Pins overmolded in an epicyclic train

What is the context and application of the customer? ‍

The customer, a recognized player in the automotive sector, needed a reliable solution for their cooling system. The system includes a motorized valve to regulate cooling flows for thermal management of the vehicle.

The mechanism is an epicyclic train controlled by a computer that activates a valve to direct the cooling fluid in different directions. The critical components of this system are made of metal, like the satellite carriers, which are overmolded in a plastic part which makes up the motor shaft.

The customer encountered a major problem related to pull-out resistance. The original solution used a knurled pin, but it did not provide sufficient performance to ensure the safety and reliability of the system.

What was the customer's fixing solution before coming to see us?

The initial fixing solution was based on a Ø1.5 diameter pin knurled to 1/4 of its length.

The assembly process consisted of overmolding the pins while injecting the main shaft.

However, this approach proved to be insufficient in terms of mechanical strength, in particular in the face of pull-out and torque forces, which are critical in a cooling flow control system.

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Principle of overmoulding:‍

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What studies have we done?

We conducted a series of tests on the pull-out resistance of knurled pins used by the customer in our Protolab.

The results confirmed that this solution did not meet the technical requirements defined in the specifications, namely 100 Newton. It was necessary to find a more efficient alternative to ensure the safety and sustainability of the system.

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What recommendation did we make?

After analysis, we proposed a fluted pin with a throat.

This new solution offered several advantages:

• The fluting allowed the overmolded plastic to fit into the grooves, removing any degree of freedom in rotation.
• The throat, on the other hand, blocked translational movements, guaranteeing perfect fixation in all directions.

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This solution made it possible to multiply by 10 the mechanical resistance to pull-out. Indeed, 100 N are reached at 100% thanks to this solution.

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What are the quantifiable benefits for our customer?

Thanks to the adoption of our fluted pin + groove, the customer was able to drastically reduce its scrap rates.

Before our intervention, it recorded up to 20% of rejects on a production of 260,000 actuators, which represents nearly 300,000 euros in loss.

Our solution eliminated this problem, ensuring 100% quality and reliability for this system.