What Works: Revamped boring machine reaps exciting ROI

A 60-tonne boring machine was reconditioned and reaped significant ROI upon completion.

Larsen & Toubro Ltd. Heavy Engineering Division manufactures process plants and special-purpose equipment for various industrial sectors in India. L&T HED (as it’s popularly known) has a sophisticated Heavy Machine Shop (HMS) where machine tools from reputable global manufacturers are installed. The HMS started up in 1968, and one of the first vertical boring machines in the workshop was made by Berthiez in France.

This machine, with a 60-tonne table capacity and maximum turning diameter of eight meters, was very unusual in those days. A robust and well designed machine, the Berthiez was one of the biggest assets of the HMS. In later years, we installed more vertical borers, some computer numeric control (CNC) and a few conventional units, but the Berthiez capacity remained unique in the shop. After using the machine for 32 years, we felt a need for a similar machine, but with CNC capabilities. Various manufacturers offered the dream machine we wanted, but at a mind-boggling cost: a new machine at $1.5 million was an unaffordable proposal.

Heavy Engineering Maintenance then accepted the challenge of revamping the Berthiez machine to give it a new look. The budget for the reconditioning and CNC retrofitting was estimated at about $110,000.

The machine engineering was done in-house. Hardware and software was purchased from a well-known CNC manufacturer, and skilled maintenance manpower was used for the reconditioning and retrofitting. We installed an unusual moving operator console, which enhanced the machine productivity to a great extent. The cost of the moving console alone was approximately $10,000.

The machine was completely dismantled and the following reconditioning activities were carried out:

  • Guideways ground and reconditioned
  • Ram and saddle reconditioned with Turcite lining to reduce frictional losses
  • X and Z axes provided with ball screws for accurate positioning
  • Moving pendent provided for ease of operation
  • Machine subassemblies such as table gearbox, gear shifting system, table shifting mechanism and lubrication system reconditioned
  • Siemens 810 D CNC controller with digital feed and table drive installed
  • Linear scales for X and Z axes provided for position feedback

Reconditioning and retrofitting costs often go out of control, but in our case, we were able to stick to the budget. The maintenance team worked on the project for three months, and the end result was satisfactory. The geometrical accuracy met the machine’s original specifications. Laser calibration showed the positioning accuracy better than new vertical borers of reputable make.

Other improvements made the machine versatile, accurate and highly productive:

  • Profile machining within 20 micron accuracy
  • Precise table speed control
  • Improved machining quality
  • Reduced machining cycle time
  • Reduced setup time through CNC features
  • Greatly reduced machine downtime
  • Reduced operator fatigue through moving pendent
  • Fault diagnostics made easy by user-friendly machine communication

The result was seen by management as a great achievement, and one of our key customers engaged the machine for three years to manufacture critical aerospace components. The return on investment was quite attractive.

Santosh P. Sapre, chief engineer, manufacturing services at Larsen & Toubro Ltd.’s Powai Works Heavy Engineering Division, Mumbai, India, can be reached at santosh.sapre@hed.ltindia.com.

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