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SCMG Lean 337 > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Smaller batch sizes yields

A

Shorter leadtime, smaller WIP, fewer defects, greater scheduling flexibility
BUT —> requires more handling and changeovers

To achieve the benefits of small batch production you must reduce change over/set up time

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2
Q

Quick change methodologies

A
  • RETAD: rapid exchange of tools and dies
  • SMED: Single minute exchange of dies
  • OTED: One touch exchange of dies
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3
Q

Most set up tasks fall into three categories

A

1) transfer and cleanup
2) remove and install
3) adjustment

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4
Q

The four steps of the SMED procedure

A

1) Study existing set up/change over methods
2) Convert as many internal steps to external steps as possible
3) Improve all steps
4) Abolish the set up

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5
Q

Step 1 of SMED: study existing method

A

• distinguish internal from external tasks
– internal tasks: must be done while machine is stopped
– external tasks: can be done while the machine is running
– unnecessary tasks: can be eliminated
• use kaizen team approach, review data, take notes

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6
Q

Step 2 of SMED: Convert internal to external

A

Convert any activity that can be done safely while the machine is running to external set up steps

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7
Q

Step 3 of SMED: Improve or shorten internal steps

A

• Shortening internal steps has immediate impact on reducing downtime
• improve every task in the set up procedure
• both internal and external time shortened
• the ultimate goal: it is so short that it no longer matters
-set up time should be less than or equal to tech time

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8
Q

Step 4 of SMED: Abolish the set up

A

1) redesign products/parts to eliminate changeover
2) use machines that can produce more than one kind of part at the same time
3) use less versatile multiple machines; dedicate each machine to one kind of product/part

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9
Q

Kanban

A

A Japanese word for card
– the card is an authorization for the next container of material to be produced
– a sequence of kanban PULL material through the process
– there are different sorts of signals, but they all are still kanban

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10
Q

Push system versus pull system

A

• push system: schedules are created by MRP system
– problem: schedules are often invalid or obsolete because they ignore interruptions and inventory builds up

• Pull system: worker at station 2 producer ONLY to satisfy demand from downstream, worker withdrawals needed material from station 1 only as needed
– worker at station 1 produces only to satisfy demand from station 2, withdrawals needed material from upstream as needed

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11
Q

Buffer stock

A

Enables station 2 to meet demand quickly and not have to wait on station 1
– the quantity remaining in buffer stock signals when station 1 should produce more

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12
Q

Guidelines for assembly area operators

A
  • apply to all parts of kanban system
    – list all the parts in the kanban system
    – the MRP work order system applies to all other parts
    – take only one container per part number from the kanban storage rack whenever you run out
    – before taking a full container of parts, return empty to rack
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13
Q

Re-Order point equation

A

ROP = LT(D) + SS

ROP: re-order point
LT: lead time
D: demand
SS: saftey stock

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14
Q

Hospital system operating rules

A

– For users withdrawing containers: take only one item per part number from the kanban storage rack
– for providers: check daily for items remaining, when number of items remaining reaches designated minimum, replenish with required number of full containers

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15
Q

Two-Bin system

A

Start with two full bins of each kind of item
– when one bin is emptied, place an order for another bin to replenish it
– by the time the order arrives, the second bin should almost be empty

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16
Q

More rules for kanban operations

A

– A card is attached to every container
– each operation produces/replenish is only the quantity specified on the card
– only non-defective items are sent downstream
– the production process is “smoothed” to achieve level production

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17
Q

Steps for continuous improvement

A

1) Slowly decrease the number of containers until an interruption occurs
2) Identify source of the interruption
3) Slightly increase the number, eliminate cause of interruption
4) Return to step one

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18
Q

Equation for the number of containers in a buffer (k)

A

k= (replenishment quantity + safety quantity) / container quantity

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19
Q

Pull will not work when

A

In general, whenever demand or lead time or variable

– demand is unstable/highly variable
– production process is not level
– too many defectives
– long set ups and frequent breakdowns

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20
Q

Necessary conditions for pull production

A
  • production on demand only
  • strive for inventory reduction everywhere
    – preventative maintenance program
    – quality at the source
    – quick set ups
    – linked, somewhat synchronous operations
    – somewhat level final production schedules
    – cooperative effort and teamwork
    – local control and visual management
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21
Q

