Vensim software work required for 3 students 3 copies

ASSIGNMENT

The University of Liverpool Management School

2022 – 2023

EBUS504 Operations Modelling and Simulation

DEADLINE: January 13th, 2023 before 12 noon

Lateness Penalty: Five percentage points shall be deducted from the assessment mark for each working day after the due date up to a maximum of five working days; however, the mark will not be reduced below the pass mark for the assessment (50%). Work assessed at below 50% will not be penalised for late submission of up to five working days. Work received more than five working days after the submission deadline will receive a mark of zero.

Cheating: This is an individual assignment. You can discuss your general understanding of the exercise with colleagues of other groups, but you must write up your unique project report yourself. Standard UoL code applies. University regulations about cheating – especially COLLUSION and PLAGIARISM (copy from sources without acknowledgement or other student reports) – apply.

Hand-in procedure: Hand your work electronically by submitting a copy through the Turnitin link on CANVAS. If your work is late for medical or other good cause, attach a copy of your certificate and/or explanation.

Notes:

You must submit:

● One electronic copy (doc, docx or PDF) through CANVAS (EBUS504_SMITH_20091234.doc)

● An electronic copy of the Witness, Vensim and Excel files developed through on CANVAS (all in one zip or rar file with your name and ID as filename e.g. EBUS504_SMITH_20091234.zip)

1. Practical questions: System Dynamics (40 Marks)

The COVID-19 pandemic has a massive negative impact on human wellbeing and the global economy

since its outbreak at the end of 2019. Early studies have shown that using Personal Protective

Equipment (PPE) helps for protection against the spread of the disease. Therefore, retailers have put

an enormous effort on the stable, reliable, and rapid management of PPE supply chain. During the

pandemic, the procurement and inventory management for PPE has gained immense attention.

Retailers believe that system dynamics might help them plan procurement, inventory and sales

planning for PPE. It is very well known that if there is no PPE inventory, there can be no sales. In other

words, PPEs are sold from inventory. It is also known that if there is no PPE procurement, there is no

PPE inventory. Each PPE item first goes into inventory once they arrive. If the PPE sales increase,

retailers purchase more PPE.

To be on the relatively safe side, retailers have a target inventory which is equal to coverage level (c

months) times PPE sales (i.e. target inventory is c months of sales). There is a time to replenish PPE

inventory and it is called lead time.

a) Draw the Causal-loop diagram, put the sign (positive or negative) for the whole model and write

equations for variables. (10 Marks).

b) A retailer has a coverage level of 4 months and the lead time of PPE is 1.5 months. Assume that the

retailer has an initial inventory level of 120000 PPE and the demand of PPE has a step-wise function.

Demand is 18000 units between 0-19 months, demand is 45000 between 25-65 months, and finally

demand is 66000 units between 75-100 months. (20 Marks).

- Establish complete model on Vensim and report model as screenshot in the report. Run this model

on Vensim for 120 months with time step of 0.35.

- Discuss results for inventory level, procurement level and show graphs of results.

- Make recommendations to the retailer.

c) Apart from retailers, governments also have a similar problem of PPE procurement and inventory

management as their frontline workers need PPE for free of charge. If you are asked to solve this

problem for a government organisation, what would change in your model and in your parameters?

Critically discuss this new setting. (10 Marks).

2. Practical questions: operations modelling (60 Marks)

a) Based on the specification of your project in Lab 1, please propose a solution in Witness to

simplify your shopfloor set-up (i.e. remove unnecessary entities) and smooth your post-split

production process (i.e. less blockage) but not to compromise your current productivity. Draw a

cross-functional flowchart to demonstrate the new production design. Upload this new model in

your ZIP file and name it as MOD1 (10 Marks).

b) Based on MOD1, if the cycle times of your oven are uniform (15,19) for I-type, normal (20, 3) for

II-type and uniform (20, 27) for III-type. Please use appropriate method to identify when your system

will reach a steady-state. Detailed analysis is expected to support your argument (10 Marks).

c) Based on MOD1, use appropriate analytical method(s) to identify the bottleneck of your model

and give detailed analysis (10 Marks).

d) Based on MOD1, assuming one of your three ovens is broken down, please propose a backup plan

(based on your current resource) to continue your production and try to make the corresponding

disruption as little as possible. Detailed analysis is expected to support your plan and your new

model should be named as MOD2 in your ZIP file (10 Marks).

e) Based on MOD2, all the paint stations are now becoming manual machines and you are given

10000 pcs P1, 10000 pcs P2, 10000 pcs P3, and 10000 pcs P4 to be planned. The initial labour source

costs you £3000/person. Assuming each labour has 100% energy at the start of your simulation and

every 480 minutes, all labours’ energy level will be reset back to 100%. It consumes 2% energy

/working minute for each labour and every one minute idle time can help a labour restore 0.5%

energy. If any job will run out of a labour’s 100% energy, he/she will refuse to carry out any further

work until it is reset to 100% and one major unsatisfaction will be marked. When any labour has

accumulated 3 major satisfactions, he or she will resign from your company and it will cost you

£5000 to recruit a replacement. If I-type product can be sold for £800/pc, II-type product can be sold

for £950/pc and III-type can be sold for £1200/pc, please advise the optimal labour size and optimal

number of I-type, II-type and III-type products to be produced based on your given inventory (i.e.

10000 pcs P1, 10000 pcs P2, 10000 pcs P3, and 10000 pcs P4). You should save your optimised

model as MOD3 in your ZIP file. Detailed analysis is required and please critically reflect the

implications of your solution with respect to real-life operations (20 Marks). Hint: 1) ISTATE(element

name) function can return you the state of a specific element when this function is called. 2) Use IF

action together with AND can verify multiple conditions at the same time. For example:

IF (A>=5) AND (B>=4)

C=C+1

ENDIF