Visual Electronic Kanban System for Small Batch Enterprises (1)
In the increasingly competitive market environment, the concept of Just In Time (JIT) has been widely accepted and advocated by many domestic and foreign enterprises. However, the traditional JIT method is summed up from the practice of Toyota Motor Corporation's large-scale production. Its ideal production environment is large-scale and repetitive production, which is very different from the current market environment of multi-variety and small-batch production. Inappropriate and unlikely to be successful.
In order to successfully apply advanced management concepts to the new market environment, "innovative application" must be carried out. Combining kanban technology with information system is a new hotspot in domestic research and application. Foreign researchers have also conducted a lot of research on kanban technology in JIT production mode; Toyota production mode is not suitable for multi-variety and small batch production. However, in these literature studies, there are few in-depth studies on the multi-variety and small-batch Kanban method.
This paper proposes a solution based on visual Kanban () technology to solve the applicability of JIT method in multi-variety and small batch production.
1. Disadvantages of using traditional Kanban for multi-variety and small batch production
The traditional JIT production method is summed up from the practice of Toyota Motor Corporation's large-scale production. It uses paper Kanban as a means and demand-driven "pull" production method, which is used for the production of multi-variety and small-batch products. disadvantages.
1) The backwardness of traditional Kanban means is not conducive to information management. Traditional Kanban adopts paper Kanban, and its data cannot be directly transmitted to the computer information system, which is not conducive to information processing, resulting in insufficient planning and forecasting capabilities.
2) For small batch production, it is difficult to realize the traditional pulling method. Due to the small batch size and short process cycle, the last process has not yet started production, and the first process has completed the entire batch production. Therefore, if there is no previous batch of WIP of the same variety remaining on site, the "demand-pull" type of production cannot be formed.
In order to realize the "continuous" pull production of small batches in the traditional Kanban method, it is necessary to keep the materials and work-in-process of various kinds of products on the production site, which results in a large amount of accumulation. Therefore, most enterprises still mainly adopt the push-type production method for small batch order production, that is, the production order is issued to each process, but it is impossible to achieve timely on-demand production.
3) When multiple varieties are frequently alternately produced, the frequent switching of traditional kanbans is prone to errors, and the storage of kanbans is also a problem. For some products, it takes a long time to produce again after one production, which makes the storage and use of Kanban more troublesome.
4) Lack of mastery of global kanban information, unable to provide a comprehensive and real-time production site kanban process and an overall description of the kanban status of each process, which is prone to confusion in a production environment where varieties and batches are frequently switched.
2. Solutions to realize multi-variety and small-batch JIT production
2.1 Application Scenarios of Visual Kanban System Visual Kanban system consists of information system, electronic Kanban and barcode scanning input terminal. The information system is an ERP system that integrates lean production methods, and a visual Kanban module is added on this basis.
2.2 Visual Kanban System Operation Process It is suitable for the operation process of the visual Kanban system for the production of multi-variety and small batch orders, and the MRP II production sequence planning module in the ERP system.
Taking the electronic Kanban of the SMT process as an example, the operation process is as follows.
1) The "production sequence plan" of the self-made parts (PWBA board) is generated by MRP-II, and the production sequence and quantity of multiple varieties are arranged for one week.
2) Using the visual kanban technology, the kanban scheduling of the process is carried out, and the sequence of the process operation is arranged.
3) Generate a new "empty" production kanban (PK), and go down to the process site through the electronic kanban; scan the barcode of the main PCB to start production, and the kanban status is "in production" at this time.
4) When the production of the specified number of products is completed and the barcode is scanned, the status of the kanban becomes "full".
5) When the number of "full" kanbans reaches the specified number, the production of the kanban will be suspended, and the production of the kanban will not be restarted until a new, supplementary "empty" kanban is issued. Unlike traditional kanbans, the system can then start production by releasing an "empty" kanban for another order according to the order in which the kanban is scheduled.
6) When the material is "taken away" in the subsequent process, if the total amount of the order has not been completed, a new "empty" kanban with a supplementary quantity will be automatically issued; if it has been completed, the cycle of the production kanban will be "finished", Next a new "empty" kanban for another order is released according to the schedule.
7) If the consumption of the material is suspended due to an abnormal situation in the subsequent process, the kanban status is always "full", then no new "empty" production kanban will be issued for the material, and the production will be suspended, thus avoiding the on-site work in process. accumulation.
