IENG 471 - Lecture 04 - 2
Schedule Design:
The Sequel
4/7/2015
IENG 471 Facilities Planning
1
Assignments
 Assignment (Due Today - Now):
 HW:
(HW 2)
 Product BOM
 Product Operation Process Chart
 Product Precedence Diagram
 Next Assignment:
 HW:








4/7/2015
(HW 3) See Assignment Link
required input for each of the workstations
equipment necessary for each machine
steady state cycle time for each machine
ideal machine assignment for each machine
compute the idle time
unit cost at each workstation
total cost per good unit
square footage for each workstation and the total space required
IENG 471 Facilities Planning
3
Equipment Requirements
 Equipment Fractions are the number of
machines of one type required to produce
the required volume of product(s)
 Some machines can be used to perform multiple
operations…
 So, if idle time on the machine exists, and there are
multiple products scheduled, then fewer total machines
may be required!
 Some machines may not be able to perform the
required operation(s) fast enough to reach the
required volume with only one machine…
 So, more copies of the machine may be required!
4/7/2015
IENG 471 Facilities Planning
4
Estimating Equipment Fractions
 The equipment fraction for each req’d machine is based on all
of the operations the machine will perform
 Good thing we got those Operations Process Charts!
 To find the number of machines of a type for the facility:
 The number of workstations for a shift (F) is:
F 
where:
SQ
EHR
 S is the standard time to perform the operation, per unit
 Q is the quota of output units per shift
 E is the efficiency of production on the machine, expressed as a
percentage of the standard operation time
 H is the hours available for production on the machine during
the shift (or whatever unit of time matches parameter S)
 R is the availability (reliability*) of the machine, expressed as %
of the “up time” that the machine is available to work (%H)
4/7/2015
IENG 471 Facilities Planning
5
Reliability
 Reliability is a measure of how often a
system fails:
 How long (on average) you can run it until it
stops working right
 How do you know that it’s not working right?
 MTTF (Mean Time To Failure) or
 MTBF (Mean Time Between Failures)
4/7/2015
IENG 471 Facilities Planning
6
Maintainability
 Maintainability (serviceability) is a
measure of how long it takes to return
the system to proper operation:
 Sum of the times required to:
 diagnose the problem
 obtain repair parts / tools
 repair the failed components
 return the unit to operating conditions
 MTTR (Mean Time To Repair)
4/7/2015
IENG 471 Facilities Planning
7
Availability
 Availability is a function of Reliability
and Maintainability:
 It is the percentage of time that you can
count on using it for production
 % Availability =
4/7/2015
MTTF
MTTF + MTTR
IENG 471 Facilities Planning
8
Equipment Fractions - continued
 Since the number of
machines is an integer
Op. No.
Equip.
Fraction
Integer
Ceiling
0109
1.1
2
0206
2.3
3
0274
0.6
1
Total
Req’d
4
6
 The lower bound on the
number of machines
required is 4 – the sum of
the equipment fractions
 The upper bound on the
number of machines
required is 6 – the sum of
the ceiling values for each
operation…
 But …
4/7/2015
IENG 471 Facilities Planning
9
Equipment Fractions - continued
 We should adjust the required number of
machines to also account for:
 Frequency of changeover (flexibility)
 Set-up times
 Preventative maintenance
 Manufacturing policies…
 Therefore, the four machines estimate might
not really be feasible … it assumed that
everything was best case scenario!
4/7/2015
IENG 471 Facilities Planning
10
Ex: Injection Mold Rubber Feet
 Process for juicer is:
 Mold & trim feet – 2% scrap rate
 Transport trimmed feet to line – 1% scrap rate
 Assemble juicer – 0.5% scrap rate
 3 grams of rubber needed per foot
 Find the number of feet to be processed at each
workstation!
 Find the raw rubber needed for this process!
4/7/2015
IENG 471 Facilities Planning
11
Ex: Injection Mold Rubber Feet
 Shift is 8 hr, but reduced by two 15 min breaks, and 35 min
machine warm-up (to heat the mold and material).
 Production schedule requires 2450 sets of feet daily
 MTTF is 38 hours
 MTTR comprises 5 min to diagnose, 55 min to obtain spare
parts, 7 min to fix, 18 min to re-warm
 Run one shift per day
 Obtain one set of four feet per cycle
 Cycle time is 40 s (steady state)
 Find the equipment fraction for this process!
4/7/2015
IENG 471 Facilities Planning
12
Questions
 What is the machine fraction if, instead:
 A Manufacturing Engineer suggests using a four unit
mold instead of a single unit mold?
 An Industrial Engineer suggests running three shifts,
eliminating daily warm-up time?
 An improved facility design reduces the time to get
spare parts to 2 min, and the re-warm time to 1 min?
4/7/2015
IENG 471 Facilities Planning
13