GEAR APPLICATION GUIDE · PLASTIC GEAR · PL05

MC Nylon Gears for Heavy-Load Industrial Applications:
Cast Polyamide Gear Drives, Large-Module Plastic Gears and Anti-Static MC Nylon

MC nylon — monomer cast polyamide 6, manufactured by casting liquid caprolactam directly into a mould rather than injection moulding pre-polymerised pellets — produces a plastic gear blank with a degree of crystallinity 5–15% higher than injection moulded PA6, significantly lower residual stress, and a much larger achievable part size than injection moulding permits. These properties make MC nylon the material of choice for large-diameter, heavy-load plastic gears (OD above 200 mm, face width above 50 mm) in industrial drives where the economics of a metal gear are unfavourable (corrosion maintenance cost, noise in populated industrial facilities, chemical media compatibility) but where injection moulded plastic gears are too small or not stiff enough for the application. Korea Ever-Power machines MC nylon gears from cast billets for applications spanning crane bridge drives, concrete mixer auxiliary gears, paper mill drive auxiliary components, and chemical plant metering drives.

MC Nylon PA6 · Oil-Filled · Anti-Static · M5–M20
OD 100–800mm · High Crystallinity · Heavy-Load
Crane · Paper Mill · Chemical Plant · Mixer · Mining

MODULE RANGE

M5 – M20

MC nylon industrial gear module range. Crane bridge auxiliary drive: M6–M10. Concrete mixer ring drive auxiliary: M8–M14. Paper mill spreader roll drive: M5–M8. Chemical plant corrosion-resistant drive: M6–M12. Large plastic worm gear (plastic worm wheel): M5–M10. The large module reflects the fact that MC nylon gears are used in large-OD, low-speed applications where the tooth must be physically large enough to be machined from the cast billet without excessive waste

OD RANGE

100 – 800 mm

MC nylon gear outer diameter range. Korea Ever-Power casts and machines MC nylon gears up to 800 mm OD from a single cast billet. The upper limit is set by the available billet casting diameter (Korea Ever-Power casts billets to 850 mm OD × 400 mm height). Above 800 mm OD, MC nylon can be cast as a ring (annular casting) or machined from a multi-segment assembly, reducing material waste for large-OD thin-rim designs

KEY VARIANTS

Natural / Oil / AS

MC nylon gear variants. Natural (MC Nylon 6): standard grade, blue-grey colour, general industrial use. Oil-filled (MC Nylon + 8% mineral oil): reduced friction coefficient (0.20 vs 0.32 unfilled), extended dry-run life — for drives without accessible lubrication. Anti-static (MC Nylon AS): surface resistivity ≤ 10⁶ Ω, for mining, petrochemical, and flour mill applications where static discharge from the gear could ignite dust or vapour

ADVANTAGES

Lower Noise & Corrosion

MC nylon gear advantages over steel in industrial heavy drives: (1) 10–15 dB(A) quieter gear mesh — significant in paper mills and crane halls where noise is a recognised health and safety issue. (2) No corrosion in humid, chemical, or outdoor environments — no painting or galvanising required. (3) Self-lubricating in the oil-filled variant — eliminates the lubrication maintenance schedule. (4) Lower inertia — density 1.15 g/cm³ vs 7.85 g/cm³ for steel, reducing the dynamic load on the motor shaft at startup

MC Nylon vs Injection Moulded Nylon — Why Cast Polyamide Outperforms at Large Size

The distinction between MC nylon (monomer cast polyamide 6) and injection moulded PA6 is not merely one of manufacturing method — it produces fundamentally different material properties that are significant for heavy-load gear applications. The casting process (where liquid caprolactam monomer polymerises in situ in the mould at atmospheric pressure and 150–170°C) produces a much more uniform crystalline structure than injection moulding (where the same polymer is injected under high pressure into a cold mould, producing a skin-core structure with a highly oriented amorphous skin and a less crystalline core). The MC nylon’s higher and more uniform crystallinity translates to a 15–25% higher tensile strength (85 MPa vs 70 MPa for injection moulded PA6), a 20–30% higher flexural modulus (3.2 GPa vs 2.6 GPa), and significantly lower residual stress throughout the billet. This lower residual stress is critical for large gears — an injection moulded PA6 gear above 150 mm OD can warp measurably during the weeks after demoulding as the frozen-in injection moulding stresses gradually relax, invalidating the tooth profile accuracy achieved by the injection mould. An MC nylon gear machined from a properly annealed cast billet has negligible residual stress — the machined dimensions are stable from machining to installation and throughout the service life.

