviation shown in Fig. 7. The change of bolt force directly reflects the elastic deformation behavior of die in radial direction reacting with the initial die-closing, upsetting, and radial extruding status.
Fig. 7. Measured bolt force changes in upper and lower die spacers.
Fig. 8. Measured bolt force changes of ring type monitoring device in upper and lower dies.
Fig. 9. Measured bolt force changes in guideposts.
Figs. 9 and 10 show the change of bolt forces located in the guideposts and sub-guideposts, respectively, measured during three forging shots. In all cases, two sensors implemented in one guidepost show the opposite tendency – a typical behavior of bolts undergoing bending loading condition of the guidepost. The behavior of subguidepost is more complex since it contains the effect of elastic deformation of dies during forming process. These results can be used effectively to detect any signal of seizure defect between guidepost and bush by confirming the rapid increase of bolt forces.
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Soo-Young Kim et al. / Procedia Manufacturing 15 (2018) 542–549 Author name / Procedia Manufacturing 00 (2018) 000–000
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Fig. 10. Measured bolt force changes in sub-guideposts.
Fig. 11. Measured bolt force changes in M42 bolt and synchronizing pin.
Fig. 11 shows the bolt force change of sensors located in the M42 bolt and synchronizing pin, respectively, measured during 30 forging shots. M42 bolt receive the total compressive force applied to lower die plate during forming and knock-out force applied to lower die pin during ejecting of forged product. From the measured bolt force, it was found that the deviation of total compressive force in lower die plate is small comparing with the bolt force change in lower die spacer (Fig. 7). It means that the total compressing force in the die-set can be different from the effective compressive force applied between upper and lower dies. On the other hands, the compressive bolt force of the synchronizing pin clearly shows the exact timing of synchronization between upper and lower closing die plates. This information would be useful to detect any abnormal behavior concerning bad synchronization timing.
Fig. 12. Difference of bolt force change in ring type monitoring devices according to change of process conditions.
Concerning the change of measured data for the irregular conditions (A) and (B), the bolt force changes in the upper ring type monitoring device were compared in this study as shown in Fig. 12. In the condition (A) using the blank of room temperature, the bolt force becomes higher in the upsetting stage comparing with normal condition (blank temperature of 200 0C) because of increasing flow stress due to temperature decrease of workpiece. However, the bolt force becomes lower around the bottom dead center due to the increase of under-filling region caused by decreasing formability comparing with warm workpiece under normal condition. In the condition (B) using the shorter blank (1.3% reduction in length), the bolt forces in the ring type monitoring devices become lower comparing with normal condition in entire range of stroke. This tendency is clearly reflecting the effect of reduction in workpiece volume comparing with the normal sized blank. The monitored tendency shown in Fig. 12 can be also verified from the inspection result of forged product as shown in Fig. 13.
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Author name / Procedia Manufacturing 00 (2018) 000–000 Soo-Young Kim et al. / Procedia Manufacturing 15 (2018) 542–549
(a)
(b)
Under-filling area
549
(c)
Under-filling area
Under-filling area
1.7 mm
4.5 mm
2.5 mm
Fig. 13. Change of under-filling area in forged product with respect to forging conditions: (a) normal, (b) condition (A), and (c) condition (B).
5. Conclusions In this paper, new possibility of sensing technology based on the bolt type piezo-sensor was introduced from the example of closed forging die-set applying 16 bolt sensors and designated monitoring system to monitor the status of forged product, tools and die-set. From the result, we could detect the under-filling defect of product due to abnormal status of initial blank. The sensing technology proposed in this study will be available to provide the useful information to understand the status of die-set and to detect any abnormal behaviors during the process. Sensing
Numerical
Design
Technology
Simulation
Know-how Simulation Results
Measured Data Improving production quality
Stochastic analysis Monte Carlo method
DOE
Optimization
Optimizing design parameters
Fig. 14. Integration of design know-how, numerical simulation, and sensing technology.
