19 Scheduling in Services
Vikas Singla
19.1 OBJECTIVES
This chapter would help students to understand:
- Importance of workforce scheduling in service firms
- Quantitative method of workforce scheduling
- Scheduling of 2 jobs on n machines.
19.2 INTRODUCTION
Generally services follow batch shop production system. Such a system is characterized by variety of jobs produced at low volumes. Also such variety of products or service is produced by same set of employees. Thus, same employees work or produce different set of goods or services. For instance a bank, a service station or a retail store indulges in provision of different services at low volumes. The major determinant in batch shop production system is demand of each kind of product or service. This factor directly influences workforce on different working days. For instance, a retail store might experience a rush of consumers on Saturdays and Sundays whereas little demand over weekdays. A bank receives lot of customers from Monday to Friday but demand of variety of bank services decline over weekends. Thus, a manager has to schedule workforce depending on:
- Number of employees required per day which varies from day to day depending on demand of each service provided.
- Employees being given weekly off of one or two days depending on legal requirements. Most of the organizations provide two day weekly off for its employees. Also, weekly off might vary from one service provider to other. A retail store works for seven days a week so it requires workforce to work for entire week. In such a case employees are given two day weekly off on different days of the week.
19.3 SCHEDULING IN SERVICES: IMPORTANCE
Services are mainly characterized by:
- Variety: a bank provide variety of services like cash deposit, withdrawal, insurance services, loan services etc.
- Demand of each service is different: some services like cash deposit and withdrawal attracts more demand than other services. Similarly, a retail store attracts more customers in grocery store than other stores.
- Demand varies on daily or hourly basis: retail stores demand is more on weekends whereas bank services are in demand during weekdays.
These aspects has direct influence on requirement of workforce. Thus in services scheduling is done for employees i.e. how many and which of the employee would work on which day
19.4 SCHEDULING IN SERVICES: Examples
- Scheduling in reservation systems and timetabling models: In reservation models jobs have very tight release and due dates. The decision maker has to make decisions regarding which jobs need to be processed and which not. Such reservation problems faced in hotel and restaurant industry can be effectively solved by scheduling in services models. Timetabling models are used in scheduling of classes, meetings and exams. Assignment of teachers to classes, classes to limited rooms under constraints of availability of teachers and other resources makes scheduling problem very important.
- Scheduling in sports and entertainment: Scheduling various sports tournaments such as basketball, football etc. is different from scheduling of hotel reservation system because of variety and number of constraints. For instance a constraint could be that no team can play two consecutive games at their home ground. So they have to alternate between a home and away game.
- Scheduling in health care: Scheduling of surgeries, nurses, doctors and other associated resources highlights the importance of scheduling in hospitals.
- Workforce scheduling: Scheduling of employees like nurses in hospitals, employees in retail sector or in banks use effectively scheduling models. For instance, a hospital works 24*7 so nurses or batch of nurses have to be scheduled in such a way that they are available all the time. Also, in a retail sector huge rush of customers is seen during weekends so they have to be a given a weekly off during weekdays.
This chapter discusses quantitative model to resolve workforce scheduling problems.
19.5 SCHEDULING IN MANUFACTURING: An Example
- For example, an assembly area needs to produce total 1600 balls in one shift. When we found the details of requirement, we got 800 basketballs, 400 footballs and 400 soccer balls needs to be produced.
- In the conventional way or Lot production System we can produce 400 Basketballs, 400 footballs & 400 soccer balls at once (One by One). But scheduling in manufacturing is done by leveling by type. So that there must be a ratio among the type of production. So basketballs, footballs and soccer balls will be produced in the ratio of 2:1:1 respectively.
- The leveling of the types means that the required production quantity ratio for all types is manufactured in a series. For example, if the production quantity ratio for products A, B and C is 2:1:1, respectively, and different types will be produced consecutively in the sequence A, A, B, C, A, A, B, C … and so on.
- Production carried out in this fashion makes it possible to pull parts from a preceding process without causing any fluctuation in quantity and types. The preceding process also need not have additional stock, labor-hours and equipment. Advantages of the such type of scheduling are following:
(i) Decreases work in process requirements.
(ii) Decreases finished goods inventory.
(iii) Increase multi-skilling of the Manpower.
19.6 SCHEDULING IN SERVICES: STEP-WISE PROCEDURE
The workforce scheduling problems discussed here follows certain assumptions which are:
- Employees have to work for five working days in a week.
- Each employee would be a given a two day weekly off.
- Slack should be as minimum as possible. Slack indicates difference between workers required on a particular day and workers available on that day. It can be possible that by following below mentioned method available workers might be more than required number of workers. So weekly offs should be segregated in such a manner that slack is as low as possible. This would result in allocating different two days weekly offs to different workers.
The steps involved in scheduling of employees in services are given below.
Step 1: Table 19.5.1 shows number of workers required by a service provider on different days of the week.
