Assembly In Action: Surface-Mount Machines Accommodate Odd-Forms
July 23, 2008
Danish pump manufacturer Grundfos Management (Bjerringbro, Denmark) produces approximately 10 million circulator, submersible and centrifugal pumps annually, for use in a wide range of applications.
Recently, the company created a new production line to build control electronics for its ALPHA2 circulation pump for household and light industrial heating. Among other things, the controllers continuously measure flow rates and then adjust power consumption accordingly to conserve energy. Despite the high cost of labor in Denmark, the company was able to retain production at home through the use automation.
Ultimately, the company implemented a dual-lane surface mount assembly line measuring 100 feet long and employing a trio of Polaris assembly machines from Unovis Solutions (Binghamton, NY). Each Polaris system includes a four-axis Cartesian gantry and can be easily adapted to perform a variety of tasks, including adhesive dispensing, vision inspection, screwdriving and packaging.
Operators are needed to load the system with round printed circuit boards and some 120 different electronic components. Otherwise, the system is fully automatic, assembling, testing and packaging a new board every 10 seconds.
Central to the success of the new line is the Polaris systems’ ability to successfully place several different types of odd-form components, including negative temperature coefficient thermistors (NTCs), varistors and a variety of oversized capacitors. The NTCs and varistors, in particular, are a challenge, because of their rounded shape, which makes it difficult for standard grippers to grasp and position them accurately. As a result, the first of the machines is equipped with a custom gripper and gripper fingers to overcome this difficulty.
The second of the three machines employs a standard servo-gripper to place a pair of large capacitors. The third machine is equipped with three separate grippers all placed in a single axis, which allows it to pick three different parts at the same time and then place them sequentially.
Initially, the Polaris systems were configured so that whenever an odd-form part failed to hit its intended placement hole, the machine would pick a second part after putting the first one in a scrap bin. However, while this proved effective in terms of quality, over time it would have wreaked havoc in terms of throughput, scrap rates and costs. In the words of Grundfos engineer Morten Leth Pedersen: “If every other component is scrapped, it gets quite expensive and slows down the line.”
To solve the problem, the three Polaris systems now employ a “retry” feature, which allows them to continue searching for the hole in the event a component doesn’t hit the target the first time. As a result, only those components that truly can’t be placed are scrapped.
For more on electronic and automated assembly, call 800-842-2878 or visit www.unovis-solutions.com.