HMC undergoes a second rebuild

A heavy duty Cincinnati HMC has been rebuilt again,this time employing the capabilities of Renishaw's calibration and machine tool performance testing systems.

HMC undergoes a second rebuild In 1989, Leeds-based Dana Spicerneeded a large, heavy duty CNC machining centre, to mill, drill,and bore the ends of 2-metre long axle beams, for heavy off-roadvehicles. The ideal machine, with a bed length of 5-metres, wouldallow pendulum machining, thereby increasing production. However,new machines of this type were costly and resulted in the companyapproaching rebuild specialist Murrall and Lang for a solution.Ten years later, it was 'd�j� vu' for theBirmingham-based company, when it welcomed the opportunity toonce again re-manufacture the machine, but this time employingthe capabilities of Renishaw's calibration and machine toolperformance testing systems.

Murrall and Lang had alreadymodified a 2-metre machining centre to accommodate pendulummachining in the summer of 1989 and convinced Dana Spicer of thecost benefits.

With a contract signed, a Cincinnati 20HC 2500(2.5 metre) travelling-column horizontal machining centre wasfound in the USA that would machine these parts, if equipped witha suitable front base.

The volume of the axle components dictatedthat a pallet shuttle system would be economic, allowingunloading and loading whilst machining continued.

To accommodatethis, Murrall and Lang designed a special shuttle table with twoindex tables and fixtures, and a CNC movement of 2.5m from oneposition to the other.

Suitable guarding protected the operator.Therefore, in addition to the usual horizontal axes of X(2500mm), Y (1000mm) and Z (600mm) and the shuttle axis, themachine has two indexing axes giving a total of 6 CNC axes.

Thisconfiguration was arrived at after joint discussions when themachine was first modified in 1990.

After producing axles fornearly a decade and having questioned the ability to maintain themachine, Dana Spicer - having once again considered new products,which still proved very costly - decided to have the machinere-manufactured by Murrall and Lang for a second time.

Havingexperienced the benefits of Renishaw's QC10 ballbar systemsin the 1990's, Murrall and Lang had no hesitation inutilising this technology and purchasing Renishaw's ML10laser calibration system to aid the re-manufacture 'asnew', of the Cincinatti HMC for a second time.

Partner, BobMurrall explained.

'We had successfully produced a machineto Dana Spicer's tolerance specifications in 1990 using asecond-hand Hewlett Packard (HP) calibration system.

Today, HPequipment is neither cost-effective nor comparable to thetechnological capabilities of the Renishaw systems.''It was our experience of the QC10 ballbar system, that ledus to invest in the ML10 laser calibration equipment,' addedMr Murrall.

'The ballbar is so reliable, it automaticallyidentifies, quantifies and prioritises machine tool errors.

Inseeing it used here, many of our customers, including DanaSpicer, have subsequently invested in the technology.' TheY2K re-manufacturing process included a complete mechanicalrebuild, with all worn parts being reconditioned or replaced, acomplete rewiring, the fitting of new digital axis and spindledrives, and a new Siemens 840D CNC control.

The process took lessthan six months and fully met customer specification.

To improvereliability, the customer wanted to maintain accuracy by axiscalibration and compensation.

This required the use of theRenishaw laser calibration system; part of Murrall andLang's quality control system.

'When you arere-manufacturing a machine, your alignments should be well withinachievable levels of adjustment, allowing the alignments set bythe original manufacturer to be achieved.

In fact, the QC10ballbar and ML10 laser system allow us to achieve tightertolerances than was possible when the machine was firstmanufactured.

Whatever we attain here, we can reproduce at thecustomers' premises.

The Renishaw ML10 laser calibrationsystem is portable, easy to use and has built-in temperaturecompensation, allowing our customers to machine components farmore accurately than once possible,' continued Mr Murrall.At Dana Spicer, the 20hp Cincinnati machine, with spindle speedsof 3300rpm, is fed by two 30-tool chain-based magazines.

Axlebeams are machined from forgings which tend to vary in size dueto the forging process.

To obtain the best metal conditions, oncethe component is mounted in the fixture, a spindle mountedRenishaw MP700 high accuracy probe is used to check length androtation.

Corrections are applied automatically to find thecomponent centre, and if necessary to rotate the programdimensions, so as to produce the best component from the forging.'The rebuild option allows a company to purchase a specificmachine at a third of the cost of a new machine.