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SUBCONTRACTING TURNING
Two into one will go
40 UK engineers visiting the Traub factory in Germany recently were impressed at
the new CNC sliding headstock technology on offer. Solutions reports.
T
urned parts subcontractors often do not know whether asset, as it covers the application range of two machines.
it will be a long or a short component, relative to its “I like the open front design of the lathe and deep swarf tray for
diameter, that they will be asked to machine next. chip management. With a 20mm machine, even on fairly intensive
Long parts require a true sliding head lathe with a guide production jobs, swarf is not normally a problem. However, if the
bush to support the bar close to the cutting tool, while short parts are material and tooling generate a lot of stringy swarf, the generous
more economically produced on a fixed head lathe. working volume could be a real plus point. If Traub decides to
With this in mind, German lathe manufacturer, Traub, has introduce a 32mm version of the lathe, the open design will be of
introduced a new CNC sliding head mill/turn centre on which it is even greater benefit.”
possible to select whether to turn a component with the support of a
guide bush, or without it. Normally, a manufacturer would need to
Ian Sheldon, managing director,
purchase two separate lathes to have the same versatility.
Designated TNL18, the machine has a capacity of 20mm.
Witon Engineering
According to Traub, it was launched to acclaim from engineers from Mr Sheldon amplified the above comments about the benefits of while the top turret has an X axis plus a simulated Y axis, whereby its
all over the world, including 40 from the UK, at an open house held at being able to operate with and without a guide bush, describing the rotation is interpolated with the X axis and the main spindle’s C axis.
Traub’s Reichenbach factory at the end of 2009. The UK party was TNL18 as an ideal subcontractor’s machine that allows a wide Turret rotation is faster than that of an indexed turret, matching the
accompanied by Geo Kingsbury Machine Tools – the sole agent in spread of mill/turn work to be carried out on one CNC lathe. linear speed of a gang tool post. Chip to chip time is under 0.3
the UK and Ireland for Traub turning machines as well as those However, he went further: “I can see situations where the machine seconds for adjacent turret stations, maintaining the same low levels
manufactured by Traub’s parent company, Index. could be set up in sliding head mode and then the decision is taken to of non-cutting time for which sliding headstock lathes are renowned.
Following the event, three UK visitors spoke very positively about operate it in fixed head mode instead, or vice versa,” he speculates. The 3-axis counter spindle is mounted on the same compound
the ‘two in one’ sliding head lathe. “The setter might change his mind as to which will produce the slide as the lower turret and swivels independently around the same
required accuracy in the shortest cycle time or perhaps production axis as the turret to offer a parted off component to seven rear
Nick Iacobucci, managing director,
has started but the bar is slightly out of round and it is proving endworking tools, three of which are live, for completion of
difficult to hold tolerance with the stock rotating in the guide bush. operations on the reverse.
DKW Engineering
“During the recession, subcontractors have changed their While work is in progress on the back of a component, front end
“The first thing that struck me was the enormous working volume of operations drastically, relying on one setter to cover three, four or turning and prismatic machining with one or two tools can be carried
the machine – more like that of a fixed head lathe. It is excellent for even five machines. However, if tool changes are frequently needed out simultaneously in the main spindle, allowing up to three tools to
setting and programming and gives good visibility all around the and the jobs run for only a short time, it can be difficult to cope with be in cut simultaneously.
machining area. all the setting quickly enough, so machines end up standing idle.
“Traub says that the machine can be swapped between operating “Mill/turn centres like the TNL18 that hold a large number of tools
with or without a guide bush in half an hour, but its engineer in their turrets are therefore very beneficial, as you can leave the > GEO KINGSBURY
converted the machine in half that time. It is certainly quick to change cutters in the machine and they will cover the majority of jobs.” www.gkholdings.com
over but I question whether many subcontractors would bother. If He continues:“The spacious
there are fixed head bar auto’s on the shopfloor, it is more likely that working area is another plus
shorter parts will be put on those and the TNL18 will be kept in full point, making it easy to access
sliding head mode. the tooling – even the reverse
“That said, the lathe would make a good entry level machine, endworking tools, when they do
allowing a start up subcontractor to cope with a wide variety of need changing. I also like the
mill/turn work economically with just one machine. robustness of the backworking
“Admittedly, the price of the Traub lathe is higher than that of an tool block and the tool clamping
equivalent 20mm slider from some other suppliers, but someone arrangement, which is more
would only need to buy one machine rather than two. Moreover, the substantial than on most sliders.
quality and robust build of the TNL suggests that the machine will go “Finally, the power of the
on forever producing top accuracy parts.” machine stands out compared
In his comments, Mr Iacobucci draws attention to the TNL18’s with others on the market.
ability to be operated with or without a guide bush. Bar may be European built machines,
gripped conventionally by a collet and fed by up to 205mm through especially those from Germany,
the guide bush, giving all the classic advantages of Swiss-type tend to have higher power and
turning, including maximum rigidity and accuracy when machining higher torque spindles
long, thin components. compared with machines from
Alternatively, the bar is clamped by a collet in the spindle and the Far East and the TNL18 is no
moved 80mm into and out of the cutting zone using the Z axis exception. Even the power to the
motion of the headstock travelling at up to 40m/minute. This set-up is driven tooling is greater.”
best for machining shorter components as there is no need to bridge
the gap between the collet and guide bush, so bar remnants are Mr Sheldon referred to the
much shorter and material is saved. large number of cutters resident
Eliminating the guide bush avoids the need to use expensive in the new Traub lathe. A
ground stock. The process is also ideal for applications where a singular feature of the machine
guide bush is impracticable, such as when producing plastic is the absence of gang tooling
workpieces and those machined from profiled stock. and the inclusion of two turrets
that are rotated as full NC axes,
Brian Owen, managing director,
instead of being indexed and
clamped. They may therefore be
Precision Products
positioned at any angle through
“Coming from a sliding head cam auto background, on which it was 360°, so multiple toolholders can
no problem to swap the guide bush in and out fairly quickly, I always be used, allowing up to 54
thought that CNC sliders were inflexible in their inability to be cutters in the working area. All
configured for both modes of operation – until now. The facility to stations can carry either a static
operate the TNL18 with or without a guide bush is undoubtedly an turning tool or a live cutter.
An eight station turret is
mounted above the spindle
centreline, below which is a
seven station turret. The latter
moves in three orthogonal axes,
www.pesmag.co.uk
Production Engineering Solutions • March 2010 31
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