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Mills CNC unveiled a new range of Doosan Puma lathes at the recent Mach exhibition.
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.
This has helped keep costs down and means that, despite a significant improvement in technology and performance, the Puma lathes don’t cost much more than the older models they have replaced.
The new Pumas’ machine base casting has been increased by up to 158 per cent; their box guideways have been made 50 per cent thicker; and 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 per cent and the mounting area for the sub-spindle increased by 50 per cent, 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, while X and Y servos have their own cooling fans.
Angular contact spindle bearings 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.
The new range of 36 machines replaces the existing Puma 1600, 2000, 2500, 240, 280 and 300 ranges - a total of 40 machines - and eliminates the model overlap that previously existed.
The range consists of three machine series - 2100, 2600 and 3100.
The Puma 2100 (8in/65mm bar) has two bed lengths - 520 and 760mm - 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; and 2100SY - with driven tools, Y-axis and sub-spindle.
This represents an extension of the technical options available over previous generations.
The Puma 2600 (10in/76mm bar) again has two bed lengths - 750 and 1,250mm - and the same six model types in each.
The Puma 3100, a true 12in chuck machine (102mm bar), has four bed lengths - 750, 1,250, 2,000 and 3,000mm - and three models in each length; there are no sub-spindle variations for this large-capacity machine.
The Puma 3100 can also support a 15in 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 is common across all new Pumas features 12 positions, but has the ability to half index such that, with special tool holders, two tools can be fitted within a single station.
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.
One feature is the automatic compensation for inertia when interpolating C-axis with others to generate surfaces, which takes account of the different characteristics associated with parts of different weight.
Tool-load monitoring is provided, 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.
The machine light turns off if the operator panel is not touched for a prescribed length of time, and 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.

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Having begun in business supplying machinery ancillaries and spares, a service company found it was subcontracting out much machining, until it decided to set up its own CNC facilities.

If it’s a fast response that’s needed, look no further than Replacement and Maintenance Supplies of Alfreton, Derbyshire where, according to Andy Douthwaite and John Whelan, “we don1t know what to expect from the time we come in to the time we go home”.

But whatever it is, one thing is certain: “When a production line is down because of, say, a broken shaft, the customer wants an immediate response”.

Before setting up the business in 1987, both directors were involved with the specialist bearing side of Unipart and this explains why, initially, Replacement and Maintenance Supplies was wholly focused on supplying bearings and related power transmission products such as gears, seals, pulleys, bushes and belting.

Today, however, it also offers a comprehensive machining service tailored specifically to repair work.

Although the company has an off-line programming capability, most of the programming takes place on the machine.

That’s why a Proturn VL 425 manual/CNC lathe supplied and installed several months ago by XYZ Machine Tools has become a firm favourite, and has now been joined by a XYZ SM 4000 manual/CNC bed mill.

Both machines are equipped with the innovative Prototrak control that makes switching between manual and CNC operation on the same set-up straightforward and fast.

“The software is brilliant and it’s ideal for one-offs,” says Andy Douthwaite, “Before we set up the machine shop three years ago, we were placing quite of a lot of work with local engineering companies and I noticed they were using XYZ machines.

Having followed their example, I am enjoying the benefits because the new machines are quick to set-up and this business is all about speed.” The 10HP/7.5kW Proturn VL 425 high-speed gap bed lathe already installed is available with either 1.25m or 2m between centres, and features an 80mm spindle bore and spindle speeds from 15 to 2500 rpm.

Constant surface speed is also standard, courtesy of the VL control that provides custom-designed screens to make every operation - whether a clearance cycle, profiling or drilling routines, or standard and custom threads - follow in a logical and clear sequence.

Unlike other CNCs, all the operator is required to do is to define the part geometry and stock dimensions.

From these inputs the toolpath, including all roughing passes and the speeds and feeds, is generated.

The emphasis on breakdown work at Replacement and Maintenance Supplies dictates a high level of individual skill and equipment that is both versatile and easy to use.

“Quantities are usually one to five-offs and most of the time we are working without drawings,” says Andy Douthwaite.

“So we only recruit highly skilled people who can deal with a job from start to finish.

This means liasing directly with the customer, measuring up on site where necessary, using every aspect of our machining facilities, including MIG/TIG welding, inspecting the end result and, above all, knowing that, once installed, the replacement part will have the customer up and running in the shortest possible time.” Since speed is of the essence, the company tends to restrict its activities to relatively local customers and refuses for the most part to quote for production-type work that could restrict the flexibility of its machining operation.

But, says Douthwaite, “we are always re-inventing ourselves and this brings us into contact with new customers.

If, for example, we are asked to machine a replacement impeller, we develop a new skill and we then look to where we can offer that particular expertise.”.

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