AMS is releasing a three part email blast series centered around the importance of checkweighers to a company’s filling process and ROI.
Schedule of Articles:
- Defining your Checkweigher Goals
- What Effects Checkweigher Accuracy and Feedback
- Calculate your Savings and ROI
The key to purchasing a checkweigher is to first understand your checkweigher goals. What do you want the checkweigher to accomplish? What aspects of the checkweigher are priority? How is a checkweigher going to affect your company’s ROI? This article will help you determine your goals, allowing you to best select a checkweigher to fit your company’s needs.
Defining your Checkweigher Goals: Verify Simplifies your Process
A checkweigher is a system that weighs your product as it passes through the production line. It then classifies your product by preset weight zones and will either accept or reject the weight in accordance to those preset standards.
When you are determining whether a checkweigher is right for your company there are several aspects to consider. The more you understand about the checkweighing process, the more likely you will find a solution that fits your needs.
The four main considerations that will help you determine your checkweigher include; environment, accuracy, line rate and package specifications.
Factors such as temperature, moisture, product corrosiveness, washdown requirements, NEMA standards, hazardous environment, vibrations and air movement can all affect checkweigher functionality. Outside environmental “noise” is a major contributor to your checkweighers accuracy and life cycle. These attributes are important in the manufacturing process of a new checkweigher and should be mentioned when speaking with your equipment provider.
- Temperature – When considering checkweigher environment and the type of product application, you should ask yourself if there are any specific temperature requirements. Will the product being weighed need to be heated or frozen? Are there any extreme temperature variations? This is usually not an issue in the checkweighing process, but could cause problems if there are large amounts of fluctuations. Once your equipment supplier is informed they will provide the necessary measures of insulating or sealing the controls and providing the correct belt for the application.
- Moisture – Another aspect of environmental factors is moisture. Moisture can occur from condensation around the items being weighed or on surfaces of the machine. If the checkweigher needs to be washed down or cleaned on a regular basis, the supplier will need to make a water-tight washdown unit to avoid corrosion.
- Product corrosiveness – The product being weighed can also affect a checkweighers accuracy and life cycle. If a product or environment contains corrosive chemicals, sugars or salts this can break down the stainless steel material overtime. If this is the case, a washdown unit should be provided to stand up against harsh conditions.
- Washdown requirements – Checkweighers also are capable of being manufactured for USDA Meat/Poultry and Dairy washdown applications. Machines have to be specifically designed to meet these requirements and follow strict policies in order to be approved. Be sure to mention to your checkweigher supplier if these standards are necessary.
- NEMA standards – The National Electrical Manufactures Association (NEMA) is the largest trade association of electrical equipment manufacturers in the US. They classify the standards for controls and systems for their ability to keep out dust or moisture from a specific enclosure. If the checkweigher environment does not follow NEMA standards then a custom machine can be manufactured to meet specific policies.
- Hazardous environment – Hazardous classified environments are defined as any space where explosive concentrations of dust or vapors may exist. If the machine purchased will be operating in a hazardous environment then special wiring or other electrical components must be set in place for safety purposes. A company must adhere to certain requirements depending on the type of classification made in order to prevent any fires or explosions from occurring. There are safety measures that can be put in place to prevent accidents from occurring such as; NEMA rated explosion proof enclosures or covers, purge systems or removing the equipment out of the classified area.
- Vibrations/Air movement – It is important to consider vibration and air movement for applications where high precision and accuracy are required. Outside “noise” can greatly affect the overall accuracy of the company’s product fill cycles. Draft shields or isolated scales can be put in place to help decrease these environmental factors.
There are several different types of load cell scale applications, ranging from strain gauge to electromagnetic force restoration technology. The type of checkweigher scale affects the level of accuracy, so determining the importance of accuracy to your company is a crucial step in defining your checkweigher goal.
- A strain gauge is a weigh cell device that measures electrical resistance or in response to pressure or strain that is applied to the device. These are very accurate devices and are ideal for dynamic applications such as filling and packaging machines.
- Another load cell technology based off of the strain gauge is an oil damped weigh cell. The oil damping helps reduce the kinetic energy caused by impact and also allows for the load cell to settle the correct weight value much quicker. It is best used to help reduce vibration during the weighing cycle.
- Electromagnetic force restoration technology is used in high accuracy type applications. This is the most expensive type of technology, but it is the most advanced with benefits of consistent repeatability, stability, accuracy and speed. By utilizing its high precision design the end user is capable of weighing a wide range of weights at variable speed requirements.
Line rate – Checkweighers can run at different speeds depending on the container and weight of the product. This can range from one to three hundred items per minute. Line rate will greatly affect the type of checkweigher selected. Most often you may have to compromise between the accuracy you would like to obtain and the rate or speed of the checkweigher. One solution to maintain higher accuracy may be to add multiple lanes within one checkweigher or add more checkweighers to the product line. Line rates can also be optimized by shortening the weigh sections over a scale. This allows for faster feedback and an increase production process.
Packaging specifications – Packaging design and specifications will help determine the type of checkweigher needed for purchase. Containers with similar properties, such as cans or cartons run well over drag chain checkweighers, while bags and flexible packages run better on belts. There are a variety of options to help assist in a checkweigher production line such as guiderails, timing screws, transfer belts and product spacing. All are available in customizing your checkweigher to fit your specific application.
- Guiderails can direct and stabilize containers to insure a smooth running production line. The items will be guided onto the conveyor in a consistent manner to allow for a centered, accurate reading.
- In some cases, certain containers require timing screws in order to space products out before reaching the scale. This is important when collecting data and allowing for item rejections.
- Side transport belts are used to transfer unstable products between conveyors and even have the capability of weighing items themselves. Rollers and dead plates can also be put in place to aid in the transfer of items between conveyors and items on and off the checkweigher. To insure proper checkweigher functions and feedback, it is crucial to only allow one item on the scale section at a time.
- When considering a checkweigher, the required speed and accuracy will help determine the type of checkweigher needed to meet your goals. In order to meet the speed requirements, product spacing needs to be put in place to avoid errors in weighing. Spacing belts are used to maintain an appropriate pitch during production and creates gaps between the items being weighed. A timing conveyor also can create a uniform spacing between items. Some suppliers even integrate checkweighers with their filling machines or other equipment to improve overall production. In this case, the filler would provide the product spacing as well as checkweigher feedback for a seamless product integration.
Once you have determined what attributes are necessary, optional and priority you can look further into the details of a checkweigher. Use the Checkweigher System Specification form to complete your checkweigher goals. The specifications will be useful when talking with a checkweigher manufacturer.
Verify Checkweighers offer a range of technology from a simple cost effective strain gauge and digital load cell to high end, high accuracy, electromagnetic force restoration, in order to meet a variety of applications. We take pride in the quality and craftsmanship of every machine that ships from our facility. We are confident that our checkweighers will enable you to work effectively while reducing product giveaway, streamlining production and improving accuracies for ensured customer satisfaction.