How accurate is a checkweigher at high speed?

A checkweigher is an inline weighing system with conveyor belts, specifically designed to check whether the weight in a package is correct. Whereas a standard scale stays in one fixed place, a checkweigher weighs products as they move through your production line.

An example: your packaging machine fills 500-gram packs of butter. That machine doses based on an approximation. With a checkweigher, you then check whether the weight in each package is actually correct.

If the weight is not correct, the product is automatically removed from the line. This prevents an underweight or overweight package from reaching your customer.

A product that is too heavy or too light is automatically removed from the line. There are several options for this:

• Air blast: suitable for light products. This is faster, which also allows you to increase the speed of your line.
• Pusher: suitable for heavier products that cannot be blown off the line. After each rejection, a pusher has to retract before the next product can pass, which takes a little more time.

Which rejection system suits you best depends on your product and the speed of your line. We are happy to advise you on this as well.

You will find the ℮-mark on many prepackaged products, for example "300 g ℮" on a jar of peanut butter. It means that the weight is monitored and recorded at batch level.

Individual packages may deviate within a certain tolerance. A jar of 298 grams is therefore perfectly fine, as is a jar of 302 grams, as long as the batch average is correct. If a package falls outside the permitted tolerance, it must be rejected. Otherwise, that package affects your batch.

If the batch average is not correct, the entire batch is rejected. The products then have to be refilled or destroyed. That is why accurate weighing and rejection are so important when working with the ℮-mark.

Working with the ℮-mark requires a certified process. This involves a number of requirements:

• Your scale must be inspected and approved.
• You will be subject to audits.
• You need a manual that documents your working method.
• All records must be retained.
• The software you use for recording must also be approved.

This comes with a major advantage: because you work at batch level, you don't need to overfill as much to meet the requirements. With large batches, this quickly saves a considerable number of extra packages. That is why it is mainly the larger producers who use ℮-weighing.

Yes, and in practice this is usually done in a single line. The process then looks like this:

• The product is first weighed by the checkweigher.
• If the weight is incorrect, the product is rejected.
• If the weight is correct, the product continues to the labelling machine or coder.

Weigh-price labelling is also possible. The product is weighed and the price is calculated directly based on the weight and the price per kilo. That price is then printed on the label.

This varies per application and depends mainly on your product. In general, the capacity ranges from 10 to 200 products per minute.

Large and heavy products are usually processed in lower numbers per minute. Lighter products, on the other hand, can run through the line at higher speeds. The way rejected products are removed also plays a role: light products can be removed with an air blast, which is faster than using a pusher.

It is also important that your product moves through the line in a stable way. The better the product is under control, the higher the speed you can achieve. Based on your product and the line speed you need, we advise which checkweigher suits you best.