As machines for the semiconductor industry operate with cycle times of one second or less, pick-and-place units must offer very high dynamic performance. A case in point can be seen at a manufacturer of chip-mounting systems, where NSK recommended a combination of its ball screw and miniature linear guide technologies to replace the existing linear motor and significantly increase dynamic capability. Assembly machines in the semiconductor industry put high demands on pick-and-place units.
With regard to the process, the pick-and-place unit of the assembly machine grips a semiconductor chip and inserts it inside a package. During this operation, the facilitating 40 mm stroke is executed at a speed of 2.5 m/sec.
The linear motor used previously was performing this task at the limit of its capability, which prompted the OEM to approach NSK for an alternative solution. After a comprehensive assessment of the application, NSK´s engineers proposed the use of a BSS Series ball screw in combination with PU Series miniature linear guides.
NSK´s PU miniature linear guides are purpose-designed for demanding applications such as those found in semiconductor manufacturing equipment and medical devices. Smooth ball recirculation enables effortless motion, while an enhanced seal prevents friction dust from entering the surrounding environment. This makes PU miniature linear guides suitable for use in clean room applications with an appropriate lubricant.
Another advantage of the PU Series is low weight: the carriage is approximately 20% lighter than comparable systems on the market, which makes a considerable difference in highly dynamic applications. The drive unit of the pick-and-place system now weighs only 1 kg, while its operating speed is 2.5 m/s (with an acceleration of 40 g). In addition, it offers a 40 mm stroke and a maximum ball screw rotational speed of 5000 rpm.
Thanks to this high-performance capability, the NSK solution delivers much higher dynamics than the linear motor it replaced. Furthermore, the manufacturer of the chip mounting systems says it is fully satisfied with the reliability and lifespan of the PU Series miniature linear guide and BSS Series ball screw.
NSK Molded-Oil bearings extend service life in food plant conveyor application
A vegetable processing plant in Germany is enjoying significant benefits following the adoption of Molded-Oil bearings from NSK. Principally, the move has helped the company extend the service life of bearings on a critical conveyor from two weeks, to 40, saving considerable maintenance costs and downtime in the process.
Keen to resolve the question of why its previous bearings were failing at such an unusually fast rate, and eliminate the associated cost and time issues, the company asked NSK to investigate.
During the inspection, NSK experts soon determined the cause. Due to the rigorous hygiene standards demanded by food industry regulations, the system was cleaned thoroughly on a regular basis. However, it was found that the cleaning process prompted considerable quantities of water to penetrate the bearings and, as a result, wash away the lubricating grease.
To help combat the challenges presented by the frequently required wash cycles, NSK recommended the use of its sealed Molded-Oil bearings.
A special tribology concept (tribology is the science of wear, friction and lubrication) has been implemented for Molded-Oil bearings. For instance, the bearings are equipped with NSK’s proprietary oil-impregnated material, which comprises lubricating oil and an oil-related polyolefin resin. This material releases the lubricant, which cannot be washed out due to its consistency, continuously over a long period. At the same time, the carrier material prevents water or solid impurities from penetrating the bearing.
By adopting the bearings, service life at the plant has increased from two weeks to more than nine months. This highly successful outcome once again confirmed NSK’s ‘rule of thumb’ that Molded-Oil bearings achieve at least twice the service life of conventional grease-lubricated bearings in water and dust-contaminated environments. In this particular case, service life increased by a factor of 40.
The plant is also experiencing many other benefits. For instance, the operating environment remains clean because no grease escapes and no oil needs to be refilled. Molded-Oil bearings are therefore ideally suited to food industry applications, where thorough and frequent cleaning processes are essential. The use of stainless steel for the bearing components also contributes to this suitability.
NSK supplied the bearings for the vegetable processing plant with highly effective contact seals (DDU) on both sides for even higher levels of protection. This option is available for the standard range of Molded-Oil ball bearings. Molded-Oil is also available on spherical roller bearings and tapered roller bearings.
The special features of Molded-Oil bearings and other bearing series developed by NSK for applications in food processing are described in a new brochure, which is available as an e-book at www.nsk-literature.com.
