Schneckengetriebe Installation and Commissioning — The Procedures That Determine Service Life

For H7/k6 (transition fit) and H7/n6 (light interference), cold pressing with a hydraulic press and correctly fitted sleeve is acceptable for bore diameters up to approximately 50 mm. For H7/p6 (medium interference) and above, or for bore diameters above 50 mm, heating the wheel hub is strongly recommended. Cold pressing a large interference fit risks bending the hub out-of-round from uneven contact during pressing. Heat the wheel in an oven at 120–150°C for 30 minutes, then assemble within 30 seconds. Do not use a torch or open flame: local hot spots can exceed the steel tempering temperature (180°C) and locally soften the bore zone.

A periodic knock that correlates with worm shaft rotation (or wheel rotation) is almost always a mechanical periodicity in the mesh. Identify the frequency by comparison: if the knock occurs once per worm shaft revolution, the cause is likely worm eccentricity, a local damage on one thread start, or worm shaft runout from incorrect bearing installation. If the knock occurs once per wheel revolution, the cause is likely wheel eccentricity (bore not concentric with pitch cylinder). A knock at z1 times per worm revolution (where z1 is the start count) suggests differential loading between thread starts on a multi-start worm. Measure the frequency with a vibration meter or phone accelerometer app, convert to RPM, and compare to the known shaft speeds.

The principle is: the worm thread must pass through oil during each revolution. For horizontal worm shaft orientation, fill to the worm wheel pitch circle centre — the standard specification. For vertical shaft: the oil must cover the worm thread to at least the full thread depth at the lowest point of rotation — this typically requires filling close to housing capacity. For any orientation where the mesh point is above the oil surface — forced oil circulation (pump or wick system) is required. If you have a non-standard mounting orientation, describe it to Korea Ever-Power with the housing drawing and we will specify the fill level before shipping.

A housing temperature 17°C higher than design indicates the actual drive efficiency is lower than calculated, or the ambient temperature is higher than assumed, or both. Three interventions in order of cost: (1) Check ambient temperature conditions and ventilation — a drive in an enclosed cabinet or near a heat source may be experiencing thermal accumulation that can be resolved by improved airflow; (2) Switch to PAO synthetic lubricant at ISO VG 460 — PAO at 72°C has better viscosity retention than mineral oil; (3) If temperature remains above 70°C after (1) and (2), investigate whether the motor is operating above rated torque or whether a multi-start worm specification would reduce heat generation.

Possibly, with conditions. If the wheel was removed after normal service (not failure), shows no scuffing, pitting, or unusual wear, and the tooth flank dimensions are within 10% of the original module depth, the wheel can typically be reinstalled. Before reinstalling: (1) Clean all tooth surfaces and inspect for micro-pitting using 10× minimum magnification; (2) Measure the bore diameter — confirm it has not been enlarged by fretting from the shaft; (3) Check keyway for fretting marks or widening; (4) If reinstalling on a different shaft, a 30-hour reduced-load run-in is still recommended — the running-in surfaces are conformed to the previous shaft geometry.

The allowable axial float depends on the start count and the backlash specification. For standard industrial drives at DIN8–DIN9 tolerance, axial float up to 0.1–0.15 mm is generally acceptable — it slightly changes the contact pattern but within normal mesh engagement variation. For precision CNC and indexing applications at DIN5–DIN7 tolerance, axial float should be kept below 0.05 mm. Axial float is controlled by bearing preload — tapered roller or angular contact bearings in paired arrangement, correctly preloaded. Check axial float with a dial indicator on the worm shaft end face while applying and releasing axial hand force before commissioning.

For storage periods of 3–12 months: (1) Fill the housing with a corrosion-inhibiting storage oil (VCI-treated oil or flushing oil with corrosion inhibitor) rather than leaving the gear dry; (2) Plug all openings with protective bungs — shaft holes, breather ports, drain plug must all be sealed; (3) Rotate the worm shaft manually one full rotation every 3–4 weeks to redistribute the storage oil film; (4) Store in a sheltered, dry location; (5) At commissioning after storage, drain the storage oil completely, flush with clean production oil (one 30-minute cycle at 20% load), drain, then fill with fresh production oil before the running-in procedure.

Housing mounting bolt torque affects gear alignment more than most engineers expect, particularly for thin-wall aluminium housings. Overtightening housing mounting bolts can distort the housing bore geometry, pulling the bearing seats slightly out of their designed position. The correct approach: (1) Follow the bolt torque specification in the housing manufacturer’s documentation; (2) Tighten in a cross-pattern sequence (opposite corners alternately) rather than in sequence around the bolt circle — this equalises the clamping force and minimises housing distortion; (3) After final tightening, recheck shaft rotation smoothness — a drive that rotated freely before final bolt tightening should rotate with the same smoothness after.