What Happens To Bad Seeds?

Thursday, February 3rd, 2022

Cimbria Heid has revamped their test lab using Danfoss frequency converters to control the drive motors of their seed cleaning and sorting machines in the lab.

CIMBRIA Heid is a big name in the manufacturing of seed and grain processing machinery industry. The vast process expertise of the product developers in Stockerau is in no small part due to many years of experiments and tests with their standard machines. In addition to tests with specific seed types in order to optimise the machines for particular applications, special set-ups for customers can be tested and systems or system components can be checked out before commissioning.

Test Lab Set-Up

The test lab in Stockerau consists of a test set-up of all standard Cimbria machines for sorting a wide variety of plant seeds. The standard machines are arranged compactly in a layout closely matching a real plant, for demonstrating to customers whether or how precisely specific products can be sorted. A total of 18 VLT Automation Drive FC301 frequency converters with power ratings from 550 W to 22 kW provide extremely precise control of equipment motions and blowers in 18 machines, including a grader, a roller seed sorter, a fluid bed dryer and weight sorters. The sequence of the machines is configured for each test according to the product to be sorted. A conveyor system, which is also controlled by Danfoss frequency converters, transports the seeds from one machine to the next.

Members Of The Machine Pool

  • Graders separate broken material and foreign seeds according to their length. The product is then sorted and rotated inside a drum with indentations matching the desired seed type. The shortest granules are collected in the indentations, while the longer ones remain on the surface of the drum and are discharged at the end.

  • Weight sorters do the same thing in a different way. The seeds are placed on an inclined shaker table, and the oscillatory motion causes seeds with different weights to move upward by different distances. This way, bad seeds are sorted out. This is assisted by an adjustable air stream directed against the bottom of the wire mesh of the shaker table. The air flow is adjusted to match specific requirements. Unsatisfactory fractions that do not fit the weight standard are also separated out. 
  • Screen cleaners (with flat or cylindrical screens) sort granules by width and thickness. They are also equipped with highly effective wind sorters.
  • Roller seed sorters separate irregularly shaped seeds from smooth, round seeds, such as clover seeds. The rough edges of the irregularly shaped seeds adhere to the velvety roller cover, so they are carried out of the machine and separated.
  • Cimbria is also experienced in seed coating technology, especially with their batch coaters, dubbed “Centricoaters”. In these machines the incoming seed is first weighed precisely, and then the corresponding amount of coating material is applied
  • The lab is now equipped with colour sorters for optical sorting, which uses an air blast to eject incorrect or bad fractions, a drying machine, and other machines necessary for handling the seeds or grains.

The precise knowledge of the Cimbria experts in sorting the characteristics of seeds is also crucial. A combination of methods and motions are used for this purpose, depending on the seed type and seed properties and any present foreign matter. The type and number of sequential operations also depend on the seeds to be sorted.

Progress From Tests And Experiments

The detailed knowledge necessary for this has always been acquired from tests and experiments. Along with the fundamental procedure, necessary. This is true not only with large customers who process seed and grain as foods in a virtually industrial manner, but also with smaller users who handle special or rare seeds and often have considerable application expertise themselves. The tests lead to a constantly growing pool of formula expertise.

In some applications, colour is also significant, especially for sorting out bad seeds. Along with the mechanical sorting machines, there are also systems that use industrial image processing and/or intelligent cameras and compressed air for sorting. 

In addition to the large test station with standard machines, there is a lab test set-up for initial testing. The large system is used to run tests under realistic conditions, optimise the capacity of the equipment or demonstrate performance, while the small system is used as a demo set-up with small quantities for initial testing. 

The VLT Automation Drive units allow Cimbria Heid to operate the machines efficiently. Due to the nature of the business, specific seeds are usually processed only a few weeks per year, which means that the highest possible processing capacity is always required with a running system. Every crop has its own time, and if the harvest is not stored for processing, a high volume of material must be processed in rapid sequence.

Operating conditions are also characterised by frequent changes in the volumetric flow of the blowers and adjustments to the shaking motion of the tables by altering drive speeds. The shaking motion causes the heavy granules on the inclined surface of the table to move upwards, while the lighter material floats downwards under the influence of gravity and the flotation effect of the uniform air stream, resulting in the two being quickly and cleanly separated. 

The drive technology is a key factor in the operational performance and cost of the equipment. Without speed control of the three-phase motors, the sorting performance would not be possible, the power consumption would be higher, and the start-up currents would cause problems for the mains network of the plant operator. However, the main consideration is that starting up the large moving masses of the separators must be carefully coordinated to prevent the development of vibrations that would be transferred to the equipment frames or stress the structure. In addition, any irregular motion has a correspondingly large impact on the sorting quality and performance of the machine. 

For the experts at Cimbria Heid, these were the decisive factors. “Operating the Danfoss frequency converters is very easy”, according to Rudolf Teufl, Electrical Engineering Manager at Cimbria. “The robustness, energy efficiency and reliability make the VLT frequency converters the first choice for us and our customers. Their systems are located all over the world.”


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