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new approach for oee calculation of cnc machines based on opc ua.

by:QY Precision      2019-10-01
Introduction to the overall equipment benefits of manufacturing industry (OEE)
Used as a common key figure in manufacturing facilities.
OEE as a measurement method is part of total productive maintenance (TPM)concept.
For the first time, 1971 was implemented in Japan.
Which member of Toyota group (Reichel et al. , 2009).
OEE has been proven in thousands of companies.
It exposes relentless losses and helps to eliminate them (Koch, 2011).
It gives a key number consisting of availability, effectiveness, and quality rate factors.
Typically, OEE is used for mass production with only a few exceptions for individual production.
Due to the lack of precise oee definitions, many of the inferences have changed over the past few years, where the following conditions exist: * \"overall line validity \"(OLE)(
Andananda talaman, 2006)
* \"Overall equipment effectiveness for manufacturing production lines \"(OEEML)(Braglia et al. , 2008)
* Overall factory benefits \"(OPE)(
Scott and pizza, 1998)
* Overall factory benefits \"(OFE)(Oechsner et al. ,2002)
* \"Overall equipment effectiveness for manufacturing production lines \"(OEEML)(Braglia et al. , 2008)
* Overall fab performance \"(OFE)(Oechsner et al. ,2002)
* \"Determine the overall equipment effectiveness of the assembly system based on product data \"(Neugebauer, R. ,2010)
* \"Random overall performance of equipment \"(Zammoriet al. , 2011)
All of these methods follow their own definition of how to calculate OEE.
ISO/DIS 22400-
2 based on the VDMA 66412 released in version 2009, there is now a \"Draft International Standard \".
Subcommittee 184 and Working Group IX of the International Organization for Standards (ISO)
Working on this standard is currently being guided in the \"query phase (ISO, n. d. ).
At ISO/DIS22400-
2 OEE is defined as follows: OEE = availability x validity x quality rate (1)
Actual production time/scheduled busy time (2)
Validity = [PRU x PQ]/APT = [
Planned run time per unit production quantity]
/Actual production time (3)
Quality rate = GQ/PQ = good/good quantity (4)
OEE should be understood as summary information based on details created primarily at the workshop level.
Therefore, the machine as an information provider should be able to evaluate the relevant kpi (e. g. effectiveness)
And automatically pass these indicators to a higher position.
For machine operators or horizontal systems.
This will be associated with the service-oriented architecture paradigm (SOA). 1. 1.
Communication between workshops and MES currently using VDI 5600 provides a guide to communication between machines and MES, which also takes into account communications from MESA, NAMUR, ISA, VDMA and ZVEI
The standard follows the requirements that can be used in heterogeneous machine parks in the manufacturing industry and does not follow the industry requirements
Weihenstephaner standard, SECS/GEM, MTConnect (VDI, 2011).
InVDI 5600 part 3 proposes a well-defined data structure for communication between machines and MES systems that act as production resources.
Since the communication technology itself does not belong to the category of OPC 5600, this paper has a unified architecture in OPC (OPC UA)
In order to facilitate semantic communication, it is recommended to use it as a promising specification. 1. 2.
Unified OPC architecture (OPC UA)
Latest specifications developed by OPC Foundation-
OPCUA is a service-oriented architecture that can penetrate into the whole information and communication structure of the enterprise.
\"The purpose of OPC unified architecture is to realize a platform --
Independent interoperable standards for mobile data/information between factory workshops and enterprises \"(Mahnke et al. , 2009).
The OPC Foundation\'s previous standards, the classic OPC, are widely used in industry for data access and are more common than subsequent standards. In Fig. 2.
The possible use range of opc ua and classic OPC shows the interface from the device layer to the enterprise level automation pyramid layer. With ISA-95 and OAGIS (
\"OpenApplications Group,\" n. d. )
Two important standards for service-based integrated applications
Architecture-oriented (Gifford et al. , 2006).
Both provide more cost.
Organizations have an effective way to vertically integrate applications in the ICT view, so opc ua integration should be considered.
As a new communication standard for manufacturing systems, opc ua has placed great hopes. g.
Robot manufacturing unit.
At present, the full functional volume of opc ua has not been applied in the field of production engineering.
It can only be used as a wrapper for data access at most. 2.
In order to meet the needs of manufacturing enterprises, new methods are needed to determine performance indicators.
The extensive automation pyramid shown in Figure 1
2 represents a hierarchical model of information technology in production enterprises.
It is based on the opposite trend of information quality and information quantity.
Today, this model is no longer consistent with reality (Kegel, 2010).
Due to the wide integration of information technology, a new reference model is required, which must include the vertical and horizontal dimensions of the information flow and the life cycle of the product (Kegel,2010).
The proposed OEE computing method follows a service-oriented architecture (SOA).
Unlike the conventional procedures for OEE computing, where a large amount of data is collected from the workshop and analyzed at the regulatory level, we suggest to calculate key performance indicators as close as possible to the data source. Fig.
3 shows the information flow between the monitoring systems (MES)
And evaluate OEE\'s workshop using the proposed method.
OEE is calculated in the supervision system based on availability, mass ratio and effectiveness.
