How to maintain carton singulation in a distribution center
When running cartons through a distribution center—particularly an operation with different sizes and shapes of products—a few things can go wrong. One of the biggest issues we’ve seen is cartons becoming side-by-side in the line. This can cause the following problems:
- Scanner will see two carton labels together and won’t be able to sort the cartons, sending them to recirculation lane which is a killer for your system’s throughput.
- Scanner will see only one label and two cartons appear as one so both cartons will go to the same destination, resulting in order inaccuracies.
- The side-by-side products will be too wide and cause a jam in the system.
- There will be insufficient gaps down the line that again result in recirculation.
Throughput and efficiency are crucial in your distribution center’s operations, and there are some steps you can take when designing and running the system to ensure that your products get—and stay—single file while they convey, accumulate and merge in order to have them sort accurately.
Keep speeds down when possible
Running your system at the extremely high speeds may seem like a way to achieve great throughput; however, this can cause serious issues in controlling your product flow. Running cartons at higher speeds than necessary can cause cartons to bounce on the rollers, which results in actual varying carton speed based on carton weight and condition. This may allow cartons to catch up with other cartons and become side-by-side. In addition, when you need to stop products to accumulate prior to merge points, your cartons may drift due to high speeds causing carton pressure resulting in side-by-sides to happen in your line.
There’s still a way to achieve high carton throughput while keeping your speeds down. To do this, you must utilize the correct mode of operation with the zero-pressure accumulation conveyor. We recommend using cascade release mode on your accumulation conveyor to maximize carton density upon release. Cascade release mode allows you to pull very small gaps between products, thus achieving high throughputs, while still being able to accumulate carton slugs with building up carton line pressure.
Another accumulation mode that is beneficial in reducing carton pressure is high speed accumulation mode. This mode allows cartons to slow their speed prior to accumulating behind the previous carton.
Brakes in accumulation zones will stop your carton from drifting forward into other products when you do accumulate. Brakes work by providing a hard stop for your product and control its inertia. In zero-pressure accumulation products, brake rollers can be utilized in each zone.
Some accumulation conveyors employ brake rollers as a standard feature, but you should always check with your material handling provider to determine how to best equip and set up your accumulation conveyor.
Justify, Justify, Justify
Justifying your product is one of the most important ways you can keep your product singulated. Keeping cartons single-file will ensure that any drift when going through the distribution center will not result in cartons creeping up alongside the carton in front of it.
To keep your product justified, implement the following solutions:
- Use a single side for merge points. Using a single-side merge ensures that all product will be justified on a single side. If you must use a double-side merge, you may need to use 10+ feet of skewed rollers to move cartons to the primary side and square them with the frame; that adds more expense to your project and should be avoided if possible.
- Use side merges for multi-lane merging rather than two-to-one and three-to-one. Not only will this keep your product aligned on one side, you can use as many merge lines as needed. When you utilize a two-to-one or three-to-one merge, you’re obviously limiting yourself to two or three lines of product.
- Use side merge on infeed ends of lines rather than curves in order to justify. Curves can be appropriate at some points, but particularly when you must create or change side justification of products, curves aren’t effective.
- Utilize skewed rollers after merge points and along the length of long lines. This helps to square your cartons with the frame and prevent shingling of product that can cause issues down the line. Note that you may need to keep friction to a minimum when utilizing guard rails.
A Note About Descramblers/Singulators
Descramblers or singulators can be used to break down consolidated bulk items into a single-file line, but it’s inefficient to use them to separate the side-by-sides in your system that shouldn’t be there in the first place. When designing your system, it’s better to prevent a problem than to fix a problem. Putting minimal expense into making sure your product isn’t scrambled when unnecessary is a better cost solution than to try to fix the issue down the line. In addition to cost, singulators are inefficient due to the used floor space in your facility.
To keep your products flowing in a single-file line, there’s a lot to consider. If you’re experiencing shingling or side-by-side products in your system, then it is definitely hurting your throughput and efficiency, and the culprit can usually be found in one of the above three points. Always consult a professional when you need to update your conveyor system, and you can prevent these problems before they happen.