What Is Drift on Interroll Conveyors? Speed Drift vs Belt Drift and How MultiControl Software Finds It

Drift on an Interroll conveyor is usually speed drift, not belt drift. If a section of line seems to get slower after warm-up or when cartons are heavier, the roller is receiving a speed command that it isn't holding. After a root-cause review of every drift call we supported in 2024, about nine out of ten were not caused by the Interroll drum motor itself. They came from the system around it: power feed, current limits, commissioning settings, or a mechanical bind that made the motor work too hard.

I'm the person who reviews conveyor assemblies before they leave our integration shop. I sign off on quality and brand compliance, which means I spend my week saying yes or no to things that will end up running in someone else's warehouse. This article is my plain-language answer to the question 'what is drift?' in an Interroll system.

What does drift mean on a conveyor?

Out on the floor, drift means two different things. One is physical, and one is electrical. Knowing which one you have is half the fix.

• Belt drift. The belt wanders sideways across the face of a roller. You see edge wear on one side, a frayed seam, or rubbing against the frame. That is a tracking problem, not a speed problem.
• Speed drift. The actual roller speed falls off from the commanded speed under load. Example: a 24 V Interroll motorized roller is set to 2.0 m/s. Under an empty belt, it runs 2.01 m/s. With a 25 kg carton, it drops to 1.93 m/s and stays low. That is speed drift.

Control engineers also use the word drift for sensors, like when a photocell output slowly shifts with temperature. But if you are searching what is drift because of conveyor timing issues, start with speed drift.

Why a 3% drift is a bigger deal than it sounds

A 3% speed error on a 2 m/s belt is only 0.06 m/s. On a stopwatch that does not look dramatic.

But watch what happens over distance. In ten seconds of travel, that error adds up to about 600 mm. In a sortation or accumulation conveyor, 600 mm is enough to put a carton in the wrong spot at a photeye or divert. If several zones each drift by slightly different amounts, carton spacing closes and every downstream decision gets late.

That's why I stopped treating drift as cosmetic. It changes where a package is at a given moment, and the system uses those moments to make decisions.

The mistake that made me change how we test

In 2024, we accepted a 12-zone carton line after no-load speed tests. Every zone was within 1%. The conveyor looked perfect on the bench.

On the first day with real loads, the zones at the far end of the 24 V feed ran almost 4% slow. Cartons started closing before a transfer stop. I was ready to replace three drum motors and blame the supplier.

I only listened to better advice after that failure. Robert White in the Interroll Wilmington NC support group asked a simple question: 'What was the drive current under load?' I had no answer. He told me to stop changing parts and run the line while watching speed and current through the Interroll MultiControl software.

When I did, the pattern was obvious. No-load current was about 0.8 A. Under load, current climbed to the controller limit and actual speed dropped. The motor was trying to run, but the feed wire was too small for the voltage drop over that distance. The fix was a separate 24 V feed for the far zones, not new rollers.

How Interroll MultiControl software helps you see drift

The first time I used Interroll MultiControl software, I treated it as a programming tool. Set ramp times, set speed, update firmware. After the Wilmington lesson, I use it as a diagnosis tool.

Here's what it lets you do in a basic drift check:

• Set a speed command.
• Run the belt under no load and read actual speed and current.
• Add a realistic load and watch what happens to current and actual speed.
• Compare the zones at the beginning and the end of the same power feed.

If current hits its limit while speed drops, assume a feed or torque problem. If current stays low but speed still drops, then the drive is not asking for enough power or something else is limiting it. Either way, you have a starting point.

When drift is not the problem

Not every slowdown is drift. This diagnostic approach assumes the roller is running smoothly and the issue is speed accuracy. If you see any of these, stop and fix the physical problem first:

• The belt is walking sideways and wearing on the frame.
• The roller or motor housing is too hot to hold your hand on.
• The roller makes a grinding or scraping noise.
• The roller does not start at all under load.

Speed drift is usually a quiet, measurable loss. If there is noise, heat, or complete jams, you are outside the scope of a drift test.

Honest limits and where I stand

As of March 2025, we still do this test on every zone with variable load before shipping. Software versions change, so the exact menus in Interroll MultiControl software may shift, but the principle does not: compare commanded speed with actual speed under realistic load.

Honestly, I'm not sure why identical-looking zones drift differently when I'm looking at a bad feed. My best guess is that small differences in cable length, connector resistance, and each drive's current limit determine which one gives up first. That uncertainty is exactly why we measure every zone instead of assuming symmetry.

If your search for 'what is drift' brought you here, the short answer is that drift is the speed error that appears when a motorized roller is under load. Don't order a new drum motor until you have watched current and actual speed under that load. If you get stuck, the Interroll Wilmington NC support people have heard the same question many times. Use them earlier than I did.