The sensing technology has been focused in these days as one of the key technologies for new trend of manufacturing industries such as IoT (Internet of Things) or Industrie4.0. The effective integration of information collected from the design know-how, numerical simulation, and measurement data from sensors would be a key issue to establish this technology into the general manufacturing industries. Fig. 14 explains the concept of integrated process design for forging process using the design know-how, numerical simulation, and sensing technology. The synergy effect by collaborating the numerical simulation and measurement data would be significant to find out new possibilities for innovative forging process as listed below: • • • •
Improvement on sensing environment (wireless connecting, user-friendliness…) Improvement of analysis method for better understanding of the measured data (AI, big data analysis…) Improvement of numerical simulation method adequate for integrating the measured data Improvement of design methodology combined with the integrated information
References [1] H. Kagermann, W. Wahlster, J. Helbig, Final report of the Industrie 4.0 working group, ACATECH, (2013) 1–82. [2] W. Faulhaber, T. Kopka, Industry 4.0 in metal forming – practical examples, New Development in Forging Technology 2017, (2017) 235– 244. [3] P. Groche, M. Brenneis, Manufacturing and use of novel sensoric fasteners formonitoring forming processes, Measurement, 53 (2014) 136– 144. [4] J. Stahlmann, M. Brenneis, Understanding and improvement of industrial production how technology paves the way for productivity, New Development in Forging Technology 2017, (2017) 257–266. [5] S.Y. Kim, M. Yamanaka, K. Tsuruoka, S. Kubota, Development of high value added cold forging product using multi-axis servo press machine, New Development in Forging Technology 2017, (2017) 109–117.
ScienceDirect ScienceDirect
Procedia Manufacturing 00 (2018) 000–000 Available online atatwww.sciencedirect.com Available www.sciencedirect.com Procedia online Manufacturing 00 (2018) 000–000
ScienceDirect ScienceDirect
www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Manufacturing 15 (2018) 542–549 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
Monitoring of process and tool status in forging process by using
MonitoringEngineering of process and tool status in forging process by28-30 using Manufacturing Society Conference 2017, MESIC 2017, June bolt International type(Pontevedra), piezo-sensor 2017, Vigo Spain bolt type piezo-sensor Soo-Young Kim*, Akifumi Ebina, Asuka Sano, Satoshi Kubota Costing models forKim*, capacity optimization in Industry 4.0: Trade-off Soo-Young Akifumi Ebina, Asuka Sano, Satoshi Kubota Yamanaka Eng, Co., 2-11-2 Osaku, Sakura, Chiba, 285-0802 Japan between Yamanaka used Eng, capacity andSakura, operational efficiency Co., 2-11-2 Osaku, Chiba, 285-0802 Japan Abstract A. Santanaa, P. Afonsoa,*, A. Zaninb, R. Wernkeb Abstract a The objective of this study is to introduce the new possibility of sensing technology University of Minho, 4800-058 Guimarães, Portugal based on the bolt type piezo-sensor to The objective of this is to and introduce thethe new possibility ofChapecó, sensing technology on the bolt type piezo-sensor to monitor the status of study workpiece tools bUnochapecó, in forging process. In order toBrazil validatebased the effectiveness of proposed sensing 89809-000 SC, monitor the the status workpiece and and toolsdesignated in the forging process.system In order to applied validateinto theaeffectiveness proposed sensing technology, boltof type piezo-sensor measurement were typical closedofforging die-set used technology, the bolt type piezo-sensor and designated measurement werethe applied into piezo-sensor a typical closed forging die-set used for the manufacturing of precision automotive part. The locations tosystem implement bolt type were selected carefully for the manufacturing of based precision The locations to implement the bolt type piezo-sensor selected carefully by the design engineers on automotive their designpart. know-how to obtain the necessary information to satisfy were the desired purpose of Abstract by the design engineers based their designresults know-how obtain thechange necessary information to satisfy desired purpose of process monitoring. From the on measurement of thetobolt force during one forging cycle, the it was found that the process results of the to bolt force change during behaviors one forging cycle, and it was found the proposedmonitoring. monitoring From systemthe canmeasurement provide useful information understand the detailed of die-set tools in thethat closed proposed monitoring can provide useful informationprocesses to understand behaviors die-set and tools in the closed Under the conceptsystem of "Industry 4.0", production willthebedetailed pushed to be of increasingly interconnected, die forging process. die forging process. information based on a real time basis and, necessarily, much more efficient. In this context, capacity optimization © 2018 The Authors. Published by of Elsevier B.V.maximization, contributing also for organization’s profitability and value. goes beyond the traditional aim capacity © 2018 2018 The The Authors. Published by Elsevier B.V. B.V. © Authors. Publishedand by Elsevier Peer-review under responsibility of the scientific committee ofthe the17th 17th International Conference onMetal Metal Forming. instead of Indeed, lean management continuous improvement approaches suggest capacity optimization Peer-review under responsibility of the scientific committee of International Conference on Forming. Peer-review under responsibility of the scientific committee the 17thmodels International Metal Forming. maximization. The study of capacity optimization andofcosting is anConference important on research topic that deserves
