Contributing Editor Rex Narraway got on his bike to see a machine designed to speed up the assembly of Triumph motorcycle engines

As part of the continuous development of the facilities in its highly automated factory, the resurgent Triumph Motorcycle Company has installed a new fully-automatic assembly machine for fitting valve guides and seats to its cylinder heads. Basically, the system employs a series of hydraulic rams, pneumatically-controlled component positioning actuators and feeding systems, all coming under the supervision of the so-called Actuator-Sensor-Interface, or ASI, technology.

For dedicated bikers, few names evoke as many feelings of reverence as that of Triumph. As a consequence, the liquidation of the Meriden factory in 1983, which followed on from the loss of the rest of the British motorcycle industry, still arouses some bitterness from its devotees. Fortunately, however, the name of Triumph has been restored in the world’s motorcycle industry and the company appears to be thriving.

Following the liquidation of the original company, Triumph undertook a complete assessment of the current motorcycle market, including a detailed evaluation of competitive products. They then set about designing and building a prototype bike which, in 1991, went into production at a new factory that had been opened up at Hinckley, near Leicester.

During the first year of manufacture, the company produced 2500 bikes in a range of six models embracing three well-known names: Trident 900 cc & 750 cc, Trophy 1200 cc & 900 cc, and Daytona 1000 cc & 750 cc. Other versions with different capacities were brought out in January 1993, together with a new Tiger model. The year after that, these were followed by a new bike resurrecting the name of the classic Thunderbird. The new T509 Speed Triple and Daytona T595 were recently announced for 1997 and, currently, some 15,000 bikes are being produced per year. The progress of Triumph over this short period has prompted the development of a new, much larger, factory at a nearby site to accomodate increased production.

Prior to the introduction of the automatic assembly system into the existing manufacturing processes, sintered steel bushes used as guides and seats for the inlet and exhaust valves on all models were manually hammered into the aluminium cylinder head after having been previously cooled to cryogenic temperatures. Not only was this method very labour intensive, it was also costing the company around £400 per week just for liquid nitrogen.

The new system is more cost effective. Using it, an operator simply fits each of the cylinder heads individually to a trunnion-type mounting table at the initial loading station and pushes a `start’ button. The trunnion then passes automatically through a combination of assembly stations arranged in two pairs. The first pair of stations fits the inlet guides and the inlet seats, after which the trunnion is tilted through the angle defined between the inlet and exhaust valves and continues its travel to the second pair of assembly stations. The use of the tilting mechanism allows the exhaust guides and seats to be fitted to the head in the same plane as that used for the inlet ports.

A row of four vibratory bowl feeders containing the guides and seats is mounted on an elevated platform above the machine. From there, the components are delivered, via a system of component chutes and orientation devices, to four magazines located at the point of assembly. They finally emerge from the feed system and are held in a horizontal position in the appropriate magazine directly opposite the valve port into which they are to be rammed.

In this way, each of the four assembly stations becomes dedicated, respectively, to inlet guides, inlet seats, exhaust guides and exhaust seats. The trunnion travels along the line to fit the bushes to each port in the cylinder head in sequence.

The cylinder heads are all of 4-valve configuration and designed on similar lines whether they are for 3-piston or 4-piston engines. As such, they can all be attached to the same trunnion using common location pins and the four hydraulically-actuated automatic clamps for fixturing.

To detect the type of head which has been attached, a proximity sensor has been mounted in the face of the trunnion and the appropriate signal is sent to a PLC. If a 3-cylinder head is being assembled, the controller ensures that the last insertion stage for both pairs of inlet and exhaust valves is bypassed.

The fact that the sintered components were to be forced into bores in the aluminium heads with 50 micron interference fit without the use of cryogenics meant a slight adjustment to the geometry to facilitate automatic assembly. It was found that, as the bushes were being inserted into the aluminium, the square corners on the mating circumferences were throwing up burrs on the faces of the bores and making penetration impossible without causing damage. However, this was easily rectified by the application of a simple 3 mm blend radius on this feature.