More equations

A

Reorder point = LT * D

K = (LT*D) / Q 
or
K = (LT*D*(1+x)) / Q
or
K = (LT+S)*D / Q
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22
Q

Process layout
Advantages
Disadvantages

A

• process layout: facility is arranged by department, function, or specialty
•Advantages:
-high flexibility can make many products,
-lower equipment costs (low Fixed Costs)
-higher work motivation, greater work variety, great employee involvement
-good for low volume, high variety output
• disadvantages:
– higher labor expenses and less efficient processes & equipment (high Variable Costs)
– higher inventory&material handling costs
- difficulty in scheduling and coordinating operations

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23
Q

Product layout
Advantages
Disadvantages

A

• product layout: arranged according to steps in a process, usually to make one product
• Advantages:
– low unit cost to the highway efficient equipment, booking processing, lower rates
– operations are easy to schedule and control
– little inventory, good for high-volume, low or no variety output
• Disadvantages:
– little or no flexibility, can only make one product
– labor problems: little work variety, boredom, low worker motivation
– higher equipment costs
– task interdependencies: when one task stops, all stop

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24
Q

Product layout versus process layout

A
  • product layout: highly efficient, high volume, low variety, but only use for for repetitive, low variety production
  • process layout: Low efficiency, low volume, high variety, but necessary for high variety production
25
Q

How do you make a variety of things efficiently

A

Identify similarities in the process steps, then exploit that similarity
– Products with similar process steps are called the product families

26
Q

A focused factory, or subplant

A

Is devoted to producing a product family
– operates largely autonomously from other areas of the plant
– has its own supervision, management, along with its own workers
– has its own internal planning and control functions
– often has its own support staff
– ideally small size, staffing, and space
– different forms of focus factors: focused flow lines (most repetitive), work cells, focused work centers (most variety)

27
Q

Advantages/benefits of a focused factory

A

– smaller physical size: requires less travel and material handling waste
– smaller size operations: simpler planning and control
– more involvement: everyone is more involved which heightens communication and problem-solving
– dedication: workers perform better and are more motivated and get things done quicker

28
Q

Disadvantages of focused factories

A

– decrease in availability of dedicated machines
– decreased machine utilization
– resistance to change
– time and expense of training workers and relocating equipment

29
Q

Product quantity analysis

A

Purpose: identify largest volume products

– form focused factories around product family starting with the highest quantity of products

30
Q

Process routing sequence

A

Form product families and focus factories by grouping commonly routing sequences

31
Q

Cluster analysis

A

Create a machine matrix, rearranging rows by common products and rearranging columns by common machines
– form focused factors around clusters
– analysis ignore sequence of operations machine utilization and machine availability

32
Q

Cycle time versus takt time

A
  • cycle time: frequency between each completed unit in a process, implies a smooth uniform rate of production
  • takt time: exact cycle time necessary to meet demand
33
Q

Assembly cells

A

Most or all work is performed by the workers

34
Q

Cycle time for assembly cells

A

CT a = the frequency between each completed unit in a process
= the time operators in the cell need to perform tasks in between stations
• when a cell has only one operator:
= sum all assembly task times at the stations + time to walk between stations

CT a = SUM(task times) + SUM(walk times)

35
Q

Capacity

A

How much the cell can produce each day

Cell capacity = time available / CT a

36
Q

To decrease cycle time and increase capacity

A

Add more operators, either by rabbit chase or dividing the cells into subcells

CTa(RC) = CTa for one worker / # of workers

CTa(Div) = maximum (CTa of Subcells)

37
Q

Machining cells

A

Much of the work is performed by single cell automatic machines

When looking at CT, must consider to CT
– machine CT, operator CT

38
Q

Machine CT versus operator CT

CT overall for machining cells

A

•Machine CT: time for machine to perform one operation before it automatically stops
mCT= runtime + load/unloading time

•Operator CT: time for operator to walk, load/unload machines, and do any other manual tasks
oCT= SUM(all manual task times) + SUM(walk times)

•CT m = Maximum (oCT, longest mCT)

39
Q

Reducing waste

A

– Any operators trimmed from the cell are reassigned to cells elsewhere in the plant
– unless demand everywhere is in continual decline, operators are not laid off but reassigned to other cells
– best operators in the cell or reassigned first since I have the greatest skill diversity and send a message that reassignment is not a punishment but a reward

