Bonfiglioli Gearboxes and Motors: A Non-Engineer's Buying Checklist

I manage purchasing for a 130-person automation equipment manufacturer. That sounds more official than it is. Most of my day is order forms, expedited shipping, and trying to get a straight answer out of suppliers. I'm not an engineer, but after five years of buying motion control components, I have learned enough to catch problems before they become emergencies.

This checklist is for people like me: non-engineers who need to order Bonfiglioli gearboxes, motors, and related components without making expensive mistakes. There are seven checks I use before every order, plus a few mistakes to avoid.

Quick caveat: this is not a sizing guide. If you are calculating torque, service factor, or inertia, you need an engineer or a proper application review. This checklist is about the practical side—what to write down, what to ask for, and what to verify before you hit 'order.'

When This Checklist Helps

Use this when you are:

• Replacing a failed gearbox or motor
• Ordering a complete Bonfiglioli geared motor for a new machine
• Buying a spare for a servo axis
• Getting quotes for a small batch of units

If your project involves a custom output flange, non-standard ratio, or unusual environment, stop and get technical support first. Honestly, that saves everyone time.

Step 1: Record the Full Model Code

I keep saying this because it matters: find the nameplate and write down every character. Don't take a photo and assume 'the engineer can read it later.' They can't, and you'll end up back at the motor cabinet.

A Bonfiglioli gearbox model is more than a series name. The full code includes size, ratio, mounting position, and output configuration. If you're replacing a unit, one character in that code can mean a different shaft height, torque rating, and mounting bolt pattern. That mistake once caused a full week of delays.

Here's where I made my own mistake. I assumed 'same specifications' meant same results across vendors. Didn't verify. Turned out the replacement we quoted had a different mounting flange. We had to pay for machining and a second shipment. Now I always ask for the complete type code and compare it line by line.

(Should mention: if the nameplate is missing, don't guess. Measure the gearbox—center distances, shaft diameter, keyway size, bolt pattern—and send those dimensions to a Bonfiglioli distributor.)

Step 2: Get the Bonfiglioli Motor Wiring Diagram Before You Disconnect Anything

Search 'bonfiglioli motor wiring diagram' and you'll get a lot of files and forum links. But the only one that matters is the diagram supplied with your motor or documented in the manual for that series.

Why it matters: a three-phase motor can be connected in star or delta. The wrong connection can cause low torque or a tripped overload—or, in the worst case, damaged windings. I don't say that to scare you. I say it because I watched an experienced electrical contractor stand at an open terminal box and ask, 'Do you remember how the wires were before?' The guy before them had taken a photo. The photo was blurry. (Ugh.)

Things to check on the wiring diagram:

• Voltage range on the nameplate (230/400 V vs. 400/690 V, for example)
• Winding connection for your supply voltage
• Thermal protector or PTC connections, if present
• Rotation direction—this is where a wrong phase sequence makes you run a conveyor backwards

I'm not saying you will ever rewire a motor yourself. But you should be able to hand a clear drawing to someone who can. If a supplier sends a quote without a wiring diagram, ask for it before you order, not after.

Step 3: Understand the Bonfiglioli Gearbox Assembly and Mounting Details

The phrase 'bonfiglioli gearbox assembly' usually shows up when someone needs to install a unit, not just buy it. The assembly itself is normally straightforward—couple the motor, bolt it down, connect the wiring. But the trouble starts when the gearbox isn't compatible with the mounting arrangement on your machine.

Ask about these before you place the order:

• Foot-mounted, flange-mounted, or hollow-shaft. Some Bonfiglioli gearboxes can be ordered with an output flange; others are foot-mounted only.
• Mounting position (M1, M2, M3, etc.). The same gearbox can be mounted in different orientations, but the oil fill must match the mounting position. This is one of those details that sounds small until oil leaks out of the vent.
• Output shaft: solid shaft vs. hollow shaft. Hollow shaft often needs a torque arm. Solid shaft needs a coupling or pulley. You can't interchange them without a different housing.
• Backlash: standard or reduced. Not usually on a replacement order, but for servo applications it matters.

One thing that surprised me: when I compared two quotes side by side—same torque, same ratio, one from a local dealer and one from an authorized distributor—the local dealer's price was lower, but the specified mounting position was wrong. They didn't ask. The authorized distributor asked more questions. That's when I realized the quote is only as good as the information behind it.