Korea Ever-Power’s MC nylon gears for heavy-load industrial applications are manufactured from in-house cast billets — Korea Ever-Power operates its own MC nylon casting facility, casting billets in standard OD sizes (150, 200, 300, 400, 500, 600, 700, 800 mm OD) and heights up to 400 mm, in natural, oil-filled, and anti-static grades. The casting process includes a post-casting annealing cycle (holding the cast billet at 100°C for 2–4 hours, depending on billet diameter, to complete the polymerisation and relieve any thermal gradients from the exothermic polymerisation reaction) that is the critical quality step — inadequately annealed billets contain residual polymerisation shrinkage stress that can cause the billet to crack during or after machining. Korea Ever-Power’s quality protocol requires a hardness check (Rockwell HRR hardness at 5 positions on the billet cross-section, confirming uniform hardness without variation that would indicate incomplete polymerisation zones) and a weight check (confirming the billet density is within ±0.02 g/cm³ of the target value, indicating complete polymerisation) before any billet is released to the machining department.

The oil-filled MC nylon variant is the most important specialty grade for heavy-load industrial gear applications where re-lubrication is impractical. The internal oil content (8% by weight of mineral oil, incorporated into the polymer during the casting polymerisation) is released at the gear tooth surface as a thin boundary film under the contact pressure of the gear mesh — this in-situ oil film reduces the boundary friction coefficient from 0.32 (dry unfilled MC nylon against steel) to 0.20 (oil-filled MC nylon against steel), reducing the gear mesh heat generation and extending the tooth wear life. The oil-filled grade is particularly valuable in applications where the gear tooth surface temperature under load approaches the PA6 glass transition zone (above 80°C) — the lower friction coefficient of the oil-filled grade reduces the frictional heat generation per mesh cycle, keeping the tooth surface temperature below the critical threshold where surface softening and accelerated wear would begin. Korea Ever-Power specifies oil-filled MC nylon as the standard grade for all crane bridge drive gears and paper mill drive auxiliary gears — the two applications where the combination of intermittent heavy load (crane) or continuous moderate load (paper mill) with limited lubrication access makes the self-lubricating grade the most practical and economical long-term choice.

MC nylon cast polyamide large gear industrial Korea Ever-Power heavy load
Korea Ever-Power MC nylon (monomer cast polyamide 6) gear range for heavy-load industrial applications — from M6 oil-filled MC nylon gears for crane bridge auxiliary drives (foreground, OD 300 mm, blue-grey colour of the natural MC nylon + oil-filled compounding) to M12 natural MC nylon gears for concrete mixer ring drive auxiliary positions (background, OD 600 mm, pale blue-grey). The distinguishing visual characteristic of MC nylon compared to injection moulded nylon is the uniformity of colour through the full cross-section — injection moulded nylon shows a darker skin layer (the rapidly cooled amorphous skin) and a lighter core; MC nylon has a uniform colour throughout because the polymerisation occurs uniformly from the billet surface inward. Korea Ever-Power’s quality inspection includes a cross-section colour check on one billet per casting batch to confirm this uniformity — a billet showing a dark skin layer more than 5 mm thick indicates an incomplete polymerisation cycle and is rejected. All MC nylon billets are tested for tensile strength and flexural modulus on test specimens cut from the billet top (the last section to polymerise, typically the least crystalline zone) before the billet is approved for gear machining.

MC Nylon Heavy-Load Gear Application Specifications

Crane Bridge and Hoist Auxiliary Drives

Oil-filled MC nylon, M8–M12, OD 300–600 mm, face width 60–120 mm, bore 40–120 mm, slow speed (10–50 RPM output), intermittent duty (crane hoist cycles). Crane bridge and overhead crane auxiliary drives (the secondary reduction stages between the main gearbox and the wheel axle, or the auxiliary drives for the festoon cable reel and the limit switch gear train) are a high-volume application for MC nylon gears in steel manufacturing plants, paper mills, and warehouse distribution centres — environments where the crane operates in a humid, corrosive, or dusty atmosphere that would require frequent painting and maintenance of equivalent steel gears. The oil-filled MC nylon gear in an overhead crane auxiliary drive requires no lubrication maintenance (the internal oil provides the boundary film for the lifetime of the gear tooth), tolerates the corrosive atmosphere without surface degradation, and reduces the gear mesh noise in the crane hall by 10–15 dB(A) compared to equivalent steel gears — a meaningful contribution to the overall noise level in a manned crane operation area. Korea Ever-Power crane bridge MC nylon gears are machined with a hub bore to H7 tolerance for press or clearance fit onto the drive shaft, and with a keyway to DIN 6885 standard for the key engagement with the shaft flat — the keyway is machined in the same CNC turning setup as the bore, ensuring concentricity of the keyway to the bore axis within 0.05 mm TIR.

