Affordable ‘ultra-precision’ machine tools

Machining to microns is a tough business that requires machines designed and built to achieve the optimum in accuracy

Posted on 02 Mar 2014 and read 7027 times
schaublin Although its roots are firmly in making machines for the watch-making industry, the Swiss company Schaublin Machines SA (www.smsa.ch) is now recognised as a manufacturer of machine tools for a diverse range of applications, including those found in aerospace, medical, optical, automotive — including Formula One — defence, micro machines and, of course, watch making.

The company has some 250,000 machines operating world-wide, and its current line-up includes conventional lathes, two- and three-axis lathes with ‘teach-in’ numerical control, multi-axis CNC turning centres and machining centres. In fact, it now has 31 different products
in its turning range and seven types of VMC.

schaublin 2However, it was Schaublin’s 102 model conventional lathe that established the company, and to date more than 100,000 of the bench-top version of this machine have been sold (the 102 is available in a variety of specifications, including those with a cast base). Moreover, they are still hugely popular within the Swiss watch-making industry, which has seen a significant resurgence in recent years, particularly in the ‘luxury’ sector. Indeed, Switzerland’s watch industry is the world’s number one, making over 30 million watches a year, producing 95% of those in the 800-plus euro price bracket, and exporting timepieces worth 17 billion euros annually.

A couple of years ago, it was estimated that this industry employed some 50,000 people in around 600 companies, with some 95% of these based around the Jura mountains in the Cantons of Geneva, Neuchatel, Jura, Vaud, Solothurn and Bern. In fact, the Canton of Bern is the second-largest watch-making Canton in Switzerland; it is also home to a significant number of machine tool manufacturers — including Schaublin.

Rolf Muster, the company’s CEO, says Switzerland’s machine tool industry was developed to support the watch-making industry, adding that the extreme accuracy and reliability for which Swiss watches are renowned come from the high levels of precision involved in making their component parts. “Precision is in the blood of people from Bévilard. For them, it is a way of life, which is why our machines are often used to produce parts that other machine tool manufacturers will not touch.”

Almost a century


Schaublin was founded in 1915 as a manufacturer of conventional lathes and milling machines. At its peak, the company employed some 1,400 people in the manufacture of machines, parts and collets. In the period 1980-2000, Schaublin was the leading company world-wide for machines producing hip prostheses; in this same period, the company had the entire world market for machines to produce hard contact lenses.

Schaublin has also achieved some notable firsts. In 1973, it was the first company in Europe to integrate a CNC system with a turning machine; and in 1983, it was the first company to build a milling machine with a vertical/horizontal head.

In 2000, Schaublin underwent a major restructuring with new shareholders, all of whom were in the machine tool industry — “a bit like Singapore Airlines, which has old pilots and stewardesses on the board,” quips Mr Muster. Schaublin Machines SA was established in 2002, and last year it moved into new premises with 9,000m2 of shopfloor area, very close to the old factory in Bevilard. The company now employs 125 people, including those at its subsidiaries in Germany, India and the UK; it also has some 80 dealers world-wide.

schaublin 4Interestingly, Schaublin no longer machines parts but sub-contracts component production to Charpie SA, a precision machining company literally across the road from the new facility. Schaublin is a major shareholder in this company and has two of the five board seats. It also transferred some 30 production machines to Charpie, along with 21 of its machine operators, when it moved to the new facility.

“Sub-contracting our machining gives us tremendous flexibility, allowing us to match output with demand — without bottlenecks in production or idle capacity,” says Mr Muster. “That said, we have retained flat grinding at our new plant, as this process is a key factor in the accuracy of our machines. We had our three Camut grinders overhauled, as we could not find new machines capable of achieving the accuracy we require; they sit on isolated foundations.

“We also buy all our cast-iron components from the Swiss company Fondrie de Cortaillod; and as with Charpie, Schaublin has a major share-holding in this company. The only exception to buying Swiss iron relates to our machining centres, which we have made to our specification in Taiwan. We fully test them in Switzerland, using laser and ballbar — plus we use our own software. Many machine tool manufacturers have adopted this approach for what we regard as medium-precision machines.

Focus on development


Schaublin has 13% of its staff devoted to research and development; this compares with around 10% for Japanese companies and 6-7% for most others. During the period 2002-2013, Schaublin developed no fewer than 22 new machines; today, Mr Muster has set the target of developing at least one entirely new machine a year, using feedback from its 80-plus representatives — and subsidiaries — to provide vital market feedback.

Schaublin’s modular approach to the design of its 136 and 142 lathe ranges was the result of such feedback. These machines, which are available with four to 11 axes, reflect the company’s obsession with accuracy and reliability, as Frank Boston — managing director of the UK subsidiary in Stockbridge, Hampshire — highlights. “These machines feature a 3.5-tonne cast-iron bed with three support points. This provides the stability that is essential for achieving high levels of surface finish, particularly when hard turning — a task for which these machines are ideally suited.

“They also benefit from our designers’ fastidious attention to thermal stability, with all the ‘nerve centres’ of the machine — some 17 in total — featuring glycol-based cooling or temperature regulation. Included are the machine base, spindles, ballscrews, all axis motors, the hydraulic system, the coolant system and the turrets. Furthermore, the turrets are built specifically for Schaublin by Sauter; they feature 12 positions — all driven by a 6kW motor to a maximum speed of 12,000rev/min.

