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The Raydafon double enveloping worm gearbox is engineered specifically for steel mill plant environments. Unlike a standard cylindrical worm reducer, the double enveloping (globoid) worm wraps around the worm wheel, engaging multiple teeth at once instead of one. The result is a step change in torque density, load sharing and meshing efficiency — which is exactly what rolling mills, conveyor drives, crane travel gearboxes and cooling tower fans in steel plants demand.
Units are built from high-grade alloy steel with CNC ground gear geometry, sealed against dust and moisture ingress, and finished with a corrosion-resistant treatment that holds up in a steel mill environment. Output shaft configurations, mounting positions, ratios and lubrication systems can all be specified to the mill layout or to the original OEM gearbox being replaced.
A double enveloping worm gearbox is specified for steel mill drives when the application needs high torque at low output speed in a constrained envelope, with tolerance for continuous shock loading. The globoid worm geometry puts 2–3 tooth pairs in mesh simultaneously, compared with roughly 1 pair on a cylindrical worm reducer. A steel mill amplifies the benefit: continuous duty, high shock loads, airborne dust, radiant heat and limited maintenance access all punish a single-point contact pattern, which is what a standard worm reducer delivers.
A double enveloping worm gearbox consists of eight core components: a globoid worm, a matched worm wheel, an alloy steel gear set, a rigid housing, heavy-duty bearings, a sealing system, a lubrication system and a modular mounting interface. Each component is specified against the actual duty cycle and mill environment rather than selected from a generic catalogue.
The worm is ground as a globoid form so it wraps around the wheel. The worm wheel is cut to match, using a hardened and ground hob that mirrors the worm geometry. Both parts are paired by serial number and are not interchangeable between units.
Worm and wheel produced from high-grade alloy steel, then case-hardened and precision ground. The tooth flank hardness is selected to resist the pitting and scoring that occur under steel mill shock loading.
Rigid housing machined in one setup to keep bearing bores coaxial. Where the mill layout requires an unusual mounting, the housing can be supplied as cast iron, cast steel or fabricated steel to match the original footprint.
Heavy-duty rolling bearings sized for the radial and axial loads of the worm and wheel. Bearing selection is confirmed at the quotation stage against the actual torque, speed and duty cycle of the drive.
Double-lip seals and labyrinth protection on input and output shafts. Dust, scale and water splash are the main causes of premature seal failure in a mill, so seal protection is treated as a primary design feature rather than an accessory.
Housing and exposed surfaces receive a multi-layer protective finish suited to the humidity and airborne contaminants found in a steel plant. This is not a decorative paint — it is specified against the actual environment the gearbox operates in.
Oil bath as standard, with forced lubrication available for high thermal duty. Oil level sight glass, breather and drain port are accessible without dismantling the unit — a direct reduction in mill maintenance time.
Input and output shaft configurations, flange patterns and mounting feet are modular. The unit can be configured to drop into an existing mill foundation, or to suit a new installation drawing.
Double enveloping worm gearboxes are used in six main areas of a steel plant: rolling mill drives, conveyor systems, cranes and lifting equipment, fans and cooling towers, mixers and agitators, and special mill equipment such as shears and straighteners. Each application shares the same underlying requirement — high torque at low output speed, in a compact envelope, with tolerance for shock loading and a dusty, hot environment.
To quote a steel mill gearbox, Raydafon needs eight pieces of selection data: output torque (continuous and peak), input speed and motor power, required output speed or ratio, duty cycle, mounting position, shaft configuration, envelope constraints and ambient environment. The table below lists the typical specification range first, then the specific data required to confirm a quotation.
