Normally found at the end of a production line, a checkweigher is a device that determines whether the weight of a packaged item is over, under, or within an acceptable weight range. If a package is outside of the acceptance range, the checkweigher will signal other equipment to take it out of the line.
While it depends on carton size and accuracy requirements, a checkweigher can weigh in e xcess of 500 items per minute. But if you’re looking for a way to reach industry best speeds and accuracy, you may want to consider Arlyn Scales’ checkweighing solutions.
With a design that features a succession of conveyor belts, checkweighing systems may also be called belt weighers, in-motion scales, conveyor scales, dynamic scales, and in-line scales as well as check scales in filler applications. There are generally 3 belts or chain beds that automate the process.
The first is an infeed belt that changes the speed of the package according to what’s appropriate for weighing a particular set of packages. Sometimes this belt will include an indexer that keeps even spacing between the packages to optimize the process or special belts or chains that position the product to be weighed.
The second and most important for our purposes is the weigh belt, which is typically mounted on a weight transducer, the most common are strain gage load cells. Older machines may actually pause the weigh belt before measuring the weight, but this seriously decreases speed and throughput.
The last is a reject belt that removes out-of-tolerance packages from the conveyor line. How this is accomplished depends on the items being packaged, but is controlled by the checkweighing device.
Improving Speed and Throughput
Unlike common strain gage load cells and electromagnetic force restoration systems, our Ultra Precision scales were designed for longevity in tough industrial conditions. Featuring our unique surface acoustic wave (SAW) technology, they can weigh objects within 0.01% and 0.005% accuracy, which is ten to twenty times better than standard strain gage load cells. And while a regular scale has a sensitivity of 0.02 lb, a 100 pound SAW scale offers an amazing sensitivity of 0.001 lb. Other capacities give similar improvements.
And because measurements are taken digitally there is no need for an ADC (analog-to-digital converter), which means measurements are taken faster and the whole process runs more quickly. We’ve helped many companies achieve industry best speeds and accuracy with this design.
Managing Tolerance Ranges
When a manufacturer prints a weight on their packages, they’re guaranteeing that that package will not contain less than that amount of product, taking into account weight loss that occurs after production due to evaporation, settling, or other circumstances. Many wholesalers charge large fees for inaccurately filled packages because consumers must be confident that they’re getting the amount of product they paid for.
However, some processing plants have minimum and maximum acceptance weights that all packages must fall between. This requires a more complex system.
Arlyn Scales’ set point controller allows manufacturing and shipping facilities to set up to eight target weights that can be set to include these minimum and maximum acceptance weights. This device can also be used to control other conveyor belts and reject mechanisms like simple pneumatic pushers, diverting arms, and reject belts.
Another method of tolerance is the European Average Weight System, which follows three specified rules (known as “Packers Rules”) and requires manufacturers to collect and archive the weight data they generate for periodic inspection. But whether or not you follow this tolerance system, this information can be used to monitor and manage your process and fine-tune its performance. We offer a variety of connectivity options including Ethernet ports, Wi-Fi, Cloud, USB, RS-232 and RS-485, analog outputs, and more.
With a zone checkweigher, data collection from various networks and local statistics can show the operator when the settings on upstream equipment need to be adjusted to better control the flow of product into packaging. For example, a dynamic scale may send a real-time signal (through a device like our set point controller) to automatically control the flow of product into the barrels, cans, bags, etc.
Custom Checkweighing Solutions
There are a lot of factors that go into the speed and accuracy that can be achieved by a checkweigher including pack length and weight, the required line speed, the nature of the product (liquid or solid), motor technology, airflow that may introduce erroneous readings, vibrations from machinery that cause unnecessary rejects, temperature sensitivity, and stabilization time of the weight transducer.
While our ultra precision load cells minimize the effects of temperature, vibration, and airflow while significantly reducing stabilization time, there are other factors (like length and width) that may require special equipment or a special configuration of the weighing components.
Arlyn Scales is a factory direct scale and weighing component manufacturer, which means we have the ability to design, develop and implement non-standard weighing solutions that meet your needs. It also means that we’re able to offer competitive pricing, since there are no middlemen to drive up costs. We’re located right here in the U.S., which means shorter than average lead times.
If you work in a wet or washdown environment, cleanroom, or classified hazardous location, we can also modify our equipment to operate safely and securely in your work environment.
Find Your Best Solution Today
If you’d like more information about our checkweighing systems, components, technology, or pricing information, contact us today. We’re here to answer your questions and help you find the solution that best meets your needs.