The watches tick differently here

Quality and precision taken to extremes

Production for the watch industry

Proart now produces exclusively for the watch brand Richard Milles. The figure shows the RM 60-01

High demands are made on precision and quality in the machining production of many industries. But the watch industry takes it to extremes: Even the slightest neglectfulness and the tiniest visual irregularity can cause a rejection here.

Machining operations in the watch industry must prove their performance capability on a daily basis and for each individual part. A company that adheres to minimum dimension tolerances is not standing out from the crowd, but is merely meeting the basic requirements. Because with watches, particularly the visible surfaces, a visually appealing finish is a decisive factor. This can only be achieved with high-end machinery equipment which is made for this kind of precision and surface quality.

Many small operations from the watch industry have settled in Jurabogen, Switzerland. In 2012, Proart Prototypes S.A. moved here into a new factory in the small village of Les Breuleux, in the Canton of Jura. The company, which originally specialized in the designing of prototypes as a one-man operation using conventional machine tools, now exclusively produces for the "Richard Mille" watch brand. The new plant was acquired after the takeover of the company by the Richard Mille Group, which became independent from other suppliers in this way. This ensures that even their small to very small production orders (which is often the case in the production of high-end watches) are promptly and reliably completed.

Since the start of 2013, 15 different precision machine tools have been in use, finishing parts for one-of-a-kind watches and small series productions of up to a maximum of 300 units. Each year, between 3,000 and 3,500 watches are produced, distributed among approx. 30 different models, in the following way: Richard Mille is responsible for the development and design of the watches; Proart produces watch parts, primarily made of titanium or gold, and performs the initial assembly steps; Guenat S.A. Montres Valgine handles the final assembly.

A new machine results in independence

Didier Habegger: "Since we do not produce any large series, it is extremely important to us that all of the tools always remain in the controller's memory. This significantly facilitates and accelerates the changeover."

With the acquisition of an EMCO MAXXturn 65, a Sinumerik-controlled turning center with a rod loader, the manufacturing company has become considerably more autonomous. Previously, Proart was dependent on the delivery of stamped blanks for the production of titanium watch casing elements. "We always had to accept several hundred of them at one time. In addition, there were always problems with the blanks during finishing, due to tensile forces and inconsistencies in the material," says Alain Varrin, General Manager of Proart. Since the commissioning of the EMCO turning machine at the start of 2014, the parts are no longer manufactured from blanks, but from the solid. As a result, the number of processing steps required was also reduced. Whereas with the stamped blanks another four to five work processes were required after the roughing, that number is now only two. "With the new machine, we are more independent and have become significantly faster – without sacrificing quality," explains Varrin. The turning center allows the finishing of the workpiece on a spindle and counter-spindle and is equipped with the most powerful Siemens CNC, the Sinumerik 840D sl. It includes all of the functions needed in order to make maximum use of the potential and precision of the turning machine.

This machine was procured via the Swiss EMCO exclusive sales, Argonag AG (Affoltern am Albis). For the special requirements, the machine tool experts developed and implemented a special solution with two high-frequency spindles mounted directly on the revolver. "These spindles can be controlled, programmed, and monitored via the CNC," explains Heinz Müller, the responsible support contact of Proart at Argonag. "Since the power is supplied internally, the die opener can swivel. This prevents damage to the power supply cable by chips or lubricants."

Assigning multiple tools to tool positions and easily managing them

For interior threads with a diameter of 0.8 mm, the vortex milling mode on the MAXXturn 65 is used

In addition to the special equipment, the EMCO machine also has many useful details, which facilitate the daily work of the machine operator: The twelve-fold servo revolver is supplemented by multitools, which allow the tool positions on the revolver to be assigned multiple times. This solves the known problem that turning machines only provide a limited number of tool positions. The tool management of Sinumerik supports this application with all of the necessary functions. The tools can be quite simply created as a multitool and be easily handled using the known functions of the convenient Sinumerik tool management system. When multiple positions are assigned, the tool list is supplemented by a column for the multitool position number. Didier Habegger, who operates the EMCO, is completely convinced by the tool management system of the operator interface Sinumerik Operate on the CNC: "Since we do not produce any large series, it is extremely important to us that all of the tools always remain in the controller's memory. This significantly facilitates and accelerates the changeover." The tool measuring sensor and the pre-defined measuring cycles of the Sinumerik also allow the measuring and break monitoring of the tool in automatic mode.

Typical workpieces produced by Proart are either part of the watch casing or are elements of the brand-specific clockworks. For example, it takes approximately 18 minutes for the so-called bezel, which is a decorative ring made of titanium that holds the watch glass on the body of the casing, is turned out by the MAXXturn 65. Pins must be milled on its exterior; there are also several interior threads with a diameter of 0.8 mm, for which the vortex milling finishing mode is used. The threads are re-measured or checked by the operator at the machine.

The size of the finishing program for a watch case, which is finished with a 0.5 mm milling tool, with splines of only 0.002 mm (2 µm), and other complex details, is approx. 2 GB. In order to not approach the limits even when working with highly complex parts, the controller's memory has been expanded. Short batch processing times make the work go noticeably faster. The CNC is also equipped with the high-speed option Sinumerik MDynamics with Advanced Surface for a high performance capacity. The production at Proart is only a one-shift operation; but since the machine is equipped with a rod loader for the loading process and a conveyor belt for removing the parts, the production can become a 24-hour operation with a graveyard shift as well, if necessary.

The material price is a relative value

Since the commissioning of the EMCO, watch case elements made of titanium are no longer manufactured from stamped blanks, but from solids. In the Figure: Various work steps, from the titanium rod to the ring-shaped watch case element.

Whereas titanium or high-alloy steel are considered expensive materials in production for the automotive industry or medical equipment, the topic of material price at Alain Varrin only evokes a slight smile: "Even with watches made of solid gold, the achieved sales price depends more on the low unit numbers, high quality, and respective brand than on the material used." The high-priced segment of the watch market in particular follows its own rules, which cannot be compared to other – these watches tick differently in every respect. This is illustrated by the "RM 27-01 Tourbillon Rafael Nadal" with a carbon nanotube case, with a manual winder that is held by wire cables, so that it can withstand 5,000 g (i.e. 5,000 times the acceleration due to gravity), or the "RM 56-01 Tourbillon Sapphire" made of solid sapphire, which is completely transparent and allows you to see the clockworks. Anyone who wants to buy such a watch not only needs to be a person of means, but must also have a certain degree of patience because the machining time for these watches can sometimes take more than three months.

About Argonag AG

The completely transparent "RM 56-01 Tourbillon Sapphire", which is manufactured from solid sapphire, allows you to see the clockworks

The family-owned, owner-operated Argonag AG has been selling machine tools and the training systems of various European machine tool manufacturers in the Swiss market for 40 years. As the world's oldest partner of the Austrian company EMCO Maier GmbH, Argonag supports (from this manufacturer alone) more than 1,100 turning and milling machines in Switzerland and Lichtenstein.

In addition to sales and service, Argonag also develops customer-specific solutions which go beyond the standard equipment of the machine tool manufacturers. In the example of Proart, two high-frequency spindles, mounted directly on the revolver, allow direct controlling, programing and monitoring via the CNC. Thanks to the power being supplied through the center, the die opener can swivel, which simplifies the programming and prevents collisions. The implementation of this customer-specific solution was done in a collaborative effort of Emco, Siemens, Sauter (tool revolver), Ibag (motor spindle), and Argonag.