| Parameter | Typical Range | Notes |
|---|---|---|
| Centre Distance | 80–500 mm | Confirmed against torque and envelope |
| Ratio | 10:1 – 60:1 | Multi-start worm configurations available |
| Output Torque | Up to 50,000 N·m | Continuous and peak ratings confirmed per order |
| Input Power | Up to 200 kW | Motor-mounted or shaft-input configuration |
| Housing Material | Cast iron / Cast steel / Fabricated steel | Matched to existing foundation where required |
| Lubrication | Oil bath (standard) / Forced (high thermal duty) | Sight glass, breather and drain port accessible |
| Sealing | Double-lip + labyrinth (standard) | Upgraded seal package available for high dust |
| Mounting | Horizontal / Vertical / Inclined | Custom to mill layout or OEM replacement |
| Input Parameter | What We Need | Why It Matters |
|---|---|---|
| Output Torque | Continuous and peak torque at the output shaft, in N·m | Determines worm and wheel size, and the bearing selection |
| Input Speed | Motor RPM and motor power, kW | Confirms thermal rating and lubrication requirement |
| Output Speed or Ratio | Required output speed, or the ratio directly | Defines worm starts and wheel tooth count |
| Duty Cycle | Hours per day, starts per hour, shock load factor | Drives the service factor and the thermal rating of the unit |
| Mounting Position | Horizontal, vertical, inclined, or specify shaft orientation | Determines lubrication path and seal arrangement |
| Shaft Configuration | Input and output shaft type — solid, hollow, splined, keyed, flange mount | Must match the existing motor, coupling and driven equipment |
| Envelope Constraints | Maximum length, width, height or existing foundation dimensions | Confirms the housing size that will physically fit the mill layout |
| Environment | Ambient temperature, dust loading, water or steam exposure | Determines the finish, seal type and IP class |
Manufacturing a double enveloping worm gearbox follows six controlled stages: material verification, CNC gear cutting and grinding, heat treatment, assembly and backlash setting, load and no-load running test, then preservation and packing. Each stage produces a record that ships with the unit, so the buyer can trace the actual process behind the gearbox.
A double enveloping worm gearbox uses a globoid worm that wraps around the worm wheel instead of running tangentially past it. The wrap-around geometry puts 2 to 3 tooth pairs in mesh at the same time, which increases torque capacity, reduces load per tooth and improves resistance to shock loading compared with a standard cylindrical worm reducer.
Where the drive needs high torque in a compact envelope at a relatively low output speed, the double enveloping worm gearbox delivers that torque density in a smaller footprint than a comparable helical or planetary unit. It also tolerates the shock loads and continuous duty of a rolling mill without the extra complexity of a multi-stage gear train.
Yes. Send the original manufacturer's model number, nameplate photo or a dimensioned drawing and we will confirm whether the unit can be matched directly. Where the original is obsolete, we can produce a functionally equivalent double enveloping reducer to the same envelope and shaft configuration.
Ratios and torque ratings are configured to the specific application rather than selected from a catalogue. Typical ratio range is 10:1 to 60:1, with output torque up to 50,000 N·m and input power up to 200 kW for standard configurations. Provide the output torque, input speed, required output speed and duty cycle, and Raydafon will confirm the appropriate unit. Where a fixed centre distance is required, the same housing can be re-geared to a different ratio.
Seals are specified as double-lip with additional labyrinth protection on the input and output shafts, the housing receives a multi-layer corrosion-resistant finish, and the lubrication system uses sealed breathers to keep dust and moisture out of the oil. For very dusty locations we can supply an upgraded seal package.
For a standard configuration built from stock castings the lead time is typically 30 to 45 days. For fully custom configurations the lead time is confirmed with the quotation. OEM and project quantities are supplied directly from our factory; MOQ depends on the specific configuration and will be confirmed when the specification is fixed.
Yes. Raydafon can supply the reducer on its own, or as a complete drive package including the electric motor, coupling, base plate and any required guard or instrumentation. This is the standard arrangement for turnkey mill upgrade projects.
Every unit ships with an outline drawing, an installation and maintenance manual, a running test report and a lubrication recommendation. Material certificates and third-party inspection reports can be provided on request when the project specification calls for them.
Confirming the correct gearbox requires the load case, not just the product name. Send the five items below and Raydafon's engineering team will confirm the specification and lead time.
Whether you are replacing an obsolete reducer on an existing mill, upgrading a rolling mill drive, or specifying a new drive package for a turnkey project, Raydafon can quote a double enveloping worm gearbox to your envelope and load case. OEM and project quantities supplied directly from the factory.
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Luotuo Industrial Area, Zhenhai District, Ningbo City, China
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