Most Innovative Project 2018: New Design of Gear Wheels

This new design of gear wheels is one of the projects ennomotive has received to compete in the ‘Most Innovative Project 2018‘ contest.

A new design and technology for the production of straight-toothed gears with a diameter from 5,500 to 20,000 mm, with a metric module from 20÷100 mm and a tooth length up to 1000 mm, is proposed to improve performance under conditions of increased abrasive and dynamic impact on the teeth.

The idea is that the toothed crown of the wheel is made of separate teeth, which allows for heat treatment of each to a hardness of 50-55 HRC, and fixed on the rim of the wheel in a special way. The basic design solutions of the precast ring gear are developed.

State of the problem

In modern mining and metallurgical complexes and production of cement and clinker unique machines and technological equipment are operated, in the mechanisms of which open gear pairs of large dimensions are used. If the diameter of the gears, generally in the range of 1000 mm, gear wheel design in the form of bandages or tavropos drives can reach up to 20000 mm.

Starting approximately with Ø5,500 mm make such wheels of 2x, 4x or more sections of cast steel. A metric module of the wheels, usually no less than m=20 mm, and therefore, the molded rim of the wheel on which you are cutting teeth shall be of a thickness not less than (4,5÷5,5)·m, i.e. ~100 mm. This rim can be manufactured, in a range of technological conditions, only by casting. Sections of such wheels can be cast only in sand and earth forms. The internal structure of such casting may have internal microcracks, micropores, which are detected only when cutting teeth and require the elimination of defects in the cutting process.

Ultimately, defects may occur during operation, for example, chipping and breakage of teeth, cracks in the gear crown of the wheel, uneven wear of teeth. The wear rate of cast teeth is unpredictable, unpredictable and breakage of teeth. The whole sum of the disadvantages of cast gears, working in mining and metallurgical complexes lead to significant financial costs in the operation of mechanisms with such gears.

What this project offers

1. A fundamental new solution.
2. Completely abandon the implementation of the crown by casting.
3. Perform a toothed crown of individual teeth.
4. Perform the body (rim) of the gear welded or welded-cast, which will reduce the metal content of the structure by 15-25%, reduce the production time, as well as reduce the cost.

What this new design achieves

1.  The ability to produce teeth from alloy steels with special heat treatment, to provide them with high hardness (50…55 HRC) and surface cleanliness Ra=3,2÷1,6 microns, to increase the service life of the teeth to 6 years, instead of the existing ~ 3 years
2. The possibility of repeated use of the gear housing. For the consumer-a reduction in operating costs, for the manufacturer – is a non-competitive receipt of orders for the manufacture of toothed crowns.
3. The ability to quickly (within minutes) replace a failed tooth during operation.
4. The opportunity exploitation process of replacing all the teeth in the crown, without dismantling the structure or perenashivanie with worn parts of teeth not worn.
5. Reducing the use of materials and energy in the manufacture of wheels.
6. The ability to produce a selection set – selection of teeth for the given gear crown, based on the output geometric parameters and the hardness of the surface of the teeth of this assembly.
7. Reduction of unexpected downtime of technological equipment by at least 50%. 8. The ability to issue a certificate of quality for this toothed crown.

The degree of readiness

1. The drawings of the principal design of the ring gear consist of individual teeth fixed on the rim (body) of the wheel in a special way. The design is intended for gears with a diameter of 5500÷12000 mm, m≥20 mm, tooth length (wheel width) up to 1000 mm.
2. The calculations of forces in the ring gear with m=20 mm at circumferential force (bending force on the tooth) Performed computer modeling efforts in a gear wreath of a new design, in cofactor of a factor of safety.
3. The design of equipment for experimental testing of teeth performance by static loading method was developed. Dimensions of equipment: 500×400×1000 mm. tooth loading Force with m=20 mm and a length of 200 mm-13000 kg (equivalent).
4. Developed and tested empirically the processes for Monotube allowing for the application of chemical-heat treatment under special conditions to obtain the surface hardness HRC 50…55 in the viscous core.
5. The patent search for the last 25 years on the basis of the Dnepropetrovsk regional patent archive was carried out, no analogs were found.

Competitiveness is ensured

1. High maintainability at low labor intensity of replacement of teeth and a gear ring as a whole.
2. Reduction of the consumer’s costs for the purchase of gears after the change of the first gear ring, as the gear housing is not dismantled.
3. Patentability of new design and manufacturing technology.

Main competitors

1. Russia: “Uralspetsmash” Magnitogorsk, “Elektrostal heavy engineering plant”, Elektrostal.
2. Ukraine: “Novokramatorsk machine-building plant” (NKMZ) Kramatorsk.
3. Germany (maybe): Siemens, ThyssenKrupp. Manufacturers of gears with a diameter greater than 5500 mm in other countries require an additional search.

Markets-countries with a developed mining industry, with the production and production of building materials, in a particular cement. For example, only in Ukraine, the cost of annual consumption of wheels will be ~ 20 000 000 $. In Russia 4 times more. To assess the total market volume, a marketing analysis together with the manufacturer is required.

The proposed technology

1. The first production of the wheel: the toothed crown consists of individual teeth weighing ~15% of the weight of the wheel.
2. The subsequent production of this wheel: the wheel housing is applied repeatedly, so the utilization rate of the metal ~of 0.85
3. Re-use of waste teeth module m1 as blanks for teeth module m2, ie m2< m1, so the metal utilization factor of ~0.9.

According to the data of mining and processing plants, minor repairs of a broken tooth with a slight abrasive wear in the form of surfacing lasts from 30-90 minutes, depending on the number of shells and defects.

Repair of a completely broken tooth or a tooth torn from the base lasts from 2.6 hours, while the tooth profile is no longer maintained. When broken or torn 2 or 3 teeth repair lasts from 9-15 hours, sometimes longer depending on the degree of destruction.

In the approximate version, it is possible to calculate losses of the enterprise for repair and simple only one mill. As a rule, the work is not limited to one mill.

Examples of breakdowns and defects

1. Abrasive wear and possible casting defects that can be detected already during operation.
2. A completely broken tooth; a torn tooth in the process.
3. Wear of the teeth of cast wheels.
4. Wheel cracks Ø8000 mm.

Written by: Maksym Gaievskyi (Design Engineer)

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