18 August 2010

New range of Doosan Puma lathes is worth a closer look

Mills CNC, the exclusive distributor of Doosan machine tools in the UK and Ireland, unveiled a new range of Doosan Puma lathes at the recent MACH exhibition.

At first glance the new machines appear very similar to existing Pumas – but a closer inspection of the new machine series reveals that there have been significant improvements made to what was already the UK's favourite, most comprehensive and fastest-selling range of lathes.

This new generation of Puma lathes has taken 3 years to bring to market and, says Andrew Jack, Mills CNC's Technical Director; 'I have never seen so much time and resource put into the development of a new range of machine tools.'

But, when one considers that the new 8", 10" 12" (15") chuck range consists of 3 different machine tool series (Puma 2100, Puma 2600 and Puma 3100) and 36 different models in total...it is clear that this was never going to be a 'rush job'.

The development phase

Recognising that it might be a tall order improving upon its highly-successful Puma range (over 50,000 machines sold since they were first introduced in 1980), Doosan set about the task by benchmarking the new, future Puma range specifications against three key competitors' 'equivalent' lathes.

The express objectives were to ensure that the new Pumas would have capacity, power and accuracy and surface finish benefits over these competitor machines.

Achieving these key objectives required attention to detail across a number of different areas including the following:-

The machine structure of the new Pumas has benefited from the application of Finite Element Analysis (FEA) to determine static and dynamic stiffness, leading to a more stable, better damped structure for increased accuracy.

Another key feature is that the range is modular, seeing the use of common parts across all models (for example the same turret type is employed across the new range).

This has helped keep costs down and means that, despite a significant improvement in technology and performance, the new Puma lathes don't cost much more than the older models they have now replaced.

Specific improvements

The new Pumas' machine base casting has been increased by up to 158%; the machines' box-guideways (a particular feature of heavy-duty Puma lathes) have been made 50% thicker; the saddle width along the Z-axis has been increased as has the distance between Z-axis slideways.

Other design and build 'mechanical' improvements have seen the mounting area for the headstock being increased by 90%, and the mounting area for the sub-spindle similarly increased by 50% increasing overall rigidity.

In addition to these improvements, the effect of heat-generating elements has also been considered. So, the heat generated by the hydraulic power pack is directed away from the machine, and hot air is driven upwards out of the control cabinet with a heat wall between it and the machine.

Heat from the main spindle's hydraulic cylinder is similarly driven up and out of the machine.

Other features include air/oil lubrication for the machines' driven tooling gear-train and ball-screws which reduce heat generation whilst X and Y servos have their own cooling fans. Angular contact spindle bearings (as opposed to roller-type), further reduce thermal effects.

Finally, all sub-spindle models supplied in the UK will have 15kW (134Nm) motors which allows heavy duty turning on second operation work. This is higher rating than many 8" chuck single spindle CNC lathes currently on the market.

The new Fifth generation Pumas

The new range of 36 machines replaces the existing Puma 1600, 2000, 2500, 240, 280 and 300 ranges, a total of 40 machines, and the new range eliminates model overlap that previously existed.
 
The range consists of three different machine series – 2100, 2600 and 3100.

The Puma 2100 (8"/65 mm bar) has two bed lengths – 520 and 760 mm – and there are six models for each bed length – 2100 (plain turning), 2100M (with driven tooling), 2100S (with sub-spindle), 2100MS (with sub-spindle and driven tools), 2100Y (with driven tools and Y-axis) , 2100SY (with driven tools, Y-axis and sub-spindle). This represents an extension of the technical options available over previous generations.

The Puma 2600 (10"/76 mm bar) again has two bed lengths, 750 and 1,250 mm, and the same six model-types in each.

The Puma 3100, a true 12" chuck machine (102 mm bar), has four bed lengths – 750, 1,250, 2,000 and 3,000 mm – and three models in each length: there are no sub-spindle variations for this large capacity machine. The Puma 3100 can also support a 15" chuck.

All new Pumas have the option of being supplied with belt-driven or built-in motor spindles, except for the Puma 3100 series which is belt-driven only

Sub-spindles can be belt-driven or built-in, and tailstocks can be tow-along or servo-driven.

The tool turret, common across all new Pumas features 12 positions, but with the ability to half index such that, with special tool holders, two tools can be fitted within a single station. And, in the case of end-working tools, on machines with Y-axes, there is the possibility to have three tools located at a single station.

The new Pumas are equipped with Fanuc CNC systems, but there are special Doosan elements included. A particularly novel feature is the automatic compensation for inertia when interpolating C-axis with others to generate surfaces. This takes account of the different characteristics associated with parts of different weight.

Tool load monitoring is a function, allowing thresholds for tools to be set during an initial cycle. There's also a CNC feature that allows for the logging of different operators' performances, while maintenance support information has also been enhanced. A utility to help users recover from turret malfunctions is another offering, while an on-screen calculator is yet another addition.

In keeping with green thinking, the machine light turns off if the operator panel is not touched for a prescribed length of time. Similarly, the machine goes into sleep mode if idle and the operator panel has not been touched for a set length of time.

Trouble-free maintenance has also been given attention, with, for example, sub-spindle alignment made simple through easily accessible adjustment screws; access to the sub-spindle itself is also straightforward and the coolant tank can be removed from the front of the machine, without the requirement to remove the chip conveyor.

Says Nick Frampton, Mills CNC's Managing Director:

'The new Pumas were launched from our Stand at MACH in June, and generated considerable interest and a high number of serious leads and enquiries.

'To cope with the high demand we have an aggressive stock programme in place to ensure that customers do not have to wait long for their new machines to arrive and be installed.

'We are now embarking on a new, imaginative marketing campaign to promote the new Pumas to customers, and invite any and every manufacturer making high-precision, complex parts to come and see the new machines in action at our facility in Leamington.

'Our doors are always open and I can promise any visitor that they'll be more than impressed with the new machines.'