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Reliability of products electronic mechanical equipment electronic desk top calculator
46
R E L I A B I L I T Y SYMPOSIUM IN JAPAN
compressor age sampling program. It seems that in the near future the establishment of the overhaul time limit should be required because of the bearing deterioration. 3.3 The maintenance concept of B747's components There are about 700 items of LRU (line replacement units) in B747 of JAL, as it is so complicated it cannot be expected (because of the effort) to monitor every LRU, then JAL classified five categories for them, and now intended to find a proper maintenance program for each component. Category I. Mechanical high-speed rotating components which their failures by wear-out affect airworthiness and cost largely. Examples: constant speed drive (CSD), hydraulic pump, generator, cabin turbo-compressor, etc. 15 items. Category II. Mechanical relatively low-speed rotating components which take major parts of the system and are supposed a wear-out at the particular area. Examples: flight power packages, major hydraulic actuators, major pneumatic valves, etc. 22 items. Category III. Electronic equipments which are composed by static parts and their failures are random, and electro-mechanical equipments which are supposed wear-out but the failures are random. Both kinds of these equipments are also major func-
tional units. Examples: black boxes of electronic equipments and communication equipments, instruments, hydraulic actuators, pneumatic valves, etc. 161 items. Category IV. Items which faU under the FAA Maintenance Significant Item List except Categories I, II and III. Examples: control surface position indicators, controls-communication equipments, tank units, locking actuators, door actuators, miscellaneous motors, etc. 199 items. Category V. Relatively low cost items which their M T B F are higher than about 20,000 hr. Examples: control surface position transmitters, clocks, antenna, temperature sensors, relays, hydraulic filters, miscellaneous hydraulic valves. 287 items. At present our Aircraft Accessories Center are monitoring the operation and maintenance status continuously by establishing monitoring standard for all Categories I, II and III. For Category IV our center is monitoring by monthly PRR list issued by Company's Inspection Section. Items exceeding 36 upper limit are analyzed in more detail. Category V is not monitored except when their failures present unusual indication. In near future more special monitoring programs for each category shall be established by analyzing modes of each category.
RELIABILITY OF PRODUCTS ELECTRONIC MECHANICAL E Q U I P M E N T ELECTRONIC DESK TOP CALCULATOR T. SASAKI
Executive Director, General Manager of Industrial Instruments Division, Sharp Corporation 1. HISTORY OF DEVELOPMENT OF DESK TOP CALCULATOR
THE history of the development of the electronic desk top calculator dates back to the Designing Stage, as shown in Fig. 1, when the development plan including the basic research for inventing a new product got under way. Then about 4 yr were required to form up what we call the birth stage through the process of materializing the plan into specific commodities (materializing stage). During such a stage, we acquired new techniques which
had been unfamiliar to manufacturers of electrical home appliances, and made market researches to bring forth an electronic desk top calculator, the first in the world (Model No. 1). The electronic desk top calculator was quite a new device throughout the world when this Model No. 1 was first introduced. Therefore we were not prepared in either technical or marketing fields, and even suffered from a bad reputation. This bitter experience, however, was very useful for us to develop into Model No. 2.
47
R E L I A B I L I T Y S Y M P O S I U M IN JAPAN In the development process of Model No. 2, we gave the importance to the following points: 1. Examination of design. 2. Improvement of element. 3. Ten-key system. 4. Modification of specification. 5. Improvement of various components. 6. Improvement of reliability. As a matter of fact, the model then introduced enjoyed a very good reputation resulting in an epoch-making sales expansion. The new models manufactured and marketed one after another have so far kept us as the leading manufacturers in this industry.
obtained, stage by stage, at plant on M T B F extracted from field data and the failure rate of the main device. Table 1 represents M T B F and the failure rate of device per set. As seen in the table, the failure rate has shown a sharp decrease over the stages from Model A with discrete components to those with M O S - I C and to those with LSI. At the same time, the reliability of the sets has been improved thanks to the decrease in number of the components as well as the jointing points by the adoption of IC and LSI. M T B F has also improved from 1500 hr on Model A to 6350 hr on Model C. The aforementioned probably explains how new
[- Quickening stage --=I-- Birth stage EDesigning _]Materializing ,~ stage T
stage
dun/60 Apr/63 Plan got Materialization under way got under way
Jul/64 Model no. I on market
--]=
Growth stage _ I_ _L_ A _ ] Ist period- [ 2nd period- [ -3rd period
Sep/65 Model no 2 on market
Feb/67 IC model on market
Sep/69 LSI model on market
FIG. 1. History of development. We call the days after the introduction of Model No. 2 the growth stage in which efforts were made in order to develop equipments with better reliabilities and smaller in size, lighter in weight and less expensive in cost. There have been various improvements on components, among which the most conspicuous was the changes in the electronic components as the main calculating element. This stage may be divided roughly into three periods. The first is for those with transistors, the second is for those with IC (bi-polar, MOS) and the third is for those with LSI. The data for the reliabilities in each period are given below.
2. IMPROVEMENTIN RELIABILITY There are such data available for checking reliability as those extracted from various test results in the plant or field data each of which has merits and demerits. Introduced here is the result
models have been developed and reliabilities of the device have been improved. It is our belief that the main factor to accomplish reliability depends on the improvement of the device, and for this purpose, it is an important key to obtain correct data and to establish right channels for feedingback comments to manufacturers.
Table 1. M T B F and failure rate by field data Stage
1st
2nd
3rd
Model
A
B
C
3640
6350
14 MOS-IC Tr., Di.
6-5 LSI
MTBF (hr) 1500 Failure rate of device ~. ( × 10-5 FR/hr) 45 Device Tr., Di.
