France: A fountain of machine-tool-savvy

What first pops into your mind when you think of France? Paris? Perfumes? Fashions? Wine? Food? Art? How about machine tools?

If you're a design engineer, you would do well to put machine tools on your shopping list when planning a trip to France. On a recent tour, this reporter got a first-hand look at what the French machine-tool industry has to offer, particularly in the areas of high-speed precision and linear drive systems. Here's a sampling of the findings:

CNC monitors jet-engine welding

The tour began with a visit to NUM Groupe Schneider (Argenteuil), a leading manufacturer of computerized numerical controls (CNCs).

One of the latest NUM products, the NUM 1050 CNC, is a fully digital system for controlling high-speed machining units. It can handle up to eight digital axes and spindles in three groups, plus three handwheels or scales. Using analog servomotors, the system can operate up to three independent spindles or axes (turrets, turntable, or gantries). The compact CNC features a built-in PLC that controls up to 336 I/Os, and a 50-key operator panel with a 9-inch monochrome or 10-inch color screen (CRT or LCD).

To illustrate the versatility of its CNC systems, NUM showed its equipment in operation at a nearby SNECMA plant that produces turbine shafts for CFM56 aircraft engines. Here, a huge inertial friction welding machine was re-engineered to improve the process. A NUM 1060 CNC with a user-friendly operator interface has replaced a programmable logic controller.

Close process monitoring and regulation is crucial. At a rate of one per millisecond, the NUM CNC acquires the parameters needed to analyze the reaction of the materials, speed of rotation, pressure applied, and material used according to the distance traveled by the rotating part.

The CNC transmits all data it acquires to the PC, which, after expressing them as curves, outputs a tracer sheet of the operation. This ensures the traceability of each part produced, an essential element that helps guarantee the quality, reliability, and safety of a critical aircraft-engine part.

Conveyor of parts and safety

Next stop on the tour was Farman (Tours), a manufacturer of accumulating conveyors and safety curtains for the machine-tool industry. Customers include: Renault, PSA-Peugeot-Citroën, Ford, Rover, Audi, Opel, Volkswagen, Saab, and Daimler-Benz.

The conveyors' carriers accumulate at the loading point, unloading point, and at a waiting point using a built-in retention system. Inductive detectors trigger the retention points, and an automatic stress system on each of the two chains reduces maintenance costs.

Each carrier features four toothed wheels where limited-friction shafts allow continuous movement and accumulation. A geared motor drive limits stress on the system. The patented drive system retains the carriers as they pivot at the end of the conveyor, and acts as a safety mechanism in case of jamming.

To improve machine-tool system safety, Farman's safety curtains serve as retractable material protectors that allow workers to manually insert parts in an automated cell. Operator safety is guaranteed by a reflex cell that stops the panel from dropping. All protection features remove easily for quick access and maintenance of the automated cell.

CNCs improve welding

From Farman, the tour continued to sister company ARO (Chateau-du-loir), which specializes in state-of-the-art welding systems. Products range from portable resistance spot welding guns for auto-body repair to heavy-duty industrial systems for light-alloy welding applications.

ARO's line of 50 or more robotic welding guns includes a CNC system that assures the weld cycle starts only when the programmed electrode force is reached. According to the company, advantages of this CNC system include: synchronization of electrode force/weld current, detection of improper electrode fit-up, geometric check of components to be welded, detection of stuck or missing electrodes, monitoring and reduction of electrode wear, low wear of mechanical gun components, shorter weld cycles, and fast build-up of electrode force.

To illustrate the efficiency of its systems, ARO presented a comparison of two welding stations: one based on the use of external transformers, the other featuring ARO's integrated transformer guns (see diagram).

Lathes shave production time

The sprawling manufacturing complex of Defontaine Automotive (La Bruffiere) turns out millions of starter rings and flywheels for automotive giants and small-engine makers of the world. Visiting Defontaine was Dominique Boussaton, president of RAMO Industries (Niort), whose company's specialized lathes labor away on the shop floor.

One of RAMO's latest offerings is the RTN30 NC lathe with a tilted bed. Customers have a choice of NUM, Siemens, or Fanuc control modules. A bidirectional electric turret has a tool-station plate for 12 tools. Three high-speed hydraulic chucks feature both hard and soft jaws. Spindle speed tops out at 6,000 rpm, powered by a 20-kW brushless motor drive. A 0.55-kW pump provides cooling.

In one-cell operation, a RAMO lathe, specially configured by Defontaine, sits in the middle of the cell turning out starter ring gears from bar stock. The operation involves cutting, welding/trimming, and annealing/forging operations.

