Heijunka 1

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Heijunka 1
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Example 1
A manufacturing facility produces 3 parts. Each
part must be processed through cut, mold, and
assembly. Setup and processing times for each
part at each machine can be determined. Schedule
parts considering available labor/machine times,
efficiency and the daily demand for each part.
Daily demand matrix
Daily demand 40-day demand / 40
Setup time matrix
(e.g. It takes 10 min. to setup the cut machine
to cut part A. It takes 4 min. to setup the
assembly machine to assemble part C)
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Example 1
Processing time matrix
(e.g. It takes 5 min. for cut machine to cut 1
part of A. It takes 4 min. to assemble 1 part C.)
Available time matrix
Total working time per day working time per
shift no. of shifts per day no. of machines
allocated Total available time per day Total
working time per day efficiency
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Example 1
Ratios determine how many times should each part
be repeated within in one production cycle.

• There will be (123) 6 slots for parts in one
  production cycle. (or may be 7 slots including
  one
• empty slot for Made to Orders.)
• This production cycle will repeat itself through
  the day.
• The production cycle sequence,

will be a bad sequence of parts since Part Cs
will be accumulating.
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Example 1
What is the ideal sequence? Scramble the parts
as much as possible to reduce the build-up of one
part only, load-smoothing. The production cycle
sequence,
will be a good sequence of parts since the
production of each part is spread almost evenly
throughout the production. Thus, the production
schedule will be,
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Example 1

• QUESTIONS
• How many setups can we afford so that we can
  determine the batch size,
• considering total time available per day,
  setup and processing times?
• What is the batch size?
• What is the schedule?

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Example 1
Total available time for a process ? Total setup
time Total production time Total production
time for Cut Daily demand for part A
processing time of one part A at Cut Daily
demand for part B processing time of one part B
at Cut Daily demand for part C processing
time of one part C at Cut (255)(503)(754)
575 minutes Total production time for Mold
Daily demand for part A processing time of one
part A at Mold Daily demand for part B
processing time of one part B at Mold Daily
demand for part C processing time of one part C
at Mold (254)(506)(752) 550
minutes Total production time for Assembly
Daily demand for part A processing time of one
part A at Assembly Daily demand for part B
processing time of one part B at Assembly Daily
demand for part C processing time of one part C
at Assemb (252)(506)(754) 650 minutes
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Example 1
Next step is to determine how many setups we can
afford so that total time availability on each
process is not violated. Setup time for part A
for Cut (SACut) nA Setup time for part B for
Cut (SBCut) nB Setup time for part C for Cut
(SCCut) nC Total setup time for Cut Setup
time for part A for Mold (SAMold) nA Setup
time for part B for Mold (SBMold) nB Setup
time for part C for Mold (SCMold) nC
Total setup time for Mold Setup time for part A
for Assembly (SAAssembly) nA Setup time for
part B for Assembly (SBAssembly) nB Setup time
for part C for Assembly (SCAssembly) nC
Total setup time for Assembly
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Example 1
Therefore, Total setup time for Cut
? Total available setup time for Cut ? Total
available time for Cut -Total production time for
Cut ?(912 min.- 575 min.) ? 337 min Total
setup time for Mold ? Total available setup time
for Mold ? Total available time for Mold -Total
production time for Mold ?(960 min.- 550 min.)
? 410 min Total setup time for Assembly
? Total available setup time for Assembly ?
Total available time for Assembly -Total
production time for AssemblyMold ?(960 min.-
650 min.) ? 310 min
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Example 1


Note i Part i ( i A, B, C) Qi Batch size
of part i Di Daily demand for part i ni
Number of setups that will be required for part
i
Number of batches of part A to be produced is the
daily demand divided by the batch size. Since
the ratio of daily demand of part A to part B to
part C is 123, it is possible to determine nB
and nC in terms of nA nB 2nA and nC 3nA
assuming a standard batch size for all parts,
i.e. QA QB QC. Although the lower batch
sizes are preferred, batch size may vary from 1
to the daily demand. 1 ? QA ? 25 1 ? QB ? 50 1 ?
QC ? 75
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Example 1
Objective Maximize nAnBnC Constraints
(SACut nA) (SBcut nB) (SCCut nC ) ?
Total setup time available for Cut (SAMold nA)
(SBMold nB) (SCMold nC ) ? Total setup time
available for Mold (SAAssembly nA)
(SBAssembly nB) (SCAssembly nC ) ? Total
setup time available for

Assembly
Objective Maximize nAnBnC Constraints
(10 nA) (4 nB) (1 nC ) ? 337 (5 nA)
(3 nB) (2 nC ) ? 410 (2 nA) (6 nB)
(4 nC ) ? 310
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Example 1
SOLUTION Insert nB 2nA and nC 3nA into
the constraints. (10 nA) (4 (2nA)) (1
(3nA)) 21 nA 337 or nA 337/21
16.04 (5 nA) (3(2nA)) (2 (3nA)) 17
nA 410 or nA 410/17 24.12 (2
nA) (6 (2nA)) (4 (3nA)) 26 nA 310 or
nA 310/26 11.92
Since the goal is to maximize 6 nA (implying
nAnBnC ), the highest value we can get for nA
is 11, when 11.92 is rounded down. SCHEDULING n
A 11, nB 2nA22, nC 3nA33.
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Example 1
This solution suggests that the production cycle
will be repeated 11 times in a day, since A
appears once at one production cycle.
1 cycle
2nd cycle 11th
cycle
empty slot for MTOs
QA Daily demand for part A / nA 25/11 2.27
? 2 parts A per batch QB Daily demand for part
B / nA 50/22 2.27 ? 2 parts B per batch QC
Daily demand for part C / nA 75/33 2.27 ? 2
parts C per batch Total part A produced (2
parts/batch) (1 batch/production cycle) (11
cycles/day) 22 parts/day Total part B produced
(2 parts/batch) (2 batch/production cycle)
(11 cycles/day) 44 parts/day Total part C
produced (2 parts/batch) (3 batch/production
cycle) (11 cycles/day) 66 parts/day
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Example 1
With this schedule 3 parts A, 6 parts B and 9
parts C are unaccounted for the daily demand.
These amounts may be scheduled as a last round of
a days shift. Total time utilization at Cut for
11 cycles excluding MTOs (11 batches part A)
(10 min setup time 10 min processing time per
batch of 2 parts A) (22 batches part B) (4
min setup time 6 min processing time per batch
of 2 parts B) (33 batches part C) (1 min
setup time 8 min processing time per batch of
2 parts C) 737 min. Available time at Cut
912 min-737 min 175 min /day for MTOs and
unaccounted parts at Cut Total time utilization
at Mold for 11 cycles excluding MTOs (11
batches part A) (5 min setup time 8 min
processing time per batch of 2 parts A) (22
batches part B) (3 min setup time 12 min
processing time per batch of 2 parts B) (33
batches part C) (2 min setup time 4 min
processing time per batch of 2 parts C) 671
min. Available time at Mold 960 min-671 min
289 min /day for MTOs and unaccounted parts at
Mold
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Example 1
Total time utilization at Assembly for 11 cycles
excluding MTOs (11 batches part A) (2 min
setup time 4 min processing time per batch of
2 parts A) (22 batches part B) (6 min setup
time 12 min processing time per batch of 2
parts B) (33 batches part C) (4 min setup
time 8 min processing time per batch of 2
parts C) 858 min. Available time at Assembly
960 min-858 min 102 min /day for MTOs and
unaccounted parts at Assembly