Edited by: Mike Santora • Contributing Editor
As a manufacturer of flexible machines for high-quality Printed Circuit Board (PCB) rework/repair, Air-Vac has addressed the issue of adhering to the International Electronics Manufacturing Initiative 2013 Technology Roadmap requiring lead-free rework of plated-through-hole (PTH) components on large, high thermal mass assemblies. The company’s PCBRM100 was specifically designed to remove, site clean and replace through hole components from large boards (26 x 26 in.).
The PCBRM100 incorporates the EZSV17 servo motion controller designed and manufactured by AllMotion. The EZSV17 measures only 1.6 x 1.6 in. and requires little to no tuning when used with most motors measuring less than 2-in. in diameter. It was designed to allow the rapid implementation of brushless dc motors or brushed dc motors in automation systems. The motion system for the PCBRM100 also includes several linear encoders operating with rotary motors that are switched back and forth between being belt driven and used in a direct drive operation. Linear motors would have been too expensive for such a large system.
When asked about the most important features, Air-Vac’s design team said price and reliability.
“We’ve used the EZSV17 on other products for years and have had absolutely no issues with the controllers. They perform just as their specifications guarantee,” said Joe Koutrakos, engineering team leader for Air-Vac.
Other key features of the controllers that Joe mentioned included the 485 communications capability at 115,200 baud, which helped to increase the speed of operations; software flexibility that allows the machine to send a command and get it instantly executed; and the use of a direct drive joystick control, which allowed easy operator interaction with the machine. Additional features of the controllers include a single 4-wire bus that can link up to 16 stepper/servomotors; a 2 A motor driver; operating voltages from 20 to 40 V, RS232, RS485, or USB based communications; on-board EEPROM for user program storage; and stand-alone operation.
The PCBRM100 is totally automatic. A carrier is programmed through the EZSV17 controller along X and Y axes through the use of linear encoder feedback for accuracy and repeatability. It moves to a taught position where a down-looking digital camera with zoom lens relays an image to the operator. The camera superimposes the image of the solder stack over the top of the board. At this point, the operator can align the part using an X-Y joystick-based control. The desired rework position can be taught on-the-fly or stored in the program. After alignment is completed, the board moves into the oven where it is heated using focused convective heating to about 150° C. Once the board reaches temperature, it comes out of the oven and returns to the previously taught aligned position where it is then lowered to 15 mm above the flowing solder. At this time, an additional nozzle is lowered to 5 mm above the part, as well. The part is now heated to 217° C and lowered into the solder for removal.
Once inside the solder flow, either a vacuum is turned on and the upper nozzle removes the loosened component or the operator manually removes the part. After the part is extracted, the board moves to 25 mm above the solder flow for solder removal. A solder scavenger nozzle is installed and lowered back to the top of the board for this purpose. Using the joystick control, an operator moves the nozzle over the barrels of the board to remove any solder left in the barrels. This process can also be automated where the machine can perform the removal with no operator interaction. Finally, the board returns to the unload position for removal. The board can now have a new component inserted and the machine can be used once again—this time to solder in the new component.
The machine has an accuracy of 0.001-in. Because the PCBRM100 is an open machine, the speed of operation doesn’t have to be fast in most cases. The joystick control does offer the operator a very accurate and easy to use interface to the machine. In addition, the software used with the machine is user-friendly for the operators. Originally, the engineer in charge of first programming the machine performs the majority of the work needed for operation. This includes the setup of part locations, board thicknesses, part thicknesses and other key data based on the particular board being worked on. Once the initial setup is complete on a particular component, it can easily be copied and pasted to similar parts or boards.
The machine itself is 120-in. long, 52-in. wide and 77-in. high. Its solder pot capacity is 90 lb, the top and bottom preheater sizes are 28 x 28 in., with a clearance of 3 in. on the top and bottom. The system also has eight thermocouple channels.
Filed Under: TECHNOLOGIES + PRODUCTS, Encoders • linear, Motion control • motor controls
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