Peening extends life
Freymatic is building shot peening plants for the construction of aircraft engines – and, to do this, it’s opting for Motion Control by KOLLMORGEN to achieve high quality requirements
The shot needs to hit accurately. This is the only way for their power to be optimally deployed. This power does not do any damage. In fact, with each hit it makes the target stronger, more solid and tougher. And this is why accuracy, air speed and the right quantity with the right measurements are so crucial. Freymatic AG from Switzerland builds shot peening systems which extend the life of heavy-duty components including those in aircraft technology. To do this, the process, similar to a blacksmith’s hammer, produces precise compression stress on the surface. Motion Control by Kollmorgen ensures that sufficient shot reaches the target – the single cable connection technology saves valuable installation time.
“When we have a breakdown, we can’t just pull over.” Those in the know describe in one sentence the safety thinking in aviation. Anyone with a broken drive shaft managing to end up relatively unscathed with their vehicle in a field or ditch would have much further to fall if they were in a similar disaster while in the air. In the face of the serious consequences of technical faults in civil aviation, all parts of an aircraft are supplied with an abundance of safety margins. One way to make heavy-duty components even tougher against the prevailing powers is using shot peening. This process is used mainly in the construction of engines.
A chain mail made of tension forces
Using pressure, the drag is able to resist a potent force. Figuratively speaking, components are placed into chain mail. The links in the chain mail consist of compression stress which the shot peen with their kinetic energy during impact with the atomic lattice. Fatigue damages only become clear later on. “Fissures in the material occur where tensile stress is prevalent,” explains Martin Hunziker, CEO of Freymatic. The connection between tensile forces and the formation of fissures is particularly critical in the construction of aircraft since it is here that lightweight construction is required. Despite their size, the blades in an engine need to be very light. This is why they are made of a titanium alloy. The next generation of engines will be even lighter – amongst other things due to the use of titanium-based compounds. But in automotive construction, too, the process is an established manufacturing practice – specifically where fatigue resistance is required.
When it comes to shot peening, manufacturers often use Roxor systems by the Swiss firm Freymatic AG. To do this, the system builders from Domat-Ems in the canton of Graubünden place an industrial robot into a hermetically sealed chamber and fully automatically equip its wrist with up to six different spray nozzles via a mechanical exchange during the machining job. While the robot takes on the motion control along the components being blasted inside the soundproofed chamber, the pressure supply and dosage unit remain outside.
The shot quantities can be selected anywhere between 1 and 10, thus achieving control deviations below three percent. This precision is necessary since it is not possible to carry out inline quality monitoring for shot peening – at least not without destroying the tool. The system operator must therefore be able to rely on the adherence to process parameters – which is why, in the field of servomotor driven dosage units, maximum precision and repeat accuracy is required. This range is achieved with a speed-controlled worm gear. The conveying screw is driven by synchronous servomotors from the KOLLMORGEN AKM series which in single cable connection technology are combined with their own AKD servo inverters.
The connection between the servo regulator and the servomotor using just one cable is also an advantage for this application since the systems can be wired up more quickly while also saving space. This is because the cable typically used for feedback signals is not required.
KOLLMORGEN opts here for a slender hybrid cable for motor and feedback.
What is special about it: The single cable connection technology works even without laborious and expensive multiturn encoders. The specialists in Motion Control and servo drive technology have developed the digital resolver SFD3 for this. The interface translates the analog data of the resolver into one digital signal which it then transfers via one cable to the regulators.
Tight tolerances in the dosage
Back to the peening system by Freymatic: In terms of construction, this consists of two pressure containers which act as a sluice between the unpressurized blasting shot store and the dosage which is under high pressure. The dosage powered by the AKM servomotors in the single-cable version represents a core function of the Roxor systems and, when operational, delivers shot quantities of between 0.1 and 12 kilograms per minute with an accuracy of +/- 5 percent. In the mixing tube and up to the spray nozzle, the shot is accelerated up to the exit speed. This speed forms the two significant process parameters and is indirectly regulated via the spray pressure in a tight window of tolerance. The pressure thus lies between one and seven bar.