“For the 136 model, which has a maximum turning diameter of 180mm, both the main spindle and the counter-spindle are identical — A2-4, 23kW and 8,000rev/min. On the 142, which has the same turning capacity, the main spindle is a larger A2-5 unit; the counter-spindle is the same as on the 136.

“As with all Schaublin lathes, the spindles have a roundness and run-out of less than 0.5µm. This level of accuracy results from a combination of many factors, including the quality of the spindle components, the quality of bearings — super-precision aerospace grade — and the quality of assembly and subsequent testing. These machines are also available with robotic load and unload, together with the automation required for extended periods of unmanned operation. Automation is a key factor in manufacturers keeping production costs down and ensuring global competitiveness.”

Combination machine


The latest machine from Schaublin is the 202TG — a high-precision production machine that combines turning, hard turning, milling and grinding with up to eight simultaneous axes.

schaublin 3Launched at last year’s EMO exhibition in Hanover, the 202TG has machining capacities of 80mm for diameter and 160mm for length — plus it offers a 19mm-diameter through bore. Moreover, part of the machine’s attraction is its ability to be integrated into an automated environment, with bar loading and an unloading arm.

“In developing the 202TG, Schaublin focused on creating a machine that is suitable for machining small diameters, while also offering modularity, flexibility and ease of use,” says Mr Boston. “As with the company’s 136 and 142 turning centres, the 202TG focuses on thermal stability for guaranteed accuracy over extended periods of operation and incorporates many of the same features — and the cross-slides feature glass scales with a resolution of 0.0005mm. By the year end, we had sold three of these machines — one to a company in Singapore and two into Malaysia — all for general production work.”

The tool turret offers 12 positions, of which six can be driven at up to 6,000rev/min. Meanwhile, the 6kW internal grinding spindle has a maximum speed of 60,000rev/min, while the 7kW external grinding spindle has a top speed of 25,000rev/min. “Moreover, the work spindles are driven by synchronous motors designed to accelerate to maximum speed and decelerate in a shorter time than competitors’ machines,” says Mr Boston.

Cost of ownership


Although machine price is important to all manufacturers, he says that, while on day one the price of a Schaublin machine might be more than many competitors’ products, it is the cost of ownership over a period of time that is paramount. To quantify this, he suggests that the manufacturer’s service/warranty costs in the first year of a machine’s use give a reliable indication of the on-going financial commitment to be expected by the end user.

“On standard manual machines, the service costs that we incur in the first year average just 0.01% of the machine price. For our CNC machines, this rises to 1.5% — considerably less than most manufacturers, which are reckoned to budget for 4-5%. Moreover, Schaublin machines are verified to VDI 3441, which is much more rigorous than the Japanese standard JIS B 6201; the latter appears to show an eight-times better repeatability than VDI testing — on the same machine!

“Precision is key to Schaublin, and Swiss-made is very important for our Asian customers, which take some 20% of our output of well over 500 machines a year. In 2013, this comprised some 250 conventional lathes, 220 CNC and ‘teach-in’ lathes and 60 VMCs.”

Schaublin’s roots — its 102 conventional lathe


Schaublin mini
Lathes like the conventional ‘entry level’ 102— suffixed N-CF — have been the mainstay of the watch-making industry for decades. Available in both bench-mounted format or with a cast-iron base, this lathe has a 1.5kW 5,000rev/min spindle drive (4.2kW for the model with a cast base), a 130mm swing over the bed, maximum distance between centres of 275mm, and either a W20 or W25 collet (14.5/19mm capacity respectively).

Over the years, the 102 has benefited from successive enhancements designed to extend its scope of application. For example, the 102 Mi-CF — again available in both bench-mounted and cast-base versions (sold in the ratio of 50:50) — features an integrated spindle motor and a top speed of 6,000rev/min. There is also a version with a C axis, and one with a lead screw for thread chasing — the 102N-VM-CF. Accessories include milling and grinding attachments, as well as vacuum clamping for thin and fragile parts.

Meanwhile, the 102TM-CNC features a Fanuc 0i control that allows the machine to be used conventionally or as a three-axis machine for prototype work or small-batch production. Top of the range is a version of this machine with a Staubli IP65 six-axis robot, which not only undertakes loading and unloading but also turns the part for back-end working.

Schaublin VMC in action



Schaublin mini 2
Raphael Blowick has spent most of his professional life working in Ireland’s medical-device design industry. When recently a surgeon approached him with a very clever idea for a new cosmetic surgery device, Mr Blowick knew that the only way he could develop this would be to invest in the right production equipment; he also knew that if he didn’t show willing the project would go elsewhere. He started Clada Medical a few months later — despite having little hands-on manufacturing experience.

Working on the premise that accuracy and process consistency were of the utmost importance for the medical parts he wanted to make, he sought advice and subsequently bought a Schaublin 48V machining centre fitted with a Renishaw OMP40 touch probe; he also bought a GibbsCAM software package, to turn his 3-D designs (made using SolidWorks) into machining programs.

Mr Blowick readily admits that he faced a steep learning curve when it came to machining. However, Schaublin Machine Tools’ Frank Boston put him in touch with Bristol-based GS Productivity Solutions (GSPS), which integrated the CAM and probing software — Renishaw’s Productivity+ — with the Schaublin 48V, allowing the whole production process (including probing) to be developed off-line. Schaublin and GSPS also helped Mr Blowick to make a calibration part incorporating most of the features that he would be likely to machine. “The probing controls the process and verifies the finished part; and if there is any variation, this can be fed back to the CNC system and adjustments made accordingly.”

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