Questions and Answers About Sortation

Steve, what are some kinds of sorters?

Tube sorters use a tube about four-foot long and 1-1/4-inch in diameter, and there might be one inch between tubes. A shoe slides across the tubes. It is preferred by some in the food industry for products that leak or for those from which small parts may be torn. These leaks or small items fall through the sorter. Now you don’t sort packs of gum with this, rather boxes, items from one to three feet long.

Slat sorter or flat-slat sorter is another kind. It uses a flat surface in place of a tube, and the shoe slides between two slats. It is used to sort small items, to about six inches long, at high speeds. Some users prefer this type of sorter even for larger items.

What are metering belts, and why are they important to sortation systems?

Metering belts are critical to sortation systems. They are used to set a space between two products. The belt adjusts the conveyor speed and the distance between products to change gap so products fits the minimum separation for the shoe sorter. The metering belt also sets the speed so that it matches the sorter speed rate. The metering belt usually includes a photoeye to measure the gap between goods before metering them.

What are sorters used for?

The sorter is used for parcel shipping, for zone skipping and for separating items for the same store order into various departments, which might be frozen goods, cold goods and typical shelf goods.

What new sorters has FKI developed recently?

The Unisort XV combines the best of Buschman and Mathews conveyor designs. It uses an all-electric, flat-slat sorter. When an item passes onto the shoe sorter, a leading shoe, plus some shoes along the length of the parcel, plus one or two trailing shoes are assigned to each package -- maybe six shoes total.

At some point you need to switch on those six shoes. In the past, these switches were typically pneumatic that required regulated pressurized air. Our new switches are all-electric. Pneumatic switches are typically less expensive than electronic, but when you add the cost of installing and maintaining a pneumatic system at the right pressure, it makes it easier to ensure that the right power is in place, so long as you have electricity. It makes for a simpler installation.

How has advanced technology affected switching for sorters?

We’ve converted to all-electric switching and a mechanical crossover switch for left and right diverts. Our new mechanical crossover switch keeps the sorter shoes aligned, and is much smaller than in the past. Before, we positioned 12-foot on-center design for switches. With our new, all-electric design, we can reduce switching distances to just four feet apart.

Why is reducing switching distance important?

Reducing distance allows us to densely pack the number of sorts. We may have a sorter that serves 50 doors, and 50 times 12 feet is a very long sorter unit. Now we can service postal or parcel sites with 150 sorting doors on just four-foot centers both left and right. This allows for shorter sortation devices and denser sorting.

How does the choice of sorter technology affect products sorted?

By using slat technology instead of tubes, we can sort CDs and video tapes, which were once predominantly the items for tilt-tray or crossbelt-type sorter in the past. This opens a whole new range of smaller-parcel sortation capability.

How does your company’s business sort out between new conveyor systems and retrofits?

Most business is in expansion of a current system -- not a lot of retrofitting. It’s not that you can’t retrofit a faster sorter into a system. The sorter is like the spine of a system. To take it out and put a new one in would shut down the operation for a period of time. That’s very difficult for customers, so a new, alternate sorter is installed alongside the old one, and the old one is decommissioned.

What is more common, then, when it comes to new systems?

Adding a new facility or a second sorter is more prevalent than replacing an old system. But for some buyers with a fixed amount of space, a sorter installed 10 years ago that limits you to 130 cartons/minute is a problem. The user asks us to install a sorter that can handle a much higher rate, so we install a second sorter on top of the first or one alongside the old system, and install new aftersort lanes.

What about increasing the speed of my current sorter?

Users might have a sorter that runs at 130 cartons per minute and is now desired to hit 200 cartons per minute. Any one of several manufacturers can install a new sorter to meet that capacity. But what most users forget is that the whole system must be redesigned to merge 200 cartons per minute for the sorter, and that is a very expensive proposition. It means putting in a new merge that can meet those rates or make significant retrofits to controls and speed changers on the existing merge to meet that higher speed. Sometimes, it is more expensive to upgrade the merge conveyor than the sorter.

What are some trends in sortation applications?

There are a lot more people looking to bypass major overnight carrier costs by working with the Postal Service with zone skipping. Users are looking at sorters to accomplish these zone skips, and payback can be less than a year on sorters given the difference in cost from overnight to Postal Service rates. In the past, it was tilt-tray or cross-belt sort. But now with the Multisort XV, it can be a shoe sorter as well.

What is zone skipping?

Depending upon what carrier you are using, there may be, for example, five hubs located across the U.S. for a contract business carrier. If you sort your product for those five hubs and put that product into five trucks and have them drive to those hubs, you get a preferred rate from the vendor. This works when you have enough packages in the truck either each day, or every other day, to make it profitable.

What should MHM readers keep in mind when buying a sortation system?

You need to buy a sortation system for the future needs of your company. For companies that may experience significant growth in three years, the sorter or the system feeding it may be out of capacity. It is very expensive to retrofit that problem. You don’t just put a new motor on it to move from 300 to 400 fpm. The control system, the merge, induction system and metering must all work at the faster speed.

What if you buy a system that can be “revved up” in a few years?

If you put in a system at 150 cartons/minute because it was relatively inexpensive and you are told by a vendor that just a gear change will raise it up to 200 cartons/minute, that is unrealistic. Increased speed changes the geometry of the conveyor. When conveyor speeds run at 300, 350, 400 fpm, you change from a 30-degree angle for guiding items off the conveyor to a much gentler 20-degree angle. In the shoe sorter market with speeds of 500 and 600 fpm, you’ll see that angle shrink to just 15 degrees. Shoe sorters can run from 100 fpm to 550-600 fpm. At those fast speeds, the physics of how air currents affect small packages becomes important. It is not difficult for items weighing just a few ounces to gain flight.

What should be understood about very fast sortation systems?

When you get into very-high-speed distribution, over 175 cartons/min, you are pushing the conveyor system so hard with varying size products from cassette tapes all the way up to television sets, that you tend to have problems with products catching each other and trying to pass each other on the conveyor. This is called side-by-sides.

When you get to a metering belt, its important to have singulated flow. The Buschman Company released a few years ago the VHS Wedge for high-speed lanes. The VHS Wedge is used on lines that accumulate product and are released together. At the point of release, the items are singulated, gapped and then released in trains at very high speeds. This tends to eliminate the side-by-sides and can raise rates to above 220 cartons/minute. There are some successful sites installed in pre-merge areas for our customers. It doesn’t affect the sorter, but it sets up a successful transition to the sorter.

What do users often overlook?

A critical area that users don’t spend enough time on is what happens after the sort. With packages coming off the sorter at very high speeds, do you want to maintain the orientation of the package, keep the label facing up or perform a secondary sort? A lot of study has to be given to the speed transition point for packages moving 500 fpm and traveling to an accumulation conveyor that feeds a truck loader. You may want that package to be handled very gently, and accumulation conveyor typically runs in the 200-250 fpm range.

FKI offers a two-speed conveyor curve that after the product is sorted, the machine changes the speed and slows the item down under control. Then the product retains its orientation. Some might try this transition with gravity conveyor and hope the box retains its orientation, but that too is a tricky method.

What’s the most important thing to keep in mind when it comes to sortation?

The sorter is only a component of a sortation system. It is like the second hand on a watch. You see that hand move the most, but you need the other two hands to complete the job. You have to really understand the induction, the merge, sort and aftersort for a successful system.

For singulation, keep in mind that items coming off a singulator may or may not have a gap. That is why a metering belt is needed to give adequate gap between items. by Christopher Trunk, managing editor

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