Oil-filled MC · M8–M12 · 300–600mm · no lube maintenance

Mining and Chemical Plant Drives (Anti-Static)

Anti-static MC nylon (AS grade, surface resistivity ≤ 10⁶ Ω), M6–M12, OD 200–500 mm, surface resistivity measured and certified per EN 13463-1 (non-electrical equipment for potentially explosive atmospheres). Mining (coal, grain, flour, wood dust) and chemical plant (flammable solvent vapour) drives require that any electrical charge accumulated on the rotating gear tooth surface from the gear mesh friction is dissipated to ground before it reaches the discharge threshold — the minimum ignition energy of coal dust in air is approximately 30 mJ, and a PVC or standard nylon gear at 100 RPM can accumulate 50–100 mJ of charge over several rotations without a discharge path. The anti-static MC nylon gear (with conductive carbon black compounded into the casting) has surface resistivity below 10⁶ Ω — any charge accumulated at the tooth surface drains to ground through the conductive gear body and the shaft bearing before reaching the ignition threshold. Korea Ever-Power anti-static MC nylon gears are supplied with an individual surface resistivity measurement certificate (measured on the gear OD and tooth surface after machining) confirming compliance with the ≤ 10⁶ Ω requirement for ATEX/IECEx Zone 2 and Zone 21 (combustible dust) drive applications.

AS-grade · ≤10⁶Ω · ATEX Zone 21 · certified

Paper Mill Spreader and Felt Roll Drives

Natural or oil-filled MC nylon, M5–M8, OD 150–350 mm, face width 50–80 mm, chemical resistance to paper mill white water (pH 4.5–8.5, 40–70°C), continuous duty at 30–200 RPM. Paper mill drives — the felt roll drives, spreader bar drives, calender auxiliary drives, and coater metering drives — operate in one of the most chemically aggressive environments in heavy industry: white water (the aqueous medium that carries the paper fibres on the paper machine) contains acidic or alkaline pH, mineral fillers (clay, calcium carbonate, TiO₂), fibre fragments, and biocide chemicals that cause rapid corrosion of unprotected steel gear surfaces and require regular maintenance of painted or galvanised steel alternative components. MC nylon gears in paper mill drives eliminate the corrosion maintenance entirely — the PA6 polymer is chemically resistant to white water across the pH range of 4.5–8.5 and to the biocide chemicals (glutaraldehyde, isothiazolinone-based) used in the paper machine white water circuit. Korea Ever-Power paper mill MC nylon gears are supplied with a chemical resistance confirmation for the customer’s specific white water chemistry if provided — the standard MC nylon grade resists all white water chemicals at the concentrations used in standard paper machine water treatment.

Natural MC · pH 4.5–8.5 · white water resistant

Korea Ever-Power MC nylon cast gear large diameter machining industrial
Korea Ever-Power MC nylon large gear machining — hobbing of a M10 MC nylon gear from a 600 mm OD cast billet on a CNC vertical hobbing machine. MC nylon machines with cutting parameters significantly different from steel: higher cutting speeds (150–300 m/min peripheral velocity at the hob vs 30–60 m/min for steel), very low feed rates (0.15–0.25 mm/rev vs 1–3 mm/rev for steel) to prevent the nylon from melting at the cutting zone, and dry cutting without coolant (cutting fluid absorption would cause the gear to swell during the machining operation, invalidating the tooth dimensions). The chips from MC nylon hobbing are long, continuous curls (unlike the short chips from steel hobbing) that must be cleared continuously from the cutting zone by a directed compressed air blast — chips allowed to accumulate at the hob contact can become entangled in the hob flutes and produce a tooth surface defect as they are re-cut. Korea Ever-Power uses a specifically designed chip extraction system on all MC nylon gear hobbing machines: a combination of compressed air blast at the hob cutting zone and a vacuum extraction port at the chip fall zone below the work table, preventing chip re-cutting and maintaining a clean cutting environment for the full cycle time of a large-OD MC nylon gear (which can be 4–12 hours of continuous hobbing for OD 400–600 mm at M8–M12).
MC nylon heavy load gear types industrial Korea Ever-Power range
Korea Ever-Power gear type range for heavy industrial applications — showing the spectrum from steel gears (in the high-load, precision end of the range) to MC nylon cast gears (in the large-OD, noise-sensitive, corrosion-resistant end of the range). The choice between steel and MC nylon for a heavy industrial drive does not depend on absolute size or absolute load — a M12 steel gear at OD 600 mm and a M12 MC nylon gear at the same OD serve fundamentally different applications: the steel gear where the load is high relative to the OD (giving a small safety factor that requires the full strength of steel), and the MC nylon gear where the load is low relative to the OD (giving a large safety factor even in MC nylon) and the material selection is driven by corrosion resistance, noise, self-lubrication, or ATEX requirements. The crossover point — the load at which MC nylon becomes structurally inadequate and steel becomes necessary — depends on the specific application, and Korea Ever-Power’s VDI 2736 calculation service answers this question definitively for any enquiry: provide the OD, module, tooth count, and application torque, and Korea Ever-Power will calculate whether the load is within the MC nylon design envelope or whether a steel gear is required.

