a2010 6 mps and mrp

Gestión de Sistemas de Producción

Planeación de los requerimientos de materiales (MRP)Planeación de los requerimientos de materiales (MRP)

2 2-508-97 Production and Operations Management

Del Plan Agregado al Plan MaestroDel Plan Agregado al Plan MaestroPlan Agregado de

Producción

Capacidad?

Plan Maestro de Producción

Es Viable?

Plan de Requerimiento de Materiales

Si

Si

No

No

¿Podemos producir 10.000 unidades equivalentes (total de los productos A, B y C) por mes para el año que viene?

¿Podemos producir 500 unidades de A, 600 B y 400 de la C a la semana durante el próximo mes?


Plan de Producción VS Plan Maestro de Producción Plan de Producción VS Plan Maestro de Producción

Mediano Plazo – Producción de las Ordenes

SKU level(stock keeping unit)

Alrededor 3 meses

1 Semana

Largo Plazo - Decisiones de Capacidad

Familia de productos(Unidades Equivalentes)

12 a 15 meses

1 Mes

Plan Agregado

Objetivo

Producto

Horizonte

Revisión

MPS


El Plan agregado y el Plan Maestro de producciónEl Plan agregado y el Plan Maestro de producción


When to Order ?Three approachesWhen to Order ?Three approaches

Reorder Point Reorder Point (continuous review system) Constant amount ordered when inventory declines to

predetermined level

Periodic Review SystemPeriodic Review System (fixed time review period) Order placed for variable amount after fixed passage of time

Time Phased Order Point Time Phased Order Point Master Production Schedule

Material Requirements Planning

Distribution Requirements Planning

REACTIVE

SYSTEMS

PROACTIVE

SYSTEMS


Objectives of the Master Production ScheduleObjectives of the Master Production Schedule

Establish and meet delivery dates

Determine launch dates for orders

Optimize the use of available capacity

Meet the objectives of the aggregate plan

Make trade-off decisions between production and marketing

Sales

Purch.

Operations

Operations

Systemic

Approach


Master Production Plan : InputsMaster Production Plan : Inputs

Inputs to the MPS are :

Beginning Inventory

Forecasts for each week of the schedule

Customer orders (quantities already committed to customers)

Total available capacity for each week of the schedule


Developing a MPSDeveloping a MPS

• Identification of individual products.

• Development of an MPS grid for each product in real units according to the available data (forecast, committed orders, inventory levels, lot sizes, lead times) and the specified constraints.

• Rough cut capacity planning in equivalent units (for all products).

• Does the plans meet all constraints? (capacity limits, stock levels, etc.)



Forecast of the demand for the products with independent demand

Firm orders received from the customers for period i.

Projected on-hand Inventory (i) = Projected on-hand inv. (i - 1) + Planned production (i)

- Max (Forecast (i) , Customer orders (i) )

Lot size 100 unitsLead time: 1 period

Periods 1 2 375 85 8080 60 55

Proj. on-hand Inv. 200 120 35 55100

100MPS - Order Release

ForecastCustomer Orders

MPS - Order Receipt


Period 1 2 3 4

Forecast 250 250 250 250

CustomerOrders 230 280 180 150

Projectedinventory 160 80 30 180

Planned receipts 0 200 200 400

Planned releases 200 200 400

Product Lot Size Lead Time

Beginning Inventory

X12DE 200 1 410

1) Forecast for products with an independant demand

2) Committed customer orders

2a) Identify the Max between forecast and customer orders

3) Planned order receipts for each period:

4) Projected on-hand inventory (i) = beginning inventory (i - 1) + planned order receipts (i) - Max (forecast (i) , customer orders (i) )

5) Planned order releases shifted back the length of the lead time



Periods 1 2 3 4 5 6 7 8 9 1050 45 45 50 50 50 40 40 40 5025 60 15 55 25 35

Projected on-hand inv. 100


Planned Order ReceiptsPlanned Order Releases

Product A

Preliminary Plan :Complete the following MPSPreliminary Plan :Complete the following MPS

Product A• Beginning Inventory = 100• Lot Size: 100 units• Lead Time: 1 week• 1 equivalent unit


Periods 1 2 3 4 5 6 7 8 9 1060 120 80 40 30 50 20 20 20 3035 150 60 30 25 35

Proj. on-hand inv. 300



Product B

Product B• Beginning Inv. = 300• Lot Size : 100 units• Lead Time: 1 week• 2 equivalent units

Preliminary Plan :Complete the following MPSPreliminary Plan :Complete the following MPS


Rough Cut Capacity PlanningRough Cut Capacity Planning

Approximate calculation of the capacity required at critical work centers to meet the demand in order to check the feasibility of a Master Production Schedule.

