Prod. Unit 5-8 Flashcards
Formal Definition of Setup
The elapsed time between making the last
good part of item A to the first good part of
item B. (Time to swap machine).
Benefits of setup reduction
- Better quality
- Lower cost (time is $)
- Better flexibility
- Better worker utilization
- Shorter lead time and more capacity
- Less process variability
What does SMED Methodology stand for, and what is it?
Single Minute Exchange of Dies
- Identify setup steps (i.e internal vs external)
- Trend towards 0 setup (i.e external better than internal)
What are the 4 types of setup?
Type 1:
Retrieving and checking stuff before and after setup.
Type 2:
Changing tooling before/after a batch.
Type 3:
Changing machine settings/calibration.
Type 4:
Making a test part for validation.
Which one of the setup types is mostly external?
Type 1 setup
How to Improve Internal setups
- Parallel setup tasks
- Quick-attachment devices
- Eliminate adjustments
How to Improve External setups
- Store fixtures, etc., near machine (minimize
travel) - Prepare setup kits and carts
- Improve material handling
How to reduce setup
- Reduce or eliminate differences in parts
- Combine parts or steps
- Dedicate machines to one part
– Many dedicated low-cost machines vs. one large
expensive machine (monument)
How to calculate MTTR (Mean Time To Repair)
repairs
total repair time /
number of repairs
What does Total Productive Maintenance emphasize?
Proactive maintenance and prevention of breakdowns
How to calculate mean time between failure (MTBF)
total running time /
number of repairs
How to calculate availabiility (A)?
Time actually running / Planned running time
How to calculate rate efficiency (RE)?
RE = (units made * actual cycle time) / actual running time
How to calculate speed efficiency (SE)?
SE = design cycle time / actual cycle time
How to calculate performance efficiency (PE)?
PE = SE*RE
What is quality rate / yield (Q)?
% of good parts
How to calculate overall equipment effectiveness (OEE)?
OEE = APEQ
7 elements of Preventative Maintenance (PM) plan
Elements of a Preventative Maintenance (PM) program
1. Operate at reduced capacity and to standards
2. Maintain equipment
3. Keep equipment and area clean and
organized
4. Monitor equipment daily
5. Schedule time for PM
–>(PM once a day, allow 15-30mins at start or end of shifts)
–>(More as needed)
6. Manage equipment information
–>Track maintenance stats (breakdowns, cost)
–>(PM procedures/schedule)
7. Use predictive (on demand) maintenance
–>(I.e infrared/ultrasound sensors)
Recall ways of doing work in factories and their relationship with volume and cost per unit
(Highest volume, lowest cost)
-Continuous
-Mass production
-Batch production
-Job shop
-Project
(Lowest volume, highest cost)
What is a Fixed Position, Process, and Product layout?
You guessed it, its in the name!
Fixed Position Layout
–product cannot be moved
Process Layout
– machines grouped by process
Product Layout
– linear arrangement of workstations to make product
In general some differences between Process and Product layouts
Product: Higher volume, standardized, efficient
Process: Lower volume, more variable and flexible, general purpose
How to setup Cellular Layouts?
Identify families of parts with similar flow paths
Group machines into cells based on part families
Arrange cells so parts movement is minimized
Locate large shared machines at point of use
Should you make steps the same if you can?
Yes
Focused Factory Layouts
Just run the examples man
- Focused flow lines
– When parts in family have nearly the same process
sequence and processing times - Workcells
– More flexible, when parts have greater differences - Focused workcentres
– Used when it’s not practical to rearrange machines
– Individual machines are dedicated to particular families
What is push production
Centralized scheduling for all machines, just shoves shit to the next one
What is Batch and Queue Production?
- A variety of jobs are processed, each using different parts of the factory
- Many orders and competition for ressources
The variety of jobs necessitates…
* Good planning, scheduling and monitoring
Objectives of Scheduling
You guessed it, common sense
- Meet customer due dates
- Minimize job lateness
- Minimize lead time
- Minimize overtime
- Maximize machine or labor utilization
- Minimize idle time
- Minimize work-in-process inventory
How to analyze queuing systems?
