Precise and gentle pacemakers

Precise and gentle pacemakers

SCHUNK Intec Ltd.

Lantek Sheet Metal Solutions

Precise and gentle pacemakers

High-performance assembly systems for the electronics industry are considered trend indicators for assembly applications. In addition to traditional Pick & Place applications, they cover an ever-growing range of parts, ensure zero defect strategies, and in some cases even flexibly adapt to changes in demand without the need for user intervention. A high-speed application of the LEM for the production of electronic components highlights the potentials wherever they are hidden, and shows how the path to pneumatic-free applications can be paved.


"Our previous systems for producing these sensors achieve cycle times of around nine seconds. With the new system, we already achieve six seconds. For future generations, it will be as few as five", reports Frédéric Cattaneo, Team Leader for Systems Construction at LEM in Geneva. That's 44% more output – with seamless component monitoring and significantly higher flexibility compared to today.


Instead of one variant, the system can produce two different component variants without the need for manual intervention. Around 3 million components are expected to leave the automated system per year in the future in 24/7 operation. The market leader for solutions for measuring electrical parameters is systematically using the full potentials of assembly automation. In this connection process stability has top priority. New technologies are always used if they can be reliably controlled.


As is the case with all high-performance assembly systems, the considerations are focused on three key issues: the costs of procurement and operation, cycle time, and process stability. All three of these factors must be optimized simultaneously to ensure an effective and competitive assembly process. There are good reasons for the fact that LEM has recourse to the system program for the modular high-performance assembly from SCHUNK. The system program covers all conceivable requirements: gripping, rotating or translatory movements, pneumatic or electrical, modular or compact – over 10,000 application variants are possible, whereby a highly precise reproducibility is ensured at all times. It also includes the necessary peripherals, including standardized pillar assembly systems, adapter plates, and planning tools. Highly efficient Pick & Place units, cross slides, rotary gripping modules, gantry systems or complete functional modules can be built with a minimum of engineering and assembly effort.


Force control for bending and pressing in


The team at LEM painstakingly analyzes the offered advantages of the various components. While at a time-critical bending station and for grippers pneumatic components have been used until today, LEM has converted the force-controlled press-in operation onto the mechatronic SCHUNK PPU-E 15 Pick & Place unit. For the freely programmable pacemakers, position and speed can be flexibly varied. The unit gently moves into the appropriate tool, then bends and presses the elements with a precisely adjusted force, before the axis returns to its original position at maximum speed and places the part onto the pallet of the linear transport system.


The PPU-E, which is linearly directly driven and thus transmissionless, is currently the fastest Pick & Place unit on the market, whereby the size is specially tailored for use in electronics and small parts assembly. Due to a width of only 60 mm and a complete media feed via the back panel, it enables a particularly compact system design. For a complete cycle with a 145 mm horizontal and 45 mm vertical stroke, the productivity booster only needs 0.6 s for 1 kg additional mass and 2 x 50 ms gripping time. At its peak, the PPU-E 15 delivers a whopping 100 picks per minute. Such high numbers of cycles are not required at LEM. It much more depends on the smooth motion profile and the repeat accuracy of the axis, which is 0.01 mm. The smoother the movements of the individual handling systems, the lower the vibrations of the entire system. That's what LEM is all about. The smoother the movement curves, the more reliably the high quality of the electronic components is achieved. For example, the tolerance in the flatness of four bent contacts is just 0.015 mm. This is exactly why LEM uses the strengths of the SCHUNK PPU-E for. Instead of using a tolerance and wear-prone transmission of movement, the unit is moved by a wear-free direct drive. This minimizes the maintenance effort, increases the permanent repeat accuracy, and simplifies the individual programming. To increase process stability, both horizontal and vertical motions can be monitored with an absolute path measuring system.


Air-sprung test station


LEM goes a step further with two test stations for optical inspection of the components: "Here we need speed combined with a particularly gentle movement,"Frédéric Cattaneo explains. 2D and 3D cameras capture the components highly accurately on all sides, measure the contacts and check the evenness of the previously bent elements. If the vibrations are too great, the quality check with the vision sensor fails. "In order to prevent vibrations, we opted for SCHUNK linear axes with servo-electric direct drives, which move both dynamically and very gently," emphasizes the experienced plant engineer. "In addition, the entire unit can be decoupled from the micro-vibrations of the environment by means of an air spring element at the moment of the measurement, so that a highly precise 3D measurement is possible." In addition to the optical test, the insulation is tested at other stations and the components are calibrated.


Linear motor axes allow gentle movement


The LDx series is regarded as a benchmark in the field of high-speed assembly. High-performance servomotors achieve particularly high outputs in a compact space. Almost all modules of the LDx series are already available as standard with absolute-value transducers, which ensure a repeat accuracy of 0.01 mm per axis. They eliminate the need for expensive reference runs when the system boots up and after emergency stops. In addition, the modules need neither end nor reference sensors, reducing the investment costs, programming effort, and the number of cables in the cable set. Since several freely programmable slides can be placed on one guiding profile if required, particularly compact and cost-efficient concepts can be implemented. The driving force is transmitted directly onto the slide by high-precision drive elements, free from play, without mechanical transmission elements. This results in short cycle times, maximum precision, and permanently high process reliability. Since the modules have almost no wearing parts, unplanned downtime and maintenance costs are reduced to almost zero.


LEM uses two module variants for its application: The SCHUNK LDN is equipped with an X profile and achieves a maximum drive force of 250 N, and a maximum nominal force of 120 N in the basic version. The SCHUNK LDH, on the other hand, is a compact Z-axis, which is designed especially for precise movements or controlled press-in operations in high-speed assembly as well as in measurement and testing technology. It is impressive due to the fast response characteristics and high positioning accuracy. The maximum driving force is 125 N, the nominal force is 52 N. Optionally, the axis can be supplied with a pneumatically operated holding brake, by which the position of the axis is reliably maintained even in the event of an emergency stop. The axes are controlled with Bosch Rexroth IndraDrive controllers as standard. The modules are available with either an incremental path measuring system (1Vpp interface) or with an absolute path measuring system (optionally with the Hiperface, SSI or DRIVE-CliQ interfaces). Due to these combination possibilities, the modules are compatible with different controllers and can thus can be quickly and easily integrated into higher-level controllers.


Pneumatic-free systems as a goal


From the point of view of Frédéric Cattaneo, the trend at LEM is clearly towards pneumatic systems. "In the future, we will mainly build electrical systems with electric grippers, electric linear modules, and electric rotary modules. The current system is an intermediate step from pneumatics to fully electric machines. "The main reasons are the elimination of valves and hoses, reduced energy costs, cleanliness within the assembly process, and the significantly reduced vibrations, especially at high speeds. Instead of radically eliminating pneumatic modules, LEM prefers a gentle way to avoid overworking of the user, and to ensure maximum process reliability at all times: Step by step, individual modules are being replaced by mechatronic alternatives from the SCHUNK range. In the next step, the mechatronic SCHUNK EGP gripper for small components will take over the tasks of the tried-and-tested pneumatic SCHUNK MPG-plus.


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