Other than the weigh scale, the second most important aspect of a checkweigher is its reject mechanism. This device is responsible for ensuring all unacceptable packages will be removed from a production line. After a product is weighed in motion across our checkweigher, if the package does not meet the customer's preferred target weight, we provide a wide array of solutions to ensure the end user does not receive less than what they paid for. With over 15 different pneumatic reject devices customized to meet the specifications of the customer’s application, we offer the quickest and safest way to remove an “out of spec” package off of a production line.

Some customers prefer to only reject underweight packages, as it is always better to give away a little bit of extra product from the end user’s standpoint as opposed to shorting the product they spent their hard-earned money on. This keeps the patron happy and the manufacturer out of trouble. Oppositely, some manufacturers may choose to remove both under and overweight packages off of the line so they can reuse the product, saving them countless dollars over the long run. We offer a toggle menu to allow the customer to make this decision. No matter the preference, All-Fill provides a reliable and effective solution to ensure the manufacturer, co-packer (if applicable), and customer are not disappointed.

Choosing a Checkweigher Reject System Device

Choosing the proper reject mechanism depends on a few variables, including:

• Type of container or package
• Weight of that container or package
• Speed at which the product is running across the checkweigher

To protect the product and prevent messes, these reject devices usually reject containers into/onto a reject tray, reject bin, or separate reject conveyor. To determine which type of reject will be most applicable to a given project, we will delve into which of the variables we mentioned match with which type of reject device we offer.

Air Jet Reject Device

For products weighing less than 1 lb, an air jet reject is the most common solution, shown on the left. An air jet will produce a sharp stream of air directed at the container to blow it off of the line. One of the many benefits of an air jet reject is its simplicity, there are no added moving parts required. Additionally, air jets are well suited for a fast production line, up to 250 packages per minute. The retraction time one would have from a reject where an arm has to extend to push the package off the line is non-existent with an air jet. An Air Jet Reject Device is most commonly used on our EW/8, PW/12, CW/10, and HP/14 checkweigher models.

Bopper Reject Device

For packages that have to run equally as fast but weigh a bit more than 1 lb, we offer a bopper reject. Built with a cylindrical shape, boppers quickly hit or “bop” a container off the conveyor. Boppers are good for products weighing under 2.5 lbs, and like an air jet reject, they can also handle speeds up to 250 cpm. A Bopper Reject Device is most commonly used on our PW/12, CW/10, and HP/14 checkweigher models.

Pusher Reject Device

Similar to a bopper but with heavier-duty capabilities is a pusher reject. Pushers use a pneumatic cylinder with a plate on the end to literally push a product off the conveyor. These rejects can push products weighing up to 8 lbs off the conveyor at speeds up to 80 cpm. This is the second most widely used reject device after the air jet. A Pusher Reject Device is most commonly used on our EW/8, PW/12, CW/10, and HP/14 checkweigher models.

Swing Gate/Diverter Reject Device

Another option for rejecting over or underweight containers is a swing gate or diverter. This reject allows products that meet the weight specification to pass through the out feed conveyor of the checkweigher and onto the next station. If a product does not meet the weight specification, it will divert it off the line - think of a gate toggling back and forth in order to separate good and bad products left or right. Some diverters or swing gates can handle products up to 5 lbs at speeds of 200 cpm. The diverter is ideal for products like an uncapped shampoo bottle, or uncapped steak sauce bottle as it allows the product to be removed from the line but remain standing up and eliminating spills. A Swinging Gate/Diverter Reject Device is most commonly used on our model CW/10.

Drop Belt Conveyor Reject Device

The last type of reject we will spotlight is a drop belt. A drop belt conveyor will lower the out feed conveyor so that the off-target package will go onto the floor or into a reject bin below the checkweigher. These are a nice option because they do not add any more space onto the footprint of the machine like a reject tray or reject bin may do. Drop belts typically handle products that weigh less than 6 lbs and no larger than 12” wide by 20” long. This device can reject containers at speeds up to 100 packages/minute. A Drop Belt Conveyor Reject Device is most commonly used on our PW/12 and MW/16 checkweigher models.

Heavy-Weight Checkweigher Reject Devices

For our middle to heavy-weight checkweighers, our Models MW/16 and HW/15, the most applicable rejects are over-head sweeper rejects, pushers, swing gates, alarm horns, and stop belt rejects. Keep in mind these rejects have the ability to handle heavier packages than what is mentioned in this blog. Nonetheless, all rejects play a large role in the overall makeup of this “quality control” machinery.

If you have any questions regarding which reject device will best suit a specific application, please feel free to give our team a call at 610-524-7350 or contact our sales team online.