Rane Madras Limited (RML)
The Chennai-based Rane Madras Limited (RML), established in 1960, maintains market leadership by supplying consistently superior quality steering, suspension linkage products and manual steering gears, and services. It serves a variety of industry segments including passenger vehicles, commercial vehicles, farm tractors, two-wheelers, threewheelers, railways and stationary engines. Its 5 manufacturing facilities, spread across India are in Chennai, Pondicherry, Mysore, Varanasi, and Uttarakhand.
RML supplies hydraulic products to Sonalika, Swaraj and Escorts, and steering systems to Ashok Leyland, Daimler India and Germany, and TAFE. It also supplies linkages to Maruti Suzuki. More than 90% of these products are manufactured in the Mysore plant and the remaining in Varanasi and Uttarakhand. Hydraulic products are only for farm tractors.
The company claims it is strong in hydraulics and is the market leader by holding 80% of share with all its customers. To grow further, RML is working on new technologies and planning to expand its business to other areas. Steering systems are of 3 types — manual, integral power steering, and hydrostatic steering. While there is no hydraulic cylinder in integral power steering, it has regular steering gear with hydraulic assistance.
Off-road vehicles like tractors, dumpers, bulldozers and loaders, which run at much lower speeds, constantly demand power assist for steering. A hydrostatic steering system is suitable for such vehicles since steering is always supported with power and requires less than 10% of the steering effort in manual systems. However, it needs high-precision manufacturing.
Rane is working on various new
technologies like providing additional port to operate other implements in the tractor. The company plans to launch this product by mid of 2018. The company is also working on anti-shock HSU system for tractors by providing anti-shock valve, which will prevent shock from passing on to the system. RML customers have evinced interest in this product. It plans to launch this product shortly.
RML is also working with many engineering experts to reduce the cost of HSU by at least 30% by simplifying it. The product is expected to hit the market in the next 12-18 months as it requires lot of testing.
Recently, Auto Components India visited RML’s Mysore plant to have a close look at its high-tech and high-precision manufacturing systems and processes. The plant, established in 1984, has 2 units – one is 20,000 sqm facility, which manufactures manual steering gear and linkage products. The other is 2500 sqm is exclusively for hydraulic products. It manufactures Hydrostatic Steering Unit (HSU), steering cylinder, steering column and transport lock valve, manual steering gear and linkages. The unit 1 has a capacity to make around 3.6 lakh steering gears and about 500,000 linkages. The second plant has a capacity to make 1.20 lakh cylinders and 0.24 lakh HSUs.
The hydrostatic steering unit used for the tractor applications, has different variants like 80cc,100cc, 120cc etc., It consists of a steering control unit, pump, reservoir with in-built filter and dip stick, hydraulic cylinder, piping and hoses. The steering control unit (also known as hydraulic steering unit) has about 28 components, all of them require micron level precision and top-class manufacturing capability. Except for fasteners, bearings, seats and springs, all the mechanical components are manufactured in-house to maintain quality.
Out of the 28 components, 6 are unique, precision components like sleeve spool (directional control valve). Here the cylinder is in 3 microns, roundness is 2 microns and the clearance 8-12 microns. Very high-precision machines are used to drill 60 different holes in various angles and directions.
Hydraulic steering gear is much more critical because of its tolerances and functionality than the manual steering gear. Therefore, RML has created an exclusive facility for hydraulics to meet the stringent dimensional tolerance and the product specification. Though the basic procedures are similar, the kind of machines used, and errorproofing methodology followed for hydraulics are very different. It has also inducted special purpose machines for high-pressure washing, right angle cross-hole drilling, dedicated ID grinding, higher accuracy surface lapping and shrink wrapping for dust-free packaging.
Housing is manufactured using SG 500/7 material. Inside the housing a lot of intercross holes have to be made for interconnection. In the HSU housing 25 different holes are made and the diameter varies from 2 mm to 15 mm. With special purpose machines the company does the operation and create chambers. These chambers are called left and right chambers. When the steering wheel is rotated, the oil from one chamber travels to the other through these holes. If they are not precise the steering gets struck.
