When Henry Ford installed the first “moving assembly line” in 1913, he increased the production of his cars eightfold – a quantum leap in production efficiency. This allowed him not only to drastically reduce the price of his Model-T but also to increase his workers’ wages. It’s no surprise that this success was soon copied. Even today, countless products are produced according to the assembly line principle.
It is, however, less suited for small series and not at all for individualised, automatic production. But this is one of the goals of Industry 4.0 and the Industrial Internet of Things (IIoT): Individual products should be designed and equipped according to customer requirements – with the highest possible level of automation. This requires flexibility in the processes that is not very compatible with the permanently installed path of a conveyor belt.
Components take a taxi
With the Prolynk technology, the configuration of the "assembly line” can be freely adapted or reconfigured, following changing requirements. The components no longer travel on a predetermined path, but instead take a taxi in the form of a small driverless transport unit (automated guided vehicle, AGV): "The part to be processed is thereby reliably transported to all required stations,” explains Antonio Sanchez, Chief Commercial Officer of Prolynk. "The processing steps, whether performed manually or by robots, can occur completely individually. Yet, the sequence is still automated.”
A platform made of standardised table-shaped modules serves as the physical basis of the system. It consists of standardised plates and can be designed freely with respect to size and shape. Simple metal plates form the base unit and serve as movement surface.
A variant of the base plate is equipped with fastening indexing units. For production steps that require high precision or for which a larger application of force needs to be compensated, they hold the vehicle and component in position. Here, the plate element also has an opening in the middle. This can be used to perform processing from below as well, as it corresponds exactly to the shape of the opening in the AGV.
Arbitrary sequence of the assembly stations
The Prolynk AGV is available in two sizes (325x230 and 450x350 millimetres); the maximum load is between 5 and 35 kilogrammes depending on the model. The component to be processed is secured for travel to the individual assembly stations via the opening in the middle. These stations can be freely attached, including manual jobs as well as tasks performed automatically by machines or robots , e.g., laser engraving, soldering, tightening of screws or performing test routines. If there is a quality problem, the vehicle can be sent to a specific station where this problem can be rectified.
“The central controller knows each AGV and its load,” explains Antonio Sanchez. “It knows which processing steps must be performed on a given part. Individual products can thereby be created in an automated process. While communicating with the Prolynk system, the PLC remains in control of all processes.” If the processing steps do not need to be performed in a certain order, there is an additional gain in efficiency: in this case, the AGV moves to a station that is currently free. There is less waiting time, utilisation increases. Another advantage of the system can be in the form of relief to the employees. Components no longer need to be moved between stations with muscle power. Constant lifting and setting down – movements with especially high risk of causing back pain – can be eliminated.
The Prolynk AGV is driven by two wheels, each of which is located in the middle of the long sides. The corners of the vehicle are supported by passive rollers. If the wheels move in opposite directions, the vehicle turns in place. This usually occurs in a 90-degree angle. It can thereby turn toward a station with a one quarter rotation or change back and forth between the parallel “lanes” on the table with two rotary movements. It should be noted that these lanes exist only virtually: The AGV remains in its lane as does a car even when there are no markings on the road.
High power and precise orientation
The vehicle receives its route guidance and driving instructions from the central controller via WLAN. It specifies the routes as well as the stations and decides which vehicle has the right of way in cases where the lanes intersect. The part taxis need only report their precise position in order for this traffic rule to function. The motion controllers of type MC 5004 P and encoders of the IE3-1024 series from FAULHABER play an important role here. They detect the rotation of the brushless motors of the BX4 series, which is used by the Prolynk electronic motherboard to do the odometry, calculate AGV position and manage motion control. The motor’s force is transferred to the drive belts of the wheels by planetary gearheads of the 32/3 design.
"If a company decides on the Prolynk solution, the small AGVs become the heart of a production process. They must, thus, function completely reliably and with a very low level of maintenance, over as long a time as possible, securing a low total cost of ownership” says Antonio Sanchez, explaining the priorities for selecting the AGV components. "With the drive unit, the quality of the products had top priority for us. FAULHABER can guarantee us not only the required quality, but the motors also offer additional advantages that are essential for our application. There is very little space in the vehicle. Even so, a great deal of motor power is needed to move what are often heavy parts at the required speed. With respect to the ratio between volume and torque, the BX4 series is a leader on the global market. This power density is a key factor in allowing us to offer our customers a solution that is as reliable as it is flexible.”
The combination of reliability and flexibility gives users of the Prolynk solution maximum flexibility in designing their production processes. They can theoretically get started with a small platform consisting of just a few plates and a single mini-AGV. The system can be freely expanded or reorganised, with high flexibility and machine adaptability. Smart functions are available and the Prolynk technology is easy to integrate into the PLC architecture. New products, new processes and technologies can also be easily integrated; the existing modules can be rearranged depending on circumstances. "There are no limits to the system's adaptability,” emphasises Antonio Sanchez. "The production capacity follows directly from the order situation.”
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