Has your company made checking the accuracy of checkweighers a top priority? If not, you might land in legal trouble before long.
Federal agencies like the U.S. Food and Drug Administration and the U.S. Department of Health and Human Services have created strict regulations when it comes to how companies label their packaged products. They must come in at or above their listed weights to remain within the limits of these laws, making checkweighers a crucial part of your production line.
If you don’t check the accuracy of checkweighers, your company might struggle to measure the weight of packaged products accurately. You might also miss issues with the different parts of a checkweigher, such as its load cell if you aren’t performing routine tests.
Discover how to check the accuracy of checkweighers below and use what you learn to take better care of your company’s checkweighers.
Step 1: Establish a Stable Testing Environment
When checking the accuracy of checkweighers, the last thing you want to do is allow outside forces to impact its readings. So, the first step you should take when testing a checkweigher’s accuracy is to create a stable testing environment. There are two simple things you can do to maintain this environment throughout your tests.
Minimize External Influences
Since you’ll be testing a checkweigher inside your facility, you might assume you don’t need to worry about external influences affecting it. But this couldn’t be further from the truth, as many outside factors — including many you can’t see — can cause a checkweigher to misweigh products. Here are just a few examples:
- Wind from a window or air currents from an HVAC system
- Vibrations from nearby equipment
- Higher or lower temperatures than usual
Your goal is to eliminate or, at the very least, minimize the external influences that can make checking the accuracy of checkweighers more difficult than it should be. These influences could doom the readings your checkweigher provides from the start, leading to wasted inventory and lost revenue.
Provide Warm-Up Time
When it’s time to check the accuracy of checkweighers, you shouldn’t simply turn one on and begin testing it without giving it a few minutes to warm up. It might not produce the same readings when it hasn’t been running for hours as it will once you allow it to get warm before putting it through the proper tests.
Turn on the checkweigher you wish to test for accuracy and let it run for a while to achieve the most accurate readings possible. You wouldn’t want to rush the production process, as this could lead to costly errors. By the same logic, you don’t ever want to rush through the process of checking the accuracy of checkweighers.
Step 2: Verify a Balanced Starting Point
After you’ve established a stable environment for performing tests on the accuracy of a checkweigher, the next thing you should do is verify a balanced starting point for it. Your checkweigher should register no weight when you aren’t running any products through it. If it’s giving you a reading at this point, you’ll need to balance it to guarantee you get accurate readings later.
You must perform a static zero check on a checkweigher and a dynamic zero check. Here is what each of these processes entails.
Perform a Static Zero Check
When your checkweigher isn’t moving items around and weighing them, it should read zero. You need to perform a static zero check to see whether this is the case. If it isn’t, you must tinker with your checkweigher to reach static zero before proceeding.
Perform a Dynamic Zero Check
When your checkweigher is turned on and its conveyor belts move without anything moving down them, it should also read zero. You need to conduct a dynamic zero check to see whether or not this is where it stands. If it’s not at zero, make the necessary adjustments to get back to this starting point.
Step 3: Test the Weight Selection
The most effective way to go about checking the accuracy of checkweighers is by taking products with known weights and letting them pass through a checkweigher to see whether it provides accurate readings. To do this, determine what these products weigh before testing your checkweigher. Use the following two-step process to test the products you’ll use when checking your checkweigher’s accuracy.
Matching Test Weights to Products
Just before you prepare to check the accuracy of a checkweigher, choose the products you’ll utilize to perform tests. Run them through other checkweighers your company uses to determine how much they weigh. Ideally, you should aim to use the same types of products you’ll weigh with a checkweigher every day once you’re finished checking the accuracy of your setup.
Verifying Test Weight Accuracy With Certified Scales
You want to be 100% sure the products you’re running through a checkweigher while checking its accuracy come in at the weights they should. To ensure this, test the accuracy of your products’ weights by putting certified scales to the test. They can minimize discrepancies and produce more accurate results when weighing products during checkweigher testing.
Step 4: Gather Information for Analysis
Once you have your checkweigher and the products you’ll put through it ready to go, you can start using your checkweigher to analyze their weights. But you will want to do more than just weigh each product once and move on as long as your checkweigher seems to produce the right readings. This is how the testing portion of this process should play out.
Running Multiple Test Cycles
The more times you test a checkweigher, the better you’ll feel about its accuracy moving forward. Allow a checkweigher to measure how much a particular product weighs once and then repeat this step over and over again.
You should test a checkweigher’s ability to measure a product’s weight at least half a dozen times. Some companies will check the accuracy of checkweighers up to 32 times, if not more, during their test cycles.
Keeping Detailed Records
As you’re running test cycles on a checkweigher, it’s easy to get confused if you don’t stay on top of keeping detailed records. Jot down the measurements a checkweigher provides for your test products so you can evaluate them at the end of your tests.
Step 5: Unveil the Accuracy Picture
When you’re done checking the accuracy of checkweighers, you should be left with a stack of readings that it provided for you on the test products you weighed. You can look through them to see how accurate your checkweigher is. Keep the following two concepts in mind while you push through this portion of the process.
Average Weight Readings
Using your detailed records, you can look at the average weight readings a checkweigher provided. These readings must be equivalent to or greater than the actual weights of the test products you used. If the average weight readings deviate dramatically from where they should be, it’ll indicate an issue with your checkweigher that must be corrected.
Standard Deviation
Every reading a checkweigher delivers would be the same weight in a perfect world. However, you’ll likely find some deviation when analyzing the readings for a checkweigher.
This shouldn’t cause too much concern unless you have a high standard deviation. This standard deviation formula can help you determine whether your readings deviate too much or fall into an acceptable range.
Step 6: Complete the Evaluation and Calibration
At the tail end of checking the accuracy of checkweighers, you’ll be left with a pile of data you can use to tweak these checkweigher machines to improve their readings. Use this data to take the following steps to see whether calibrating a checkweigher is necessary.
Comparing Average Weight To Test Weight Value
Take the average weight of one of the test products you used to check the accuracy of a checkweigher and compare it to its original test weight value. If these two numbers aren’t close to one another, it might suggest your checkweigher could benefit from calibration.
Analyzing Standard Deviation for Repeatability
In addition to running comparisons between your average weight readings and test weight values, pay close attention to your standard deviation and ensure it’s within a repeatable range. Too much deviation could have a detrimental impact on your checkweigher’s ability to weigh items accurately time and time again.
Performing Calibration as Necessary
Is your checkweigher having a hard time weighing products accurately? This is a sign that it needs calibration. A checkweigher with a high-sensitivity load cell shouldn’t need daily calibrating, but calibration will need to play a big part in your maintenance process.
Contact Us To Get Help With Checking the Accuracy of Checkweighers
Don’t want to worry about checking the accuracy of checkweighers on your own? TDI Packsys can help you do it when you invest in a checkweigher from us. We can provide annual testing, emergency repair services, and calibrations for our checkweighers.
Reach out to us for more information on checkweigher products and services.
