Authored by:
Brad Dixon
Gus Geil
Mike LeBlanc
Bob Martucci
Shawn Thompson

Applications Engineers
MicroMo Inc.
Clearwater, Fla.
Edited by Kenneth J. Korane
ken.korane@penton.com
Key points:
• Customized components can improve machine performance and streamline manufacturing.
• Skilled vendors can often modify standard products in days or weeks.
• Talk to a supplier’s engineers to get the most out of customization.
Resources:
The Machine Lab
MicroMo Inc.
ReconRobotics
Stratasys

In a perfect world, no matter the application, commercial off-the-shelf (COTS) components would provide the exact performance required and be just the right size and shape. In reality, almost every design involves trade-offs and compromise. Sometimes, the process is painless, requiring some give on low-priority parameters. Other times, the leap is simply too big. Projects can get sidetracked as designers surf from one Web site to another or call around for catalogs, desperately searching for products that are in the right ballpark. What’s often needed is customization.

Engineers involved with motion-control applications may not realize that the catalog is often only the start. Many suppliers customize offerings to suit specific needs, support R&D with design insights fueled by experience, and even help with troubleshooting. Partnering with knowledgeable vendors can improve the final product and speed commercialization. Here’s how.

Custom brings benefits
Customization sounds time consuming and expensive, but it doesn’t have to be. In the simplest form, customization involves a vendor modifying its COTS products to save an OEM time, cost, and headaches.

Perhaps the most basic example is adding cables to a motor. Many motors come with bare terminals, and users must connect the cables themselves. It’s a simple task but not nearly as forgiving as many would like. Bend the terminal once, it’s not a problem. Bend the terminal twice and it often breaks. Ideally, the motor would be sent back for repair, but if the break takes place on a busy production floor during crunch time, the motor may simply be discarded.

Sometimes, soldering applies so much heat to a terminal that the motor’s brushes burn up, turning a valuable component into a paperweight. In either case, manufacturers wind up losing money twice: once on scrap and again on lost production time.

Having the supplier attach cabling is an easy solution. They remove the terminals, make the connections, perhaps even add a strain-relief element. The key is they put in the production time, not you. Even better, they take the risk while you receive 100% usable products.

In many cases minor modifications are all that’s necessary for customization. Suppliers with skilled machinists and the right tools can quickly modify motors and assemblies by adding mounting plates and brackets, pulleys and gears, even leadscrews. They can drill cross holes into output shafts. If a planetary gearbox suffers from pin walk, they can weld the pins to the carrier. Simple changes such as these can dramatically increase a product’s value to the OEM.

For instance, when The Machine Lab Inc. of Fort Collins, Colo., a company that makes bomb-disposal robots, started buying MicroMo motors, they wanted to use up inventory of custom mounting hardware from a previous vendor. The problem was, the new motor measured 30 mm in diameter while the clamps were sized for a 32‑mm motor. MicroMo accommodated the older clamps by epoxying a sleeve into place and anodizing the entire package. The gearmotors arrived ready to fit in the mounts, saving the OEM time and money.

Surveillance-robot specialist ReconRobotics of Edina, Minn., focuses its in-house engineering efforts on value-added controls and software and outsources noncore tasks wherever possible. In this vein, MicroMo delivers an integrated package of motor, gearhead (including a ReconRobotics-designed pinion), and leads. It lets the manufacturer drop the package into the robot, plug into the boards, and be up and running quickly.

Some jobs require more than just a few quick modification. One robot manufacturer bought a motor and planetary gearhead for a prototype that met performance specs, only to discover it was too long to fit the allotted space. To fix the size mismatch, MicroMo’s engineers designed a 1:1 spur gearbox that transfers motor output to the planetary gearbox, cutting package length in half.

The process sounds complex, but these types of modifications can take place surprisingly quickly — in this case from concept to delivery in about three weeks. Customization means users are no longer tied to choosing certain subsets of mechanically compatible components. Suddenly, the sky is the limit.