Accompanying the high adjustment range in the drive control designed by TBM Automation is above all the challenge of being both delicate and fast. To do this, the drive axles regulate the speed of the dosing screw via the signals from throughput sensors. “If there is too much material, the speed drops and vice versa,” explains Silvester Tribus, managing director of TBM Automation AG. The company from Widnau, south of Lake Constance, has been working closely with Freymatic for some time already as a system integrator. The specialists in Motion Control and servo drive technology belong to the group of certified system and distribution partners of KOLLMORGEN with highly specialized engineering competence.
Precision from zero speed
To ensure that the adjustment is carried out swiftly and precisely, Urs Tobler, from the TBM management team and specializing in control technology in blasting systems, has equipped the Motion Control with a few special features. “After all, we want the system to start up quickly and need a correspondingly short amount of time until the quantity and pressure have precisely engaged.” Urs Tobler looks back to make a comparison with a time when dosage drives were still driven by DC motors which were hard to regulate, especially with small quantities, and only delivered reliable values in the upper speed range. With an additional linearization of the control performance with analog values, using the KOLLMORGEN AKMmotors, it has now been possible to “be precise even from zero speed upwards.” This control quality is said to make the process reliable across the entire adjustment range. This aspect is particularly relevant for shot peening since, after peening, it is not possible to carry out a quality analysis without damaging components.
Shot firing which is too low also results in poor values, following the motto “more is more”.
To determine where the optimum value lies, system operators can only do this with “Almen strips”, thus measuring the effect of the shot impact by the distortion of a standardized surface. The Almen values determined by the distortion of a metal measurement strip then provide conclusions as to the effectiveness of the process. This must later precisely and continuously follow the previously determined key values so that the desired effects of the compression stress is set. In a further consequence, this process only functions in conjunction with regular calibration.
The complex processes in the mechanical strengthening of metal components using shot peening shows what a significant role the precise and, above all, repeat accurate servo drive technology plays. The automation conceived by TBM Automation AG for Freymatic AG is also set up in a user-friendly way for the operator and offers a cleanly structured visualization.
Atlas Servo Amplifiers can now communicate with range of controllers
INMOCO the Daventry based specialist servo company has announced its ATLAS digital amplifiers can now be used with third party microprocessors or field programmable gate arrays (FPGAs) via Serial Peripheral Interface (SPI) communications. ATLAS digital amplifiers are made by Performance Motion Devices Inc, a leading US provider of innovative, high performance integrated circuits, boards and drive-based motion control solutions to OEMs around the globe.
Originally designed to be used in conjunction with Performance Motion Devices’ Magellan motion control ICs, ATLAS digital amplifiers can now also communicate through SPI with other controllers. This significantly increases the range of applications where ATLAS amplifiers can be deployed, and includes robotics, medical devices, laboratory equipment, scientific instruments, fan and pump control, precision motion and industrial motor control.
“The new controller options combined with the ATLAS amplifiers’ high power density, digital current loop, and IoT (Internet of Things) capability results in a powerful and flexible amplifier,” says Gerard Bush of INMOCO.
ATLAS digital amplifiers are compact single-axis modules that provide high-performance torque control of DC brush, brushless DC and step motors. Featuring the highest power density in the industry, ATLAS versions are available in 75W, 250W, and 500W power configurations in two module sizes: 27 x 27 x 13mm and 39 x 39 x 15mm.
For additional flexibility, ATLAS package options can be mounted to a printed circuit board in either vertical or horizontal configurations depending on application requirements and customer preference. ATLAS amplifiers integrate a field-oriented control (FOC) digital current loop, which enables finely-tuned motor current control and lower power consumption and noise.
“The amplifiers can record IoT information such as commanded current vs. actual current, temperature, bus voltage, etc, enabling host processor access to critical motion control parameters,” explains Gerard. This enables users to monitor system performance and proactively address problems before they arise.”
The amplifiers are powered from a single supply voltage, and provide automatic protection from overcurrent, under-voltage, over-voltage, over-temperature, and short circuit faults. Other advanced ATLAS features include; programmable gain parameters and performance trace.
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