Dalam sistem Just - in - Time (JIT), aliran kerja di kendalikan oleh operasi berikutnya, dimana setiap stasiun kerja menarik out put dari stasiun kerja sebelumnya sesuai dengan kebutuhan. Dalam sistem JIT, pesanan produksi (production order) dapat dikomunikasikan dengan berbagai cara, dapat menggunakan alat elektronik seperti lampu, alat transportasi seperti konteiner, atau alat paling banyak digunakan adalah semacam tanda yang disebut sebagai kamban. Kamban adalah suatu istilah dalam bahasa Jepang yang serupa artinya dengan visible record or signal. Pada umumnya alat kamban yang dipergunakan adalah kartu, sehingga sering disebut kartu kamban. Kamban dipergunakan sebagai tanda (signal) kepada stasiun pemasok bahwa stasiun pengguna sedang membutuhkan material, sehingga stasiun pemasok (pelanggan) harus segera mengirimkan material itu sesuai dengan kebutuhan yang tertera dalam kartu kamban. Pada dasarnya sistem JIT merupakan suatu konsep filosofi yaitu, memproduksi produk yang dibutuhkan, pada saat dibutuhkan oleh pelanggan, dalam jumlah sesuai kebutuhan pelanggan, pada tingkat kualitas prima, dari setiap tahap proces dalam sistem manufakturing, dengan cara yang paling ekonomis dan efisien melalui eliminasi pemborosan (waste elimination) dan perbaikan proses terus menerus (countineous process improvement). Konsep just in time adalah suatu konsep di mana bahan baku yang digunakan untuk aktifitas produksi didatangkan dari pemasok atau suplier tepat pada waktu bahan itu dibutuhkan oleh proses produksi, sehingga akan sangat menghemat bahkan meniadakan biaya persediaan barang / penyimpanan barang / stocking cost.
Teori konsep just in time ditemukan oleh seorang berkebangsaan jepang bernama Taiichi Ohno dari perusahaan kendaraan motor Toyota. Perhitungan serta kerja sama yang baik antara penyalur, pemasok dan bagian produksi haruslah baik. Keterlambatan akibat salah perhitungan atau kejadian lainnya dapat menghambat proses produksi sehingga dapat menimbulkan kerugian bagi perusahaan.
FALSAFAH JIT
Menyediakan kebutuhan yang cukup pada waktu yang tepat.
JIT sebagai suatu sistem perbaikan yang berkelanjutan, dapat mengatasi kesia-siaan & variabilitas.
Produk yg disimpan, terlambat diproduksi, produk yg mengantri, produk yg rusak merupakan kesia-siaan.
Variabilitas adalah setiap penyimpangan dari proses optimal yg mengantarkan produk sempurna tepat waktu.
Pengelolaan JIT bertujuan untuk menghapuskan segala sesuatu yang tak bernilai tambah pada setiap saat.
Prinsip ini berasal dari pengamatan sederhana: konsumen hanya bersedia membayar nilai tambah yang kita hasilkan. Semua yang lain adalah Muda atau tak bernilai tambah. Oleh karena itu tujuan pengelolaan JIT terfokus pada penghapusan semua bentuk pemborosan (Muda). JIT juga adalah sistem yang mengejar kesempurnaan (nilai yang esential) saat Muda atau pemborosan dihapus.
Rantai pemasokkan yang ramping
Perubahan dari produksi tradisional menjadi rantai pemasokkan (supply chain) yang ramping adalah salah satu tahapan penting dalam pengelolaan JIT. Alran barang dan lairan produksi satu unit (one piece flow) diterapkan untuk memproduksi beragam produk industri, dengan ukuran lot yang kecil, secara ekonomis dan dalam jumlah yang sesuai dengan permintaan pasar.
Standarisasi kerja
Merupakan kunci sukses sistem JIT. Standarisasi kerja merupakan sarana pelatihan bagi para karyawan guna memastikan tindakan yang tepat dengan urutan kerja yang tepat pula dan kerjasama team. Ini pula yang merupakan jaminan kualitas dan produktivitas.
Just-In-Time (JIT) Manufacturing (Page 1 of 2)
Just-In-time manufacturing, or JIT, is a management philosophy aimed at eliminating manufacturing wastes by producing only the right amount and combination of parts at the right place at the right time. This is based on the fact that wastes result from any activity that adds cost without adding value to the product, such as transferring of inventories from one place to another or even the mere act of storing them.
The goal of JIT, therefore, is to minimize the presence of non-value-adding operations and non-moving inventories in the production line. This will result in shorter throughput times, better on-time delivery performance, higher equipment utilization, lesser space requirement, lower dpm’s, lower costs, and greater profits.
JIT finds its origin in Japan, where it has been in practice since the early 1970’s. It was developed and perfected by Taiichi Ohno of Toyota, who is now referred to as the father of JIT. Taiichi Ohno developed this philosophy as a means of meeting customer demands with minimum delays. Thus, in the olden days, JIT is used not to reduce manufacturing wastage, but primarily to produce goods so that customer orders are met exactly when they need the products.
