Utilising additive manufacturing techniques to simplify the accordion production process

Abstract

This thesis focuses on the utilisation of additive manufacturing (AM) technologies for the production of accordions. The goal is to reduce the man hours required in the production and repair of the instrument. The client, Pigini Nederland, currently produces a small accordion for children and adults: the MiniMouse. This instrument is sold for 999 euros, which is a relatively low price for the amount of man hours invested. Pigini Nederland wants to lower the threshold of becoming familiar with the accordion by reducing the price of an entry-level instrument, similar to the MiniMouse in terms of functionality.

The sound of an accordion is produced by a reed: a piece of spring steel that vibrates when air flows past. To create a tone, the reed’s valve needs to be opened and an airflow needs to be created using the bellow. A mechanical structure of aluminium bars forms the connection between reed valve and button. A torsion spring keeps the valve in a closed position and creates resilience for the button.
The production of an accordion is a complex process consisting of mostly manual operations. Some of these operations are rather time and labour intensive, such as shaping the body and inner mechanics, and creating the bellow. The repair of an instrument can be an inefficient process: the complete disassembly of certain components is sometimes necessary to replace a single component.

Producing parts with complex geometry is one of the strengths of AM. This can lead to a reduction in tooling and inventory and part consolidation. This is an important driver for choosing AM as a means of production.
Fused Deposition Modeling (FDM) is chosen as the production technique for this project. FDM prints have good mechanical properties and require little post-processing. There is a wide range of materials available and the process and printer are relatively cheap. Pigini Nederland is interested in in-house production, which is realisable using an FDM printer.

The assignment focuses on the right hand side of an accordion, which has been fully designed and 3D printed. The fundament of the design is the instrument body. Multiple components are attached to it, resulting in a full-fledged instrument. For these attachments, non-printed connectors have been used as little as possible so that assembling the instrument is easy.
The mechanical structure consists of separate arms that are placed in the body using snap fits. A printed spring-like element is incorporated so that the arms of the structure bend when a button is pressed to open the reed valve. As the material loses its natural resilience during the expected 10 year product lifetime, a steel compression spring is added to regulate the button pushing force.
The buttons are attached to the mechanical structure using a snap fit. This makes it possible to quickly detach all buttons when repairing the instrument. In a conventional instrument, buttons are attached using glue and need to be broken off in such a scenario.
The reeds of a conventional accordion are attached using molten wax. Since this is labour-intensive during production and repair, the reeds in the printed instrument are clamped onto the body using a rubber gasket, nuts and bolts. The size of the reed sound chambers is determined by analysing sound samples and comparing them pairwise in a user test.

The project outcome provides an indication on how to use AM for accordion production. A printed proof of concept showcases that the instrument is fully functional, while minor design recommendations need to be addressed. An estimation of the material cost and labour during production is made, and a cost reduction of roughly 15% of the full instrument is established. This is a large step forward, as only the right hand side of the product has been redesigned. It is a clear indication that additive manufacturing can be a valuable tool in lowering the engagement threshold for future accordionists.