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Filler/Checkweigher Feedback: The Basics

Often times All-Fill customers will purchase a filling machine when they already have an Alpha Checkweigher, or vice versa. They then ask us, “can this filler accept feedback?”  

First, let’s give an easy explanation of the concept of feedback. Checkweighers are typically purchased because packagers need to ensure that underweight or overweight packages do not go out to consumers. The packager wants to ensure that their label weight is properly delivered to their customers. All-Fill typically calls this checkweigher a “traffic cop.”

“Alpha’s model EW-8 and PW-12 checkweighers are most commonly used as traffic cop checkweighers,” explains Bobby Kelley of Alpha Checkweighers. “Imagine the package traveling down the assembly line the same way that you travel down the highway in your car. If you speed on the highway, you are bound to be pulled over, the same way anything under or overweight is rejected off the assembly line so that it does not get packaged.” A traffic cop is great for some, but for those packagers that want the checkweigher to ensure that their products are being packaged to weight but also adjusting to ever changing environmental conditions, filler/checkweigher feedback is the key!

Let’s assume that we are attempting to get feedback from a standard Alpha model PW-12 checkweigher with a model SHA-SV-600 automatic auger filling machine. It is important to note that the auger filler is an automatic filler with servo-motor driven auger. As packages are transferred across the checkweigher, the operator sets a window of accept/reject parameters for which they are willing to accept. For example, on a 454 gram fill, the packager may be willing to accept a low weight of 454 grams and a high weight of 458 grams. As soon as a

weight passes across the checkweigher that is outside of the acceptable range, the filler does not start making feedback corrections (although it could be pushed aside as a reject if set up that way in the recipe/program). Instead, the checkweigher looks for weight trends, not a single out of spec weight to over react to. The operator can set a sample of feedback ignore samples and a range of weight to evaluate as samples. “Typically, we are simply looking for the checkweigher to monitor product density shifts or changes or product high/low limits and report that back to the filling machine,” exclaims Kelly.  

As the checkweigher begins to detect a trending high or low weight from the filler in the example mentioned above, it will send a correction signal back to the filler that adjusts the revolutions. This will bring the average weight back into the acceptable range. Obviously the filler likes consistency in order to work as best as possible. When the filler is properly set up mechanically and the proper tooling is installed in the filler, checkweigher feedback works very well. It is not uncommon for the average fill weight to be the programmed target weight once a shift of a few hundred fills is complete.  

The Alpha Checkweigher is obviously capable of working with All-Fill fillers, but it is also common for Alpha Checkweighers to work with any OEM filler just like All-Fill fillers can also work with any OEM checkweigher. Alpha Checkweighers are sold with and without the feedback capability so please make sure to ask your salesperson to include feedback should that be a feature you plan on utilizing. For all fill by weight applications involving auger fillers and linear net weigh vibratory fillers, checkweigher feedback is not needed, but is often utilized for final weight confirmation to double check.

For more information and to determine if feedback is a feature that your facility can utilize, please contact your Alpha Checkweigher or All-Fill filling machine salesperson at 610-525-7350. You can also chat with us online and email our sales team directly while here at