Power Transmission and Motion Control

Technology Focus part 2


Motion Processor Boosts Wafer Throughput
by John DeGaspari		 Delicate silicon wafer handling that is performed during the semiconductor manufacturing pro-cess necessitates that equipment used to handle these wafers be fast and very precise—typically down to the submicrometer level or less. These were the primary requirements by Eaton Corp.'s Implant Systems division of Beverly, Mass., in selecting a motion processor to handle silicon wafers in its medium and high current ion implanters. The processor chosen for the task—the MC1401A motion processor, supplied by Performance Motion Devices, Inc. of Lexington, Mass.—provides S-curve motion profile capability, reducing cycle times for certain moves by as much as 20 percent. The processor is a programmable chipset, available in one-, two-, or four-axis configuration that performs complete motion sequences, according to PMD. It consists of a processor for profile and PID calculations, as well as a logic device to handle motor-specific functions such as encoder feedback.

Eaton Corp.'s Implant Systems division has achieved higher throughput of its silicon wafer handling with PMD's MC1401A motion processor in a three-axis motion controller.

Eaton has integrated PMD's processor into a small, three-axis motion controller called the Micro3, which is used in the company's newest 300-mm medium current ion implanter, the MC3. The Micro3 motion controller is designed to control low current dc brush-type motors and associated sensors and actuators. It will be used in several different applications, including a wafer aligner and energy analysis slit controller, transfer arm, load lock, and extraction manipulator controllers.

Prices of the MC1401A motion controller range from $57 for the single-axis version to $99 for the four-axis version in OEM quantities.

One-Card Robotic Controller
by Greg Paula		 EuroServo, a three-axis servo module from Baldor Optimized Control in Fort Smith, Ark., is providing Automated Assemblies Inc. in Clinton, Mass., with a motion controller for its new low-cost robot, Optimum. The robot is designed to remove plastic parts after they have been created with an injection-molding process so that they can be moved to an unload station and stacked or palletized. The controller replaces a programmable logic controller (PLC) that was used on earlier entry-level robots.

A key goal for Automated Assemblies was to produce a low-cost robot with a teach-and-replay capability, which enables users to program new parts-removal tasks in minutes. EuroServo's built-in programming language, MINT (for motion intelligence), makes this possible. MINT is a language similar to Basic with motion-embedded commands, such as accelerate, decelerate, and contour. It can also store and replay movement sequences in an array.

Furthermore, because EuroServo's onboard MINT interpreter enables instant testing of motion programs, product optimization can be performed quickly. According to the robot's designers, programming the same functions using a PLC would take far longer. Automated Assemblies developed the motion software for the robot in less than 10 weeks.

The company also used two of Baldor's add-on modules to provide a complete off-the-shelf control system. A 24-channel digital module handles all the robot's gripper status, end stop, safety interlock, and other I/O signals. The company's low-cost operator panel, with its numeric keypad, four-line display, and programmable keys, provides an intrinsically simple-to-use man-machine interface for the kind of factory environments in which Optimum will be installed. It is capable of unload cycles upward of 7 or 8 seconds.

Rip Detection System
by Jennifer Hughes		 The Bridger Coal Co., in Point of Rocks, Wyo., recently managed to save its 15,000-foot, 42-inch-wide conveyor belt when a chunk of metal began tearing it in half, thanks to an advanced rip-detection system marketed by Goodyear Engineered Products.

Goodyear's Sensor Guard 2000 system limited damage by sensing a tear and stopping the Bridger Coal Co.'s 15,000-foot conveyor belt.

In 1996, Bridger Coal upgraded its three conveyor belts, including a main conveyor line spanning more than two miles to the power plant, which transport coal overland 7,500 feet. The company had used Goodyear Flexsteel belts containing a first-generation rip-protection system and changed to Goodyear Sensor Guard 2000.

"Belts are critical for our conveying system sending coal exclusively to the Jim Bridger Power Plant adjacent to our site," said Mike Castleberry, conveyor supervisor at Bridger Coal. "With a 13-mile-long active pit producing 30,000 tons of coal daily, our customer and our operation can't afford lengthy belt downtime."

According to Castleberry, the tear occurred when a jagged end of a metal signpost punctured the belt and began "ripping it into what could have been two extremely long, narrow strips of conveyor belting."

The Sensor Guard 2000 detected the rip and shut down the conveyor system. The belt, carried by momentum and the weight of the material being transported, coasted to a stop with only 117 feet torn.