Table 19.5.1
| Days | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday |
| Number of workers
required |
4 | 3 | 4 | 2 | 3 | 1 | 2 |
From give data it can be deduced that maximum four workers are required by the service provider. So, manager has to schedule four workers. From given schedule of workers find sum of workers required on two consecutive days. This sum should be lowest and should be on consecutive days. In this case lowest sum of workers required on two consecutive days is on Saturday and Sunday i.e. 1+2 = 3. In case of tie i.e. if there is more than one such consecutive day then it is better to ask the workers which days they would like to have off or Assign Saturday and Sunday pair as off days.
Step 2: Assign one of the workers to five days except with lowest total requirement for two days. In this case first worker would be assigned Monday to Friday as working days and Saturday and Sunday as off days.
Step 3: For worker 2 subtract 1 from number of workers required for working days of worker 1. This indicates that one less worker is required on these days because one worker has already been assigned. Then repeat the procedure of step 1 and step 2 as shown in following table.
| Days | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday |
| Number of workers required | 4 | 3 | 4 | 2 | 3 | 1 | 2 |
| Worker 1 | √ | √ | √ | √ | √ | Off | Off |
| Remaining workers | 3 | 2 | 3 | 1 | 2 | 1 | 2 |
|
Now there is a tie of three workers on two consecutive days of Thursday-Friday, Friday-Saturday and Saturday-Sunday. In this case, as one worker has already been given Saturday and Sunday as off so we can decide that worker two be given Friday-Saturday as two off days. |
|||||||
| Worker 2 | √ | √ | √ | √ | Off | Off | √ |
| Remaining workers | 2 | 1 | 2 | 0 | 2 | 1 | 1 |
|
Now there is a tie of two workers on two consecutive days of Wednesday-Thursday, Thursday-Friday and Saturday-Sunday. Worker 3 would be given mandatory Saturday-Sunday off. |
|||||||
| Worker 3 | √ | √ | √ | √ | √ | Off | Off |
| Remaining workers | 1 | 0 | 1 | 0 | 1 | 1 | 1 |
| Worker 4 can be given off on pair of Tuesday-Wednesday | |||||||
| Worker 4 | √ | Off | Off | √ | √ | √ | √ |
Example 19.5.1: The number of workers required on each day for a service station is given below. The manager needs a workforce schedule that provides two consecutive days off preferably Saturday-Sunday.
Table 19.5.2
| Days | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday |
| Number of workers required | 6 | 4 | 8 | 9 | 10 | 3 | 2 |
Solution: Friday requires maximum workers i.e. 10. So, manager requires scheduling ten workers. Saturday-Sunday pair requires lowest total amount of workers. So, first worker would be given this pair as weekly off. Remaining workers also scheduled according to procedure discussed. Detailed solution is given in following table.
| Days | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday |
| Number of workers required | 6 | 4 | 8 | 9 | 10 | 3 | 2 |
| Worker 1 | √ | √ | √ | √ | √ | Off | Off |
| Remaining workers | 5 | 3 | 7 | 8 | 9 | 3 | 2 |
| Lowest sum of workers is still for Saturday-Sunday. So, worker 2 would be given Sat-Sun as off days. | |||||||
| Worker 2 | √ | √ | √ | √ | √ | Off | Off |
| Remaining workers | 4 | 2 | 6 | 7 | 8 | 3 | 2 |
| Lowest sum of workers is still for Saturday-Sunday. So, worker 3 would be given Sat-Sun as off days | |||||||
| Worker 3 | √ | √ | √ | √ | √ | Off | Off |
| Remaining workers | 3 | 1 | 5 | 6 | 7 | 3 | 2 |
| Lowest sum of workers is for Mon-Tue days. So, worker 4 can be given off on pair of Mon-Tue. | |||||||
| Worker 4 | Off | Off | √ | √ | √ | √ | √ |
| Remaining workers | 3 | 1 | 4 | 5 | 6 | 2 | 1 |
| Lowest sum of workers is for Saturday-Sunday. So, worker 5 would be given Sat-Sun as off days | |||||||
| Worker 5 | √ | √ | √ | √ | √ | Off | Off |
| Remaining workers | 2 | 0 | 3 | 4 | 5 | 2 | 1 |
| Lowest sum of workers is for Mon-Tue days. So, worker 6 can be given off on pair of Mon-Tue. | |||||||
| Worker 6 | Off | Off | √ | √ | √ | √ | √ |
| Remaining workers | 2 | 0 | 2 | 3 | 4 | 1 | 0 |
| Lowest sum of workers is for Saturday-Sunday. So, worker 7 would be given Sat-Sun as off days | |||||||
| Worker 7 | √ | √ | √ | √ | √ | Off | Off |
| Remaining workers | 1 | 0 | 1 | 2 | 3 | 1 | 0 |
| Worker 8 can be given Mon-Tue or Sat-Sun as off days. Company policy provides Sat-Sun as off days in case of tie. | |||||||
| Worker 8 | √ | √ | √ | √ | √ | Off | Off |
| Remaining workers | 0 | 0 | 0 | 1 | 2 | 1 | 0 |
| Worker 9 | off | off | √ | √ | √ | √ | √ |
| Remaining workers | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
| Worker 10 | √ | √ | √ | √ | √ | Off | Off |
| Remaining workers | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Capacity | 7 | 7 | 10 | 10 | 10 | 3 | 3 |
| Requirement | 6 | 4 | 8 | 9 | 10 | 3 | 2 |
| Slack | 1 | 3 | 2 | 1 | 0 | 0 | 1 |
Above illustration clearly illustrates the steps involved in scheduling of employees. There can be other variants of such schedule depending on company policy of giving weekly offs. In case of tie of lowest sum of workers required on two consecutive days company might give liberty to workers on choice of weekly offs. This would result in different variants of schedule chart. Manager might decide on the best variant of schedule chart depending on minimum slack and fulfillment of demand requirements.
