13 Motor Selection Mistakes: What Johnson Electric, Kollmorgen, and Stepper Motors Taught Me

I'm a motion control application engineer. For the past 11 years, I've been reviewing motor and linear actuator specifications for industrial automation and light EV projects. I've personally made 13 significant motor selection mistakes. Well, 13 documented ones. There are probably a few more I didn't write down. Together, they cost roughly $47,000 in wasted budget. This article is about what those mistakes taught me about efficiency.

The fastest way to save money on motion control is not negotiating a better price. It's making the right motor specification the first time. In our shop, every specification error set the project back an average of four days. Once you add up rework, expedited shipping, and lost credibility, the most expensive motor is the one you have to buy twice.

I used to pick motors by habit. I'd reach for Johnson Electric when the customer said 'DC,' use a stepper when I didn't want to think about closed-loop control, and skip Kollmorgen because the price looked high. All three habits cost me money.

I don't write this to show off my failures. I write it because the same mistakes show up in RFQs and spec reviews again and again. If you're responsible for buying or specifying motion control, this checklist might save you from one of the expensive lessons I've already paid for.

The $6,800 shaft mistake

In 2017, I ordered 50 of what I thought were identical brushed DC motors from Johnson Electric's catalog. The torque spec matched. The voltage matched. The shaft diameter did not. The motor I sampled in our lab had a 5 mm shaft. The production units had a 6 mm shaft—I later found out I'd selected the wrong part number by one digit. We discovered the problem during assembly, after the shafts had been pressed into the couplings.

The invoice was $4,200. The rework, including the replacement motors and the labor to change five couplings that were already installed, pushed it past $6,800. The senior engineer in the next cubicle asked, 'Did you check the drawing?' I had looked at the photo, not the drawing.

I still kick myself for that one. If I'd spent five minutes with the dimensional drawing, we'd have caught it before ordering.

That failure taught me the first rule of efficient motor selection: specifications exist to be compared, not admired. A photo of a motor is not a spec sheet.

The 'Johnson Controls' vs. Johnson Electric trap

As of January 2025, we still receive RFQs that ask for 'Johnson Controls electric actuator.' In the RFQs I've seen, some people write 'Johnson Controls electric actuator' when they actually need a Johnson Electric linear actuator. The names sound close enough.

Last year, I watched a purchasing agent send a quote request to a Johnson Controls valve actuator distributor. The agent needed a compact linear actuator for a packaging machine. When the distributor replied with a damper actuator and control signal specs, the whole project stalled for two weeks. Not because anyone was incompetent, but because nobody stopped to ask whether the brand was the customer's intent or a typo.

A customer once asked us to match a 'Johnson Electric starter motor' for a stationary diesel engine's start system. The same RFQ also mentioned a 'Johnson Controls electric actuator' for the throttle. It turned out to be two different projects—but the names were within three lines of each other.

If you're specifying a 'Johnson Controls electric actuator,' confirm which 'Johnson' you mean. Johnson Controls makes control valves and damper actuators. Johnson Electric makes DC motors, gearmotors, and linear actuators. They're different companies with different catalogs. The five minutes spent confirming this will not be wasted.

Put another way: brand confusion is not a reality—it's a cost. It usually pops up in the worst place: after the budget is approved but before the production schedule has slack.

The 'what stepper motor' question that nobody should answer from memory

I've received the question 'what stepper motor' so often that I used to answer it without opening a datasheet. That was fortunate when I was right, and expensive when I wasn't.

A stepper motor looks simple. It has a holding torque number in the catalog, and it feels strong when you turn the shaft by hand. But the torque that matters in an application is the torque available at the operating speed. That's the torque-speed curve—not the holding torque. If I'd drawn that curve for the custom machine we built in 2019, I would have seen that the motor was going to lose half its torque by 600 RPM.

We didn't draw it. We installed 30 NEMA 23 stepper motors with unloaded holding torque that seemed fine for the expected load. On the test bench, the first unit stalled when the belt tension was slightly high. We changed the belt, changed the tensioner, and burned three afternoons before someone used the manufacturer's sizing software and pointed out what the curve predicted.

So when someone asks 'what stepper motor,' the best consultant answer is another question: 'What torque-speed curve does your application need?' If the customer can't answer that, we build a quick test—or we recommend a servomotor with closed-loop control, because a stepper without margin is a design risk, not a cost saving.