Availability is the ratio of actual production time (APT)
Busy hours that can be passed through the machine and planned (PBT)
This can be obtained from job shop scheduling.
Calculate the mass ratio from a good quantity (GQ)
Quantity of production (PQ)
Delivery is confirmed by order through Workshop data collection terminal.
Validity is based on the data generated in the machine and will be calculated in the machine.
We suggest to implement opc ua server in machine tool control, allowing the monitoring system to query the actual production time (APT)
Validity of a given evaluation period by opc ua method call.
The input parameters are the start and end times of the evaluation cycle.
They can be selected either by the machine operator or automatically by the theme (e. g.
Automatic evaluation of the effectiveness of each work).
Calculate APT and validity using equations (5)and (6)
For giventime intervals that use historical data on opc ua servers. 2. 1.
Calculate the actual production time (APT)
In the case of CNC machine tools, the machine status can be \"inactive \"(no machining), \"active\" (
Processing)or \"fault\" (
Processing interruption).
APT can be understood as the time when processing is going on. In Fig.
4 An exemplary sequence of related machine state changes is shown as an asa set of time slices.
Each time slice represents the production time (active)or a downtime (
Not active or faulty).
With equation (5)
APTcan can be calculated with a given input value [t. sub. start]and tend.
These values are first compared to the historical timestamp of the opc UA variable representing the state of the machine.
As shown in the figure, the slice is indexed. 4.
In which time periodt. sub. start]or [t. sub. end]
The waterfall corresponding to the given time range is split.
For each slice, check the history Machine status to determine if the slice represents an inactive or faulty time period ([a. sub. i]= 0)
Or active period ([a. sub. i]= 1). [
Mathematical expressions that cannot be reproduced in ASCII](5)2. 2.
The validity calculation of the validity evaluation based on the equation (3)
Product of unit plan run time (PRU)
Quantity of production (PQ)is needed.
For a single production, the PRU is usually roughly estimated or delivered by CAM (
Computer-aided manufacturing
Results of machining simulation.
We have come up with a simple solution.
In the case of CNC machining, the planned running time can be defined as the processing time with the planned processing parameters.
When the machine is running at a programmed feed rate, when no unplanned interrupt occurs.
If the feed speed changes due to excessive feed during processing, the processing time will change significantly.
After understanding the timestamp of the feed override value and feedoverride, the scheduled run time is changed \"(PRU x PQ)
Equation can be used (6), with [f. sub. i]
When the feed overrides the value of time slice I (0 < [f. sub. i]< 1. 2)and [a. sub. i]= {0, 1}. [
Mathematical expressions that cannot be reproduced in ASCII](6)3.
Prototype implementation of new methods for production engineering and Laser Technology Research Institute (IFT)
The Vienna University of Technology developed an opc ua server prototype for the lathe \"Emco concept to 55\", which is mainly used for industrial training (
Ayatollah and others. , 2013).
The OPCUA server runs in the CNC of the machine tool.
The server not only collects data through the overlay system, but also allows remote control of the machine tool using the opc ua method.
As part of the ongoing further development of the opc ua server, the proposed approach has been integrated into the address space of the machine tool (Fig. 6). Since the MES-
The scope of this development is not the machine interface. we just implemented the calculation method of opc ua mentioned above.
The data required to evaluate the APT and validity of the machine is the historical state variable \"machine--
Status and Feed--Override\".
In this prototype, \"Machine--
Status \"can have three different string values.
Factors whenever value is \"active [a. sub. i]
For the time period in the equation (5)and (6)
It is set to 0 in any other case.
Variable \"Feed--
Override \"is an integer whose value is 0 to 120.
The appropriate value used in the equation (6)as [f. sub. i]
So divide by 100. 4.
Conclusion The Prototype Development described in this paper is an attempt to decompose the part of OEE calculation into machine level.
The evaluation of some key performance indicators, such as effectiveness, requires only machine-generated data and can be integrated directly into the opc ua server at the machine level.
Get the scheduled run time (PRU x PQ)
It is reasonable to calculate the actual timestamp generated during the manufacturing process, because the running time of the NC program can only be affected by unplanned interruptions (fault)
Or change in feeding speed.
Both events can be monitored through the opc UA server and used to adjust the scheduled run time.
Today, kpi is evaluated at management in many manufacturing enterprises.
Feedback on the operation performance of the workshop will arrive at the machine operator at a certain delay.
Since the operator has a great impact on the performance of the production unit, especially in the case of small batches and separate production, up-to-
Date calculations close to the data source seem promising.
For further testing and validation, the proposed approach will be implemented as the next step in the actual production environment. 5.
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, ISSN 00207543 author data: Ayatollah I [man]*; Ao. Univ. Prof. Dipl. -Ing. Dr. techn. Kittl B[urkhard]*; MSc. Pauker F[lorian]*; MSc. HackhoferM[artin]
**, ** University of Technology, Karlsplatz 13,1040, Vienna, Austria, ** Hackhofer EDV, Im aicheteld 45,4490, St.
Florian, Austria;
* University of Technology, 1040, Vienna, Austria, Ayatollah @ ift. at, kittl@ift. at, pauker@ift. at DOI: 10. 2507/daaam. scibook. 2013.
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