Is aluminium always cheaper?

Not always. Small aluminium units often cost less to handle and ship, but custom servo flanges and special bores dominate price more than the metal. Continuous-duty cast iron that lasts longer can be lower lifecycle cost.

Can aluminium run 24/7?

Only if thermal calculations allow — smaller aluminium bodies reject less heat. For continuous high load, cast iron or forced cooling is the safer default.

Do you machine specials in both materials?

Yes. Double output, hollow ends, and orientation specials exist in cast iron NU/Adaptable; servo flanges and light specials are common in aluminium.

Buyer Guide July 17, 2026 • 7 min read

When to Choose Aluminium NMRV vs Cast Iron Worm Gearboxes

A duty-first decision guide — not a catalogue brochure. Choose aluminium for compact automation; cast iron for thermal mass and harsh continuous duty.

Anand Gears manufactures both aluminium NMRV/ALM-class worms and cast iron industrial worms. The wrong material choice usually shows up as overheating (aluminium undersized for continuous heat) or wasted mass and cost (cast iron on a light intermittent packaging axis). This article is a buyer decision guide; for a materials deep-dive see also NMRV vs Cast Iron comparison.

Quick rule of thumb

Choose aluminium NMRV / ALM when weight, compact servo flanges, and intermittent packaging duty dominate.
Choose cast iron when continuous thermal load, vibration damping, outdoor/dusty plant duty, or high CD torque dominate.

What the catalogue ranges look like

Cast iron worm: sizes about 50–305CD, power into the tens of kW (up to ~25 kW class on the standard line), torque to thousands of Nm, ratios 5:1–100:1.
NMRV aluminium: sizes 025–150 class, power roughly 0.37–18.5 kW, torque to ~1550 Nm class, ratios 5:1–100:1.

Choose aluminium when…

The axis is servo-driven packaging or light automation with frequent starts but not continuous full-load heat.
You need a custom servo flange and short stack length.
Machine mass budget is tight (robot tool, mobile frame, cantilevered axis).
Corrosion is moderate and you can protect the housing if needed.

Choose cast iron when…

Duty is continuous or near-continuous at high load (mixers, outdoor plant, heavy conveyors).
Ambient is hot or airflow is poor — cast iron’s thermal mass and surface help.
You need larger CD sizes and higher torque than the aluminium series comfortably covers.
Vibration damping and long outdoor life matter more than kilograms.

Self-locking is about ratio, not housing metal

Self-locking depends mainly on ratio, efficiency, and lubrication — not on whether the housing is aluminium or cast iron. If hold-without-brake is mandatory, specify ratio high enough (often 40:1+) and confirm with our engineers for your lubrication and orientation.

Hybrid reality in the shop

Many plants run both: aluminium on packaging cells, cast iron on process mixers. Anand Gears can standardise shaft end conventions across both so maintenance stocks fewer coupling sizes.

Talk to Anand Gears

Send CD, ratio, mounting, shaft ends, duty, and a photo of your existing unit (or a sketch). We manufacture cast iron worm, NMRV aluminium, KL bevel, Adaptable, NU, and custom specials from our shop in Bhayander East, Thane.

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