For the assembly and testing of proportional solenoids, 50 individual processes had to be brought together in a single system. Linked rotary indexing tables would have compromised accessibility and the cycle rate of conventional linear transfer systems was too low. As a “straight rotary indexing table” the LS280 linear assembly system from WEISS offers fast and precise positioning and access to the workpiece carriers from above and below.
A 35-metre line for a couple of millimetres of extra stroke – this would be the brief description of the special machine for assembling proportional solenoids, as Stefan Schnurrenberger, Managing Director and Technical Director at Gluth System – technik, explains. Even the fact that it is possible to hold a relaxed conversation in front of the machine is just one of the many reasons why Schnurrenberger and his colleagues opted for the LS280 linear assembly system from WEISS as the backbone of their machine:
“Thanks to its special design, the linear assembly system from WEISS is far quieter than comparable systems. It also has lower wear and energy consumption.”
To be precise, this “special design” is not actually so special for WEISS. When it became necessary to
develop a linear system over ten years ago, the engineers in Buchen thought back to the strengths of
their most successful product: the rotary indexing table. Its cam drive is well-known for enabling low cycle times, the greatest precision and gentle, jolt-free movement. So why not use the same technology for a linear transfer system?
The LS280 thus came into being, an “opened-up rotary indexing table” with a classical belt system for transporting the workpiece carriers from one process to the next and cam drives on the processing stations for fast and precise positioning. Thanks to the transport cam at the decisive position there is no need to stop and lift out the workpiece carriers – a highly- time and energy-consuming
process that generally requires expensive compressed air and causes a lot of jolting.
QUIET AND PRECISE
The resulting quiet operation allows Schnurrenberger to explain the details while standing immediately in front of the machine:
“We assemble proportional solenoids here, such as those used in electro-hydraulic control blocks for transmissions. The system consists of three blocks of four modules each, which in turn bring together up to three assembly or testing processes. There are buffer sections between the blocks.”
Of course, the modular design of the LS280 linear assembly system would have enabled a continuous, 35-meter-long line, which is not practical, however, without buffer sections a single malfunctioning process would bring the entire system to a standstill. Moreover, a split production line is more flexible and can be installed around a corner if necessary.
A high degree of flexibility was certainly required when developing the system. The main customer of Gluth is the automotive industry, for which the innovative system integrator in the Lower Bavarian town of Straubing offers modular automation and testing technology. Automobile manufacturers are not only known for their great diversity of variants, but also for the stringent demands they place on their suppliers. And this case was no different:
“On top of the large number of product variants, for this system we also had a very short implementation time of only ten months,”
remembers Schnurrenberger,
“so we had to place our trust in a functionally tested and reliable basic system.”
After they decided against rotary indexing tables due to access problems and classical belt systems because of the long workpiece changing times, the company examined the innovative linear assembly system from WEISS. For Schnurrenberger this was no coincidence:
“Whether rotary indexing tables or handling modules – WEISS is our first choice for tasks that demand high precision and reliability.”
It quickly became clear that the LS280 meets all requirements while also – literally – leaving
room for the required flexibility and the unpredictable factors that are unavoidable with such a short design and construction period.
For example, the workpiece carriers of the LS280 are easily accessible both from above and below – a real bonus with the multitude of different assembly and testing steps required to make a functioning proportional solenoid out of a housing, contacts, magnet, rod and end plates.
“It also made it possible to consistently separate feeding and operation,”
adds Schnurrenberger with pride. Indeed, the individual parts are fed in and the finished proportional solenoids removed solely at the back of the system, which leaves room for operation on the front side and makes it easier to access the system for changeovers.
When changing variants, this can take place in a record time of just 12 minutes thanks to the generous use of AnyFeeders in combination with the system’s easy accessibility. For the combination of vibrating plate, image processing and robots, only the grippers and program need to be changed during changeovers.
FAST AND CONVENIENT
Speed is of course key for a mass-produced article and here, too, the linear assembly system from Buchen provides the scope needed. Because starting up, slowing down and pre- cise positioning are a single, cam-controlled process, the workpiece holder changing time of the LS280 is a mere 0.6 seconds. This corresponds to a gain of up to a second compared to conventional systems with indexing, which can then be used either for the process itself or for a reduction of the cycle time – or both.
After all, in contrast to its cousin, the rotary indexing table, the LS280 allows several indexing pitches to be combined within a single system. For example, a 280 mm basic stroke and a 500 mm double stroke. By skillfully arranging the parallel processes, the engineers in Straubing were thus able to decouple the different process times and achieve a cycle time for the whole system of just 3.5 seconds, to the great satisfaction of the end customer.
To ensure that the total of 50 processes do not drift out of sync with these short changing times, a lot of effort has to go into controlling the system. The customer’s main computer communicates with nine control elements – one for each system module – which in turn control the conveyors, grippers and inspection sensors of the individual processing stations.
The LS280 from WEISS also needs little attention from the operator:
“The linear assembly system merely needs a handshake, that’s all we have to do”,
explains a clearly happy Schnurrenberger.
Thanks to the cam drive, the optimum ramps are specified and, after the start/stop command, the linear assembly system fulfills its task completely autonomously without further burdening the higher-level control system – plug and produce in its purest form. For Stefan Schnurrenberger this is yet another reason to employ the LS280 even more in the future. The current system for assembling proportional solenoids is already the second of its kind, and additional long, quiet and powerful lines are sure to follow.