Method and software for controlling just in time item production via kanban cards

A system, comprising:

• production pairs each containing one workstation and an assigned buffer;
• a raw material buffer;
• means for controlling a just-in-time (JIT) item production via kanban cards in the system, items being transformed according to a flow shop containing said raw material buffer followed by a sequence of said production pairs, each of said workstations producing an item to be moved into said assigned buffer, a first workstation of said workstations producing the item starting from said raw material buffer and each other remaining said workstations produces the item starting from said assigned buffer assigned to a previous adjacent said workstation, each of said workstations being able to produce more than one type of item according to requests received by means of different sets of different one of the kanban cards associated to different item types, each set of the kanban cards consists of a given number of kanbans, wherein each of the kanban cards can have two statuses including an empty status denoting that item replenishment is requested and a full status denoting that a produced item is ready in the assigned buffer, said means programmed to:
• a) provide a local buffer threshold parameter denoting a desired safety stock of the items of a specific type in said assigned buffer for each of said production pairs, for each specific item type and at given points in time;
• b) provide a global demand threshold parameter denoting a quantity of the items of the specific item type required along a downstream process to satisfy an estimated demand for each of said production pairs, for each of the specific item types and at other given points in time;
• c) at each of said production pairs, whenever the kanban card associated to an item of the specific type switches status, assign to the kanban card one of four priority levels indicating a priority level of a production request of the associated item type, according to the following logical rules:
• assign a first priority level to the kanban card if a number of full kanban cards of items of a same specific type at said assigned buffer is greater than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type along the downstream process is greater than the global demand threshold parameter;
• assign a second priority level to the kanban card if the number of full kanban cards of items of the same specific type at said production pair is lower or equal than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type in the downstream process is greater than the global demand threshold parameter;
• assign a third priority level to the kanban card if the number of full kanban cards of items of the same specific type at said production pair is greater than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type along the downstream process is lower or equal than the global demand threshold parameter;
• assign a fourth priority level to the kanban card if the number of full kanban cards of items of the same specific type at said production pair is lower or equal than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type along the downstream process is lower or equal than the global demand threshold parameter;
• d) produce, at each of said production pairs, the item of a type whose priority level is highest according to a given priority model defining a priority sequence of the four priority levels for production requests for different item types.

A non-transitory computer-readable medium having computer-executable instructions executed on a processor for controlling a just-in-time (JIT) item production via kanban cards in a discrete manufacturing production system, items being transformed according to a flow shop containing a raw material buffer followed by a sequence of production pairs containing one workstation and an assigned buffer, each of the workstations producing an item to be moved into the assigned buffer, a first workstation producing the item starting from the raw material buffer and each other remaining workstation produces the item starting from the buffer assigned to a previous adjacent workstation, each of the workstations being able to produce more than one type of item according to requests received by means of different sets of different one of the kanban cards associated to different item types, each set of the kanban cards consists of a given number of kanbans, wherein each of the kanban cards can have two statuses including an empty status denoting that item replenishment is requested and a full status denoting that a produced item is ready in the assigned buffer, the instructions which comprises the steps of:

• a) providing a local buffer threshold parameter denoting a desired safety stock of the items of a specific type in the assigned buffer for each of the production pairs, for each specific item type and at given points in time;
• b) providing a global demand threshold parameter denoting a quantity of the items of the specific item type required along a downstream process to satisfy an estimated demand for each of the production pairs, for each of the specific item types and at other given points in time;
• c) at each of the production pairs, whenever the kanban card associated to an item of the specific type switches status, assigning to the kanban card one of four priority levels indicating a priority level of a production request of the associated item type, according to the following logical rules:
• assigning a first priority level to the kanban card if a number of full kanban cards of items of a same specific type at a production pair buffer is greater than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type along the downstream process is greater than the global demand threshold parameter;
• assigning a second priority level to the kanban card if the number of full kanban cards of items of the same specific type at the production pair is lower or equal than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type in the downstream process is greater than the global demand threshold parameter;
• assigning a third priority level to the kanban card if the number of full kanban cards of items of the same specific type at the production pair is greater than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type along the downstream process is lower or equal than the global demand threshold parameter;
• assigning a fourth priority level to the kanban card if the number of full kanban cards of items of the same specific type at the production pair is lower or equal than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type along the downstream process is lower or equal than the global demand threshold parameter;
• d) producing, at each of the production pairs, the item of a type whose priority level is highest according to a given priority model defining a priority sequence of the four priority levels for production requests for different item types.

A non-transitory computer-readable medium having stored thereon a data structure to be performed by a processor for controlling a just-in-time (JIT) item production via kanban cards in a discrete manufacturing production system, items being transformed according to a flow shop containing a raw material buffer followed by a sequence of production pairs containing one workstation and an assigned buffer, each of the workstations producing an item to be moved into the assigned buffer, a first workstation producing the item starting from the raw material buffer and each other remaining workstation produces the item starting from the buffer assigned to a previous adjacent workstation, each of the workstations being able to produce more than one type of item according to requests received by means of different sets of different one of the kanban cards associated to different item types, each set of the kanban cards consists of a given number of kanbans, wherein each of the kanban cards can have two statuses including an empty status denoting that item replenishment is requested and a full status denoting that a produced item is ready in the assigned buffer, the instructions which comprises the steps of:

• a) providing a local buffer threshold parameter denoting a desired safety stock of the items of a specific type in the assigned buffer for each of the production pairs, for each specific item type and at given points in time;
• b) providing a global demand threshold parameter denoting a quantity of the items of the specific item type required along a downstream process to satisfy an estimated demand for each of the production pairs, for each of the specific item types and at other given points in time;
• c) at each of the production pairs, whenever the kanban card associated to an item of the specific type switches status, assigning to the kanban card one of four priority levels indicating a priority level of a production request of the associated item type, according to the following logical rules:
• assigning a first priority level to the kanban card if a number of full kanban cards of items of a same specific type at a production pair buffer is greater than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type along the downstream process is greater than the global demand threshold parameter;
• assigning a second priority level to the kanban card if the number of full kanban cards of items of the same specific type at the production pair is lower or equal than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type in the downstream process is greater than the global demand threshold parameter;
• assigning a third priority level to the kanban card if the number of full kanban cards of items of the same specific type at the production pair is greater than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type along the downstream process is lower or equal than the global demand threshold parameter;
• assigning a fourth priority level to the kanban card if the number of full kanban cards of items of the same specific type at the production pair is lower or equal than the local buffer threshold parameter and if the number of full kanban cards for the items of the same specific type along the downstream process is lower or equal than the global demand threshold parameter;
• d) producing, at each of the production pairs, the item of a type whose priority level is highest according to a given priority model defining a priority sequence of the four priority levels for production requests for different item types.