JIT is also known as lean production or stockless production, since the key behind a successful implementation of JIT is the reduction of inventory levels at the various stations of the production line to the absolute minimum. This necessitates good coordination between stations such that every station produces only the exact volume that the next station needs. On the other hand, a station pulls in only the exact volume that it needs from the preceding station.
The JIT system consists of defining the production flow and setting up the production floor such that the flow of materials as they get manufactured through the line is smooth and unimpeded, thereby reducing material waiting time. This requires that the capacities of the various work stations that the materials pass through are very evenly matched and balanced, such that bottle necks in the production line are eliminated. This set-up ensures that the materials will undergo manufacturing without queueing or stoppage.
Another important aspect of JIT is the use of a 'pull' system to move inventories through the production line. Under such a system, the requirements of the next station is what modulates the production of a particular station. It is therefore necessary under JIT to define a process by which the pulling of lots from one station to the next is facilitated.
JIT is most applicable to operations or production flows that do not change, i.e., those that are simply repeated over and over again. An example of this would be an automobile assembly line, wherein every car undergoes the same production process as the one before it.
JIT has likewise been practiced successfully by some semiconductor companies. Still, there are some semiconductor companies that don’t practice JIT for the simple reason that their operations are too complex for JIT application. On the other hand, that’s precisely the challenge of JIT – creation of a production set-up that is simple enough to allow JIT.
Guidelines for Successful JIT Implementation
1) Make the factory loadings uniform, linear, and stable. Fluctuations in manufacturing loadings will result in bottlenecks.
2) Reduce, if not eliminate, conversion and set-up times.
3) Reduce lot sizes. This will smoothen out the flow of inventories from one station to another, although this may necessitate more frequent deliveries or transfers.
4) Reduce lead times by moving work stations closer together and streamlining the production floor lay-out, applying cellular manufacturing concepts, using technology to automate processes and improve coordination.
5) Reduce equipment downtimes through good preventive maintenance.
6) Cross-train personnel to achieve a very flexible work force.
7) Require stringent supplier quality assurance since an operation under JIT can not afford to incur errors due to defects.
8) Use a control system to convey lots between workstations efficiently; the use of a kanban system is an example of this
Kanban Systems
Kanban systems are often associated with JIT implementation. In fact, some people have the misimpression that JIT requires the use of a kanban system. Having a kanban system is not a strict requirement of JIT implementation, but their use as a tool for practicing JIT has become quite popular owing to its simplicity.
A kanban is a card attached to the carrier or container of a lot used to match what needs to be produced in a work station and what needs to be delivered to the next station. As mentioned, a JIT system is basically a 'pull' system, which means that what needs to be produced in a particular station depends on what the next station needs. Ultimately the production is therefore modulated by end customer orders. Kanbans, which contain information about the lots and quantities involved, are therefore used to facilitate the execution of this 'pull' system. With this 'pull' system, no parts that can not be processed in succeeding stations will be produced.
There are two types of kanban assigned to every lot, namely, a production kanban (P-kanban) and a conveyance kanban (C-kanban). The P-kanban denotes the need to produce more parts while the C-kanban denotes the need to deliver more parts to the next station. No parts can be produced unless authorized by a P-kanban. On the other hand, a C-kanban triggers the 'pulling' or 'withdrawal' of units from the preceding station. C-kanbans are also known as 'move' or 'withdrawal' kanbans.
Teori konsep just in time ditemukan oleh seorang berkebangsaan jepang bernama Taiichi Ohno dari perusahaan kendaraan motor Toyota. Perhitungan serta kerja sama yang baik antara penyalur, pemasok dan bagian produksi haruslah baik. Keterlambatan akibat salah perhitungan atau kejadian lainnya dapat menghambat proses produksi sehingga dapat menimbulkan kerugian bagi perusahaan.
FALSAFAH JIT
Menyediakan kebutuhan yang cukup pada waktu yang tepat.
JIT sebagai suatu sistem perbaikan yang berkelanjutan, dapat mengatasi kesia-siaan & variabilitas.
Produk yg disimpan, terlambat diproduksi, produk yg mengantri, produk yg rusak merupakan kesia-siaan.
Variabilitas adalah setiap penyimpangan dari proses optimal yg mengantarkan produk sempurna tepat waktu.
Pengelolaan JIT bertujuan untuk menghapuskan segala sesuatu yang tak bernilai tambah pada setiap saat.
Prinsip ini berasal dari pengamatan sederhana: konsumen hanya bersedia membayar nilai tambah yang kita hasilkan. Semua yang lain adalah Muda atau tak bernilai tambah. Oleh karena itu tujuan pengelolaan JIT terfokus pada penghapusan semua bentuk pemborosan (Muda). JIT juga adalah sistem yang mengejar kesempurnaan (nilai yang esential) saat Muda atau pemborosan dihapus.
