AGMA 6034-C21 PDF

Applicability

This standard covers the wear rating and strength rating of wormgearing. This standard applies to the rating and design of enclosed cylindrical wormgear speed reducers and gearmotors having either solid or hollow output shafts and single or multiple reductions that may include other types of gearing used in conjunction with cylindrical wormgearing. The rating and design considerations contained in this standard are valid for rotational speeds of the worm not greater than 3600 rpm and sliding velocities at the mesh of not more than 6000 ft/min.

This standard applies only to cylindrical worm gear meshes where the worm is made of surface hardened steel and the worm wheels are made of bronze provided that all limits of application as outlined in 1.2 are adhered to.

The knowledge and judgment required to evaluate the various rating factors come from years of accumulated experience in designing, manufacturing, and operating gear units. Empirical factors given in this standard are suited to the particular use shown. This standard is intended for use by the experienced gear designer, capable of selecting reasonable values for the factors. It is not intended for use by the engineering public at large.

No limitation is placed on the method of producing the worms and gears, but the tooth form of the gear must be conjugate to the thread form of the worm. See ANSI/AGMA 6022, Design Manual for Cylindrical Worm Gearing.

Limits on the application of this standard

The equations and tables in this clause result in wear and strength ratings for wormgearing at a 1.0 service factor provided that:

a) The worm and gear design guidelines specified in ANSI/AGMA 6022 are followed;

b) The gear ratio is greater than or equal to 3.0;

c) The rotational speed of the worm does not exceed 3600 rpm;

d) Steel worms have a surface hardness and typical material found in Table 1;

e) Steel worms are ground, polished, or rolled to a maximum surface roughness Ra of 16 microinches;

NOTE: If the mesh center distance deviates from this value, the rating results may differ significantly from those calculated by this standard.

NOTE: The calculation method for worm deflection can be found in ANSI/AGMA 6022.

i) Gears are made of bronze. Allowable alloys are:

– UNS C90700;

– UNS C91700;

– UNS C67300.

NOTE: UNS 67300 is normally forged and is typically used for smaller size gear blanks where sliding velocities are less than 1000 feet per minute.

Allowable casting methods are:

– sand;

– static chill;

– centrifugal.

Exceptions

This standard does not apply to cylindrical wormgear reducers which are designed or used as speed increasers.

The rating method described by this standard does not apply to worm wheels made of ductile iron, aluminum bronze, manganese bronze, complex copper alloys, and plastics; although such materials are commonly used in worm gearing. Ductile iron can present additional challenges for the gear designer that are not covered by this standard including increased risks for fretting with the steel worm when vibration is present.

System considerations

This standard does not attempt to address complete drive systems, torsional vibration, critical speeds, or other types of vibrations which may affect operation of enclosed cylindrical worm gear reducers.