Accuracy of weighers that dose with one or two belts
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Pesadoras que dosifica con un o dos cintas
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The double or single belt dosing weighers are accurate when the onions or potatoes are relatively small and the packaging (bags), relatively big.

Accuracy of a double track weigher (in this case; double elevator belt).

The simulation tool below shows that the double belt weigher/filler is accurate when packing bags of 5 kilograms or more and not very accurate when the bags are 500 grams or less.

Try it out for yourself using two examples with different extremes, one for big onions and one for small onions, as seen below.

Example 1:
Big onions in small bags.
Example 2:
Small onions in big bags.
Type in the following data in the  green squares  below
and click on CALCULATE.
  • Diameter of smallest onions: 7cm
  • Diameter of biggest onions: 9cm
  • Bag weight: 500 grams
  • Amount of product to be packaged: 1.000 tonnes
  • Price of product: $ 0.35 per Kilogram
Type in the following data in the  green squares  below
and click on CALCULATE.
  • Diameter of the smallest onions: 3.5cm
  • Diameter of the biggest onions: 5cm
  • Bag weight: 5000 grams
  • Amount of product to be packaged: 1.000 tonnes
  • Price of product: $ 0.35 per Kilogram
Result of example 1 Result of example 2
Packing 1.000 tonnes of Big Onions in 500 gram bags means a giveaway of 252 tonnes of onions or $ 88,356 Packing 1.000 tonnes of Small Onions in 5,000 gram bags means a giveaway of 4 tonnes of onions or $ 13.967

Conclusion: Don't pack relatively big products in relatively small bags.

Simulation of a dosing system weigher.

Typing in different scenarios in the green boxes and clicking CALCULATE, you will quickly realise that these kinds of weighers are good for big products in big bags and if you try to weigh your big product into small bags you're giveaway will be considerable.

Furthermore these weighers have a limited capacity, more than 320 bags with 25 per hour (8 tonnes per hour) is difficult to achieve, unless a semi-automatic or automatic bagging machine is used.

We will return to this in the PACKING section.

small cm
big cm
bag gr.
Price per
KG in $
Total amount
to be packed in tonnes
Number of bags Weight of packed bag in kg Average weight in gr. Kgs packed above nominal % of packed weight above nominal Money lost from giveaway when packing.
result result result result result result
Target weight per bag isActual average weight per bag is

Your conclusions having played with various scenarios will be:

  • These weighers work well with products of all sizes in big bags.
  • These weighers work reasonably well with small products in bags of 2kg minimum
  • Relatively big products in small bags would be your downfall because of the amount of giveaway.

Furthermore it is much better to classify the product before weighing and packing.

How does this simulation programme work?

The principle is as follows:

(big diameter - small diameter) multiplied by a random number between 0 and 1 (2 decimals) plus the small diameter, gives a random diameter within the classification range.

With this random diameter a random content is calculated and after this a random weight or the weight of an imaginary onion.

This generator of onions with random weights fills an imaginary bag until the weight exceeds the target weight or nominal weight of the container. This process is repeated until the required quantity of tonnes is reached.

You will notice the following: the greater the number of tonnes to be packed and the lower the weight per bag, the longer your navigator will take to finish the calculation. It may even "crash", but don't worry, this won't cause any damage, but if you don't want this to happen don't go over 10.000 tonnes.

We hope you find this tool useful for making decisions when it comes to purchasing machines.

In practice, these weighers/fillers work well filling bags of 5 or more kilograms.

To see how these ingenious and robust machines work, see: Working of a semi-automated system.

To see just how accurate they are, type the maximum and minimum diameters of the onions, the size of the bag in grams, the quantity of tonnes that you want to package and the price per kilogram of the onions into the simulation form.

The results will immediately will show you how much you can earn when you use these machines correctly, and how much you can lose when using these machines incorrectly.

To mechanise your post harvest processes:
contact us:
+1 239 3002374
or use our (preferable)
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