Dynamic Ear Company – Automated assembly of filters

Gerelateerde afbeelding

Dynamic Ear Company:

Dynamic Ear Company produces hearing protection since 2007. The company was founded to develop its patented Dynamic Sound Technology, which is implemented in all of its products. Its products include hearing aids, hearing protection and headphones. Most notably are the linear filter  products, which allow for the undistorted damping of sound. These are targeted towards music purposes, as regular filters dampen certain frequencies differently, thus changing the sound. Other products include acoustic filters for industrial applications and impulse filters which protect are used by military personnel.

The challenge:

The main challenge for this project was the automated assembly of 3 components: the casing, the washer and the impulse disk (photo). Currently, Dynamic Ear does this process by hand. For this they use a tray containing the casings. They place the optional impulse disk, and press in the linear filter to complete the assembly of the filter. This is a part of the complete production process, and only this part is reviewed for this project.

The implementation:

For the assembly the following setup is proposed (photo).

A tray containing empty housings is placed in 1.
A container with the linear filter washers is placed in 2.
The impulse disks are stored in 3. The machine operates as follows:

The dispenser for the impulse disks has an Archimedes screw in the interior wall similar to a cement mixer. With each rotation, it dispenses a controlled amount of impulse disks in the shaker below. This (orbital) shaker can disperses the disks, and with vision the singled out disks can be selected for pickup.

The washers are picked up from a storage container via the cyclonic vacuum. After the vacuum turns off, the valve below opens up to dispense the stored washers. The conveyor belt moves the washers to the pickup location. Vision is used to determine the location of the washers and to select one with the right side up. The unselected washers are returned to the feed container, this facilitates easy changing of filter type between batches or even during a batch.

One of the key points in the design is the required sub-millimeter precision of the machine. This resulted in the choice of the delta robot for the basis of the machine. Not only are the precision and speed comparable (if not better) than the robotic arms available, its compact size and far lower price makes for a attractive economical and scalable solution.

The washers are picked up on the conveyor belt on the left, the impulse disks from the shaker on the right, and they are assembled into the shells in the tray in the center

BuilT to order:

Because Dynamic ear produces mostly custom made products, a wide variety of components are used on a regular basis. The shape of the casing might differ drastically, the washers differ In color and the impulse disks are not always required. This does not even consider the additional components in some of Dynamic Ear’s newer products. An attempt was made to incorporate some flexibility in the final design. For example the washers can be changed depending on the product. One needs only to empty the washers in rotation and dispense them all back in the container, which can then be swapped. Future iterations can include a system to automatically rotate the containers, so the filter assemblies can be customized and built to order automatically. The impulse disks are used in a separate loop. Currently, it follows the “fill and forget” pattern, where one can load a large quantity in the dispenser from which the system can retrieve when needed.

The tray is placed by hand in this setup. The shape is derived from the casing, though most variants currently in production should fit, a substantially different design would require a specialized tray.
In the current production cycle of Dynamic Ear the tray is used as a carrier for the product. In accordance with this principle, the tray is used as a central carrier in the automated assembly as well. By automating the loading of the trays in the machine and their subsequent retrieval, one can simply integrate this solution in a larger production process.


In conclusion, the chosen solution is capable of automatically assembling the filter components. Several choices are incorporated in the design to ensure scalability to increase production and automate build-to-order. This machine can assemble the casing, washer and impulse disk for entire tray’s, or customize each position.
The current dual-purpose end-of-arm tool is not the best option for picking up the impulse disks, this will require further investigation, potentially a tool changing end effector, or splitting up assembly between two machines.