Published June 30, 2015
By Cris Anderson
Project Consultant, Tompkins International
Sorters are commonly used elements in many material handling automation systems. A sorter is basically a device that can receive inputs (usually products, in single unit or full case form) in any order and separate it into multiple, discrete channels without human intervention. The main function of a sorter is to allow the decision of what products belong together in one order to be completed without depending on people. Instead, we will need to use a warehouse management system (WMS) to know all the products that need to go into an order and a collection of machinery to automate the movement of those products. The machines need to be able to read which product it is receiving and to physically move the correct product to the correct area, together with other products that belong to the same order.
Sortation systems are most often used toward the end of the order selection and build process. This way, pickers/product selectors in the warehouse or distribution center can select many products at once, for many orders, also known as batch picking, without separating the products manually. This increases human picker efficiency as it maximizes the amount of product that can be selected in one trip without requiring the person to count out product for each order, or return to the same warehouse location multiple times for each order.
Selecting which sortation system best fits your need requires evaluating several factors. Some things to consider are:
- What is to be conveyed and sorted? Cases? Totes? Units?
- Which sortation system will be able to handle the product throughput? (i.e. How many units per hour are flowing through it?)
- What kind of space is available for the sorter and order build area and how does that impact the design of thesortation?
- What is the required angle of the divert? 30, 45, or 90 degree transfer?
- Is sortation limited to a single side, or is a two-sided divert required?
- Are the products in a format that can be handled by the selected sortation system? (I.e. cases, poly bags, units, etc.)
There are many types of sorters to choose from, including:
- Shoe sorters: Movable pucks, called shoes, slide perpendicular to the conveyor and travel to certain points to gently move the products to the designated area. These are suitable for many product types because they push gently and consistently.
- Narrow belt: Narrow conveyor belts move the product through the sorter, while rollers positioned at exits pop-up underneath the products to move them off the sorter path at the right time. These are suited for cases or totes that have a hard, flat bottom.
- Pop up roller: Rollers move up from underneath conveyor to divert the product off of the main conveyor and on to other conveyors or gravity flow lanes. Similar to narrow belt sorters, these need products to have hard, flat bottoms for best results.
- Tilt tray: Trays move around a circular or oval track and tilt sideways at the right moment to drop the product down a chute when it comes to the right lane. These can be run at high speed and can also handle a variety of product shapes and sizes.
- Bomb bay: Similar to a tilt tray in that it product is placed onto a tray that moves in a circular track. This tray is split into two pieces down the middle, and when the product arrives at the correct location; both sides tilt inward and drop the product to the correct location. This must be used with product that can handle dropping.
- Cross belt: Another type of sorter that moves along a track as one product is placed onto sections of a conveyor belt that run perpendicular to the forward movement around the track. The conveyor belt activates at the right time and moves the product off of the sorter. This has more flexibility than bomb bay and can handle heavier products.
- Hanging Garment Sorter: This moves product, usually garments, that are hanging from hooks off of the main transport lane to either gravity down lanes or other hanging garment conveyor sections as needed.
While sorters can increase efficiency in many warehouses, each application needs to be carefully considered and designed to work with the rest of the material handling automation system. In addition to carefully evaluating the engineering requirements of the sortation system, the overall business requirements for each situation need to be considered, including capital expense, future maintenance costs, and future growth requirements.