Rate x Flexibility = Sliding Shoe Sorter

Sort Rate Reliability & Flexibility Rolled Into One

The sliding shoe, or slat sorters are the topic of discussion today. A prudent discussion to say the least, and by no means am I recommending sliding shoe sortation based on this blog alone.  Even if your business falls into one or several of the categories below it is important to look at each application carefully.  I have run across misapplied sortation equipment in many customer’s facilities in the Discovery stage.

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I have been witness to misapplied shoe sorters where the customer ended up spending much more than they needed buying a shoe sorter that didn’t offer them the ROI they bargained for, when a much less costly sorter would do the same job. Getting the RightFit system for the job is of the utmost importance, this can can save quite a staggering amount of time and money in the long run.

How Does It Work?

This type of sorter is highly effective when implemented in the correct environment. Reliability and Flexibility are the selling points of this type of system.  Sliding shoe sorters are typically driven by a large chain that contains slats (the carrying surface) and shoes (the diverting mechanism).  Each divert location is controlled by a switch.  Items are tracked to a specific point and the controls system sends a signal to the switch to open a gate for a period of time.  This period of time corresponds with the length of the carton to be diverted.  The shoes push the carton across the conveyor and onto another “takeaway” conveyor to route the carton to a dock door, a buffer lane, or another processing area.  Sounds simple, right?  Well, as they say, the devil is in the details.

Sliding Shoe Sorter Video

Courtesy of Intelligrated 

Shoe sorters are best at delivering a high case rate, while being less costly than unit sorters. Sliding shoe sorters are adept at sorting a wide range of products at speeds of up to 650 FPM (Feet Per Minute), however do not confuse speed with throughput.  There are other factors that determine how many cases per minute (CPM) can be consumed by the sorter.  You must take case length and gap requirements along with downstream availability, and re-circulation potential into the equation.

Shoe sortation is also adept at handling a wide range of products. Shoe sorters are the most versatile pieces of equipment when your product mix varies light or heavy, very long or short.  In fact they can handle mixed items better than almost any other technology out there.  This can be very helpful for a company when projecting where they may be 5 or 10 years from now.   While your distribution needs may be on the fence for sliding shoe sortation now, what about volume growth, SKU proliferation, or shipping medium changes (eg. shipping bagged items).

Sliding shoe sorters are also great for products that need to be handled gently.  If you are traveling at high speeds, the less gentle the product will be handled.  In recent years Conveyco has added soft touch shoe diverts to take extra care of products that could be damaged at high speeds.  Recent improvements in soft touch technology allow breakable products to be sorted accurately and quickly with increased throughput.  Try doing that with a pusher sorter (sounds about as violent as it is).

It sounds like this sorter is a fantastic piece of equipment… which it is.  However, as in sports, the sorter is only one player of a larger team and the sorter is only as good as the equipment on either side of it. The accumulation conveyors, and merge systems you are using will have to be able to match, or exceed the rate of your sorter.  If this does not happen, sorter starvation occurs.  You will also need to think about the divert type.  If you are sorting at fast speeds you need to be able to get products out of the way of the next carton?  Would a 30 degree spur do the trick?  Or do you need 20 degrees?  What about the processes downstream of the sorter?  Are you going to fill up downstream lines so the sorter will have to recirculate cartons, lowering your actual rate (even though the machine rate stays high)? Many little questions answered properly with the correct RightFit solution add up to a system running like a well trained team.

In material handling today there are many different types of sortation equipment.  Choosing the solution the best fits is a   decision that must be made carefully. This equipment can be expensive, and will be the backbone of your entire picking and shipping system for years to come.  In addition it is unwise to look at the sorter in a bubble, or focus on the flashy rate and speed numbers without focusing on the system wide details and making sure everything is in balance.  Sliding Shoe sorters are a very robust piece of conveyor sortation equipment.  When applied correctly they should provide your company with increased throughput, less breakage, and higher accuracy.  These all lead to a stronger bottom line, and a stronger company.