- Queuing theory
– Mathematical models of simple systems
– Based on probability theory - Discrete-event simulation
– Simulate the system by generating random events
based on given probabilities
– Used for complex (and realistic) systems
Some issues in batch production with scheduling and lead times
-Lead times hard to predict accurately bc they are dependent on all the various active orders going on
-Uncertainty in orders leads to more conservative lead time estimates
-This makes scheduling suck balls
What is pull production
Last station/operation ‘orders’ parts and sends a signal to stations or processes feeding into it, no parts wait around and only the final step is scheduled
Conditions for pull production
- Continuous, stable demand
- Uniform (level) production schedules
- Short setup times
- Limited product variety
- Continuous flow
- Equipment must be reliable
Is having a small amount of buffer stock important for pull production?
Yes, otherwise orders get delayed, as you wait for stuff to move upstream
What is a Kanban
Something, (can literally be anything) to signal downstream to make stuff
Rules of Kanban
- Downstream operations withdraw only the
quantity of items needed from upstream
operations. This quantity is controlled by the
number of cards - Each operation produces items in the
quantity and sequence indicated by the cards - A card must be attached to a container. No
withdrawal or production is permitted
without a Kanban - Only non-defective items are sent downstream.
Defective items are withheld and the process
stopped until the source of defectives is
remedied. - The production process is smoothed to achieve
level production. Small demand variations are
accommodated in the system by adjusting the
number of cards. - The number of cards is gradually reduced to
decrease WIP and expose areas that are
wasteful and in need of improvement
What does Kanban control?
- Kanban card indicates standard quantity of production
- Kanban maintains discipline of pull production
- Production kanban (empty carton) authorizes
production - Withdrawal kanban (full carton) authorizes movement
of goods
Why have a 2 bin system and what are the names of each bin type?
Helps so if one bin fills up and the station can keep producing and not have to wait for the 1 bin to return
How to calculate Reorder point (ROP)
ROP = demand * lead time + safety stock
Under what theoretical conditons can safety stock be equal to zero?
- If the demand, D and the lead time, LT are
equal, then SS can equal 0. - The greater variability between D or LT, that
larger the value of SS
In terms of Pull Production, what is meant by lead times?
- Time required to replenish a container
- Usually composed of two components
– Conveyance time C to move empty container
upstream and full container downstream
– Production time P to setup and produce required
parts
How to calculate lead time (LT)
LT = Production time + Conveyance time
True or false, the demand is the demand averaged over sometime
Yes, god I hate writing these
How to calculate number of Kanbans needed (K)?
K = Reorder point (ROP) / container size (Q)
When and why do we split Kanbans into Production and Conveyance Kanbans?
When distance between stations is longer
Difference between conveyance and production Kanbans?
Conveyance Kanbans tell the upstream (previous stations) when and how much stuff to move
Production Kanbans tell the upstream process when to make more stuff
How to calculate conveyance time (C) for Kanbans
C = Idle time at mailbox (station) + time to move upstream + time to move downstream + idle time in downstream buffer
How to calculate production time (P) for Kanbans
P = Idle time at mailbox (station) + time to move upstream TO FIRST OPERATION + idle time at FIRST OPERATION + Time to fill container + time to move to downstream buffer + idle time in downstream buffer
How to apply continuous improvement to Pull Production
- Slowly decrease the number of containers
until an interruption occurs
(or, slowly decrease the units per container) - Identify the source of the interruption
- Increase the number slightly; try to eliminate
the cause of the interruption - After the cause has been eliminated, return
to step 1
When does Pull not work?
- Variable assembly time
- Lengthy, difficult, unshortenable setup
- Too many options (too much buffer stock needed)
- High, unreducible defect rate (too much interruption)
- Products must be produced in integrated batches for quality
control or certification (e.g. pharmaceuticals)
Does every process have push and pull
Yes
(This is what out tuition goes to)
Important to have buy in from people
Yes, having everyone agree to SUPPORT the plan, not the plant itself is important
