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Innovative core of the mail-sorting process

Innovative core of the mail-sorting process
Dutch Design Award GIO

Ergonomically correct mail-sorting with new logistic aid

To ensure the sufficient volume of input for PostNL’s mail-sorting machines, we developed a multifunctional kart called the ISM (Intermediate Storage Means). Main goal was to minimize the physical strain on the employees operating the sorting line.

Changes in the world of mail

The world of mail is ever-changing at a rapid pace. The volume of letters sent is shrinking, while the amount of larger pieces and parcels expands. This change in content requires different solutions for the process of sorting and compiling the steady stream of mail that runs through the system. The expectations are that this change from less smaller letters towards more, larger parcels and packages will continue furthermore.

We helped PostNL in visualizing the contours of the ideas for a new mail sorting process that is flexible enough to cope with the changes in mail’s sizes and weights and reduce the physical demands on the employees.

Innovative core of the mail sorting process

The mail that exits the new sorting machines has to be collected, transported and re-entered into the machines. We developed the ISM as a transport aid that optimizes this process. It ensures that a sufficient volume of mail can be processed fully automated.

The deceptively simple looking kart hides many smart features to enable linking and stacking, which contributes to simplifying and speeding up the process. By doing this, the ISM makes the mail-sorting process highly efficient and helps lightening the workload for the people working in the sorting centres.

In the end we have succeeded in meeting the shear amount of demands and still managed to develop a simple looking trolley and tray combination
Jacco de Haan

Smart solutions

Reliability and durability were pivotal demands for PostNL. The ISM is packed with smart solutions to take care of this.

By making clever use of gravity (the most reliable force of all), we make sure that the handles and levers always work and the red mail-tray sits stable on the frame.

An innovative addition to the caster wheels ensures the ISM effortlessly rides over bumps and thresholds. Karts link together cleverly and can be moved en masse. Because of the specially designed frame, a forklift can transport a stack of karts in one go. Once emptied, the karts nest together in an extremely compact configuration.

What amazed us was that already during the pilot phase the ISM was almost part of the day to day routine of the PostNL operators.
Ronald Lewerissa

Process 'fail quickly and cheaply'

A close collaboration with PostNL’s project-team and Solystic – the French manufacturer of the sorting machines – led to an optimal design solution.

‘Fail quickly and cheaply’: throughout the development process we made numerous wooden prototypes that taught us a lot about the workings and usability of the aid. Going through a number of iterations this way, we finally landed on the optimized design.

FLEX/the WORKSHOP then made steel prototypes with plastic trays. Extensive testing at the manufacturers of the sorting machines led to some final adjustments and the final design. Technical documentation and specifications in hand, we set up a pilot production run of 300 units. These were tested in a sorting centre to eliminate the last problems.



5000 units of the final product were made in 2014 and are now in use in combination with sorting machines throughout the Netherlands. Several companies like PostNL in other European countries have shown interest and will be using our solution in the future.

Improved ergonomics

Improved ergonomics

Mail consists mainly of paper and paper is heavy. When processing the required volume of mail for the new sorting machines, the sheer weight of the processed amount would lead to strains on the operators that would exceed legal and desirable limits. The ISM makes these processes ergonomically viable. It’s no longer needed to lift the mail; instead the workers can simply slide the mail onto the kart.



The judging panel of the Dutch Design Awards (DDA) 2015 choose our logistical aid for PostNL as one of five finalists in the ‘Product’ category. According to the judges, our design is “a smartly executed solution that ergonomically improves working conditions”. The ISM has already won a GIO-award in 2014.

ISM in action

The different possibilities and smart features become apparent when you see the ISM in action. We made video of people of PostNL using the ISM in the sorting centre.