19.7 SCHEDULING OF N JOBS ON TWO MACHINES
Two jobs job 1 and job 2 to be processed on n machines follows following assumptions:
- The technological flow of each job on given ‘n’ machines is pre-decided. Both jobs might not follow same flow.
- Each machine can process only one job at a time.
- Processing time of each job on all ‘n’ machines is known with certainty.
The methodology is explained by using following illustration.
Example 19.6.1: Determine the minimum time needed to process two jobs on four machines. Processing time of each job on each machine is given in table 19.3.1
Table 19.6.1
| Job 1 | Sequence | M1 | M2 | M3 | M4 |
| Processing time (hrs.) | 5 | 7 | 8 | 4 | |
| Job 2 | Sequence | M4 | M2 | M1 | M3 |
| Processing time (hrs.) | 9 | 8 | 5 | 6 |
Machine Chart
The above shown machine chart depicts the flow job 1 and job 2 goes through on four given machines. As indicated by sequence job 1 first goes through machine 1 for 5 hours. During that time machine 4 is idle so job 2 occupies machine 4 for 9 hours. After getting processed at machine 1 job 1 enters machine 2 and occupies it for next 12 hours. The sequence of job 2 indicates processing on machine 4 and then on machine 2. Job 2 has to sit idle for 3 hours as during that time machine 2 is occupied by job 1. Similarly rest of the chart is drawn.
According to chart:
Total time for processing two jobs on four machines = 31 hours
Idle time for job 1 = 31 – 24 = 7 hours
Idle time for job 2 = 3 hours
19.8 SUMMARY
This chapter has discussed quantitative method of workforce scheduling. Sequencing employees is predominantly discussed under scheduling of services. Provision of services require varied amount of workforce on different working days. Services are different in nature and ask for different skill set and resources for their delivery. Thus, production of services at low volumes requires a set of employees trained in different skill set. Also, demand of each type of service provided by a service centre varies depending on the need of customer. So, it becomes very important for a manager to schedule workforce in such a manner that varied demand gets fulfilled. Scheduling of services require deciding on which days should be assigned as working and which as weekly offs for different workers. Also, this chapter discusses scheduling of two jobs to be processed on more than two machines. Each job is assumed to use different flow of machines.
19.9 REFERENCES/ SUGGESTED READINGS
- Chase, B.R., Shankar, R., Jacobs, F.R. and Aquilano, N.J., Operations & Supply Chain Management, 12th Edition, McGraw Hill.
- Stevenson, W.J., Operations Management, 9th Edition, Tata McGraw Hill.
- Lee J. Krajewski, Operations Management, Prentice-Hall of India, New Delhi, 8th Edition.
19.10 SHORT ANSWER QUESTIONS
1. Scheduling of n jobs through two machines require ordering of jobs on machines
(a) In similar manner (b) differently
Answer: b
2. Workforce scheduling requires:
(a) Minimum total slack (b) Weekly offs to be as segregated as possi (c) Both
Answer: c
3. Pair of weekly off to be given to employees in case of tie should be selected on the basis of
(a) Company’s policy (b) Choice of employees
(c) To reduce difference between available and required workforce (d) All of the above
Answer: d
19.11 MODEL QUESTIONS
- Use the following information to create a five days on and two days off schedule:
| Days | Mon | Tue | Wed | Thu | Fri | Sat | Sun |
| Number of workers required | 2 | 2 | 1 | 3 | 3 | 4 | 2 |
- Calculate minimum possible time needed to process two jobs on five machines. Processing time and sequence of each job on each machine is given.
| Job 1 | Sequence | M1 | M2 | M3 | M4 | M5 |
| Processing time (hrs.) | 2 | 3 | 4 | 6 | 2 | |
| Job 2 | Sequence | M3 | M1 | M4 | M5 | M2 |
| Processing time (hrs.) | 4 | 5 | 3 | 2 | 6 |