You can use an automated check weighing process for a wide variety of applications including verifying package contents, checking product tolerances, identifying parts, classifying product and checking for overload safety. Usually the check weighing station is an inspection station after the manufacturing or packaging (Pack) process. Important reasons to use a check weighing system are increased accuracy, increased line speed, quality control, and to meet government regulations.
Check weighing system controls range from manual to fully automatic :
A manual (static) check weighing operation requires an operator, or a mechanically automated piece of equipment, to place the item on a scale and observe Under/Accept/Over lights.
A fully automated system is where the item is automatically weighed in-motion. The check weight controller then directs downstream diverter gates to route product based on weight. Automated control is done by a host computers (PC), Programmable Logic Controllers (PLCs), Programmable Automation Controllers (PAC) or Distributed Control Systems (DCS) communicating with the Hardy check weighing front-end. In-motion check weighing is made possible with the Hardy WAVERSAVER® technology, which ignores plant and process mechanical vibrations such as those created by the conveyor belts.
In addition to verifying the weight and directing product flow, a check weighing system also provides valuable statistical information. This information can be used for SPC (Statistical Process Control) to support the requirement for quality and governmental requirements. By analyzing and feeding back the results of the check weighing operation, the source process can be adjusted to optimize product quality and lower costs.
Verify Package Contents
Hardy weight controllers and load cell(s)/platform scales are used to weigh packages to confirm that they have been filled to the proper level or that they contain the correct number of parts. A wide variety of products ranging from boxed food, bagged grain and glass bottles to gas cylinders can be weighed to verify the contents. Check weighing can determine whether or not the correct number of items is in a box, the right number of boxes is in a carton, and the correct number of cartons is on a pallet. For example, the beverage industry weighs kegs and canisters to make sure they are empty prior to filling and full and within tolerance after filling.
Check Product Tolerance
Checking a manufactured product’s weight verifies if it is within design tolerances. For example, an injection molding company can detect improperly produced product by using a Hardy weight controller and load point(s)/platform scale to check weigh each part as it falls out of the mold. In a coating process, the quality and thickness of the coating can be verified by the additional weight.
A mix of different items can be sorted by weight and diverted to the proper packaging station for classifying or grading purposes. For example, variable weight products such as fruit and vegetables can be classified or graded by their weight class using a Hardy weight controller and load point(s)/platform scale. If the check weighing process is in-motion, set points from a Hardy controller can be set to divert the product to the proper station.
Items with different weights can be identified automatically by a check weighing system. For example, assembly processes use Hardy weight controllers and load point(s)/platform scales to verify the correct parts have been delivered.
Overload Safety Check
Items are often weighed to ensure they do not violate safety limits. For example, a train car is weighed with a Hardy weight controller and load point(s)/platform scale to make sure it doesn’t exceed the weight tolerance to meet interstate load requirements.