Frequently Asked Questions — MC Nylon Heavy-Load Gears

Q 01

We want to replace the M10 steel gears on an overhead crane bridge drive with MC nylon to reduce noise in our automotive production plant. The crane lifts up to 8 tonnes. What gear dimensions and safety factors should we check before making the switch?

Replacing M10 steel crane bridge drive gears with oil-filled MC nylon is a well-established practice in European automotive and steel plants, and Korea Ever-Power has supplied this replacement for several crane builders in Germany and the Netherlands. The safety factor check before confirming the material switch: (1) Output torque at the crane bridge drive gear: an 8-tonne crane lifting at 0.1 m/s with a drum diameter of 300 mm produces a hoisting torque of 8,000 × 9.81 × 0.15 = 11,772 N·m at the drum. If the bridge drive reduction is separate from the hoist (which it usually is — the bridge traversal and the hoist are independent drives), the bridge drive torque is determined by the bridge travel force (typically 1–3% of the crane weight × gravity × wheel radius), not the lifted load. For a 5,000 kg crane bridge at 3% rolling resistance: F = 0.03 × 5,000 × 9.81 = 1,471 N; at 250 mm wheel radius: T_bridge = 1,471 × 0.25 = 368 N·m at the wheel axle. If the M10 gear is the last reduction stage at, say, 5:1 ratio, the input torque to that stage is 368/5 = 73.6 N·m. (2) MC nylon tooth bending safety factor at 73.6 N·m, M10: for a M10, 30T MC nylon gear with 60 mm face width, the VDI 2736 bending stress is approximately σ_F = F_t × YF × YS / (b × m) = (73,600/0.15) × 1.6 × 1.0 / (60 × 10) = 490,667/600 = 817 N/mm² — wait, this exceeds the MC nylon bending strength. Recalculate: F_t = T/r = 73,600/0.15 m = 490 N. σ_F = (490 × 1.6 × 1.0) / (60 × 10) = 784/600 = 1.31 MPa. The MC nylon bending fatigue stress limit at 10⁶ cycles: approximately 12–16 MPa. Safety factor S_F = 12/1.31 = 9.2 — very comfortable. (3) Contact fatigue check: equally comfortable at these torques. The MC nylon gear will handle the 8-tonne crane bridge drive load with large safety margins. Korea Ever-Power performs the complete VDI 2736 calculation as part of every MC nylon replacement gear quotation — provide the gear OD, tooth count, face width, and the application torque for a confirmed calculation within 3 working days.

Q 02

How does Korea Ever-Power verify that the anti-static MC nylon used in an ATEX Zone 21 coal handling drive complies with the surface resistivity requirement, and what certification documentation is provided?