When the capacity required exceeds the capacity available the MPS must be adjusted before proceeding to the MRP.


100 0 100 0 100 0 0 100 0 00 0 200 0 200 0 0 0 0 0

100 0 300 0 300 0 0 100 0 0

Prod A - Planned Order Releases

Prod B - Planned Order Releases

Total

Products A and B

Total capacity is 200 equivalent units per period. Establish the final MPS for each product.

• Because the total planned order releases of products A and B is superior to 200 units in periods 3 and 5, we must move the release of one of the two articles to periods 2 and 4.

• We decide, for example, to move the release of product A to periods 2 and 4.

• We must then complete the final plan for both products.

Final MPS :Rough Cut Capacity PlanningFinal MPS :Rough Cut Capacity Planning


Periods 1 2 3 4 5 6 7 8 9 1050 45 45 50 50 50 40 40 40 5025 60 15 55 25 35

Proj. on-hand inv. 1000 100 0 0 100 0

100 0 0 100 0 0



Product A

• Planned Order Release is moved from period 3 to period 2.

• Consequently, Planned Order Receipts are moved from period 4 to period 3.

• Projected on-hand inventories must be recalculated to account for the changes.

50 90 145 90 140 90 50 10 70 20

10001000

10001000

Final MPS :Modifications to the Preliminary PlanFinal MPS :Modifications to the Preliminary Plan


Periods 1 2 3 4 5 6 7 8 9 1060 120 80 40 30 50 20 20 20 3035 150 60 30 25 35

Proj. on-hand inv. 300 240 90 10 70 40 90 70 50 30 00 0 0 100 0 0 100 0 0 00 0 100 0 0 100 0 0 0 0



Product B

• Since we’ve made no changes to the planned order releases of prodcut B, le preliminary and final plans are identical.

Final MPS :Modifications to the Preliminary PlanFinal MPS :Modifications to the Preliminary Plan


ReadingReading

MPS: Pages 466-473

Not:

• example 6 (pages 467-468)

• Available to promise (page 472)

•Stabilizing MPS (page 473)


Demand CharacteristicsDemand Characteristics

11 22 33 44 55WeekWeek

400 400 –

300 300 –

200 200 –

100 100 –No

. o

f ta

ble

sN

o.

of

tab

les

Continuous demandContinuous demand

M T W Th F M T W Th FM T W Th F M T W Th F

400 400 –

300 300 –

200 200 –

100 100 –No

. o

f ta

ble

sN

o.

of

tab

les

Discrete demandDiscrete demand

Independent demandIndependent demand

100 tables100 tables

Dependent demandDependent demand

100 x 1 = 100 x 1 = 100 tabletops100 tabletops

100 x 4 = 400 table legs100 x 4 = 400 table legs


On-hand

inventory

Inventory of tables

Time

Quantity

Demand for the tables

Time

Reorder Point System VS MRPReorder Point System VS MRP


Reorder Point System VS MRPReorder Point System VS MRP

Quantity

Inventory of the table legs

Quantity

Demand for the table legs


Objectives of MRPObjectives of MRP

Calculate with precision the quantities of components, parts and raw material that must be produced or purchased in order to realize the MPS

→ HOW MANY ?

To determine when to release production or to place the orders in order to receive the required units at the right moment

→ WHEN ?


Material Requirements Planning : Information StructureMaterial Requirements Planning : Information Structure

- Stocks on hand- Safety stocks- Lot sizes - Economic Order Quantities- Lead time

Item MasterFile

ForecastsCustomer

Orders

Bill of Material

MRP

MPS

Aggregate Planning


Bill of Materials (BOM)Bill of Materials (BOM)

X

Y (3) Z (2)

Y (1)W (2)

Level 0

Level 1

Level 2

For each product X we need 3 «Y» and 2 «Z»For each product Z we need 2 «W» and 1 «Y»

Product Structure Tree

Parent

ParentComponent

Component


ProblemsProblemsS&H (2007) p.515 #3 - S&H (2004) p.628 #3

Item Lead Time Amount on Hand

Direct Components

End 1 0 L(2), C(1), K(3)

L 2 10 B(2), J(3)

C 3 15 G(2), B(2)

K 3 20 H(4), B(2)

B 2 30

J 3 30

G 3 5

H 2 0


MRP MatrixMRP Matrix

Note: The book from Stevenson shows the projected inventory at the beginning of the period, this is not the usual way to do it, so we will always show the projected inventory at the END of the period

Note: The book from Stevenson shows the projected inventory at the beginning of the period, this is not the usual way to do it, so we will always show the projected inventory at the END of the period


MRP calculation processMRP calculation process

Always process the items in the order of their low level code: level 0 level 1 level 2

When an item appears at different levels of the product structure(s), the lowest level (highest number) is the level that we must use.