40
Q

Minimum tolerable cycle time

A

“Cycle of woe” for many assembly line workers
– minus boring, causes mistakes, absenteeism, turnover
– instead of using 20 assemblers on a single line, form 4 cells with 5 assemblers each

41
Q

Group technology

A

Cellular manufacturing benefits from this which is identifying commonalities among the processes for different products and parts
– grouping products that have similar processes together into product families

42
Q

Quality of conformance

A

Output a process conforms to the requirements
– monitoring a process: inspection

When on the process to inspect?
– before and he reversed.
– before of stuff that renders inspection difficult or impossible
– before an expensive stuff

43
Q

Purpose of an inspection

A

1) inspection for acceptance: to determine if the process is producing acceptable results, meet specifications
2) inspection for process control: to determine if the process has changed, or is no longer doing what it was

44
Q

Statistical process control

A

Using control charts and statistics to keep a process in control
• why the variation, inspection results
– common cause: variation is caused by random factors, is inherent to the process, the process has not changed and is in control
– special cause: variation caused by non-random factors, a process has changed, it is out of control and should be stopped

45
Q

The purpose of control charts

A

To monitor a process and identify when it might have changed, indicate when a process should be scrutinized for possible problems
– assumption: the process is being monitored already does a good job and conforms for specifications
– charts alone do not remove problems, improve quality

46
Q

Process capacity

A

Just because of processes and control does not mean it is a good process
– to be good it must meet specifications
– specifications are the target features of a product
– process limits
– tolerance limits

• Continuous improvement: not only keeping standard deviation reduced but also moving the tolerance value is closer to the target

47
Q

SPC‘s limitations

A

– it relies on sampling to identify changes in the process
– it can miss fleeting changes
– it can miss defects not caused by inadvertent mistakes or changes in the process
– it does not prevent inadvertent mistakes

48
Q

Jidoka

A

No mistake or defect is allowed to proceed in the process

49
Q

Andon signals

A

A visual signal to indicate an abnormal condition
– often it is a light that is switched to green yellow or red depending on the situation

•Types:
– Equipment: signals in the operating status of equipment
– caution: a warning that something will interrupt process flow, often associated with kanban
– paging: signals of request for forms, materials, or people

50
Q

Pokayoke

A

Any device that:
– prevents a mistake
– stops the process or
– signals an alert that a mistake is about to happen or has already happened

51
Q

Levels of mistake proofing

A

1) Prevent a mistake from ever occurring
2) Detect a mistake before it becomes a defect
2) Detect mistake that is caused defect but prevent defect from causing damage

52
Q

Mistake proofing process steps

A

Plan do check act

1) document the mistake/defect
2) look for red flags: repetition, and frequent operation, high volume
3) determine the root causes: five why, cause-and-effect diagrams, mag 7 analysis tools
4) generate ideas
5) develop the device/method

53
Q

Standard work

A

Is necessary for sustaining the gains and preventing backsliding
– is also necessary for training, monitoring, and continuous improvement
– It is difficult and often overlooked
– is measured and set by the workers
– is provisional and subject to change
– it is essential for kaizen
– always room for improvement

54
Q

TPS Elements off Standard Work

A

1) Cycle Time: to satisfy demand, actual cycle time should be less than or equal to takt time
–TT=avil time/demand

2) procedure, tasks, and sequence: processes, operations, and individual tasks, and the sequence in which operations and tasks are performed is the standard work address

3) work in process (WIP): # of units w/in the process necessary to enable smooth flow
– clearly marked so anyone can readily see discrepancies between standard and actual WIP

55
Q

Standard worksheet or work combination sheet

A

Shows the task within a single operation

Or shows elapsed time for sequence of tasks or operations

56
Q

To make works standard it needs to be

A

Repetitive as much as possible

–the same steps at the same time in the same order

57
Q

Obvious sign of need for improvement

A

If there’s a difference between the actual cycle time in the takt time

58
Q

Reducing takt time

A

Put stress on the system so standard work is reassessed and changed
– culture is crucial with lien, and managers must understand workers
– each leader has a standard work as well, they must visit gumbo of a process to check conformance to standard work, review and shortfalls, and assess any countermeasures

SCMG Lean 337 (2 decks)

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