Robots hard at work

Visitors can get a first-hand look at how robots improve production-line efficiency at the giant Renault complex in Cléon. The plant turns out pinion gears and primary and secondary shafts for automatic-drive gearboxes.

Since September 1995, 21 RX90 Series and 10 RX130 Series robots from Staübli Robotics Div. (Faverges) have performed effortlessly in Renault's gearbox pinion and sliding shaft manufacturing centers. "Their efficiency and performance is proven daily," reports Harry C. Beaver, Staübli's national sales manager for the U.S.

What makes the robots so efficient, Beaver says, is their ability to reduce cycle times through rapid acceleration and high-speed performance for increased production throughput. Precise path performance adds to that efficiency, as does a rigid mechanical structure for material removal, polishing, and grinding applications. A patented gear-reduction system reduces backlash to zero, while integrated solenoid valves and the robot's forearm cable permit easy end-of-arm tooling integration.

Both robots feature the CS7 controller and user-friendly V+ programming language to instantly display the number of parts machined by shift, the work rate of the machines, and any errors made during production.

Milling center handles the hard stuff

With a 100-year history, Huron Graffenstaden (Illkirch) has installed more than 100,000 of its milling machines throughout the world. Building on this success, Huron decided to explore high-speed cutting, not for aluminum but for cast iron and other hard, difficult-to-mill materials. Huron's R&D department came up with a machine equal to this task--the Huron EX multiple-axis machining and milling center.

The EX provides continuous head movement in the vertical plane and 3-, 4-, and 5-axis machining. Other EX features include: machinable volumes from 1,200 × 700 × 600 to 2,400 × 700 × 800 mm; a 14,000-rpm, 25-kW, 250-Nm spindle; a 24,000-rpm, 30-kW, 56-Nm spindle; and vertical- and horizontal-plane head positioning.

Huron's larger KX10 vertical-spindle machining and milling centers feature a numerical controller that searches for the shortest machining time, increases machine accuracy, and produces an exact finish in the shortest period of time. It includes a Pentium PC, hard-disk drive with 200 Mbytes of work-piece program storage, Windows 95, 1.5 Mbytes of RAM, 1.5-Mbaud transmission speed from PC to NC, 10m/min working feeds, and a NURBS universal interpolator.

Jet-engine parts test milling machine

Milling composite parts for a next-generation jet engine can test the capabilities of any machine. But machines from Forest-Liné (Capdenac) produce parts for CFM International's 737 jet engines without breaking a sweat.

"Our ongoing target is to decrease production costs for manufacturers, without reducing the quality of parts or productivity," says Claude Jean Mege, Forest-Liné's general manager, commerce and marketing.

Mege showed off a prototype of Forest-Liné's latest machine, the LINEAR MINUMAC. Initial machines will come with vector-controlled HF spindles in a power range of 20 to 75 kW with speeds from 16,000 to 40,000 rpm. Axis feed rates will run as high as 40m/min, and may be increased to 60m/min, depending on the application.

Modular units adapt tomanufacturing needs

The last stop of the week-long tour was the Renault Automation factory (Castres). The company specializes in the design and production of modular machining and assembly units for the automotive industry, including transfer lines, or flexible cells, that quickly adapt to changing production rates.

"In building their new-generation engines, car manufacturers are taking new approaches, but no standard production architectures are to be found on their shop floors," notes Jean-Paul Bugaud, Renault Automation's executive vice president, machining.

For example, Fasa-Renault is installing highly flexible machining lines designed to adapt to the evolution of cylinder block designs for its new Kxx engines. The objective: change production from one variant to another in less than 15 minutes. The lines combine Renault Automation's high-speed Urane machining center and Saturne machines equipped with multi-spindle heads. With its single spindle, the Urane can be retooled in an instant to machine new components. Urane features include autosynchronous linear motors on three axes, horizontal electric spindle, and 20,000-rpm spindle speed.

At BMW, says Bugaud, tests with the Urane machine proved it to be the most economical alternative for several 10- to 12-year-old machines due to be replaced. The tests demonstrated that Urane would reduce cycle times on a variety of engine parts by 50 to 80%. They also showed that the machine's linear motors performed better than machining centers fitted with ballscrews, which provided only a 15 to 30% cycle-time improvement.

EMO show previews tooling for 21st Century

You can "test drive" all of the machines described in this story--and many more--at this year's EMO show in Paris's North Expo Center from May 5 to 12. More than 2,000 exhibitors from five continents are expected to display everything from machine tools, assembly and welding equipment, and advanced accessories to components, controls, tooling, and automation systems and software. Pre-registration ( www.emo-paris.com ) will get you into the show free.