Checkweighers: In Motion and Static

Checkweighers are weighing systems used to verify that the weight of an item or product is within preset limits. If your looking for a way to make sure that your products are within a preset weight limit, then you have two choices. Checkweighers can be either in motion or static. They can weigh items that move along an automated production line and can either accept or reject an item as being within or outside a preset limit, or they can be used to weigh items manually with an especially configured static scale. Both the static and in motion checkweighers can in-line checkweighers, i.e., be installed in a production line along with a reject mechanism and a metal detector as an option.

We offer static checkweighers such as the FS-i Series from A&D Weighing as an excellent example of a value packed static checkweigher or our own ISI 500 Checkweigher and the Ultimate bench scale checkweigher. Our in motion checkweighers also include our own custom designed in motion checkweigher the 920i shown below.

In Motion Scales: checkweighers | rail scales | grading systems | conveyor scales

Checkweighers

Choosing the Right Checkweighing System

A checkweigher allows you to grade identical items for quality or consistency using a preset target weight and over and under tolerances. If you need a checkweighing system for weighing objects as they move along a conveyor belt, then a typical in motion checkweigher should have an in-feed conveyor which assists with product spacing, an actual weighing conveyor, and an outfeed conveyor which assists in clearing the weighing conveyor of products to ensure there is no backing up of product onto the weighing conveyor. An intelligent weigh indicator which ideally could store a number of preset over and under weight values would complete the system.

If all you need is a simple static checkweighing scale, then the weigh indicator should have the ability to be programmed with over and under weight categories and there should be some sort of visual or audio alarm or a combination of both to warn the operator when a product is out of tolerance.

Checkweighers are used in applications as diverse as food and beverage, plastic extrusion, metal stamping and pharmaceutical. They can be made of many different composite materials which can include mild steel and stainless steel. They can be washdown capable and be able to withstand extreme temperatures and pressure.

Important Performance Specifications:
Here are some important considerations to think about as you choose your checkweigher:

Linearity: measures the closeness in weight between an actual package and a test package. The difference or error between these two measurements indicates the degree of linearity.
Mean Error: is the absolute value of the difference between an item's actual weight and the average weight as reported. Repeatability: is measured with standard deviation in order to describe the variance in weight from weighing the same mass multiple times. As a rule, checkweighers with greater repeatability or precision have lower standard deviations. Accuracy: is a measure of checkweigher uncertainty. Since load cells vary in terms of settle times, most manufacturers offer products with a range of accuracy's. Higher accuracy costs more, but can provide cost savings by reducing rework and overfilling.

Applications:
Checkweighers are suitable for a variety of applications. Some are used to identify underweight and overweight packages. Others are used to check process performance and measure production line efficiency.

Plastic Extrusion: To verify that the product meets design specifications.
Metal Stamping or Fabricating: To verify that the product meets design specifications. Printing: checkweighers are used to capture production totals by day, shift, batch, or production run.
Food, Beverage, and Pharmaceutical: checkweighers are used to capture information such as out-of-tolerance conditions for regulatory agencies. In the United States, they are used to indicate whether products meet Food and Drug Administration (FDA) or U.S. Department of Agriculture (USDA) reporting standards.

Interweigh Systems Inc. 51 Bentley Street, Markham, Ontario, Canada, L3R 3L1
Phone: (416) 491-7001 ~ Toll Free: (800) 268-3269 ~ Fax: (905) 940-1711
Or contact us at one of our four locations: Markham, Mississauga, Woodstock and Montreal