图 Chapter 7 Production Planning ◆Introduction 0 Master Production Scheduling (MPS) Material Requirement Planning (MRP) ● Capacity Planning ·Improvement in MRP
Chapter 7 Production Planning • Introduction • Master Production Scheduling (MPS) • Material Requirement Planning (MRP) • Capacity Planning • Improvement in MRP
The calculation of MPS 1.The first step is to calculate the gross demand(Gross Requirement,GR) Suppose the gross requirement of product i in period t is GR,(t),then D,() t≤ta GR,(t)=max(D,(t),F(t)) ta≤t≤tp E() 1<t where,D(t)is the real demand from orders of product i in period t; F,(t)is the forecasted demand of product i in period t; t is the demand time fence; p is the plan time fence; Week Now 1 2 3 4 5 6 7 8 9 10 Forecasting 20 20 20 20 20 20 20 20 20 20 Order 25 18 23 16 28 15 24 18 20 18 GR 25 18 23 20 28 20 24 20 20 20 Demand time defnece Plan time defence
The calculation of MPS 1. The first step is to calculate the gross demand (Gross Requirement, GR) Suppose the gross requirement of product i in period t is GRi ( t), then where, Di ( t) is the real demand from orders of product i in period t; Fi ( t) is the forecasted demand of product i in period t; td is the demand time fence; tp is the plan time fence; max , < i d i ii d p i p Dt t t GR t D t F t t t t Ft t t Week Now 1 2 3 4567 8 9 10 Forecasting 20 20 20 20 20 20 20 20 20 20 Order 25 18 23 16 28 15 24 18 20 18 GR 25 18 23 20 28 20 24 20 20 20 Demand time defnece Plan time defence
The calculation of MPS 2.Determine the Scheduled Receipts,SR The scheduled receipts is that has been ordered or produced,and will be due in period t. SR,(t)is the scheduled receipts of product i in period t
The calculation of MPS 2. Determine the Scheduled Receipts, SR The scheduled receipts is that has been ordered or produced, and will be due in period t. SRi ( t) is the scheduled receipts of product i in period t
The calculation of MPS 3.Calculate the Projected On-Hand,POH If there is no Planned Order Receipts in period t,then the inventory at the end of period is POH,which is used to determine whether there is net demand. POH in first period:POHi(1)=OH+SRi(1)-GRi(1) POH in other periods:POHi(t)=PABi(t-1)+SRi(t)-GRi(t) Where OH is the initial inventory,P4B,(t-1)is the projected available balance of product i in period t-1.We will explain it later
The calculation of MPS 3. Calculate the Projected On-Hand, POH If there is no Planned Order Receipts in period t, then the inventory at the end of period is POH, which is used to determine whether there is net demand. POH in first period：ܱܲܪ 1 ൌ ܱܪ ܴܵ 1 െ ܩ ܴ1 POH in other periods: ܱܲܪ ݐ ൌ ܲܤܣ ݐ െ 1 ܴܵ ݐ െ ܩ ܴݐ Where OH is the initial inventory, PABi ( t-1) is the projected available balance of product i in period t-1. We will explain it later
The calculation of MPS 4.Calculate the Net Requirement,NR Suppose that the net requirement of product i in period t is NR(t), If safety inventory is not considered, NRi(t)=GRi(t)-SRi(t)-PABi(t-1) If safety inventory SS is considered, NRi(t)=SS+GRi(t)-SRi(t)-PABi(t-1)=SS-POHi(t) If NR is negative,there is not net requirement;otherwise,there exists net requirement
The calculation of MPS 4. Calculate the Net Requirement, NR Suppose that the net requirement of product i in period t is NRi(t)， If safety inventory is not considered, െ1ݐ ܤܣܲ െ ݐ ܴܵ െ ݐ ܴܩ ൌ ݐ ܴܰ If safety inventory SS is considered, ݐ ܪܱܲ െ ܵܵ ൌ 1 െ ݐ ܤܣܲ െ ݐ ܴܵ െ ݐ ܴܩ ܵܵ ൌ ݐ ܴܰ If NR is negative, there is not net requirement; otherwise, there exists net requirement