Tapping knowledge
OEMs generally have core expertise they leverage in the products they build. As good as their design teams are, however, they may not be motion-control specialists. Then again, they shouldn’t have to be. The right vendor can leverage decades of engineering experience to supply out-of-the-box motion packages that help OEM engineers efficiently prototype, qualify, and move devices from concept to production.

A good example involves a customer who recently called our sales department for an encoder. They initially elected not to buy, deciding that standard products didn’t fit their needs and budget. When a MicroMo applications engineer called back to discuss the project in more detail, he saw an exploded view of the encoder assembly in the context of the application. He noted the parts lent themselves to being housed and shafted in a freestanding unit, and the customer jumped on the idea. A standard encoder was rebuilt into something entirely new that better served the application, eventually involving a gearmotor as well, for a fully integrated subassembly. In less than three weeks, the project went from drawings to shipping parts.

This example underscores a critical aspect of customization — communicating with the vendor. Don’t just talk to order takers, get in touch with the engineers. They’ve spent years thinking about the best way to move something from point A to B accurately, repeatably, and economically. Their experience and knowledge of both motion technology and product capabilities may result in designs you wouldn’t dream of, but provide the ideal solution to motion-control problems. With little or no work on your part, you can end up with not just a part but a subassembly that improves the final product and the bottom line.

Testing 1, 2, 3
Good vendors don’t just offer modifications, they offer diagnostic capabilities that help troubleshoot design, manufacturing, and product acceptance. A supplier with a sophisticated in-house test lab, for example, can do everything from determining brush wear in a motor under load to analyzing the effects of extremely low temperatures on a motor assembly. And a quality test facility not only diagnoses problems, it can provide R&D teams with a clear understanding of how specific conditions will affect components prior to field trials, letting OEMs navigate the process more efficiently.

One customer qualifying products asked us to put six motors through varying durations of accelerated lifetime testing, stopping one after 1,000 hr, one after 2,000, and so on. Our lab evaluated each in detail, delivering data on wear to the bearings and brushes, lubricant breakdown, and more. The document provided not just detailed results, but historical information to help the customer’s R&D team determine how long the motor should last in the field.

Testing helped Stratasys Inc., Eden Prairie, Minn., uncover an unexpected trouble spot. The company builds rapid-prototyping machines that extrude plastic to form parts in a process that sometimes runs a week straight. Annual machine utilization rates run as high as 90%, making reliability paramount.

When failures started cropping up on a new model, they turned to MicroMo’s lab for help. Initial tests showed the problem wasn’t the motor but premature gearhead wear, which then overstressed the motor to trigger failure.

Further analysis, however, revealed the real problem was lubricant breakdown in the gearhead. Synthetic lubricant seemed to be the answer, letting gearboxes last about five times longer. The downside: it took three times more current to drive the grease, which mandated a more-powerful motor to accommodate the intensive duty. With the change, failures dropped from 15 to 30 per month to just three over nine months.

But lifetime testing on the motors suggested even that rate was far too high. Additional investigation revealed that failures didn’t lie with the motors at all. Encoders were getting knocked loose in the course of normal operations because the new motor was 18 mm longer than its predecessor. MicroMo’s machine shop shortened the flange, motor shaft, pinion, and screws to reduce the overall assembly length. They also added a protective aluminum cap over the encoder to transfer any impact to the motor housing.

As a result of the changes, Stratasys prototyping machines can run at high duty cycles without risk of downtime. To date, the motors have performed well with few field issues, and Stratasys expects them to last for 10 to 15 years.

Skilled vendors that provide value-added capabilities like customization, design collaboration, and testing can help solve the thorniest motion problems. In the process, they enhance new-product development, streamline manufacturing, and speed commercialization. A vendor shouldn’t just take your money and dump packages at your door, they should be a partner who helps you find the right solution for your problem — even if it has to be developed from scratch.

© 2011 Penton Media, Inc.