Before it is inserted, each guide or seat has to be orientated to align with its mating bore in the cylinder head. This is performed by an arrangement of chutes and guides before the component reaches its final location in the magazine between the insertion ram and the cylinder head. The various changes of direction of the bush as it passes through the feed system are controlled by escapement mechanisms which are actuated by a series of pneumatic cylinders supplied by Festo. At each stage, the position of the bush is monitored by a proximity sensor to ensure that it is actually present and of correct orientation. A 1/2 tonne hydraulic ram is used to apply the force required to insert the seats while a 1 tonne ram is used for the guides.

The trunnion is mounted on a rotary shaft and carried on a saddle which travels along the line of assembly stations by the action of a lead screw under precise position control from a Mitsubishi A1J programmable logic controller. Tilting of the trunnion is effected by means of a hydraulic cylinder and its rotary movement is monitored with aid of two limit switches. The amount of travel between each station, and the point at which the trunnion’s angle is readjusted to align with the exhaust ports in the cylinder head, are pre-set in the control system.

The data link from the PLC to the sensors and actuators is provided via an Ecosys ASI bus system supplied by ifm Electronics. Use of this has enabled Triumph to considerably reduce the amount of wiring in the assembly system. This not only saves on build-time but also simplifies construction of the ladder diagram for programming the sequence of movements. As a result, it has been estimated as taking between 4 and 5 weeks to complete the wiring for the whole machine, whereas it probably would have taken at least 15 weeks using conventional methods.

The main reason for the difference lies in the design of the ASI system itself. Instead of using conventional parallel wiring from the sensors and actuators back to the PLC, it uses a 2-core serial communications link. The cable costs little more than £1/metre, as opposed to approximately £35-40/metre for multicore cable which would have been necessary if a more conventional parallel bus system had been used.

The cable has been designed specifically for use with ASI and makes use of isolation displacement technology (IDT). It comprises two cores embedded in an insulating sheath – normally yellow – with a cross-section in the form of a shallow `T’. The various slave and master modules that have been designed for use with the ASI system incorporate a slot in order to accommodate the special T-section of the cable.

Located within the slot are two sharpened pins, sometimes referred to as vampire teeth. To make a connection, the cable is simply laid inside the slot and the cover is attached. As it is screwed down, the pins penetrate the insulation to make sound electrical contact with the cores. When the cable is removed, the punctures caused by the pins self-heal and the module can be reconnected to a different point in the communications link.

The cables are able to transmit up to 124 inputs and 124 outputs within the ASI system, as well as carrying the power supplies to the slave modules mounted on the assembly machine and to the sensors. The DSNU pneumatic cylinders used to actuate the escapement mechanisms are controlled by a Festo valve terminal which contains its own solenoid valves together with an ASI interface. These modules are also included in the control bus.

The whole system is controlled by a master module which provides facilities for connecting up to 124 conventional sensors or actuators and contains the necessary circuits to send or receive signals in ASI format via the 2-core cable. In practice, by sending out a 16-bit message – which includes the slave’s address – communication takes place between the master module and each slave in turn, once every 5 msecs. If an actuator is involved, the message also includes instructions to turn it `on’ or `off’. The slaves reply with an 8-bit message which, in the case of sensors, indicates their status.

The master module is also able to convert ASI signals into a format that can be used by the control system. In the Triumph assembly machine, as well as being directly connected to all the slave modules by the ASI cable, it is also connected to the Mitsubishi PLC via an RS232C coupler. As far as the PLC is concerned, the signals look just like conventional inputs and outputs so there is no need to make any allowances when writing the control programmes. What is more, the need for the normal I/O rack is virtually eliminated. However, since the PLC selected does not support the ASI system, ifm Electronics had to write a special protocol so that it could properly interface with the Triumph control system.

The new assembly machine came on line in July 1996 and, partly as a consequence of using ASI technology, it was designed and built in only about nine months. It was developed to accommodate the cylinder heads of all currently manufactured Triumph models with the exception of the T595. In this case, the guides and seats are both larger and of slightly different shape, so a new simplified version of the machine, based on the existing one, is now under development. According to Triumph, this will be on line later this year.

{{Triumph MotorcyclesTel: Hinckley (01455) 251700Enter 470

FestoTel: Fleet (01252) 775000Enter 471

MitsubishiTel: Hatfield (01707) 276100Enter 472