Gross requirements for an item are calculated by:

Multiplying the quantity of the planned order release(s) of the parent(s) of the item by the quantity required as per the BOM for the specific parent-component relationship(s).


Lot Sizing in MRP SystemsLot Sizing in MRP Systems

Lot-for-lot (L4L) ordering policy

Minimum order quantity (Ex: Min 250)

Multiple order quantity (Ex: X100)

Economic order quantity (Ex: 350; annual demand: 4 200)

Periodic order quantity (Ex: 2 months)


ExampleExample

A company is manufacturing several office supply items among which we have: Clipboard Lapdesk etc.


Product StructureProduct Structure

Top clip (1) Bottom clip (1)

Pivot (1) Spring (1)

Rivets (2)Finished clipboard Pressboard (1)

Clipboard


Product Structure TreeProduct Structure Tree

Clipboard Level 0Level 0

Level 1Level 1

Level 2Level 2Spring

(1)Bottom Clip

(1)Top Clip

(1)Pivot

(1)

Rivets (2)

Clip Ass’y (1)

Pressboard (1)


MRP: Example (cont.)MRP: Example (cont.)

Product Structure RecordProduct Structure Record

Clipboard

Lapdesk

Pressboard(2)

Trim(3’)

Beanbag(1)

Glue(4 oz)

Level 0Level 0

Level 0Level 0

Pressboard(1)

Clip Ass’y(1)

Rivets(2) Level 1Level 1

Level 1Level 1


ITEM: PRESSBOARDITEM: PRESSBOARD LLC: 1LLC: 1 PERIODPERIOD

LOT SIZE: MIN 100LOT SIZE: MIN 100 LT: 1LT: 1 11 22 33 44 55

Gross RequirementsGross RequirementsScheduled ReceiptsScheduled ReceiptsProjected on HandProjected on Hand 150150Net RequirementsNet RequirementsPlanned Order ReceiptsPlanned Order ReceiptsPlanned Order ReleasesPlanned Order Releases

ITEM: CLIPBOARDITEM: CLIPBOARD LLC: 0LLC: 0 PERIODPERIOD

LOT SIZE: L4LLOT SIZE: L4L LT: 1LT: 1 11 22 33 44 55

Planned Order ReleasesPlanned Order Releases 100100 100100 100100

ITEM: LAPDESKITEM: LAPDESK LLC: 0LLC: 0 PERIODPERIOD

LOT SIZE: MULT 50LOT SIZE: MULT 50 LT: 1LT: 1 11 22 33 44 55

Planned Order ReleasesPlanned Order Releases 5050 5050

MRP: Example (cont.)MRP: Example (cont.)M

.P.S

.M

.R.P

.


M.P

.S.

M.R

.P.



Gross RequirementsGross Requirements 100100 100100 200200 100100 00Scheduled ReceiptsScheduled ReceiptsProjected on HandProjected on Hand 150150Net RequirementsNet RequirementsPlanned Order ReceiptsPlanned Order ReceiptsPlanned Order ReleasesPlanned Order Releases







x2x2 x2x2

x1x1 x1x1x1x1



M.P

.S.

M.R

.P.



Gross RequirementsGross Requirements 100100 100100 200200 100100 00Scheduled ReceiptsScheduled ReceiptsProjected on HandProjected on Hand 150150 5050 5050 00 00 00Net RequirementsNet Requirements 5050 150150 100100Planned Order ReceiptsPlanned Order Receipts 100100 150150 100100Planned Order ReleasesPlanned Order Releases 100100 150150 100100









Planned Order ReportPlanned Order Report

PERIODPERIOD

ITEMITEM 11 22 33 44 55

ClipboardClipboard 100100 100100 100100

LapdeskLapdesk 5050 5050

PressboardPressboard 100100 150150 100100


Item Lot size LTProduct A 200 1

MPS 1 2 3 4 5 625 25 25 25 25 2530 20 15 10 5

Projected inventory 135 105 80 55 30 5 180200

Order releases 200

Item Lot size LTProduct Z 500 2

MPS 1 2 3 4 5 630 30 30 30 30 3035 20 15 20 10 5

Projected inventory 135 100 70 40 10 480 450500

Order releases 500

Item Lot size LTSub-ass. B 1 500 2

MRP 1 2 3 4 5 6Gross Requirements Prod. A 0 0 0 0 400 0Gross Requirements Prod. Z 0 0 1 500 0 0 0

