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

• US 8,805,564 B2
• Filed: 12/27/2011
• Issued: 08/12/2014
• Est. Priority Date: 12/27/2010
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Fontanot, Paolo, Haase, Antje, Sala, Fabio
• Primary Examiner(s): KASENGE, CHARLES R
• Application Number:
  US13/337,644
• Publication Number:
  US 20120165968A1
• Time in Patent Office: 959 Days
• Field of Search: 700/95, 700/97, 700/99, 700/100, 700/101, 700/103, 700/106
• US Class Current: 700/101
• CPC Class Codes: G05B 19/41865 characterised by job scheduling, process planning, material flow
• CPC Class Codes: G05B 2219/31388 Just in time JIT, kanban is box to control flow of workpiece
• CPC Class Codes: G05B 2219/31389 Pull type, client order decides manufacturing
• CPC Class Codes: G05B 2219/32266 Priority orders

Abstract

A method and a system control just in time item production via kanban cards. The items are 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. A local buffer threshold parameter is provided and denotes the desired safety stock of the items of the specific type in the buffer. A global demand threshold parameter is provided and denotes the quantity of items of the specific item type required along the downstream process to satisfy the estimated demand. Whenever a kanban card is associated to an item of a specific type switches status, it is assigned one of four priority levels indicating the priority level of the production request. At each production pair, an item is produced of a type whose priority level is the highest according to a given priority model.

Claims

1. A method 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 method 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.

2. The method according to claim 1, wherein at step c):

whenever the kanban card associated to the item of the specific type switches status it switches from one of empty to full or from full to empty;

or

whenever the kanban card associated to the item of the specific type switches status it switches from empty to full or whenever the kanban card associated to the item of the specific type switches status it switches from full to empty.

3. The method according to claim 1, wherein:

the production pairs include a production pair “

j”

being one of a generic production pair of “

N”

production pairs where “

j”

is comprised between “

1” and

“

N”

; and

at step b) the global demand threshold parameter for the production pair “

j”

is calculated as a number of finished good items of the specific type, required in an average lead time interval, defined as an average time for an item of a certain type to move from the assigned buffer “

j−

1”

to the assigned buffer “

N”

of a production flow; and

the number of full kanban cards for the items of the same specific type along the downstream process is calculated as a sum of the full kanban cards contained in each of the assigned buffer belonging to each of the production pairs comprised between the production pair “

j−

1” and

the production pair “

N”

.

4. The method according to claim 1, wherein the kanban cards assigned to different priority levels are marked with different colors.

5. The method according to claim 4, wherein the kanban cards are marked with colors as follows:

the kanban card of the first priority level is assigned with a green color;

the kanban card of the second priority level is assigned with a blue color;

the kanban card of the third priority level is assigned with a yellow color; and

the kanban card of the forth priority level is assigned with a red color.

6. The method according to claim 1, wherein information on the kanban cards are visualized on a screen via an electronic kanban-board (EKB) at a workstation via a manufacturing execution system (MES) which is provided with real time information (RIT) on movements of produced items and of the kanban cards.

7. The method according to claim 1, which further comprises providing the kanban cards with an RFID tag and equipping the assigned buffers with an RFID antenna.

8. 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.

9. 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.

10. 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.