A wooden block of hard-wearing beech is one of the key features on one of the world's most successful range of combine harvesters.It ensures the vital thrashing operation inside the heart of the top-of-the-range combine is completed as efficiently as possible in the testing conditions of the harvest field.

A wooden block of hard-wearing beech is one of the key features on one of the world's most successful range of combine harvesters.

It ensures the vital thrashing operation inside the heart of the top-of-the-range combine is completed as efficiently as possible in the testing conditions of the harvest field.

The partly-hollow beech blocks, soaked liberally in natural oils, are made in two halves to house the shaft of the moving straw walkers.

If the "wooden bearings" ever fail, which rarely happens, it is relatively easy to remove and replace, while a failure of a steel or solid "bearing" could mean a major, very costly, repair job.

Engineers at John Deere have investigated many alternatives but returned each time to the tried and tested system.

In the highly competitive field of combine design, John Deere has kept ahead of the competition as it has launched more new models to serve markets around the world. It was just seven years ago that the CTS (Cylinder Tine Separator) machines were launched, and senior executives have hinted that even bigger, more powerful models will be emerging before long.

With demand rising for larger combines with even greater harvesting capacity, this is the next major challenge.

The 1,100 staff at Zweibrucken make combines and forage harv-esters for worldwide distribution.

The party of 41 Norfolk farmers and contractors watched the operation from the start, when an engineer picked up a single sheet of metal. Every day, a total of 16 machines are completed - all to meet a specific order - for customers ranging from the United States and across Europe.

A docket with the customer's order number and details moves from stage to stage at every point in the manufacturing process.

During the three-hour tour, work was completing apace on a 150-strong order for combines from Turkmenistan - a mere 10 days' work for 900 engineers and staff at the combine factory.

By the end of the season, John Deere will have made about 4,500 harvesters, all ordered by a specific customer. Without a firm order, a machine will not be made - this is the ultimate bespoke machinery business.

The factory, which covers 100 acres (40 hectares) is split by a working railway line marking the old border between France and Germany (that now runs a couple of miles away). Many of the workers, who arrive to start at 6am, commute from home in France and work a basic 35-hour week. There is no paid overtime, but if extra time is worked it can be added to the 30-day holiday entitlement or taken in lieu.

Staff work in teams, or cells, each responsible for the quality of their collective work, and tend to switch to different tasks about every month. This ensures they all remain multi-skilled.

A gradual introduction of more specialist machinery has included nine of the latest robots for ultra-high-quality welding, working to a precision of 0.15mm. These are used to weld combine parts which are exposed to the heaviest wear and stress, especially in the harvesting and threshing operations.

They also have five computer-controlled lasers to cut sheets of steel of at least 4mm thickness. One cuts seven metres a minute, and the process is relentless. It leaves the metal parts for the combines even smoother than silk, cut to a tolerance of 0.0005mm. And a new laser cutter, installed last year at a cost of £250,000, can slice through 6mm steel at a rate of 10 metres a minute and is operated three shifts a day, six days a week.

The drive for first-time quality at every stage is regularly and randomly checked and eliminates the scope for potential problems further down the production cycle. It takes about a week to assemble all the various parts from the start of the entire operation to build a combine or forage harvester.

A new range of JD 7070 forage harvesters, with a 56kph road speed, is being introduced. Again, these specialist machines, which are fitted with three metal detectors, have a choice of curved, angled or straight cutting blocks to deal with various crops from maize to grass. A clever design also makes it possible to change the blocks, which have wolfram carbide toughened knife edges, from working to transport position within minutes.

The visitors, guests of John Deere and representing two Norfolk dealers, Ben Burgess and Co from Norwich, Aylsham and Beeston, and Evergreen Tractors, of St Germans, near King's Lynn, were all highly impressed by the level of precision, dedication and testing demanded at every stage.

It was absolutely fascinating to watch the construction of the 6.5m metre long discharge arm - capable of unloading at a rate of 80 litres per second or 116 litres a second from the largest machines with a 10,600 litre tank - roughly 10 tonnes in 91 seconds.

Once in the harvester assembly area, the various elements were brought together. At every stage, the machinery was tested before final testing.

Combine specialist Rob Stanton, based at John Deere's UK head-quarters at Langar, Nottingham-shire, said: "We can tell you to the day, hour and almost minute when your combine will be finished."