0 0 1 500 0 400 0Projected inventory 200 200 200 200 200 1 300 1 300

1 300 2001 500 1 500

Planned Order Releases 1 500 1 500

Item Lot size LTComponent C 4 500 1

MRP 1 2 3 4 5 6Gross Requirements Prod. A 0 0 0 0 200 0Gross Requirements Sub-ass. B 4 500 0 4 500 0 0 0

4 500 0 4 500 0 200 0Projected inventory 4 600 100 100 100 100 4 400 4 400

4 400 1004 500 4 500

Planned Order Releases 4 500 4 500

Item Lot size LTComponent D 10 000 1

MRP 1 2 3 4 5 6Gross Requirements Prod. Z 0 0 1 000 0 0 0Gross Requirements Sub-ass. B 6 000 0 6 000 0 0 0

6 000 0 7 000 0 0 0Projected inventory 6500 500 500 3 500 3 500 3 500 3 500

6 50010 000

Planned Order Releases 10 000

Sales ForecastCustomer Orders

Gross Req. Tot.

Planned Order ReceiptsNet Requirements

Net Requirements

Gross Req. Tot.

Order Receipts

Planned Order Receipts

Gross Req. Tot.

Net RequirementsPlanned Order Receipts

Sales ForecastCustomer Orders

Order Receipts

Component C(1)

Sub.-Ass. B(2)

Component C(3)

Component D(4)

Product A

Component D(2)

Sub.-Ass. B(3)

Component C(3)

Component D(4)

Product Z

0 1 2 3 4 5

Gross Requirements 75 350 200 750 1000

Lot-for-lot (L4L) ordering policy Net Requirements 75 350 200 750 1000Planned order receipts 75 350 200 750 1000Projected on-hand inventory 0 0 0 0 0 0

Fixed-size lot ordering policy (Ex: 500)Net Requirements 75 125 375 875Planned order receipts 500 500 500 1000Projected on-hand inventory 0 425 75 375 125 125

Minimum order quantity (Ex: Min 250) Net Requirements 75 175 125 625 1000Planned order receipts 250 250 250 625 1000Projected on-hand inventory 0 175 75 125 0 0

Multiple order quantity (Ex: X100) Net Requirements 75 325 125 675 975Planned order receipts 100 400 200 700 1000Projected on-hand inventory 0 25 75 75 25 25

Economic order quantity (ex: 700; Ann. Dem: 4200)Net Requirements 75 675 975Planned order receipts 700 700 1400Projected on-hand inventory 0 625 275 75 25 425

Periodic order quantity (2 months)Net Requirements 75 200 1000Planned order receipts 425 950 1000Projected on-hand inventory 0 350 0 750 0 0

Month


Establishing the Minimum Planning HorizonEstablishing the Minimum Planning Horizon

9 periods

4 periods

7 periods

A

B C

D(2) E

Lead Time = 2 periods


Lead Time = 2 periods Lead Time = 4 periods



Establishing the Minimum Planning HorizonEstablishing the Minimum Planning Horizon

A

BC

D(2)

E

LT = 2 periods

LT = 3 periods

LT = 2 periods

LT = 4 periods

LT = 2 periods

LT 2 3 4 5 6 7 8 9 10A Assembly 2 100 100B Purchase 2 100 100C Assembly 3 100 100D Purchase 2 200 200E Purchase 4 100 100

Periods


Bill

of

mate

rials

MPS / MRP PROCESS MPS / MRP PROCESSPlanned Order Receipt

Planned Order Release

Ref.: adapted from D. A. Turbide, MRP+, Industrial Press, 1993.

Level 0


Supplier

Gross Requirements

Net Requirements

Planned Order Receipt

Level 2


Gross Requirements

Net Requirements

Planned Order Receipt

Level 1 On-hand Inv.

Lot Sizing

Lead time

MP

SM

ater

ials

Req

uir

emen

t P

lan

nin

g

MinimumPlanningHorizon


ReadingsReadingsReview problems:

To be announced

Review Reading for MRP:S&H 2007, 484-497

Readings for next class (scheduling) : S&H 2007, chap. 15 pp 547-560

a2010 6 mps and mrp

Documents

reorder point

planned order

planned order

planned order

lapdesk lot

clipboard

preliminary

1 lot size