Engineering and production of couplers for outdoor play units

IJreka Playground Equipment

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For our customer IJreka Playing Environments from Dalfsen, QDP has provided the engineering and production for 3 different connectors that will be used in their playground equipment. They have a great range of unique playground equipment built different materials. At IJreka, the customer’s wishes are central and this is reflected in their leading products.


Because safety is paramount for playground equipment in public spaces, QDP paid careful attention during the project to validating the requirements set for the connecting pieces. The two main requirements are; The coupling piece must be able to bear a weight of at least 350 kilos (for the model shown above) and because the playground equipment is outside, the materials must be UV-resistant.


The playground equipment frequently comes into contact with UV radiation. Radiation from the sun can damage the molecules in plastics, resulting in accelerated aging of the material. This can cause the material to break more quickly. Therefore, a material with high UV resistance is needed to minimize quality degradation.


QDP decided Nylon was the best option for production. This plastic is known for its hardness, toughness and wear resistance, making it suitable for heavy dynamic loads. In addition, Nylon has good aging- and UV resistance.

‘Discover, meet, play and experience. The keywords for creating the right play design

FEM Analysis
To ensure that the design and material choice of the connectors are suitable, QDP performed a FEM analysis on the 3D models. The FEM analysis was done with Autodesk Inventor Pro. The software calculates how much force can be applied to a part until it breaks and shows where the part will break first. The FEM analysis showed a number of force concentrations. These were remedied by adding extra material and increasing the radii.

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Isotropic structure
Satisfied with the results of the FEM analysis, QDP printed a high-quality prototype with the CARBON 3D printer with RPU-70, a material that has almost the same properties as Nylon. The CARBON 3D printer uses a printing technique that creates parts that can be loaded equally in every direction, also called an isotropic structure. This would have been impossible with traditional printing techniques such as FDM or SLS as this technique prints the product in layers.

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DLS Technique
One of the advantages of printing with the CARBON 3D printer is that no tooling is required to validate whether a design is strong enough for production. The DLS technique (Digital Light Synthesis) determines the shape of the object by UV light. After that, the model is baked in a special oven. Baking causes the molecules to bond with each other in all directions. This results in a solid object that is equally strong in all directions.


In this way, IJreka was able to validate the prototype directly by means of a physical test. This saves time and money because the mold only needs to be made after the prototype has been approved. As a result, there is always the certainty that no adjustments need to be made to the mold later on.

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IJreka then physically tested the prototype model and the first out of tool (FOT). They did this by hanging bags of concrete mortar from the prototype and the FOT, then increasing the weight until something broke. Funnily enough, the screws broke and bent earlier than the coupler itself. Ultimately, the test components failed after a load of 400 kilos, well above the project requirements. Moreover, both parts broke exactly at the spots indicated in the results of the FEM analysis.

By first analyzing the design with FEM software and making a high-quality prototype that was suitable for a physical test, considerable savings were made on time and costs. The results spoke for themselves and production has started with certainty.


View the coupling pieces that we have produced for IJreka below.

Rik Wouters

Would you like to know more about the project or our method of working? Then contact project manager Rik Wouters.


Rik Wouters
Senior Product Developer
Tel:      +31 (0) 85 047 6615

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