Korea Ever-Power’s anti-static MC nylon gear verification and certification process for ATEX Zone 21 applications: Material-level verification: the AS-grade MC nylon billet is manufactured with a compounded carbon black content (typically 2–4% by weight) that provides the required conductivity. The billet resistivity is measured before machining using a two-electrode method per IEC 62631-3-1 at 5 positions on the billet outer surface — this confirms the casting has achieved uniform conductivity throughout the billet before any gear machining is performed. Acceptance criterion: volume resistivity ≤ 10⁸ Ω·cm (equivalent to surface resistivity ≤ 10⁸ Ω on the billet surface). Finished gear verification: after machining, the finished gear is measured for surface resistivity on the tooth flank surface (the surface that will be in tribological contact with the mating gear) and on the bore and OD faces (the surfaces that will contact the shaft and housing). The measurement uses the method of EN 1149-1 (surface resistance measurement for electrostatic properties of protective clothing — the same measurement principle is applicable to engineering components). Acceptance criterion for Zone 21 coal dust: surface resistivity ≤ 10⁶ Ω (the IECEx criterion for components in Zone 21 combustible dust environments per IEC 60079-31). Documentation provided: (1) Material certificate confirming AS-grade compounding and carbon black content from the polymer supplier; (2) Billet resistivity measurement report (pre-machining); (3) Finished gear surface resistivity measurement report on the gear OD, tooth flanks, and bore, with individual measurement values at 4 positions; (4) Korea Ever-Power declaration of conformance stating the gear complies with the surface resistivity requirement for ATEX Zone 21 / IECEx Zone 21 use per IEC 60079-31 (non-electrical equipment category). Note: Korea Ever-Power’s documentation supports the machine builder’s own ATEX certification process — Korea Ever-Power does not independently hold ATEX product certification (which would require third-party notified body involvement), but provides all the material and measurement data needed for the machine builder’s technical documentation submission to the notified body.

Q 03

What is the expected service life of an oil-filled MC nylon gear in a crane bridge auxiliary drive, and what are the visual signs that indicate it needs replacement before tooth fracture?

Expected service life of oil-filled MC nylon in a crane bridge auxiliary drive: based on Korea Ever-Power’s field experience and customer feedback from European industrial crane applications, oil-filled MC nylon M10 gears in overhead crane bridge drives at the loads typical for 5–20 tonne cranes (bridge drive torques of 100–500 N·m at the MC nylon gear) achieve 10–20 years of service life before replacement — significantly longer than the equivalent steel gears would require (steel auxiliary drive gears in crane bridge applications corrode and wear in the typically humid crane hall environment, requiring replacement every 5–8 years). The service life variation is wide because it depends on the crane utilisation (hours per day, starts per hour) and the bridge drive torque relative to the gear design safety factor — a crane used for 2 starts per hour (light crane application) at 30% of the calculated design torque will achieve the upper end of the life range; a crane used for 15 starts per hour (heavy crane, continuous operation) at 80% of design torque will achieve the lower end. Visual replacement indicators — inspect at each annual crane maintenance: (1) Tooth tip wear: measure the tip diameter of 5 teeth evenly spaced around the gear and compare to the new-condition tip diameter. A reduction of more than 10% of the original tip height (e.g. tip height reduced from 10 mm to 9 mm for M10 gear) indicates significant wear — replace before the tip wear reaches 15% of tip height, at which point the tooth form becomes non-involute and gear mesh efficiency drops sharply. (2) Tooth root cracking: inspect the tooth root zone (the transition between the tooth flank and the gear body) using a 5× magnifying glass. Visible cracks propagating from the root fillet radius indicate bending fatigue accumulation — replace immediately if root cracks are found, as these can propagate to tooth fracture within 100–500 operating cycles. (3) Surface softening or deformation: press a thumbnail into the tooth flank surface — if the tooth surface leaves a permanent impression under thumbnail pressure (which requires roughly 5 N force), the gear surface has softened, indicating the tooth surface temperature has exceeded the MC nylon service limit. Reduce the drive torque or improve ventilation around the gear, and replace the gear at the next scheduled maintenance. (4) Oil-film depletion (oil-filled grade): a new oil-filled MC nylon gear has a slight oily sheen on the tooth flank surface when pressed with a tissue paper. After 10+ years of service, the internal oil may be partially depleted — if the tissue paper test shows no oil transfer and the tooth flanks appear dry, apply a light surface coat of mineral gear oil (SAE 90 or equivalent) and monitor wear rate — the gear can continue in service with surface lubrication if the tooth flanks are still within the tip-height and root-crack criteria above.

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Need MC Nylon Gears for Heavy Industrial Applications?

Korea Ever-Power manufactures MC nylon heavy-load gears from in-house cast billets — natural, oil-filled (8% mineral oil), and anti-static (AS grade, ≤10⁶Ω certified). M5–M20, OD 100–800 mm, machined from billet to OEM drawing. Crane, paper mill, chemical plant, and mining applications. ATEX Zone 21 surface resistivity measurement certificate. VDI 2736 gear capacity analysis included. Minimum 1 piece. Lead time 10–25 days. ISO 9001:2015 certified.

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