New electrified monorail system for cab conveyors in John Deere tractor assembly plant

By the end of summer and beginning of autumn, work in the fields begins to hot up. It is harvest time. Tractors towing suitable trailers set to work cutting crops, gathering hay bales, transporting the harvested grain from the field or plowing the newly harvested fields.

To ensure a sufficient supply of new tractors, the distinctive green and yellow agricultural machines roll off the production line at the John Deere factory in Mannheim at three-minute intervals. They leave the factory in different sizes and equipped with different engines depending on the requirements of their future owners.

Harvest time without the powerful agricultural machines is totally unimaginable. The tractors, with their striking color and design, are a frequent sight in our farms and fields, serving as the perfect global advertisement for the American company John Deere, which is headquartered in Moline, Illinois.

Every three minutes, a "Johnny", as the agricultural machines are affectionately known at John Deere, rolls off the conveyor belt in Mannheim. But what does the production of John Deere tractors in Mannheim have to do with Bruchsal? Two things: Firstly, the driver's cabs come from the sister plant in Bruchsal. Secondly, the safe drive technology used in the manufacturing process comes from SEW‑EURODRIVE in Bruchsal.

Reliable drive and automation solutions combined with outstanding service from SEW‑EURODRIVE have ensured that high productivity has been maintained in both plants for decades. After all, quality, safety and comprehensive service are just as important to SEW‑EURODRIVE as they are to the agricultural machinery manufacturer.

This was justification enough for the decision-makers at the John Deere tractor plant to put all their faith in SEW‑EURODRIVE when it came to modernizing the aging cab conveyor in Mannheim. The German subsidiary of John Deere decided not to replace just single drives, opting instead for a complete drive technology retrofit solution, which took the form of an electrified monorail system equipped with optimum safety technology.

The engines for the tractors are manufactured at the John-Deere production plant in Saran near Orléans in France. However, the tractor manufacturer produces the driver's cabs in Bruchsal – not far from the SEW‑EURODRIVE headquarters. Due to the synchronized cab and tractor production processes at John Deere, the cabs arrive shortly before assembly. The lead time is just two days.

When the cabs come out of storage in Mannheim, there are still some small work steps to be completed in pre-assembly. From there, they are taken to a rotary table, on which the cabs are aligned for attachment to the lift frame of the electrified monorail system. To do so, anchors move under the cab at the rear like forklift arms.

Even though the cabs all have different designs depending on the type and size of the future tractor, this intra-plant process is always identical at John Deere. Based on the principle of self-clamping, the cab is then secured in place by its own weight during transportation. Once prepared in this way, the cabs wait until they are retrieved. The tractor to which they will later be assigned is already determined in the material flow.

One after the other, the transport carriages in the electrified monorail system convey the driver's cabs towards the joining process. Because the joining process takes longer than three minutes in the "marriage" (connection of the cab with the powertrain of the tractor), joining takes place on two parallel lines to enable the three-minute cycle in the material flow to be maintained. A switch allocates the incoming cabs to the left and right. Double the cycle time is thus available for this process step in the John Deere factory.

How well and how quickly the material flow works depends both on the coordination of in-plant processes as well as on tailor-made drive and automation technology in the conveyor system.

One of the important features of the fully modernized electrified monorail system: Thanks to the modular MAXOLUTION® system solution EMS safety with its compact decentralized structure, the new cab conveyor system fits perfectly into tight spaces.

Once at the assembly site, the driver's cab is first automatically lowered to a preliminary height at which nobody can be injured. Only then does the John Deere operator take over with a hand-held terminal, moving the cab manually into the correct joining position above the drive train and then lowering the lift frame of the electrified monorail system further to the joining level.

Who doesn't love a wedding? SEW‑EURODRIVE is lucky enough to be a permanent guest at the John Deere tractor production plant. Although the many marriages that take place here each day – every three minutes in fact – are not really of the romantic kind, they do offer ample security and perfect prospects for the future.

The marriage ceremony initially sounds adventuresome, as due to the assembly process, the operator must at times remain under the suspended load and thus between the cab and the powertrain (the tractor's engine, axles and hydraulics). However, sophisticated safety technology is absolutely essential in this assembly station. To ensure that the John Deere employees can go about their work between the components safely, redundant measures in the electrified monorail system provide double on-the-job safety throughout the process.

The right solution for optimum occupational safety: consistently redundant design of the belt pairs and drive technology ensures double protection: Not one, but two pairs of belts made from a highly stable material are used to ensure optimal hold of the lift frame and driver's cab in the "MAXOLUTION®" electrified monorail system. In turn, each of these belt pairs is wound around a central shaft in the middle of the EMS in two layers (bifilar). This enables symmetrical lifting and lowering of the cabs.

The drive technology in the electrified monorail system is also redundant: Two motors, each of which would be capable of moving and braking the lift frame on its own, guarantee double the safety. Two sensors, known as draw-wire encoders, ensure a safe lifting height and speed. These can also detect and notify workers in good time of any deviations from symmetry or misalignment of the lifting frame.

Doubly protected in several respects by this state-of-the-art safety system, the employees at John Deere can reach under the suspended load to attach electric cables, hydraulic hoses and bolted connections without any worries – ensuring everything runs smoothly in the marriage of the driver's cab with the drive train.

Currently, the heaviest driver's cab at John Deere weighs 850 kg. The cab conveyor's capacity limit is 1500 kg so there is plenty of room to play with.

More than just gearmotors: The retrofit of the John Deere cab conveyor involved virtually the entire MAXOLUTION® range from SEW‑EURODRIVE. The "EMS safety" electrified monorail system solution uses distributed, i.e. near-field electronic drive solutions to supply lifting drives. These take up comparatively little space and are vibration-proof. The two helical-bevel gearmotors, which work together to lift and lower a lift frame and a cab, are each designed for an output of 5.5 kW. A MOVIPRO® SDC supplies the pair of motors as a group drive with a nominal output of 11 kW. The 0.55 kW drive motor is controlled by a MOVIFIT® controller.

The time frame for the entire retrofit for John Deere was just two weeks during the plant vacation over Christmas and New Year 2016/2017. The MOVIVISION® plant software proved invaluable in this case. This software reduces programming effort and enables the exact simulation of a virtual startup. Usually, the underlying calculations are carried out well before the conversion when planning the plant. At John Deere, it was therefore possible to speed up the actual startup considerably. But that's not all: The software also provides a valuable service during operation by enabling permanent monitoring and diagnostics, including condition monitoring, without interrupting the plant.

The basic requirements for the occupational safety of John Deere workers are the secure position of the vehicles, a secure lifting position and a safe lifting speed. All of these safety features run on the MOVISAFE® HM31 safety controller from SEW‑EURODRIVE. It also controls the SBC (Safe Break Control) safety function, which ensures the correct distance is maintained between the tractors in the production line, making a mechanical distance sensor superfluous.

After each rotation, all seven electrified monorail system transport carriages must undergo an automatic brake test for the lifting drives. The control center receives a message in the case of any events. The exact position of the carriage at any time is also sent to the control center and displayed on the visualization screen.

In the case of an error message, the system acts autonomously, identifies the EMS carriage in question and directs it immediately to the maintenance area, thus preventing costly downtime for John Deere.