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Cliff Holste

Supply Chain Digest
Material Handling Editor

Logistics News

Cliff Holste is Supply Chain Digest's Material Handling Editor. With more than 30 years experience in designing and implementing material handling and order picking systems in distribution, Holste has worked with dozens of large and smaller companies to improve distribution performance.

May 11, 2016

Logistics News : Understanding Sorting System Fundamentals


Automated Sortation Systems typically include (3) Integrated Subsystems

 

In the order fulfillment process sorting systems are often used to rapidly and accurately consolidate random flows of products into discrete orders for shipping. Essentially, there are two basic approaches to developing a sorting system solution; sortation as a standalone operation sorting products into consolidation lanes, or as an integrated component of an overall order picking solution. The latter is the most comprehensive because it takes into consideration all possible product mixes from all production areas. Typical, such systems consist of a mix of conveyors, equipment, and controls that are tied together (integrated) through the Warehouse Management System (WMS) and/or Warehouse Control System (WCS).

Data that impact on sorting equipment selection include: case/container size, weight and handling characteristics, required throughput capacity (cases per minute), space constraints, and system layout configuration. Once the physical requirements have been considered, the next step is to determine what level of sorting sophistication is needed.


Holste Says...

Working within budget constraints, the best strategy is to deploy the most flexible and adaptable sorting equipment and subsystems available capable of handling a large variety of products while operation at peak capacity.

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Automation should be considered when two or more of the following requirements exist:

 

  • Throughput – 10,000 or more cases/containers processed per eight hour day or work shift
  • Shipping accuracy rate (99% or greater)
  • Minimize product damage
  • Increase productivity (reduce incremental increases in headcount)
  • Optimize capacity of existing facility and processes
  • Grow the business

 

Once it is determined that automated sorting is justified, there are (3) Subsystems that comprise a properly deployed integrated automated sorting system: Induction, Sortation, and Aftersort.

 

1. INDUCTION SUBSYSTEM

 

The Induction Subsystem receives cases of product from upstream processing lines, merges and combines the cases into a single line, establishes the proper space/gap between cases, and feeds the cases onto the sorter at the maximum machine rate (referred to as the Demonstrable Rate expressed in cases per minute CPM). The following chart lists principle functions of the induction subsystem:

 

Function

Technology

Objective

Identification

Bar Code, RFID, Camera

High read rate & accuracy

Merge & Combine

Accumulation lines

Saw-tooth merge (30º spur)

Wide belt combiner

Multiple lines merge into one main in-feed line with smooth flow

Gapping

(space between cases)

Gap Optimizer

Accurate positioning for space between cases and side-to-side alignment

 

2. SORTATION SUBSYSTEM

The Sortation Subsystem includes a broad range of technologies. The table below lists key characteristics for the types of sorters most often used:

 

Sorter

Type

CPM

Case Size

L x W

GAP

No. of Diverts

Divert Angle

Speed

FPM

Induction

*

Cost Level

Application

**

Manual

5 - 20

***

24 in.

***

N/A

N/A

Manual

Lowest

1, 2

Deflector

10 - 25

***

3-5 ft.

***

30º Max.

<120

BSB*

Low

1, 2

Right Angle

10 - 30

***

24 in.

***

30-90

120

BSB*

Low Med

1, 2, 3

Pusher

10 - 40

24 in.

20 in.

***

90

120 - 200

BSB*

Low

Med

1, 2, 3

Puller

10 - 25

24 in.

24 in.

***

90

<120

BSB*

Low

1, 2, 3

Pop-up

Wheel

Diverter

60 - 80

9–42 in

6-27 in

12 – 18 in.

1 - 13

30

<300

BSB*

BMB

BMB-HS

Low

Med

High

4

Sliding Shoe

80 - 350

9–42 in

6-30 in

6-12 in.

10 - 100

20-30

200 - 600

VFD Servo

High

5, 6

Tilt Tray

80 – 400+

2-30 in

2-30 in

N/A

100+

90

600+

Servo

Highest

5, 6

Cross Belt

80 – 200+

2-30 in

2-30 in

N/A

10 - 100

45-90

200 - 600

Servo

Highest

5, 6

 

*Induction: BSB = Brake Spacer Belt; BMB = Brake Meter Belt; BMB-HS = High-speed Brake Meter Belt

** Applications: 1 = Low speed distribution; 2 = Low speed in-plant processing; 3 = Case reorientation;

                            4 = Medium speed distribution; 5 = High speed retail, mail order, item/postal/parcel;

                            6 = high speed item/parcel, baggage

*** No limitations

 

3. AFTERSORT SUBSYSTEM

The Aftersort Subsystem transports and stages/accumulates product from the sorter prior to packing, palletizing, or fluid loading onto shipping trailers. The following chart lists important considerations:

 

Function

Technology

Objective

Deceleration

Gravity or controlled flow conveyor

Minimize product damage

Case Alignment

Manual; skewed roller conveyor

Minimize jams, smooth flow

Case Sequencing

Manual or automated queuing

Packing, palletizing, shipping

 

The above three subsystems are essential elements of the automated sorting system solution. Their proper design and application is critical to the performance of the overall material handling system. They should be located in an area within the facility that will not be considered for expansion anytime in the foreseeable future. For example: locating the sorting equipment over the shipping dock doors is definitely worth considering as this space is seldom used efficiently.

In facilities that have a clear height of 30 feet or more, installing the induction and sortation subsystems on a floor supported mezzanine takes advantage of the buildings cubic space while creating unobstructed floor space underneath for staging, as well as the efficient movement of personnel and mobile equipment.

Of course, the software that integrates the sorting system into the DC’s business processes and physical flow patterns, i.e., WMS & WCS, are the “brains” that drive the automation and provide the highest level of overall system performance, flexibility and adaptability.

 

Final Thoughts

Many logistics companies are concerned about unforeseen changes in their business model and the effect those changes could have on bolt-to-the-floor sorting systems. Working within budget constraints, the best strategy is to deploy the most flexible and adaptable sorting equipment and subsystems available capable of handling a large variety of products while operation at peak capacity.

 

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