Chapter 12, Problem 14P

Using the accompanying diagram, do the following:

a. Draw a tree diagram for the scissors.

b. Prepare an MRP plan for scissors. Lead times are one day for each component and final scissor assembly, but two days for the plastic grips. Six hundred pairs of scissors are needed on day 6. Note: There are 200 straight blades and 350 bent blades on hand, and 40 top blade assemblies on hand.

Use lot-for-lot ordering for all items.

Summary Introduction

To prepare: Tree diagram for the scissors.

Introduction: Materials Requirement Planning (MRP) is the planning or scheduling system, which can be used in the manufacturing process. It is used to plan the number of items required to produce one unit of finished goods (end item).

Explanation of Solution

Given information:

Lead-time is one day for all the components except plastic grips, which has the lead-time of 2 days. 600 pairs of scissors are needed on day 6. There are 350 bent blades, 200 straight blades, and 40 top blade assemblies on hand. Lot size is lot-for-lot ordering for all items.

In addition to that, following diagram is given:

Prepare tree diagram for the scissors using given diagram:

Summary Introduction

To prepare: A Material requirement planning for scissors.

Introduction: Materials Requirement Planning (MRP) is the planning or scheduling system, which can be used in the manufacturing process. It is used to plan the number of items required to produce one unit of finished goods (end item).

Explanation of Solution

Given information:

Lead-time is one day for all the components except plastic grips, which has the lead-time of 2 days. 600 pairs of scissors are needed on day 6. There are 350 bent blades, 200 straight blades, and 40 top blade assemblies on hand. Lot size is lot-for-lot ordering for all items.

In addition to that, following diagram is given:

Develop material requirement planning for scissors:

• It is given that 600 pairs of scissors are needed on day 6.
• Beginning inventory is 0 units.
• Net requirement can be calculated by subtracting the projected on-hand from the gross requirement. Hence, the net requirement is 600 units in week 6 (600-0).
• Planned order release is the order given by the company and planned order receipts is the order received by the firm.
• Lead-time is given as 1 week. Company requires 600 units in the beginning of Week 6. Hence, they need to order for 600 units (as the lot size is lot-for-lot) on previous week (as the lead-time is 1 week). Thus, company need to order the required units in week 5.

Develop material requirement planning for bottom blade assembly:

• Scissor is the parent for bottom blade assembly. Hence, the planned order release of the scissor would be the gross requirement of the bottom blade assembly. As number of units required is 1 for bottom blade assembly, the planned order release row of scissor should be multiplied with 1 to attain the gross requirement column of bottom blade assembly.
• Beginning inventory is 0 units.
• Net requirement can be calculated by subtracting the projected on-hand from the gross requirement. Hence, the net requirement is 600 units in week 5(600-0).
• Planned order release is the order given by the company and planned order receipts is the order received by the firm.
• Lead-time is given as 1 week. Company requires 600 units in the beginning of Week 5. Hence, they need to order for 600 units (as the lot size is lot-for-lot) on previous week (as the lead-time is 1 week). Thus, company need to order the required units in week 4.

Develop material requirement planning for top blade assembly:

• Scissor is the parent for top blade assembly. Hence, the planned order release of the scissor would be the gross requirement of the top blade assembly. As number of units required is 1 for top blade assembly, the planned order release row of scissor should be multiplied with 1 to attain the gross requirement column of top blade assembly.
• Beginning inventory is 40 units.
• Net requirement can be calculated by subtracting the projected on-hand from the gross requirement. Hence, the net requirement is 560 units in week 5 (600-40).
• Planned order release is the order given by the company and planned order receipts is the order received by the firm.
• Lead-time is given as 1 week. Company requires 560 units in the beginning of Week 5. Hence, they need to order for 560 units (as the lot size is lot-for-lot) on previous week (as the lead-time is 1 week). Thus, company need to order the required units in week 4.
• Projected on hand inventory for week 6 is 0 units. Calculation is as follows:

$\begin{array}{c}\text{Projected on hand for Week 6}=\left\{\begin{array}{l}\left(\begin{array}{l}\text{Projected on-hand}+\text{Planned order receipt}\\ -\text{Gross requirement}\end{array}\right)+\\ \text{Scheduled receipt}\end{array}\right\}\\ =\left(40+560-600\right)+0\\ =0\end{array}$

Develop material requirement planning for screw:

• Scissor is the parent for screw. Hence, the planned order release of the scissor would be the gross requirement of the screw. As number of units required is 1 for screw, the planned order release row of scissor should be multiplied with 1 to attain the gross requirement column of screw.
• Beginning inventory is 0 units.
• Net requirement can be calculated by subtracting the projected on-hand from the gross requirement. Hence, the net requirement is 600 units in week 5 (600-0).
• Planned order release is the order given by the company and planned order receipts is the order received by the firm.
• Lead-time is given as 1 week. Company requires 600 units in the beginning of Week 5. Hence, they need to order for 600 units (as the lot size is lot-for-lot) on previous week (as the lead-time is 1 week). Thus, company need to order the required units in week 4.