In order to successfully apply advanced management concepts to the new market environment, "innovative application" must be carried out. Combining kanban technology with information system is a new hotspot in domestic research and application. Foreign researchers have also conducted a lot of research on kanban technology in JIT production mode; Toyota production mode is not suitable for multi-variety and small batch production. However, in these literature studies, there are few in-depth studies on the multi-variety and small-batch Kanban method.
This paper proposes a solution based on visual Kanban () technology to solve the applicability of JIT method in multi-variety and small batch production.
1. Disadvantages of using traditional Kanban for multi-variety and small batch production
The traditional JIT production method is summed up from the practice of Toyota Motor Corporation's large-scale production. It uses paper Kanban as a means and demand-driven "pull" production method, which is used for the production of multi-variety and small-batch products. disadvantages.
1) The backwardness of traditional Kanban means is not conducive to information management. Traditional Kanban adopts paper Kanban, and its data cannot be directly transmitted to the computer information system, which is not conducive to information processing, resulting in insufficient planning and forecasting capabilities.
2) For small batch production, it is difficult to realize the traditional pulling method. Due to the small batch size and short process cycle, the last process has not yet started production, and the first process has completed the entire batch production. Therefore, if there is no previous batch of WIP of the same variety remaining on site, the "demand-pull" type of production cannot be formed.
In order to realize the "continuous" pull production of small batches in the traditional Kanban method, it is necessary to keep the materials and work-in-process of various kinds of products on the production site, which results in a large amount of accumulation. Therefore, most enterprises still mainly adopt the push-type production method for small batch order production, that is, the production order is issued to each process, but it is impossible to achieve timely on-demand production.
3) When multiple varieties are frequently alternately produced, the frequent switching of traditional kanbans is prone to errors, and the storage of kanbans is also a problem. For some products, it takes a long time to produce again after one production, which makes the storage and use of Kanban more troublesome.
4) Lack of mastery of global kanban information, unable to provide a comprehensive and real-time production site kanban process and an overall description of the kanban status of each process, which is prone to confusion in a production environment where varieties and batches are frequently switched.
2. Solutions to realize multi-variety and small-batch JIT production
2.1 Application Scenarios of Visual Kanban System Visual Kanban system consists of information system, electronic Kanban and barcode scanning input terminal. The information system is an ERP system that integrates lean production methods, and a visual Kanban module is added on this basis.
2.2 Visual Kanban System Operation Process It is suitable for the operation process of the visual Kanban system for the production of multi-variety and small batch orders, and the MRP II production sequence planning module in the ERP system.
Taking the electronic Kanban of the SMT process as an example, the operation process is as follows.
1) The "production sequence plan" of the self-made parts (PWBA board) is generated by MRP-II, and the production sequence and quantity of multiple varieties are arranged for one week.
2) Using the visual kanban technology, the kanban scheduling of the process is carried out, and the sequence of the process operation is arranged.
3) Generate a new "empty" production kanban (PK), and go down to the process site through the electronic kanban; scan the barcode of the main PCB to start production, and the kanban status is "in production" at this time.
4) When the production of the specified number of products is completed and the barcode is scanned, the status of the kanban becomes "full".
5) When the number of "full" kanbans reaches the specified number, the production of the kanban will be suspended, and the production of the kanban will not be restarted until a new, supplementary "empty" kanban is issued. Unlike traditional kanbans, the system can then start production by releasing an "empty" kanban for another order according to the order in which the kanban is scheduled.
6) When the material is "taken away" in the subsequent process, if the total amount of the order has not been completed, a new "empty" kanban with a supplementary quantity will be automatically issued; if it has been completed, the cycle of the production kanban will be "finished", Next a new "empty" kanban for another order is released according to the schedule.
7) If the consumption of the material is suspended due to an abnormal situation in the subsequent process, the kanban status is always "full", then no new "empty" production kanban will be issued for the material, and the production will be suspended, thus avoiding the on-site work in process. accumulation.
The main function of the Withdrawing Kanban (WK) is to indicate the location and quantity of the pick-up when the supplementary materials are received. It can usually be used repeatedly, and the reclaiming process does not take up time in the process. Therefore, the form of reclaiming kanban in the visual kanban system can still use printed, barcoded paper kanbans to run and circulate in the traditional way. Of course, RFID-based electronic signage can also be used.
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