Two CNC chucking lathes running on very short work cycles have more than lived up to expectations in machining cast cooling system parts for automotive diesel engines.
Two Colchester Tornado A50 CNC lathes running on very short machining cycles have more than lived up to expectations at the West Midlands works of precision subcontractor H L Engineering. Supplied by local distributor Datamach of Coventry, these two chuckers now form the heart of a dedicated production cell set-up last year to machine a family of cast cooling system parts for automotive diesel engines. Combined with a refurbished vertical machining centre, the GBP 110,000 cell handles three different types of stainless steel intercooler component and can machine up to 1,200 castings over two shifts each day.

When planning began for the three machine cell, the company's engineers decided that the two CNC lathes required had to achieve minimal lost time during machining cycles and had track records of high reliability because finished machined castings had to be delivered once a day to the customer's strict Just-in-Time schedules.

As director Robert Laing recalled: 'We looked at several makes of two-axis lathe, but the overall speed, performance, rigidity, track record and value for money of the Tornado package best met our all-round production requirements.' He follows on to recall that as these automotive parts have short turning cycles, the company wanted to keep non-cutting time to the minimum.

'The A50 chuckers had fast acceleration and rapid spindle braking, which were ideal for this sort of work.

We also liked the Fanuc control, as our operators are very familiar with programming this system, and the inclusion of swarf conveyors on both machines was considered an added bonus,' he says.

As part of the Engineering Diamonds Group, H L Engineering is a precision subcontracting company which specialises in the machining of components for the automotive, defence and construction sectors.

Employing 11 people, the Exhall, Coventry-based business has 10 CNC machine tools.

The 5,000ft2 factory is split into two main sections - one for low to medium batch work where batch sizes from one to several hundred are produced and the higher volume area where quantities up to 1,500 a day are machined.

The Tornado cell is installed in the high volume area, near to a vertical machining centre with twin pallets which is mainly used to produce brackets for window systems.

Installed in October 2000, the two Colchester lathes are sited close together and at right angles so that one operator can easily run both machines.

The project involves machining three different 304 stainless steel investment castings, two header components and one gas box.

The turning cycle dominates the cell operation as the twin-pallet vertical machining centre is only used for tapping and chamfering tasks.

Each component requires two main turning operations, one at each end, so the two Tornado A50s are set-up to produce the operations in batched sequence.

Typically, the lathes are run for up to three days on a specific component, in which time between say 3,000 and 5,000 are turned, before being re-set.

All three of the cooling system elements are basically funnel-shaped units measuring 53mm diameter.

The two header components are 23mm long and they feature a flange face on the back end which is tapped and chamfered on the machining centre.

However, the gas box element measures 36mm long and has a main outside diameter which is offset by some 5.7mm.

The turning cycle performed on the headers involve facing, turning, and a boring operation for location.

When the part is reversed, additional facing, counter-boring and chamfering cycles are performed.

Around 1mm is removed from all the machined faces and the total cycle time for each header is 75 seconds.

Similar operations are performed on the gas box, but, a two-jaw chuck is used in order to accommodate the 5.7mm offset of the main diameter.

Narrow recessing operations involve careful removal of some 4mm of material from the neck of the part but still the cycle is very short at 55 seconds.

Tolerances on all three parts have to be maintained at around 0.15mm.

While the speed and performance of the Tornado A50s has enabled H L Engineering to effectively produce all three components, the company has also devised several combined tooling systems in order to further reduce non-cutting time.

Chief production engineer Trevor Weston explains: 'In order to optimise machining efficiency we have tried to limit turret indexing.

On the headers, for example, the first Tornado operations can now be carried out without indexing the turret because two tools are mounted in a single holder allowing us to combine turning and boring.

For header operations on the second machine, we have combined three tools into a single holder, which accommodate rough and finish boring and profile turning.' Combined tooling is also used on the gas box, when three tools are mounted in one holder in order to carry out all the first operation machining cycles.

However, for the second operation the turret has to be indexed one position and with two tools located in one holder, boring and turning are combined.

For the second station, a separate recessing tool is used.

'The use of combined tooling has shaved quite a few seconds from the total machining time,' outlines Trevor Weston.

Coated carbide tooling is used throughout and the operators carry out their own inspection tasks on the intercooler parts with all key diameters inspected 100 per cent.

'But the consistency of machining means there are very few problems in maintaining size or finish.

Concludes Trevor Weston: 'The installation of the two Colchester Tornado A50 lathes has proved to be a highly productive and cost-effective method for machining these cooling system parts.

Both machines have been extremely reliable in service and when there has been the odd minor problem, this has also been sorted out quickly by Datamach, often over the 'phone.'