Keywords: Bolt type piezo-sensor; Process monitoring; Tool status monitoring; Forging process; Closed-die forging contributions from both the practical and theoretical perspectives. This paper presents and discusses a mathematical Keywords: Bolt type piezo-sensor; Process monitoring; Tool status monitoring; Forging process; Closed-die forging model for capacity management based on different costing models (ABC and TDABC). A generic model has been developed and it was used to analyze idle capacity and to design strategies towards the maximization of organization’s 1. Introduction value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity 1. Introduction optimization might hide operational inefficiency. The sensing technology has been focused in these days as one of the key technologies for new trend of © 2017 Authors. Published by Elsevier B.V. The The sensing technology hasas been (Internet focused in days as one of the technologies for trend the of manufacturing such of these Things) or Industrie4.0 [1].key How to visualize andnew quantify Peer-review underindustries responsibility of theIoT scientific committee of the Manufacturing Engineering Society International Conference manufacturing industries such as IoT (Internet of Things) or Industrie4.0 [1]. How to visualize and quantify the process status to detect the abnormal behavior efficiently during the process has been an important issue for the shop 2017. process status toindetect the abnormal behavior efficiently the process has been an important for the shop floor engineers manufacturing industry. Especially in during the forging industries, the monitoring andissue management of floor engineers in manufacturing industry. Especially in the forging industries, the monitoring and management of Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency
1. Introduction
* Corresponding author. Tel.: +81-43-498-3492; fax: +81-43-481-5100. * E-mail Corresponding Tel.: +81-43-498-3492; fax: +81-43-481-5100. 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 Peer-review underThe responsibility of theby scientific committee 17th International on Metal Forming. in several©ways: tons of production, available manufacturing, etc.Conference The management of the idle capacity 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.2018.07.275
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tool status is one of most important issues in quality control and productivity of forging process. In general, the abnormal behaviors of forging tools are closely related with the quality trouble of forged product since the tools including dies and punches are directly contacted with the workpiece during forging process. Also in terms of productivity, it is not difficult to image the serious decrease of production efficiency in forging process caused by the abrupt termination of process due to unexpected tool failure. Most usual method applied to confirm the tool status is the visual inspection during the process maintenance occurred periodically in the mass production. It is a traditional and effective method to detect any abnormality of forging tools but still it is difficult to determine the adequate period for inspection and to evaluate the inspection result quantitatively. Several practical monitoring solutions for parts forming machines have been developed and introduced already as referred in the publication by Faulhaber et al. [2]. In these solutions, the forming load in each forging stand were measured by implementing piezo-electrical pressure sensor to the inside parts of forming machine. The abnormal status of process could be detected by recognizing the change of forming load comparing with the normal status. Also, various sensors and monitoring systems have been widely applied in the sheet metal forming and stamping industries. In general forging processes using the press machines, the quality control of product and management of tool status are still based on human senses and skills such as visual observation. In the present study, new possibility of sensing technology to monitor the status of forging process and tools was proposed. The main objective of the investigation is to evaluate and validate the effectiveness of proposed sensing technology in the practical forging process. A typical closed die forging die-set was re-designed to have a monitoring ability using the bolt type piezo-sensors. Several test measurements were carried out to analyze the tool status during the forging process. Designated measurement system
Bolt type piezo-sensor
Touch panel interface
(Front view)
Active/Deactivate switch
Wire type linear sensor
(Rear view)
Channel box
Signal processing unit
Fig. 1. Exterior of bolt type piezo-sensor and designated measurement system used in this study. Process monitoring Warning
Bolt Force
Warning
Designated Measurement System Cur. Ref. Dif.
