Assembly in Action: CD and DVD Duplicators Benefit From Motion Control
Some people believe in love at first sight. Others are more skeptical, believing that true love takes time to grow and flourish.
John Klein, a design engineer with Amtren Corp.'s Optical Systems Group, falls into the first group. Once he and other representatives of Amtren (Montgomery, AL), a manufacturer of compact disk (CD) and digital video disk (DVD) systems, saw Kerk Motion Product's (Hollis, NH) ScrewRail, they realized that it could have a positive impact on the company's recording products.
Turning to Kerk was an easy decision, because the company was already in place as one of Amtren's primary vendors. In fact, Kerk had already been supplying conventional leadscrews and linear rails for Amtren's existing designs.
The quick adoption of the ScrewRail reaped some very quick rewards. "I'm convinced the ScrewRail has taken our product up a notch," says Klein. "We had other designs that performed the same basic function, but I'm certain they would not have had the consistency and smooth performance of the ScrewRail. Ultimately, we've been able to reduce the cost of the motion system by 40 to 50 percent over the cost of the alternate design."
What's most impressive about Amtren's rapid adoption of the ScrewRail technology is that it is used in one of the duplicator's most critical operations. The ScrewRail element is used in a vertical orientation on the duplicator's pick arm assembly.
The pick arm is the only moving component. It rotates into position, picks up a CD or DVD from a stack of blanks, rotates it into position, and drops it into the disk drive. It then picks up the CD or DVD out of the drive and rotates it to an output stack.
The ScrewRail combines drive, support and guidance functions into a single, compact, coaxial component. Its design eliminates the need for any external rail-to-screw alignment. It
also delivers 3D motion from a single unit, allowing it to simultaneously lift and rotate when mounted vertically, which is a crucial capability in Amtren's application.
The ScrewRails that Amtren uses are from the 4000 series. They feature TFE coating that increases lubricity and extends the normal nut life. It eliminates the need for external lubrication.
Besides providing Amtren with the ScrewRail, Kerk also undertook an extensive design effort, which led to a change in the structure of the gear that is also a part of the duplicator pick arm assembly. Amtren had been investigating designs to decrease cost and provide a better quality product, when the ScrewRail was introduced. Previously, Amtren had employed several different designs in this essential part of its CD and DVD duplicators, all of which, while serviceable, were more unwieldy and expensive than the company wanted. In the previous design, Amtren would purchase a machined gear, place it on the duplicator and put in the setscrews. Afterward, it would determine exactly where the flag needed to be, drill holes and align the entire assembly. It was a difficult and sometimes imprecise process.
Consequently, Kerk created a design for an injection-molded gear. The design incorporated features that align to the rail, and already includes the flag positioning. To mount the gears, engineers simply press them onto the rail, then snap a few parts into place. This has simplified the assembly process and eliminated alignment.
"Kerk worked very closely with us on the gear redesign," says Kirk Lamberth, president of Amtren. "They knew what we needed for the gear interface, and we knew what was required for the screw interface. Our collaboration created a gear that is a quantum improvement over the previous design."
The ScrewRail, along with its design capabilities, enabled the company to produce millions of CD or DVDs without any maintenance or adjustment.
For more information on screw rails, call 603-465-7227 or visit www.kerkmotion.com.