CNC machining improves harmonica quality

Harmonica manufacturer said it effected an immediate improvement in component quality, because close tolerance CNC machining gives total control of the volume of air in the product.

The late harmonica virtuoso Larry Adler hated seeing his musical instrument of choice described as a 'mouth organ', but loved the way in which a small Lincolnshire, UK-based business headed by Antony Dannecker repaired and re-tuned his Hohner harmonicas.

Still a consultant to Hohner of Germany, Antony Dannecker's workshop is also home to the Dannecker Blues Harmonica, a world-renowned combination of Hohner reed plates and covers and the patented Dannecker Blues comb.

Every chrome-plated brass comb is machined by M and M Precision Engineering, a 10-strong sub-contract company that relies on machine tools supplied by XYZ Machine Tools to meet the stringent quality demands of this master craftsman.

The end result, according to musicians such as Paul Jones, a '60s legend with Manfred Mann, Joe Brown and Huey Lewis, is a musical instrument with a full rich tone and an unsurpassed dynamic range.

For M and M Precision's Mike Szebeko, it is another chapter in the search for new ways to manufacture precision machined components more cost-effectively without compromising quality.

He and co-director Mick Buceero started the sub-contracting business 'from nothing' in 1988 and sustained investment allows the ISO 9002-accredited company to design and machine a wide range of complex components in various materials and in high or low volume quantities.

Recent purchases include a 10HP, 6000 rev/min, XYZ VM 5000 manual/CNC bed mill equipped with ProtoTRAK control and a 13HP, 8000 rev/min XYZ Mini Mill 560 compact vertical machining centre supplied with Siemens 810D ShopMill conversational CNC.

Both machines are part of what Paul Lowey, M and M Precision's general manager, described as: "A programme of continuous improvement that enables M and M Precision to quote profitably and confidently on projects that other companies cannot tackle.

According to Szebeko, the Dannecker Blues comb is a classic example of the type of work that the Peterborough-based sub-contractor thrives on.

"We effected an immediate improvement in component quality," he said, "Because close tolerance CNC machining gives total control of the volume of air passing through each 'pocket' of the comb.

However, as well as implementing machining changes we have also contributed to design improvements, such as a tip radius to each 'tooth'.

This makes it easier for the player to 'tongue block' a particular note.

The Dannecker Blues is claimed to be the most air-tight harmonica available in the world today, a crucial factor in ensuring that air goes straight to the reeds being played and nowhere else.

This makes for a more responsive instrument and one that does not require great lungfuls of air to play it.

Deceptively simple in appearance, the comb's profile determines the notes produced by the finished instrument and any deviation from the extremely close tolerance profile is unacceptable.

Burrs, too, must be avoided during the machining process as the air tightness of the assembled harmonica is also the key to optimum reed responsiveness and fine tuning.

Although unwilling to divulge precise details of the machining process, Szebeko admitted to having spent 'quite a few hours' on the XYZ-supplied Bobcat CAD/CAM system when designing the fixturing system used on the XYZ machines.

This had to be capable of holding multiple brass strips already precision machined on their top and bottom faces.

The absolute priority, he said, is to avoid distorting the workpiece while enabling the complex profile of individual combs to be machined in a single pass.

M and M Precision's success can be measured in terms of current batch quantities of 300 combs and an assembly time for each Dannecker Blues Harmonica of minutes rather than hours - because each comb is virtually note perfect.

Said Dannecker: "M and M Precision's professional approach and design input has enabled us to produce what is constantly described as 'the best blues harmonica available in the world today'.

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