Bolt type load sensor
Stop Time or Stroke
Feed-back control
Fig. 2. Typical concept of process monitoring in forging process using bolt type piezo-sensor.
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2. Sensor and measurement system The sensor used in the current study is a bolt type piezo-sensor based on the “Sensoric Fastener” technology proposed by Groche and Brenneis in Technical University of Darmstadt [3]. Fig. 1 shows the exterior of bolt type piezo-sensor and measurement system used in this study. The bolt type load sensor “PiezoBolt” is a piezo-electric load sensor developed by ConSenses GmbH [4] and can be applied to the conventional mass-production environment of manufacturing processes easily by replacing the existing bolt in assembly structure to the bolt type piezo-sensor. It provides highly reliable and sensitive sensing environment to measure the change of local bolt force in the repeated manufacturing process. The designated measurement system “ProductionSenses” can measure the signals from 8 different bolt sensors simultaneously. The signals can be synchronized based on the reference signal obtained from the wire-type linear sensor measuring the distance between upper and lower die plates. Fig. 2 explains the concept of process monitoring presented in this study. The bolt type piezo-sensor is applied to the die-set and tools for the forging process. Adequate location of bolt replacement is chosen carefully considering the purpose of measurement and the abnormal behaviors that want to be detected during the process. The force follow-up ability between the bolt force change and the major loading component related with monitoring parameter is the most important factor in this choice. In the manufacturing process, the measured sensor signal is compared with reference signal obtained during the normal process status. Then, the abnormal status can be detected easily by just analyzing the difference between two signals. If any feed-back control scheme is applied to the measurement chain, adequate process control to avoid any abnormal status becomes possible with relatively simple modifications of manufacturing facility. The typical abnormal patterns according to various defect types are depicted in Fig. 3. The defects directly related with forming load such as under-filling can be detected by applying the bolt type piezosensor to the place receiving the forming load. Unbalance of process such as eccentricity of product or unrequired thrust force can be recognized from the change of balance between the signals from multiple bolt sensors distributed circumferential direction. Also, the indication of seizer defect and fatigue failure, which are two representative tool failure patterns in cold forging process, can be visualized by detecting the abnormal increase of knock-out force during ejection of workpiece and the shock reaction force occurring at crack generation, respectively.
KO pin Stroke
S1
OK NG
S1 Crack generation
Stroke of KO pin
Bolt force
S1
OK NG
Tool failures Detection of impact load by crack generation
Seizure / frictional defect Increase of friction force
Bolt force
S2
Bolt fore2 Bolt force1
Eccentricity / unbalance Change of load balance
OK NG
Stroke
Fig. 3. Several patterns of bolt force change with respect to various abnormal behaviors occurred in forging process.
3. Experimental conditions In the present study, these sensors and measurement system was applied to the closed-die forging process to monitor the status of tools and die-set during the forging process. Fig. 4 shows the image of closed-die forging process applied in this study since the real process details cannot be opened in public because it contains the confidential information. Initial blank
Closed-die forging equipment
Product
Fig. 4. Image of closed forging die-set and typical forging product.