The system uses a computer to monitor embedded sensors that detect tears in a belt and protect against costly downtime. Active sensor loops pass by detectors and transmit pulses to an electronic monitoring system. A damaged loop automatically shuts down the conveyor belt.

Torn belts are fixed by splicing in sections of stock belt, which contain no sensors. The newer Goodyear system is designed to keep more sensors available and working after a repair than the older system could.

Precision Motion Control at Lower Cost
by John DeGaspari		 Specifying high-performance motion control can be a challenge in extremely cost-sensitive applications. With that goal in mind, Galil Motion Control of Mountain View, Calif., has developed its new DMC-18X2 PCI bus motion controller, which retains many high-performance features at about half the cost of the company's fully loaded motion controller.

The new DMC-18X2 motion controller from Galil Motion Control is designed for high- performance, cost-sensitive applications.

The new controller drops some features—such as uncommitted analog inputs, a secondary FIFO, optoisolation, and auxiliary encoders—thus enabling it to eliminate a second 100-pin high-density connector, yet provides the same motion, memory, and speed performance as its high-end Optima model, according to Lisa Wade, vice president of sales and marketing. Standard high-performance features include program memory with multitasking, symbolic variables and arrays, uncommitted digital I/O, and control of both step and servo motors on any combination of axes.

In addition to lower cost, the new controller incorporates a PCI bus. Moishe Shloush, director of motion control R&D at Robotic Control Group of Oak Ridge, Tenn., which is conducting beta tests for the new card, says that, in general, a PCI bus offers faster communication between the computer and the motion control card, making it possible to send commands on the fly. This can be an advantage in complex programs, because it avoids filling up the buffer on the controller, he says.

The DMC 18X2 is available in one-, two-, three-, and four-axis versions. Modes of motion include linear and circular interpolation, contouring, and electronic gearing. Prices for the DMC1842 four-axis controller is $1,195 each sold individually and $795 in quantities of 100.

Quick-Release Belt Take-Ups Save Time
by John DeGaspari		 In manufacturing, time is money. However, Interstate Brands Corp., a bakery in St. Louis, was throwing some away every day, because the oil from its bread dough required daily washdowns and frequent maintenance checks of its conveyor lines. Oil-saturated belts can stretch on the plant's dough-divider inclined discharge conveyors, leading to tracking problems.

The Quick-Release Telescoper take-up reduces a 30-minute-plus washdown process to just a few minutes at Interstate Brand's St. Louis bakery.

Seeking a way to speed the process, Interstate worked with its belt supplier, Midwest Industrial Rubber Inc. of St. Louis, which recommended spring-compression quick-release take-ups to replace conventional screw-type devices. Quick Release Telescoper take-ups, supplied by Bryant Products Inc. of Ixonia, Wis., helped cut down on the time needed to slacken, then restore belt tension and tracking.

Midwest replaced the woven cotton-polyester belt with a thermoplastic belt, which provided higher flexibility for splice retention, better oil resistance, and no edge frame (fraying on the edges that can make the belt susceptible to contamination). The belt change and switch to quick- release take-ups have eliminated unscheduled interruptions and reduced sanitary shutdown time by more than 75 percent, according to Mark Lang, chief engineer of the bakery.

Reducing maintenance needs and the time needed to clean various components was a prime target for efficiency improvements. During a typical washdown, conveyor belts are slackened so that 100 percent of the belt's underside area can be cleaned or sterilized. Originally, the final washdown step required repositioning pulleys, refastening take-up devices, then tinkering and jogging to ensure proper belt tracking.

Now, the procedure has been simplified to releasing the take-up's toggle clamp, and moving the pulley back to slacken and prop up the belt to let sanitation personnel clean under it. Once the washdown is complete, belt props are removed, the pulley is moved into position, and the take-up is reclamped to its original position. The spring-loaded action of the take-up returns to the original tension and tracking setting, so there is no need for time-consuming tension and tracking adjustments, says Lang.

The key to the take-up's performance is an easy-to-operate, lock/ release pull-action toggle clamp, which eliminates the requirement for all pulley and belt tracking adjustment. With the Quick Release Telescoper, releasing the toggle clamp allows belt slack, but does not disturb the Telescoper's take-up position. After the washdown cycle is complete, relocking the clamp resets take-up and tracking to the previous position.


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