Check Weigher: Revolutionizing Quality Control with Computer Vision

By Fouad Sabry

What is Check Weigher

The weight of packaged goods can be determined with the help of a checkweigher, which can be either an automatic or manual machine.The offgoing end of a production process is typically where it is located, and its purpose is to guarantee that the weight of a pack of the commodity is within the limitations that have been defined. Any packs that are outside of the tolerance are automatically removed from the line of sight.

How you will benefit

(I) Insights, and validations about the following topics:

Chapter 1: Check weigher

Chapter 2: Conveyor belt

Chapter 3: Weigh in motion

Chapter 4: Belt (mechanical)

Chapter 5: Beltweigher

Chapter 6: Conveyor system

Chapter 7: In-motion scale

Chapter 8: Multihead weigher

Chapter 9: Mettler Toledo

Chapter 10: Packaging machinery

(II) Answering the public top questions about check weigher.

(III) Real world examples for the usage of check weigher in many fields.

Who this book is for

Professionals, undergraduate and graduate students, enthusiasts, hobbyists, and those who want to go beyond basic knowledge or information for any kind of Check Weigher.

• Language: English
• Publisher: One Billion Knowledgeable
• Release date: May 4, 2024

Book preview

Chapter 1: Check weigher

A checkweigher is either an automatic or manual device for weighing packaged goods. It is often located at the conclusion of a production process and is used to confirm that the weight of a package of a product falls within predetermined parameters. Any packages that exceed the tolerance are automatically removed from the production line.

A checkweigher is capable of weighing more than 500 objects per minute (depending on carton size and accuracy requirements). Checkweighers can be used in conjunction with metal detectors and X-ray equipment to check and act on other pack characteristics.

A succession of conveyor belts are utilized by an automatic checkweigher. These checkweighers are also known as conveyor scales, in-motion scales, dynamic scales, and in-line scales. In applications using fillers, they are known as check scales. There are typically three belts or chain beds:

A conveyor belt that can alter the package's speed and bring it up or down to the desired speed for weighing. The infeed is also occasionally employed as an indexer to select the ideal distance between products for weighing. Occasionally, customized belts or chains are utilized to position the product for weighing.

A weighted vest. Typically, this is positioned on a weight transducer, which can be a strain-gauge load cell, a servo-balance (also known as a force-balance), or a split-beam. Some older machines may pause the weigh bed belt prior to measuring weight. This may restrict line velocity and throughput.

A reject belt that removes out-of-tolerance packages from the conveyor. The rejection can vary depending on the application. Some applications necessitate an air amplifier to blow small items off the conveyor belt, whereas heavy applications necessitate a linear or radial actuator. Certain fragile products are rejected by dropping the bed so they can slip softly into a bin or other conveyor.

Electromagnetic force restoration (EMFR) load cells are suitable for use in high-speed precision scales. This technology charges an inductive coil, essentially suspending the weighing platform in an electromagnetic field. When the weight is added, the movement of a ferrous material through the coil generates a proportionate fluctuation in the coil's current. In addition, strain gauges and vibrating wire load cells are employed.

Typically, a built-in computer takes many weight readings from the transducer while a product is on the weigh bed to assure an accurate weight reading.

Calibration is necessary. A laboratory scale, which is typically contained in an isolated chamber pressured with dry nitrogen (at sea level), can weigh an object to within plus or minus one hundredth of a gram, but ambient air pressure is a factor. This is clear when there is no motion, but when there is motion, there is an element that is not immediately apparent: noise from the movement of a weigh belt, vibration, air-conditioning, or refrigeration that might generate drafts. Torque on a load cell results in inaccurate values.

A dynamic, in-motion checkweigher collects and analyzes samples to determine an exact weight over a specified length of time. In most cases, the passage of a package is signaled by an optical (or ultrasonic) trigger mechanism. After the trigger is pulled, a delay is programmed to allow the package to move to the sweet spot (center) of the weigh bed in order to obtain a weight sample. The weight is collected for a certain period of time. If either of these times is incorrect, then the weight will be incorrect. There does not appear to be a scientific mechanism for predicting these times. Some systems provide a graphing capability for this purpose, but an empirical approach is often more effective.

A reject conveyor that allows out-of-tolerance packages to be separated from the usual flow while maintaining the conveyor's speed. The reject mechanism might be of various varieties. Among these are a basic pneumatic pusher to push the reject pack from the belt to the side, a diverting arm to sweep the reject pack to the side, and a reject belt that lowers or raises to divert the pack vertically. Typically, a checkweigher features a bin for collecting out-of-tolerance packages. These bins are sometimes equipped with a lock to prevent out-of-specification objects from being fed back onto the conveyor belt.

There are numerous tolerance techniques:

The conventional minimum weight system, in which weights below a predetermined minimum are rejected. Typically, the minimum weight is the weight that is printed on the package or a weight level that surpasses that to account for post-production weight losses such as the evaporation of commodities with a high moisture content. Larger wholesale organizations have mandated that all products transported to them undergo accurate weight checks so that customers may be certain they are receiving the quantity of product they paid for. These wholesalers impose substantial costs for