Stepmotor Selection via the Web — An Engineer's Perspective

Ben Buell
Project Engineer
TriContinent Inc.
Grass Valley, Calif.

A recent project brought to light some new motor-selection tools that saved a lot of time and effort. This particular project needed a motor for a linear-drive system that used a leadscrew. Time to market was an issue, but we still needed to evaluate cost and performance options. Off-the-shelf motion systems looked at cost too much.

A preliminary review of the drive specs pointed toward a rotary stepper motor. Although other rotary motors such as BLDCs and servos are widely available, they looked like over-kill for this project. More to the point, stepper systems presented other benefits that would help keep costs low.

Motor selection in the past wasn't always pleasant. It usually meant hours of pouring over spec sheets and comparing ratings. The Web was tried to help speed things up.

Googling the term "stepmotor" yielded over 3 million responses! Fortunately, several sites offered online selection tools. For example, Designer's Corner is an online stepmotor selection tool from Lin Engineering that promised to help me "Select your Step Motor in 3 Easy Steps.". Likewise, the product search-engine Global Spec claimed to have detailed motor specifications available from 250 companies, including the ability to search by certain specifications.

The great thing about the tools from Global Spec and Designer's Corner was the ability to access them without downloading any software. The use of both tools is free after a relatively painless registration process.

After spending several minutes going through Global Spec, the inefficiency of the process dawned on me. Most companies presented anywhere from two to a few hundred different motors. The experience was like browsing through a catalog, something I could do just as well offline.

Global Spec's advance search function was better. It asks questions about factors ranging from performance needs to shaft and housing options. I was unsure about all of the specs for some of the listed options, but those I did know helped reduce the potential suppliers to five — a big difference. At this point, I could ask each company for samples to evaluate performance.

Lin Engineering's Designer's Corner works somewhat differently. It gives the ability to go through a motor-selection process based on different application types: direct drive, conveyer belt, leadscrew, and rack & pinion. Designer's Corner then asked a number of specific questions about our application such as the leadscrew diameter, direction of movement, and load weight.

Next came the selection of a Lin motor series based on the size and amount of torque needed. Preliminary torque estimates from the mechanical team indicated either a NEMA-14 or NEMA17 frame motor. Designer's Corner had also calculated the amount of torque needed based on the original specs. This could be used to verify the design estimate. Selection of a motor brought up a projected performance curve based on the information supplied. The curve added confidence that the motor fit the application. Similarly, other motors and their curves could be compared. This was a definite way to save both time and money.

Both Global Spec and Designer's Corner were much more helpful than simply browsing through a catalog. Global Spec let us filter out hundreds of motors that didn't fit the application. Designer's Corner let me quickly select a motor and see a performance curve in three steps. It also had several other helpful tools and information for selecting motors. Although these tools can't apply for every stepmotor application out there, both sites presented advantages that I will use in the future.

MAKE CONTACT
Global Spec, www.globalspec.com
Lin Engineering, www.linengineering.com