Publication date: 15 April 2010
The rumor that a ball screw drive is better than a belt drive, keeps for years, especially when it comes to SMD placement machines. Therefore, Essemtec's engineers have intensively tested these two drive systems, among others, in intensive practical tests, before they started to design the new Paraquda SMD pick and place.
But with the test results, the decision was easy: The main drive system of the machine shall be designed using a belt drive in combination with a real-time control system. The pick and place head shall be mounted on a H-portal, which gives the machine excellent static and dynamic properties.
Essemtec also did intensive basic and operational research for the optimal design of the placement head and the vision system, especially for vision lighting. For this development, boundary conditions were only customer's requirements and the state of the art of technologies.
Thanks to these freedoms, the Paraquda has become the most advanced and most modern placement system in the world. Most modern regarding the technical implementation, the software and operation, and also most advanced regarding the component spectrum and application range. The Paraquda is well prepared for today's and future electronics manufacturing.
It is clear, that a belt drive on its own does not make a viable drive system for an SMD pick and place machine. It also requires a high resolution measuring system and an extremely fast and reliable drive control system. However, a combination of the right components can form a drive system superior to a ball screw.
The benefits are in the higher maximum speed, the longer life time, lower cost and easier maintenance of the belt drive. With this drive type, the assembly head of the Paraquda can be positioned much faster and the throughput is higher. The mass of the head assembly is relatively high, as well as the acceleration forces that occur. With such strains, a belt shows significantly less wear out and is therefore more durable than a metal spindle. And: a belt can more easily be exchanged in the field. Thanks to the the field-proven belt drive system, Paraquda can mount faster, more reliably and at lower cost than other machines in its range.
The well-known disadvantage of the belt drive, the overshoot due to the belt elongation, can be reduced to an extent that it is meaningless even for the most precise applications. This is, the appropriate dimensioning of the belt and the use of a real-time control system. Therefore, the Paraquda features a high-speed bus and regulation system which can evaluate the current location values immediately and readjust the position without delay.
The placement head is mounted on an H-drive system. The X and Y axes are autonomous, which allows a dynamic travel path optimization. The Y-Axis is driven with AC servo motors on both sides, therefore mechanical transmission errors are completely avoided. For the exact positioning and parallelism linear measurement systems are used, which transmit the current position values without delay to the machine control system. The built-in linear scales have a resolution in the micrometer range, which allows Paraquda to place ultra-fine pitch and 01005-components.
The four placement axes of the pick and place head are arranged in a square. This arrangement was chosen because of two reasons: first, the Paraquda can always pick two components at the same time, regardless of whether the feeders are in front, rear, left or right. If the axes were arranged in a row, this would not be possible. The other reason is the speed increase over the vision system: The 2-megapixel camera can take a pictures of all four parts at once and the image processing (Cognex SMD-4) can operate in parallel.
The Parquda vision system has a very special lighting with three independent lighting levels. This overcomes the drawback of most other image processing systems: different components often require different lighting. Therefore, for four different components four different pictures would be needed. The special illumination of the Paraquda is optimized in a way, that different components are properly lighted and only one picture must be taken.
Each of the four placement spindles is independent of the others. Each has its own vertical and rotational drive. The latter sits directly on the rotation axis and is therefore precise and playfree. That is why each axis can place the complete component spectrum from the smallest of chips to large QFP and BGA. The optimization software that optimizes the assembly sequence and minimizes the travel path, therefore always can use four equivalent resources. The assembly machine is redundant, flexible and much faster than other four-spindle assembly machines.
Paraquda is the first machine that uses ePlace for operation and programming. ePlace is an intuitive, graphical user interface that provides a level of comfort heretofore unseen on a pick-and-place machine. ePlace makes operation secure, offers tool-tips and context-sensitive help, completes entries automatically, searches intelligently, and sorts lists usefully. In short, ePlace always reacts the way the user expects it to and provides help when needed.