Develop material requirement planning for straight blade:

• Bottom blade assembly is the parent for straight blade. Hence, the planned order release of the bottom blade assembly would be the gross requirement of the straight blade. As number of units required is 1 for straight blade, the planned order release row of bottom blade assembly should be multiplied with 1 to attain the gross requirement column of straight blade.
• Beginning inventory is 200 units.
• Net requirement can be calculated by subtracting the projected on-hand from the gross requirement. Hence, the net requirement is 400 units in week 4(600-200).
• Planned order release is the order given by the company and planned order receipts is the order received by the firm.
• Lead-time is given as 1 week. Company requires 400 units in the beginning of Week 4. Hence, they need to order for 400 units (as the lot size is lot-for-lot) on previous week (as the lead-time is 1 week). Thus, company need to order the required units in week 3.
• Projected on hand inventory for week 5 is 0 units. Calculation is as follows:

$\begin{array}{c}\text{Projected on hand for Week 5}=\left\{\begin{array}{l}\left(\begin{array}{l}\text{Projected on-hand}+\text{Planned order receipt}\\ -\text{Gross requirement}\end{array}\right)+\\ \text{Scheduled receipt}\end{array}\right\}\\ =\left(200+400-600\right)+0\\ =0\end{array}$

Develop material requirement planning for straight plastic grip:

• Bottom blade assembly is the parent for straight blade. Hence, the planned order release of the bottom blade assembly would be the gross requirement of the straight blade. As number of units required is 1 for straight blade, the planned order release row of bottom blade assembly should be multiplied with 1 to attain the gross requirement column of straight blade.
• Beginning inventory is 0 units.
• Net requirement can be calculated by subtracting the projected on-hand from the gross requirement. Hence, the net requirement is 600 units in week 4 (600-0).
• Planned order release is the order given by the company and planned order receipts is the order received by the firm.
• Lead-time is given as 2 weeks. Company requires 600 units in the beginning of Week 4. Hence, they need to order for 600 units (as the lot size is lot-for-lot) before two weeks (as the lead-time is 2 weeks). Thus, company need to order the required units in week 3.

Develop material requirement planning for bent blade:

• Top blade assembly is the parent for bent blade. Hence, the planned order release of the top blade assembly would be the gross requirement of the bent blade. As number of units required is 1 for bent blade, the planned order release row of top blade assembly should be multiplied with 1 to attain the gross requirement column of bent blade.
• Beginning inventory is 350 units.
• Net requirement can be calculated by subtracting the projected on-hand from the gross requirement. Hence, the net requirement is 210 units in week 4 (560-350).
• Planned order release is the order given by the company and planned order receipts is the order received by the firm.
• Lead-time is given as 1 week. Company requires 210 units in the beginning of Week 4. Hence, they need to order for 210 units (as the lot size is lot-for-lot) on previous week (as the lead-time is 1 week). Thus, company need to order the required units in week 3.
• Projected on hand inventory for week 5 is 0 units. Calculation is as follows:

$\begin{array}{c}\text{Projected on hand for Week 5}=\left\{\begin{array}{l}\left(\begin{array}{l}\text{Projected on-hand}+\text{Planned order receipt}\\ -\text{Gross requirement}\end{array}\right)+\\ \text{Scheduled receipt}\end{array}\right\}\\ =\left(350+210-560\right)+0\\ =0\end{array}$

Develop material requirement planning for bent plastic grip:

• Top blade assembly is the parent for bent plastic grip. Hence, the planned order release of the top blade assembly would be the gross requirement of the bent plastic grip. As number of units required is 1 for bent plastic grip, the planned order release row of top blade assembly should be multiplied with 1 to attain the gross requirement column of bent plastic grip.
• Beginning inventory is 0 units.
• Net requirement can be calculated by subtracting the projected on-hand from the gross requirement. Hence, the net requirement is 560 units in week 4 (560-0).
• Planned order release is the order given by the company and planned order receipts is the order received by the firm.
• Lead-time is given as 1 week. Company requires 560 units in the beginning of Week 4. Hence, they need to order for 560 units (as the lot size is lot-for-lot) on previous week (as the lead-time is 1 week). Thus, company need to order the required units in week 3