The starting operation is turning and boring and it is performed in 1 axis machine. The second operation, called milling, is done in the Vertical Machining Centre (VMC) where 52 inter-connected holes are made in 3 phases. Angular drills are also made here. The cycle time to make a HSU housing is 9 minutes. The hi-tech drilling machines complete its processes in 2 minutes and thus saves time.
The third operation is called cross hold drilling which is a unique operation followed by lapsing, and the fifth operation is blind bore honing. After the processes, the product goes for washing. Totally, there are 6 operations needed to complete the housing machining. Then, it will go for heat treatment followed by honing. Then the external grinding is done through match grinding for the perfect measurement of internal holes in components.
The metering unit is called stator and rotor and together it is called gerotor. In the gerotor there are 7 lobes, where the length and area of each lobe is calculated for the number of rotations. Normally 3.5 rotations from one end to the other is called steering movement, and so the number of rotations is considered to be primary. Based on the customers’ requirement, the company manufactures the gerotors in terms of ‘cc’. Gerotor is made from 16mmCR5 case carburising material.
After turning and grooving, profile grinding is done for the gerotor, which is an important and unique operation. Later profile machining is done followed by drilling and heat treatment. The same process is done for rotor and both are matched. While matching, there should not be any variation between the lobes and it should be 30 microns. A gerotor undergoes 7 operations.
The RML Mysore unit has a dedicated assembly line for power steering. Before assembling HSU, all the components undergo ultrasonic washing, where electrical energy is converted to mechanical energy. There are 4 chambers with 2 micron filters, one with 25 micron and another with 10 micron filter. In the first filter the product undergoes high pressure washing, turbulence washing, ultrasonic washing and drying. Then it goes through the second filter where the contamination level will be brought down to 6mg. In this process, 5 HSU sets can be washed at a time.
Assembling of the HSUs are in semi-automated stations, which has 24 poka yoke for error
proofing. Once the component is mounted, oil seal and bearing washer is assembled and the spring tension is checked. Then gerotor is assembled and bolting is done. After ensuring that the product is error less, it goes for testing, where 100% inspection will be done for hydraulic steering, power steering and other products. A product is inspected based on 12 parameters which include internal leakages, pressure variation, end-lock positioning, input variation where 2 Nm torque is required.
Piston & rod
For piston and rod the raw material is cut suitably and then facing, turning, thread cutting, thread rolling, and induction for hardness are carried out. Tempering is done to give uniformity in the flow of the internal structure. Then is the grinding followed by chrome plating for corrosion resistance and surface hardness. After this the product goes to the assembly line. Once the piston and rod are assembled into a unit, leak testing is done to detect even minute leaks at 240 bar pressure, though the normal working pressure is only 40 bar.
After the testing for HSU and cylinder the unit goes for primer painting and drying processes. After coming out of the oven, the products reach the PDI and are packed and dispatched to the respective customers.
The TQM way
RML started TQM activities in 2001 and by continuous improvement year after year it received Deming Prize in 2007 and Deming Grand Prize in 2012. RML’s strength in technology has received a boost with improved quality levels. The Mysore plant is certified for ISO 9001/2001, OHSAS and TS 16949. Last year this plant recorded a turnover of Rs 225 crore and this year, it is anticipating10-12% growth.
The company’s focus is on hydraulic products, since the growth of the manual steering gears are coming down. In the hydraulics business the company started with Rs 9 crore turnover. This year it is expecting Rs 30 crore and by FY 19-20 Rs 50 crore. The change from manual steering to hydraulic steering was about 30% last year and this year it will reach up to 40-45%. RML has started supplying power steering to Mahindra & Mahindra, which accounts for more than 54% of the domestic sales.
The second unit of RML Mysore plant has the capacity to make 1.20 lakh cylinders and 0.24 lakh HSUs
Gowri Kailasam, President, Steering & Linkage Business, RML (third from left) and D. Satheesh Kumar, Vice President - Operations, RML (fifth from left) along with the core team.
The Unit 1 of the Mysore plant manufactures steering gear & suspension linkages, and has a capacity to make 3.6 lakh gears.