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Synchronizing pin Timing of synchronization Failure of synchronizing pin [PB08-05] Ring type monitoring device Elastic deformation of tool Crack generation Ring type monitoring device [PB08-06 ~ PB08-07]
Front Front [PB12-05]
[PB12-01 ~ PB12-04]
M42 bolt Balance of die-closing force
Die spacer bolts Balance of die-closing force KO force monitoring
[PB12-06 ~ PB12-09]
[PB08-01 ~ PB08-04]
Guideposts & Sub-guideposts Irregular motion of die-set Prediction of seizure defect
Fig. 5. Locations of bolt type piezo-sensors implemented in closed forging die-set used in this study. Table 1. Major specifications of bolt type piezo-sensors used in this study. Code
Serial No.
Bolt size
Length (mm)
Piezoelectric coefficient (pC/N)
Implemented position
PB08-01
PB08YxK6
M8
42
4.883
Sub-guidepost (Back side 1)
PB08-02
PB08YxA17
M8
42
7.313
Sub-guidepost (Back side 2)
PB08-03
PB08YxK4
M8
42
5.295
Sub-guidepost (Front side 1)
PB08-04
PB08YxK5
M8
42
5.894
Sub-guidepost (Front side 2)
PB08-05
PB08YxAx006 M8
55
7.276
Synchronizing pin
PB08-06
PB08YxAx008 M8
55
7.276
Ring type monitoring device (Upper)
PB08-07
PB08YxAx007 M8
55
8.057
Ring type monitoring device (Lower)
PB12-01
PB12YxAx026 M12
75
3.870
Die spacer (Upper 1)
PB12-02
PB12YxAx027 M12
75
3.197
Die spacer (Upper 2)
PB12-03
PB12YxAx024 M12
75
3.115
Die spacer (Lower 1)
PB12-04
PB12YxAx025 M12
75
1.994
Die spacer (Lower 2)
PB12-05
PB12YxAx030 M12
110
2.704
M42 bolt
PB12-06
PB12YxAx009 M12
65
2.719
Guidepost (Back side 1)
PB12-07
PB12YxAx010 M12
65
2.725
Guidepost (Back side 2)
PB12-08
PB12YxAx011 M12
65
2.078
Guidepost (Front side 1)
PB12-09
PB12YxAx012 M12
65
2.851
Guidepost (Front side 2)
The location of sensors and the major objective of monitoring in each sensor are explained in Fig. 5. Four sensors (PB12-01 ~ PB12-04) were applied to the inside of the die spacers in upper and lower closed-dies to visualize the behaviors related with the closing die force and forming load. Also, for the same purpose, another additional sensor (PB12-05) was implemented to the inside of M42 bolt located at the bottom die plate. To understand the behavior of sub-guideposts during the forming process, four M8 size bolt sensors (PB08-01 ~ PB08-04) were applied to two sub-guideposts located at the front and back sides. On the other hand, four M12 size bolt sensors (PB12-06 ~ PB1209) were implemented to the guideposts located at the front and back sides to detect the defects such as seizure or abnormal deflection. To monitor the status of synchronization between upper and lower closing die plates, a M8
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sized bolt sensor (PB08-05) was applied to the synchronizing pin. Finally, two ring type monitoring devices implementing M8 sized bolt sensor (PB08-06 and PB08-07) were applied to the outside of upper and lower dies, respectively, to monitor any abnormal behavior of product and tools such as under-fill of workpiece or crack generation of tool. The concept of ring type monitoring device is referred in the publication [5]. The signals measured from the ring type monitoring device clearly shows the abnormal curve patterns caused by the impulsive load pattern generated due to the crack generation. The detailed specifications of sensors used in this study are listed in Table 1. Each sensor has its own piezoelectric coefficient obtained from calibration test carried out individually. Table 2. Test forging conditions applied in experiment.
Synchronizing pin
Ring type monitoring device
Guidepost
Subguidepost
Wire type linear sensor
Fig. 6. Exterior of closed forging die-set.
