Packing Activities Component – subcomponent of the previous one –

The packing process contains various activities including 1) visual inspection of the product, 2) removing defective items, 3) adjusting products weight subject to designated packing units (e.g., bag, punnet etc.), 4) placing products into boxes and 5) wrapping boxes. The boxes are then moved, manually or by conveyors, to the pallets. These tasks are manually executed by seasonal workers hired daily. The level of labourer’s experience, skills, and productivity have a significant impact on packing line productivity, product wastes, and quality of the final product. Each worker is modelled as an independent agent with a set of unique characteristics reflecting their experience and skills variations.

Figure 5-13 presents the building blocks of packing activities. At the beginning of the season, packing station managers receive rough estimates of the expected harvest quantities that would be received at the station. The products that need to be packed on any given day is estimated by “Simulate Daily Quantities at Receiving Area”. The number of packers is then simulated based on this quantity and the productivity of packers. The “Seasonal

Workers Recruiting” block simulates the hiring process of the packers. They are then moved

and distributed on the packing tables waiting for the raw products to commence packing

“Start Packing Activities”. Once the crate is placed on the packing table, packers follow the

and performance indicators are calculated for the packing house and the individual worker in

“Update Packing House Metrics” and “Update Worker Metrics” blocks respectively.

Figure 5-13: Packing Activities Building Blocks

1- Simulate Daily Quantities at Receiving Area Block: The estimated quantity of raw

produce at the receiving area (!_"#_{) is the main driver for the number of seasonal workers to}

be hired on any given day. This quantity is a sum of 1) estimated harvest quantity (!_$%_{), 2)}

unpacked quantity of previous day (!_&#_{) and 3) outsourced quantity !}'_{, the following}

equation expresses this summation:

(₎* _{+ = (}

./ + + (1* + − 1 + (4(+) (8)

The unpacked quantity is calculated using the following:

2- Seasonal Workers Recruiting Block: after estimating product quantity, the number of

seasonal workers is determined using the following equation: 8* _{+ =}9:;(<)

*;_(<) (10)

Where ## _{is the perceived worker productivity, which is determined by the manager.}

3- Start Packing Activities Block: packing operations begin when crates are placed on the packing tables. Packers are assigned to the tables based on the built-in state charts which control the sequence of packing operations (Figure 5-14). A pool of packers is available for

hiring and initialised at “Un-Recruited” state. When the number of packers (=#_{) is}

determined in “Seasonal Workers Recruiting” Block, the status of the packers is transferred into “Recruited”. The recruited packer status is then changed to“Arrived” while waiting for the commencement of operations. By beginning packing operations, packers are assigned to packing tables, and their status is transferred into “At_Packing_Table” state. Meanwhile, raw products pallets are supposed to be moved to packing lanes where these tables are attached, and crates are placed on tables for processing and packing raw products.

At packing table state, every packer is assigned to one of the three states. In

“Preparing_Product”, packers inspect the raw products and dispose of any defected or

unqualified items. The inspected products are then adjusted, weighted and fitted into designated packing unit (e.g., punnets or plastic bags), “Placing_in_Packing_Units”. The packed products are then placed in a bigger boxes or packages “Wrapping_Packed_Box”

It is noticed that packing waste and losses mostly occur in the first two stages. The packing processing time and rate of loss vary based on packers’ experience level. Similar to harvesters, packers experience level is a proxy variable that is used to reflect skill variations. Packers experience improves over time if they are recruited for the next working day as explained in Block 4. When all available quantities in receiving, area are packed or work finish time is reached, packing agents stop receiving more crates on tables and finish all available work on the table, then move into “Work_Finished” state before they turn again into “Un-Recruited” state.

4- Update Worker Metrics Block: At the end of working day, all packers are released from

the packing house, and a set of metrics are updated including 1) number of working days

(>#_{) and 2) experience level (?}#_{). The number of working days for each worker is updated}

as follows: @_A* _{+ =} @A * _{+ − 1 + 1, CD EFGHIG C CJ GIKGLC+IM N+ MNO +} @_A* _{+ − 1 , P+ℎIGECJI} ∀ C = 1,2, . . , U * ₍₁₁₎

Where V# _{is the size of all seasonal packing agents pool.}

Packers' experience levels are updated based on continuous improvement and learning curves by using the following equation:

W_A* _{+ = min (W}

[\]* , WA* 0 ∙ I)`∙ab ; _<

) ∀ C = 1,2, . . , U* ₍₁₂₎

Figure 5-14: Packing Worker Agent State Chart

5- Update Packing House Metrics Block: This block updates a set of metrics including 1)

handled quantity (!_$#_{), 2) packed quantity (!}

h

#_{), 3) wasted quantity (!}

i

#_{), 4) average worker}

productivity (##_{) and 5) perceived worker productivity (#}#_{). Handled quantity is simply}

the sum of weight for all pallets moved from receiving area to packing lanes. Similarly, the daily packed and wasted product quantities are the sums of the packed and disposed boxes during packing activities respectively. Average packer productivity is calculated using the following equation:

j* _{+ =} 9k;(<)

l;_(<) (13)

The perceived productivity is modelled using a first order delay function (=mifn_o)

introduced by Sterman (2000) as follows:

j* _{+ = 8IpNO}

q (j* 0 , j* + , Nr) (14)

Where #s _{d is the initial value for the perceived worker productivity, and f}

t is time to