Authored By:
Scott Zerkle, Makoto Murakami
Yamaha Motor IM America, Inc., Kennesaw, GA USA
Summary
Today's robots can solve these manufacturing issues, allowing for more productive and efficient lines.
In addition, the robots themselves are more cost effective than the ongoing costs of human labor. The cost of a robot is normally a capital investment that is analyzed by management for Return on Investment (ROI). To do this, you must look at the overall cost of the operator, their production speed, and any quality deficiencies.
The purchase of a robot is normally a 3 to 5 year payoff, after which the expense is reduced to maintenance and utilities. A robot that matches the cycle time of the manual operation will most certainly surpass a human in efficiency over time. Robots are mechanical machines that are computer or PLC (Programmable Logic Controller) controlled. Calibration routines allow them to be tuned for accuracy and they are sold based on the repeatability. Properly maintained robots will run processes they are designed to perform for thousands of hours without any change in accuracy or cycle time changes.
When a process requires vision, robots use camera systems that are far beyond the capabilities of the human eye and can ensure better accuracy and quality. The majority of SMT machines in the market today are designed to pick and place from tape, tray, and sticks. There are also parts without packaging that must be part of the line's process. Robots can handle these unique placements far more efficiently than an operator working on his own.
These components without packaging can be placed on a pallet. The robot then brings in the pallet and finds the parts that can be placed, using a camera system. The robot then picks and places all possible parts. Afterward, the operator can shuffle or rearrange any parts left and retry. This eliminates the costly attempts to design packaging and feeding mechanisms for these parts. Some parts are presented for placement with leads parallel to the PCB surface rather than perpendicular. This poses a problem for the standard SMT machine's capability. This problem is easily overcome using a robot with a swing nozzle.
The swing nozzle can pick a component and then swing the leads up to ninety degrees to make them perpendicular with the PCB for placement. This eliminates the need for an operator at a hand placing station or expensive repackaging of the part. Stick feeding is common for SMT but large or unique components in stick have often required expensive and one off designs.
Since robots have started to be used in the SMT process stick feeders that allow for the stick handling portion to be adjustable and only the actual component track to be customized have been developed. These stick feeders are less expensive and make it more possible for PCB manufactures to handle a larger range of stick components. SMT machines are built for speed and accuracy. With that in mind, the SMT machines typically have height restrictions as well as only moving in X, Y, R, and Z. A robot on the other hand, can have less height restrictions and more moving axis.
With the added height those tall or overly large parts can now be placed. Additional axes allow robots to do more than pick and place. Robots can pick up screws from a feeder and torque the screw into position; they can assemble cases in final assembly areas. Another solution robots in SMT have brought about is finding lead tips of Plated Through-Hole (PTH) parts, which typically give SMT machines difficulty with vision. New camera technology now can find the lead tips of PTH parts significant distances from the component body, allowing insertion without damage to the leads.
Conclusions
SMT machines are robots, but normally with a very specific set of specifications, allowing the machine to be fast enough for SMT production. These specifications keep SMT robots from being able to do the "out of spec" processes.
The robots that have been discussed are robots that have very large component range, specialized software that allow them to be used for hybrid uses and many variable component inputs. Robots have shown the ability to increase production and increase quality of many processes; still human operators will be needed to supply the components to the robot.
Robots have a place in SMT production and with increased capabilities being innovated; many companies can begin to see the reduction in overhead costs, the increased production, and the increase in quality. Robots have a "correct" place in SMT.
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