Condition name
Forging condition
Channel combination*
N
Normal-1
Normal
Pattern 1
30
Normal-2
Normal
Pattern 2
30
Normal-3
Normal
Pattern 3
5
Irregular-A
(A) Blank temperature: RT
Pattern 2
3
Irregular-B
(B) Blank length: 1.3% shorter
Pattern 2
3
* Channel combinations Pattern 1: PB12-03, PB12-05, PB08-03, PB08-04, PB12-08, PB12-09, PB08-05, PB08-07 Pattern 2: PB12-01, PB12-02, PB12-03, PB12-04, PB08-06, PB08-07 Pattern 3: PB08-01, PB08-02, PB08-03, PB08-04, PB12-06, PB12-07, PB12-08, PB12-09
The developed die-set for the current closed-die forging process and the measurement system used for the experiment are depicted in Fig. 6. Due to the limitation in the number of channels (maximum 8) of the measurement system, several experiments were planned as listed in Table. 2. Three types of channel combination were applied in the experiments. The channel combination pattern 1 is using 8 bolt sensors selected from entire measurement locations to confirm the overall response. The channel combination pattern 2 is composed of 6 sensors selected from the die spacers and the ring type monitoring devices located at upper and lower dies. In the channel combination patterns 3, the sensors implemented at the sub and guideposts are monitored. The measurements were carried out under normal process condition (N = 30 for channel patterns 1 and 2, N = 5 for channel pattern 3). To confirm the detect ability of monitoring system, additional forging try was carried out under two irregular process conditions descripted below (N = 3 per each condition): • Condition (A): Initial temperature of blank is changed to room temperature (200 0C in normal condition) • Condition (B): Length of blank becomes 1.3% shorter comparing with normal condition The sampling rate was 1 kHz for all measurement conditions and the stroke range for data measurement was set to 150 mm from the bottom dead center of the press machine. The stroke of press was measured using the wire type linear sensor as shown in Fig. 1. 4. Result The changes of bolt force in the upper and lower die spacers are shown in Fig. 7. The average and min/max curves obtained from measured data of 30 forging shots are plotted in each graph. The measured results show that all sensors in this location undergo the compressive force during the process. It clearly shows the compressive load from the hydraulic equipment for closing upper and lower dies. The maximum compressive force appeared at the bottom dead center of the press machine. Based on the average data, the maximum compressive forces of sensors are -3.6 and -5.3 kN in the upper die spacer and -4.2 and -4.3 kN in the lower die spacer, respectively. The deviation of the measured data is ranged from 11% to 20%. The information obtained from these results can be useful to understand the variation of total die closing force and the local balance of loading status in upper and lower dies.
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The bolt force change of ring type monitoring devices is shown in Fig. 8. As same as the previous figure, three curves (average, minimum, and maximum) are plotted using the measured data of 30 forging shots in each graph. The deviation between minimum and maximum data is small comparing with the deviation shown in Fig. 7. The change of bolt force directly reflects the elastic deformation behavior of die in radial direction reacting with the initial die-closing, upsetting, and radial extruding status.
Fig. 7. Measured bolt force changes in upper and lower die spacers.
Fig. 8. Measured bolt force changes of ring type monitoring device in upper and lower dies.
Fig. 9. Measured bolt force changes in guideposts.
Figs. 9 and 10 show the change of bolt forces located in the guideposts and sub-guideposts, respectively, measured during three forging shots. In all cases, two sensors implemented in one guidepost show the opposite tendency – a typical behavior of bolts undergoing bending loading condition of the guidepost. The behavior of subguidepost is more complex since it contains the effect of elastic deformation of dies during forming process. These results can be used effectively to detect any signal of seizure defect between guidepost and bush by confirming the rapid increase of bolt forces.
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Soo-Young Kim et al. / Procedia Manufacturing 15 (2018) 542–549 Author name / Procedia Manufacturing 00 (2018) 000–000
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Fig. 10. Measured bolt force changes in sub-guideposts.
Fig. 11. Measured bolt force changes in M42 bolt and synchronizing pin.
Fig. 11 shows the bolt force change of sensors located in the M42 bolt and synchronizing pin, respectively, measured during 30 forging shots. M42 bolt receive the total compressive force applied to lower die plate during forming and knock-out force applied to lower die pin during ejecting of forged product. From the measured bolt force, it was found that the deviation of total compressive force in lower die plate is small comparing with the bolt force change in lower die spacer (Fig. 7). It means that the total compressing force in the die-set can be different from the effective compressive force applied between upper and lower dies. On the other hands, the compressive bolt force of the synchronizing pin clearly shows the exact timing of synchronization between upper and lower closing die plates. This information would be useful to detect any abnormal behavior concerning bad synchronization timing.
