The goal with any packaging line is to maximize throughput. The last thing you want is for the line to slow down, or even worse, shut down. The design of your packaging systems is key to making sure you are getting the best performance. Beyond equipment selection, there are three key aspects that need to be carefully incorporated into automated packaging line design to maximize your line throughput.
KEY ONE: Automated Packaging Line Balance
A balanced packaging line matches feed rates and speeds of individual pieces of equipment to adjacent machines, and is adjusted for changes in product flow to each piece of packaging equipment. The concept is easiest to understand with an example:
The primary objective with line balance is to avoid starts and stops for each piece of equipment on the packaging line. If a bottle filling line can fill 12oz bottles at 120 bottles/minute, with 12 bottles/case the case packer would need to fill a minimum of 10 cases per minute. If the case packer cannot run 10 cases per minute, bottles would back up and accumulate before the case packer eventually stopping the filler.
The case packer will only be in balance as long as it runs slightly faster than the flow of bottles from the filler. Each piece of equipment in sequence on the packaging line must run slightly faster than the flow coming to it (and hence the equipment upstream of it), to keep bottles constantly flowing through the line. If a photo eye before the case packer senses the lack of bottle supply on the conveyor, the case packer will be put into a “holding pattern” until the photo eyes senses enough bottles in the cue to fill case.
Where this gets more complicated is when a line is designed to run more than one size container. In our example above, if the line will also run 6oz bottles, which typically fill faster than 12oz bottles, a case packer that can function for the faster of the two bottle sizes, assuming both are 12 pack cases, would need to be purchased. Whichever size container has the faster cases/minute run-times will be the determinant for a minimum required speed on the equipment.
Line balance is a careful consideration of the relationships between your individual pieces of packaging equipment and all potential run scenarios. A balanced line will constantly maximize throughput.
This leads us directly into the next topic. Flow.
KEY TWO: Managing Product Flow
Line flow centers on the flow of products from one piece of equipment to the next. It is based on available line accumulation and equipment speeds upstream and downstream.
The objective in managing product flow is to gently accumulate product to take full advantage of the available accumulation while minimizing back pressure to maintain high quality standards for your product. You want to minimize the number of sliding containers on a moving conveyor, because this buildup creates back pressure between bottles and inside the packaging equipment. This could potentially cause damage to your containers, if backpressure is allowed to build beyond an acceptable tolerance. A small amount of accumulation is typical and often desired, but you don’t want to run your conveyor faster than needed for accumulation.
When the product changes state from “moving with the conveyor chain” to “sliding” the conveyor will backup with bottles and block a photo eye and pause the upstream equipment. This photo eye position will maximize accumulation on the conveyor with an acceptable backpressure on the bottles. The speed of this accumulation conveyor should be slightly faster than the downstream equipment speed to maximum throughput and deplete the accumulated bottles on the conveyor.
For example, we have a line running 210 bottles per minute on the filler. The same line, packs 6 bottles into each case, which means the filler produces enough bottles for 35 cases/minute. To keep line balance, the case packer should be designed to run approximately 10-15% faster than the filler, packing 240 bottles per minute, or 40 cases per minute. This increase assures the packer will always pull the flow away from the upstream equipment. Additionally, the upstream accumulation can minimize instances of filler stoppage as a result of a delay in adequate case supply to the case packer equipment or minor jams.
To maintain line flow, you may want to consider bottle accumulation between the filler and case packer. Machine speeds and historical downtime data are helpful pieces of information to examine when designing solutions to line flow. You need to have enough bottle accumulation between the filler and case packer to allow for minimal downtime on equipment from the case packer and downstream equipment to prevent filler stoppage.
When determining the amount of accumulation required, historical downtime data is very helpful. If Mean Time To Repair (MTTR) and Mean Time Before Failure (MTBF) information for the machine is available they can provide guidance for designing an acceptable amount of accumulation. Going back to the primary objective of reducing the amount of start and stop cycles on a machine, the MTBF indicates (on average) how often the machine will stop.
If a packer is stopped the accumulation upstream is building. The MTTR tells you (on average) how long it takes to bring the machine back to a running state. The amount of accumulation required would be designed for this duration and would allow the upstream equipment to continue running based on the time required to bring the downstream equipment back on line.
KEY THREE: Line Supply and Backup Capabilities
The last key to maximizing packaging line throughput is to make sure all necessary packaging materials are available to the line. How do you ensure there is a constant stream of labels? Bottles? Ink? Do you need redundant equipment? Can minimal line stoppage for replenishing materials be absorbed in the available accumulation? A common example is making sure to buy labelers with a two roll carrier for labels so the line can keep running while you replenish an empty roll.
Thinking through the logistics of material supply on the line before it’s up and running is key to keeping it running.
EPIC Packaging Solutions
We help you develop efficient lines that are balanced, have optimal flow and have a constant supply of materials to keep running 24/7/365. If you need help improving your line efficiency, upgrading your line or adding better line controls, contact one of our automated packaging line experts today.