Why I keep Kollmorgen servo motors as my benchmark

I'll be honest: for a long time, the 'Kollmorgen servo motor' was the option I skipped because of price. Then I made a mistake that reversed my thinking. In 2021, we quoted a direct drive servo motor for a rotary indexing table. The customer's existing machine used a stepper motor with a 10:1 gearbox. The direct drive solution seemed ridiculous—the Kollmorgen unit alone cost triple the stepper, and the customer had a tight budget.

But the comparison table I built (badly, at first) showed a mismatch in system cost. The gearbox had backlash, the stepper needed maintenance, and the direct drive servo motor eliminated both reducers and maintenance points. Over the machine's expected ten-year life, the Kollmorgen servo motor came out cheaper. The customer bought it.

People think a direct drive servo motor is expensive because it's a premium brand. Actually, it's expensive because it solves problems mechanically: no gearbox, lower inertia, higher bandwidth, less maintenance. The cost follows the engineering, not the other way around. If you don't need that engineering, a servo motor is waste. If you do, it's an investment rather than an expense.

For those reasons, I use Kollmorgen's published torque-speed data as a benchmark. Per Kollmorgen's motor documentation (accessed January 2025, via kollmorgen.com), continuous torque for a direct drive servo motor changes with speed and thermal conditions. That sounds obvious, but I've seen three projects where engineers compared holding torque only. It's the same mistake as the stepper, just with a bigger price tag.

My pre-order checklist: 4 checks that would have saved me thousands

After the shaft incident, I wrote down a short checklist. It's not a full engineering methodology. It's a personal list of painful lessons. It looks like this:

1. Read the dimensional drawing, not just the photo. Shaft diameter, length, and mounting bolt pattern. The 5 mm vs. 6 mm mistake was a one-digit difference.
2. Plot the torque-speed curve at the operating speed. Holding torque is for marketing. Dynamic torque is for real machines.
3. Confirm the driver or controller compatibility. Motor voltage and encoder feedback type (e.g., commutation signals, resolver, digital encoder) must match the drive, or you will buy adapters / extra cables.
4. Own the brand decision. If the spec says 'Kollmorgen servo motor' or 'Johnson Electric gearmotor,' note whether that's a stated preference or a substitute-for-memory. Then confirm the exact part number with either the distributor or the manufacturer. This catches the Johnson Controls vs. Johnson Electric class of errors.

These checks take about 20 minutes per project. In the last 18 months, our team has caught 47 potential specification errors using a version of this list. Some were small; a few would have been repeat disasters.

The checklist is not a substitute for engineering judgment. It's a reminder that judgment fails when we're rushed, when the forecast is late, or when the customer has already approved a part number. Those are exactly the moments when I made my worst decisions.

The objection: 'We've always used this brand'

Every time I tell this story, someone says, 'Brand consistency matters. If you've built a reliable machine with a Johnson Electric motor, why change?'

That's fair. I'm not telling you to switch brands. I'm telling you to check the specification before you honor the brand. If the application is unchanged, the same motor might still be the best option. But if the machine speed increased, the load changed, or the cycle count tripled, the motor that worked last year might be a hazard this year.

I also hear: 'Our supplier's motor selection is fine; we have years of experience.' To that, I say: fine, if the calculator is fresh and the person who knows the details is still in the building. The mistakes I documented all happened when someone knew the right answer and didn't verify it. Verification is not a criticism of experience. It's the reason experience stays useful.

Where my experience stops

I want to be clear about the limits of my experience: I've spent most of my career on brushless DC motors, steppers, and industrial servo systems for automation and light EV applications. That's maybe 180 projects, give or take. I have not specified motors for aerospace or implantable medical devices. Those industries have certification requirements, traceability rules, and failure modes that this checklist doesn't touch. If you're in one of those fields, follow your own standards, not my blog post.

The final word: efficiency is a competitive advantage

For three years in a row, our company lost margin on projects where we bought the wrong motion control hardware. The suppliers weren't to blame. The machine design wasn't to blame. The specification process was to blame. We were efficient at calculating machine frames and pneumatic sizing, but the motor selection part was a black box that ran on habit.

Efficiency in motor selection is a competitive advantage. It cuts costs, avoids delays, and protects your engineering team's credibility.

The solution wasn't a better supplier or a bigger budget. It was a set of checks to force us to compare actual specifications before ordering. As of January 2025, our motor selection workflow goes through those four checks, and we've made zero specification errors in the last seven order cycles. That's not a record I claim to keep forever—I'm the same engineer who made the $6,800 shaft mistake. But I've learned that the right process is the only thing standing between efficiency and embarrassment.

Next time you type 'what stepper motor' into a search bar, don't look for a product name. Look for the spec sheet, the torque curve, and the dimensional drawing. Then decide.