Step 4: Confirm the Environment and Duty Cycle

I know, 'service factor' is the kind of term that makes a non-engineer's eyes glaze over. But here's a simple rule: don't buy a gearmotor that is exactly at the edge of the load. A little more service factor means a longer life, easier maintenance, and fewer middle-of-the-night calls.

Also, be honest about the environment. If the motor is going to be washed down or outdoors, you need a higher IP rating. I once saved about $180 by choosing a lighter-duty unit because it was in stock. That choice ended up costing $1,800 when the replacement had to happen inside a shutdown window. (Thankfully, the shutdown was scheduled—barely.)

If you're not sure what IP rating you need, ask. Many stock Bonfiglioli gearmotors come with IP55 or IP65 protection, but your facility could be different. The cheapest unit is not necessarily the least expensive.

Step 5: For Servo Applications, Remember the Controller Is Separate

If you're ordering a servo gearbox, you're probably not buying the whole motion control system from the same order. A servo motor needs a drive, and the drive is usually matched to the motor's feedback type and encoder configuration. In many cases, servo motor controllers are separate components.

This is where project teams run into trouble. Sometimes they order a beautiful servo gearbox and motor, then realize the servo motor controllers are a different line item entirely. Servo motor controllers are not interchangeable just because the connector looks the same. They need to match the motor's current rating, feedback type, and communication protocol.

If you are doing servo motor control in a new machine, write down:

• Controller brand and model
• Feedback type (absolute or incremental; resolver or encoder)
• Communication protocol (EtherCAT, PROFINET, analog, etc.)
• Cable lengths and connector types

When in doubt, ask the distributor to confirm compatibility. No one wants to receive a beautiful new servo axis that won't talk to the PLC.

Step 6: If You're Comparing Stepper Motors, Know the Speed Limit

I've lost count of how many times a project owner has asked me, 'How fast can a stepper motor turn?' The answer is not a single number. A typical stepper motor can run at speeds around 200–600 RPM without much drama, some can go to 1,000 RPM or more, but torque drops as speed rises. The exact speed depends on the motor, driver/controller settings, supply voltage, load inertia, and wiring. Check the motor's torque-speed curve if you need the real limit.

So yes, 'how fast can a stepper motor turn' is the right question—but it's rarely the most useful one. The better question is: 'Can a stepper motor maintain the torque I need at that speed?' If you need high speed with constant torque, a servo system is usually a better idea. If your moving part is small and positioning is more important than speed, a stepper is often fine.

I'll be honest: I'm not an expert in stepper tuning. I've never fully understood why driver current settings seem to be treated like a black art. My best guess is that the interaction between motor inductance and supply voltage is more subtle than it looks. That's why we ask the motion control engineer to make that call.

Step 7: Ask for Documentation at the Quote Stage

I've learned to add a documentation checklist to every PO. For Bonfiglioli orders, I ask for:

• Bonfiglioli motor wiring diagram
• Gearbox assembly drawing
• Mounting position diagram
• Oil type and quantity
• Maintenance intervals

If you can't get these from a reseller, go to a Bonfiglioli distributor or use their official documentation. As of early 2025, the Bonfiglioli website has product literature and manuals. Official sources won't always give you the exact wiring diagram for a custom motor, but they're the right starting point.

One small thing: when a salesperson says 'it's the same as the old one,' ask them to verify. It's not personal. It just isn't your job to fix a wrong shipment at 4:55 PM on a Friday.

Common Mistakes to Avoid

• Ordering by memory. Write the model code on the PO exactly as it appears on the nameplate. Don't rely on your own shorthand.
• Assuming the voltage is standard. Some facilities run 460 V, some run 575 V, and a 400 V motor will not be happy in either.
• Skipping the wiring diagram. 'We'll figure it out at installation' works until the motor doesn't turn.
• Forgetting accessories. Bell housings, torque arms, encoders, brakes, oil seals—all of those need to be specified at order time.
• Ignoring the oil fill. Gearboxes ship without oil or with a shipping fill. Which one depends on the unit. Check the manual and the shipping note.

Final Word: This Is a Starting Point, Not an Engineering Manual

This checklist will not replace a properly sized drive system. But it will help you ask the right questions and avoid the kinds of order mistakes that turn into project delays. In my experience—call it five years and maybe 180 orders, give or take—most problems aren't caused by bad products. They're caused by missing information.

If you're looking at Bonfiglioli gearboxes or motors and you're not sure where to start, start with the nameplate. Then ask for drawings and the wiring diagram. Then get an engineer to verify the selection. That order of steps has saved me more money than any 'special deal' I've ever negotiated.