Assembly line balancer

• US 5,177,688 A
• Filed: 01/13/1992
• Issued: 01/05/1993
• Est. Priority Date: 12/01/1989
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Stevens, David B., Rentschler, David
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): GORDON, PAUL P
• Application Number:
  US07/821,331
• Time in Patent Office: 358 Days
• Field of Search: 364/138, 364/148, 364/468, 364/401, 364/403, 364/474.11, 395/550, 395/912, 395/919
• US Class Current: 700/101
• CPC Class Codes: G05B 19/41835 characterised by programme execution
• CPC Class Codes: G05B 2219/32056 Balance load of workstations by grouping tasks
• CPC Class Codes: G06Q 10/06 Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

Assembly line balancer groups tasks of multi-sided, mixed model assembly lines on the basis of per side and per model constraints. Resulting compound tasks involve less computational time and power in balancing the line.

Claims

1. A method for balancing the assignment of a plurality of tasks to a plurality of workstations, comprising the steps of:

(a) providing a plurality of partially ordered sets of tasks, each of which tasks has an assigned task time;

(b) linearly ordering each of said sets by a ranking technique based on said task times;

(c) grouping a plurality of said tasks between said sets on the basis of a first class of constraints;

(d) linearly reordering each of said task sets by a ranking technique based on said task times wherein the rank of a task in one of said groups is replaced by the maximum of the ranks of the tasks in said group during said reordering; and

(e) selecting for assignment to workstations groups of tasks in order of their rank and without violating a first plurality of constraints, wherein each of said workstations has a cycle time.

2. The method of claim 1 wherein said ranking technique ranks said tasks by said task time plus the sum of all said task times of all subsequent tasks.

3. The method of claim 1 comprising the further steps of:

(a) repeating the steps (b)-(e) at least once with a different cycle time for each repetition; and

(b) selecting one of the resulting assignments of tasks to workstations.

4. The method of claim 1, comprising the further steps of:

(f) regrouping a plurality of said tasks between said sets on the basis of a second class of constraints; and

(g) second linearly reordering each of said task sets of a ranking technique based on said task times wherein the rank of a task in one of said regroups is replaced by the maximum of the ranks of the tasks in said regroup of step (f) during said second reordering;

(h) wherein step (e) applies to said regroups instead of said groups.

5. The method of claim 4 wherein said second ranking technique ranks said tasks by said task time plus the sum of all said task times of all subsequent tasks.

6. The method of steps (a)-(b) of claim 4 comprising the further steps of:

(a) repeating the steps at least once with a different cycle time for each repetition; and

(b) selecting one of the resulting assignments of tasks to workstations.

7. The method of claim 4, wherein said ranking technique of step (g) is the same as the ranking technique of step (d).

8. The method of steps (b)-(e) of claim 1 comprising the further steps of:

(a) repeating the steps at least once with a different cycle time for each repetition; and

(b) selecting one of the resulting assignments of tasks to workstations.

9. The method of claim 1, further comprising the step of displaying a range of possible outcomes of an assembly line balance by providing at least one of a plurality of displays, said plurality including:

(i) a display of the number of required workstations and the cumulative idle time for an input range of cycle times;

(ii) a display of the required cycle time and the cumulative idle time for an input range of the number of required workstations;

(iii) a display of the number of required workstations and the cumulative idle time for an input range of production rates.

16. The method of claim 7, further comprising the step of displaying a range of possible outcomes of an assembly line balance by providing at least one of a plurality of displays, said plurality including:

(i) a display of the number of required workstations and the cumulative idle time for an input range of cycle times;

(ii) a display of the required cycle time and the cumulative idle time for an input range of the number of required workstations;

(iii) a display of the number of required workstations and the cumulative idle time for an input range of production rates.

10. A system for assembly line balancing the assignment of a plurality of tasks for a plurality of models of a product to a plurality of workstations based on precedence and grouping constraints, comprising:

(a) a knowledge base wherein task parameters and said precedence and grouping constraints are input and stored; and

(b) processing circuitry coupled to said knowledge base for linearly ordering each of said tasks by a ranking technique based on said task parameters, grouping of a plurality of said tasks on the basis of said grouping constraints, linearly reordering of each of said tasks by a ranking technique wherein the rank of a task in one of said groups is replaced by the maximum of the ranks of the tasks in said group during said reordering, and selecting for assignment to said workstations of groups of tasks in order of their rank and without violating said precedence and grouping constraints.

11. A method for balancing the assignment of a plurality of tasks to a plurality of workstations, wherein said tasks are for a plurality of models of a product, each of which models has a plurality of sides, comprising the steps of:

(a) providing for each of said sides of each of said models a partially ordered sets of tasks, each of which tasks has an assigned task time;

(b) linearly ordering each of said sets by a ranking technique based on said task times;

(c) grouping a plurality of said tasks between said sides on the basis of a first class of constraints;

(d) linearly reordering each of said task sets by a ranking technique based on said task times wherein the rank of a task in one of said groups is replaced by the maximum of the ranks of the tasks in said group during said reordering;

(e) regrouping a plurality of said tasks between said models on the basis of a second class of constraints;

(f) second linearly reordering each of said task sets by a ranking technique based on said task times wherein the rank of a task in one of said regroups is replaced by the maximum of the ranks of the tasks in said regroup of step (e) during said second ranking; and

(g) selecting for assignment to workstations regroups of tasks in order of their rank and without violating a first plurality of constraints, wherein each of said workstations has a cycle time.

12. The method of claim 11 wherein said ranking technique ranks said tasks by said task time plus the sum of said task times of all subsequent tasks.

13. The method of claim 11 wherein said cycle time is equal for all of said workstations.

14. The method of claim 11 wherein, given n workstations running in parallel, and a nominal cycle time T, the cycle time of each of said n workstations is n×

T.

15. The method of claim 11, wherein said ranking technique of step (d) is the same as the ranking technique of step (f).