R E L I A B I L I T Y SYMPOSIUM IN JAPAN
compressor age sampling program. It seems that in the near future the establishment of the overhaul time limit should be required because of the bearing deterioration. 3.3 The maintenance concept of B747's components There are about 700 items of LRU (line replacement units) in B747 of JAL, as it is so complicated it cannot be expected (because of the effort) to monitor every LRU, then JAL classified five categories for them, and now intended to find a proper maintenance program for each component. Category I. Mechanical high-speed rotating components which their failures by wear-out affect airworthiness and cost largely. Examples: constant speed drive (CSD), hydraulic pump, generator, cabin turbo-compressor, etc. 15 items. Category II. Mechanical relatively low-speed rotating components which take major parts of the system and are supposed a wear-out at the particular area. Examples: flight power packages, major hydraulic actuators, major pneumatic valves, etc. 22 items. Category III. Electronic equipments which are composed by static parts and their failures are random, and electro-mechanical equipments which are supposed wear-out but the failures are random. Both kinds of these equipments are also major func-
tional units. Examples: black boxes of electronic equipments and communication equipments, instruments, hydraulic actuators, pneumatic valves, etc. 161 items. Category IV. Items which faU under the FAA Maintenance Significant Item List except Categories I, II and III. Examples: control surface position indicators, controls-communication equipments, tank units, locking actuators, door actuators, miscellaneous motors, etc. 199 items. Category V. Relatively low cost items which their M T B F are higher than about 20,000 hr. Examples: control surface position transmitters, clocks, antenna, temperature sensors, relays, hydraulic filters, miscellaneous hydraulic valves. 287 items. At present our Aircraft Accessories Center are monitoring the operation and maintenance status continuously by establishing monitoring standard for all Categories I, II and III. For Category IV our center is monitoring by monthly PRR list issued by Company's Inspection Section. Items exceeding 36 upper limit are analyzed in more detail. Category V is not monitored except when their failures present unusual indication. In near future more special monitoring programs for each category shall be established by analyzing modes of each category.
RELIABILITY OF PRODUCTS ELECTRONIC MECHANICAL E Q U I P M E N T ELECTRONIC DESK TOP CALCULATOR T. SASAKI
Executive Director, General Manager of Industrial Instruments Division, Sharp Corporation 1. HISTORY OF DEVELOPMENT OF DESK TOP CALCULATOR
THE history of the development of the electronic desk top calculator dates back to the Designing Stage, as shown in Fig. 1, when the development plan including the basic research for inventing a new product got under way. Then about 4 yr were required to form up what we call the birth stage through the process of materializing the plan into specific commodities (materializing stage). During such a stage, we acquired new techniques which
had been unfamiliar to manufacturers of electrical home appliances, and made market researches to bring forth an electronic desk top calculator, the first in the world (Model No. 1). The electronic desk top calculator was quite a new device throughout the world when this Model No. 1 was first introduced. Therefore we were not prepared in either technical or marketing fields, and even suffered from a bad reputation. This bitter experience, however, was very useful for us to develop into Model No. 2.
47
R E L I A B I L I T Y S Y M P O S I U M IN JAPAN In the development process of Model No. 2, we gave the importance to the following points: 1. Examination of design. 2. Improvement of element. 3. Ten-key system. 4. Modification of specification. 5. Improvement of various components. 6. Improvement of reliability. As a matter of fact, the model then introduced enjoyed a very good reputation resulting in an epoch-making sales expansion. The new models manufactured and marketed one after another have so far kept us as the leading manufacturers in this industry.
obtained, stage by stage, at plant on M T B F extracted from field data and the failure rate of the main device. Table 1 represents M T B F and the failure rate of device per set. As seen in the table, the failure rate has shown a sharp decrease over the stages from Model A with discrete components to those with M O S - I C and to those with LSI. At the same time, the reliability of the sets has been improved thanks to the decrease in number of the components as well as the jointing points by the adoption of IC and LSI. M T B F has also improved from 1500 hr on Model A to 6350 hr on Model C. The aforementioned probably explains how new
[- Quickening stage --=I-- Birth stage EDesigning _]Materializing ,~ stage T
stage
dun/60 Apr/63 Plan got Materialization under way got under way
Jul/64 Model no. I on market
--]=
Growth stage _ I_ _L_ A _ ] Ist period- [ 2nd period- [ -3rd period
Sep/65 Model no 2 on market
Feb/67 IC model on market
Sep/69 LSI model on market
FIG. 1. History of development. We call the days after the introduction of Model No. 2 the growth stage in which efforts were made in order to develop equipments with better reliabilities and smaller in size, lighter in weight and less expensive in cost. There have been various improvements on components, among which the most conspicuous was the changes in the electronic components as the main calculating element. This stage may be divided roughly into three periods. The first is for those with transistors, the second is for those with IC (bi-polar, MOS) and the third is for those with LSI. The data for the reliabilities in each period are given below.
2. IMPROVEMENTIN RELIABILITY There are such data available for checking reliability as those extracted from various test results in the plant or field data each of which has merits and demerits. Introduced here is the result
models have been developed and reliabilities of the device have been improved. It is our belief that the main factor to accomplish reliability depends on the improvement of the device, and for this purpose, it is an important key to obtain correct data and to establish right channels for feedingback comments to manufacturers.
Table 1. M T B F and failure rate by field data Stage
1st
2nd
3rd
Model
A
B
C
3640
6350
14 MOS-IC Tr., Di.
6-5 LSI
MTBF (hr) 1500 Failure rate of device ~. ( × 10-5 FR/hr) 45 Device Tr., Di.