Above all, ePlace makes controlling a complex machine an easy task. Because not every operator speaks English and a staff with language skills is expensive, the software uses graphical representations to create clarity, and when text is unavoidable, the support of multiple languages is prepared. Education lessons are integrated as well, allowing new staff to be trained quickly.
Working with ePlace on the Paraquda requires neither mouse nor keyboard ― the software is directly controlled via a 19" wide ergonomic touch screen. The screen can be adjusted vertically and angled into a position that is most convenient for the user. ePlace also supports users with unlimited zooming functionality and optimizes views for less scrolling and clicking.
Setup and placement errors must be avoided because they can lead to costly repairs or can turn a complete series into electronic waste. Therefore, ePlace gives Paraquda a quality and job management system that controls the main source of error ― the human.
The base is a job management with archiving system on which other functions build up, such as a job planning module, a setup optimization routine, a setup list generator, component storage management and more.
For feeder setup and retrofitting, a bar code reader is used, which is the safest and fastest way to assign a component to a feeder. Setup errors are excluded and the stock of available components is updated automatically.
The only error sources left are mislabelling or mix-up from the vendor because most of the SMD components look very much the same. However, the Component Verification Unit (CVU) option provides protection against these errors. It checks the electrical values of a component before mounting, for example, the resistance, the capacity or the polarity.
The Paraquda is four machines in one: a chip placer, a fine-pitch placer, a special component placer and a dispensing machine. In addition to the SMD mounting head, up to two dispensing valves can be integrated. Those can be used to dispense solder paste, adhesives, flux or other liquids. Dispensing of lines, curves or dots is possible. With this, a Paraquda can also be a die bonder, an IGBT assembly machine or it can be used for hybrid technologies.
The placement head is equipped with four axes, each one of them with its own vertical and rotation drive system and each can be controlled individually. The range of components that can be placed with this head is vast: It spans from 01005 resistors up to 100 mm square components. The maximum component height is specified with 25 mm, the minimum pitch with 0.3 mm.
To work flexibly with an SMD pick-and-place system, three things are required: A large feeder capacity, intelligent feeders that are automatically recognized and feeders that can be exchanged during production. Essemtec has more than 18 years of experience in the construction of highly flexible assembly systems. Therefore, the Paraquda offers these qualities.
Essemtec always has built the narrowest SMD feeders in the world ― thanks to Swiss watch technology ― and these are used on the Paraquda, too. They are the same feeders as on the FLX pick-and-place systems. Therefore, a customer can easily switch to the faster Paraquda, whose feeder capacity is also higher: 240 feeder slots are available on a standalone machine, 120 to 200 on an in-line model, depending on the PCB width.
The large feeder capacity handles fixed feeder sets that allow the production of several jobs without the requirement for feeder changeover at all. Additionally, it produces PCBs with very high complexity, where on other machines at least two or more passes would be necessary.
As previously mentioned, Essemtec feeders are intelligent. They are recognized automatically by the Paraquda and they can be retrofitted while the machine is running. This shortens the changeover effort, reduces standing time between two jobs to almost nothing and increases the system’s utilization rate. Therefore, the Paraquda can generate significant savings in setup costs, an important contribution to the reduction of manufacturing costs.
The Paraquda is available in two models, a standalone and an in-line system with SMEMA interface, which enables an easy connection to other in-line machines. Essemtec also provides all other machines required for functional SMT assembly from one source, such as printers, dispensers, soldering and curing ovens, handling modules, storage systems and software for production planning.
The Swiss machine manufacturer Essemtec is a market leader in manufacturing flexible production systems for industrial users. Essemtec has been developing, manufacturing and marketing Swiss quality equipment and machines for the electronics industry since 1991. Today, the company’s well-developed network of partners and subsidiaries provide expertise and high-quality support worldwide.
With the Paraquda, Essemtec introduces a new product destined to become a leading position in the pick-and-place market. The technologies developed for this machine such as the ePlace user interface, the high-speed vision system or the new damping materials are used for the first time in pick-and-place machines and are trendsetting.
For More Information, Please Visit www.essemtec.com