Rantai pemasokkan yang ramping
Perubahan dari produksi tradisional menjadi rantai pemasokkan (supply chain) yang ramping adalah salah satu tahapan penting dalam pengelolaan JIT. Alran barang dan lairan produksi satu unit (one piece flow) diterapkan untuk memproduksi beragam produk industri, dengan ukuran lot yang kecil, secara ekonomis dan dalam jumlah yang sesuai dengan permintaan pasar.
Standarisasi kerja
Merupakan kunci sukses sistem JIT. Standarisasi kerja merupakan sarana pelatihan bagi para karyawan guna memastikan tindakan yang tepat dengan urutan kerja yang tepat pula dan kerjasama team. Ini pula yang merupakan jaminan kualitas dan produktivitas.
Just-In-Time (JIT) Manufacturing (Page 1 of 2)
Just-In-time manufacturing, or JIT, is a management philosophy aimed at eliminating manufacturing wastes by producing only the right amount and combination of parts at the right place at the right time. This is based on the fact that wastes result from any activity that adds cost without adding value to the product, such as transferring of inventories from one place to another or even the mere act of storing them.
The goal of JIT, therefore, is to minimize the presence of non-value-adding operations and non-moving inventories in the production line. This will result in shorter throughput times, better on-time delivery performance, higher equipment utilization, lesser space requirement, lower dpm’s, lower costs, and greater profits.
JIT finds its origin in Japan, where it has been in practice since the early 1970’s. It was developed and perfected by Taiichi Ohno of Toyota, who is now referred to as the father of JIT. Taiichi Ohno developed this philosophy as a means of meeting customer demands with minimum delays. Thus, in the olden days, JIT is used not to reduce manufacturing wastage, but primarily to produce goods so that customer orders are met exactly when they need the products.
JIT is also known as lean production or stockless production, since the key behind a successful implementation of JIT is the reduction of inventory levels at the various stations of the production line to the absolute minimum. This necessitates good coordination between stations such that every station produces only the exact volume that the next station needs. On the other hand, a station pulls in only the exact volume that it needs from the preceding station.
The JIT system consists of defining the production flow and setting up the production floor such that the flow of materials as they get manufactured through the line is smooth and unimpeded, thereby reducing material waiting time. This requires that the capacities of the various work stations that the materials pass through are very evenly matched and balanced, such that bottle necks in the production line are eliminated. This set-up ensures that the materials will undergo manufacturing without queueing or stoppage.
Another important aspect of JIT is the use of a 'pull' system to move inventories through the production line. Under such a system, the requirements of the next station is what modulates the production of a particular station. It is therefore necessary under JIT to define a process by which the pulling of lots from one station to the next is facilitated.
JIT is most applicable to operations or production flows that do not change, i.e., those that are simply repeated over and over again. An example of this would be an automobile assembly line, wherein every car undergoes the same production process as the one before it.
JIT has likewise been practiced successfully by some semiconductor companies. Still, there are some semiconductor companies that don’t practice JIT for the simple reason that their operations are too complex for JIT application. On the other hand, that’s precisely the challenge of JIT – creation of a production set-up that is simple enough to allow JIT.
Guidelines for Successful JIT Implementation
1) Make the factory loadings uniform, linear, and stable. Fluctuations in manufacturing loadings will result in bottlenecks.
2) Reduce, if not eliminate, conversion and set-up times.
3) Reduce lot sizes. This will smoothen out the flow of inventories from one station to another, although this may necessitate more frequent deliveries or transfers.
4) Reduce lead times by moving work stations closer together and streamlining the production floor lay-out, applying cellular manufacturing concepts, using technology to automate processes and improve coordination.
5) Reduce equipment downtimes through good preventive maintenance.
6) Cross-train personnel to achieve a very flexible work force.
7) Require stringent supplier quality assurance since an operation under JIT can not afford to incur errors due to defects.
8) Use a control system to convey lots between workstations efficiently; the use of a kanban system is an example of this
Kanban Systems
Kanban systems are often associated with JIT implementation. In fact, some people have the misimpression that JIT requires the use of a kanban system. Having a kanban system is not a strict requirement of JIT implementation, but their use as a tool for practicing JIT has become quite popular owing to its simplicity.
A kanban is a card attached to the carrier or container of a lot used to match what needs to be produced in a work station and what needs to be delivered to the next station. As mentioned, a JIT system is basically a 'pull' system, which means that what needs to be produced in a particular station depends on what the next station needs. Ultimately the production is therefore modulated by end customer orders. Kanbans, which contain information about the lots and quantities involved, are therefore used to facilitate the execution of this 'pull' system. With this 'pull' system, no parts that can not be processed in succeeding stations will be produced.
There are two types of kanban assigned to every lot, namely, a production kanban (P-kanban) and a conveyance kanban (C-kanban). The P-kanban denotes the need to produce more parts while the C-kanban denotes the need to deliver more parts to the next station. No parts can be produced unless authorized by a P-kanban. On the other hand, a C-kanban triggers the 'pulling' or 'withdrawal' of units from the preceding station. C-kanbans are also known as 'move' or 'withdrawal' kanbans.
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