Fig. 12. Difference of bolt force change in ring type monitoring devices according to change of process conditions.
Concerning the change of measured data for the irregular conditions (A) and (B), the bolt force changes in the upper ring type monitoring device were compared in this study as shown in Fig. 12. In the condition (A) using the blank of room temperature, the bolt force becomes higher in the upsetting stage comparing with normal condition (blank temperature of 200 0C) because of increasing flow stress due to temperature decrease of workpiece. However, the bolt force becomes lower around the bottom dead center due to the increase of under-filling region caused by decreasing formability comparing with warm workpiece under normal condition. In the condition (B) using the shorter blank (1.3% reduction in length), the bolt forces in the ring type monitoring devices become lower comparing with normal condition in entire range of stroke. This tendency is clearly reflecting the effect of reduction in workpiece volume comparing with the normal sized blank. The monitored tendency shown in Fig. 12 can be also verified from the inspection result of forged product as shown in Fig. 13.
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Author name / Procedia Manufacturing 00 (2018) 000–000 Soo-Young Kim et al. / Procedia Manufacturing 15 (2018) 542–549
(a)
(b)
Under-filling area
549
(c)
Under-filling area
Under-filling area
1.7 mm
4.5 mm
2.5 mm
Fig. 13. Change of under-filling area in forged product with respect to forging conditions: (a) normal, (b) condition (A), and (c) condition (B).
5. Conclusions In this paper, new possibility of sensing technology based on the bolt type piezo-sensor was introduced from the example of closed forging die-set applying 16 bolt sensors and designated monitoring system to monitor the status of forged product, tools and die-set. From the result, we could detect the under-filling defect of product due to abnormal status of initial blank. The sensing technology proposed in this study will be available to provide the useful information to understand the status of die-set and to detect any abnormal behaviors during the process. Sensing
Numerical
Design
Technology
Simulation
Know-how Simulation Results
Measured Data Improving production quality
Stochastic analysis Monte Carlo method
DOE
Optimization
Optimizing design parameters
Fig. 14. Integration of design know-how, numerical simulation, and sensing technology.
The sensing technology has been focused in these days as one of the key technologies for new trend of manufacturing industries such as IoT (Internet of Things) or Industrie4.0. The effective integration of information collected from the design know-how, numerical simulation, and measurement data from sensors would be a key issue to establish this technology into the general manufacturing industries. Fig. 14 explains the concept of integrated process design for forging process using the design know-how, numerical simulation, and sensing technology. The synergy effect by collaborating the numerical simulation and measurement data would be significant to find out new possibilities for innovative forging process as listed below: • • • •
Improvement on sensing environment (wireless connecting, user-friendliness…) Improvement of analysis method for better understanding of the measured data (AI, big data analysis…) Improvement of numerical simulation method adequate for integrating the measured data Improvement of design methodology combined with the integrated information
References [1] H. Kagermann, W. Wahlster, J. Helbig, Final report of the Industrie 4.0 working group, ACATECH, (2013) 1–82. [2] W. Faulhaber, T. Kopka, Industry 4.0 in metal forming – practical examples, New Development in Forging Technology 2017, (2017) 235– 244. [3] P. Groche, M. Brenneis, Manufacturing and use of novel sensoric fasteners formonitoring forming processes, Measurement, 53 (2014) 136– 144. [4] J. Stahlmann, M. Brenneis, Understanding and improvement of industrial production how technology paves the way for productivity, New Development in Forging Technology 2017, (2017) 257–266. [5] S.Y. Kim, M. Yamanaka, K. Tsuruoka, S. Kubota, Development of high value added cold forging product using multi-axis servo press machine, New Development in Forging Technology 2017, (2017) 109–117.