Product category:
CNC turning centres, mill/turning, multi-tasking centres, horizontal and VTLs.
News Release from: Traub Heckert UK | Subject: Traub CNC turning centres and Hermle VMC
Edited by the Manufacturingtalk Editorial
Team on 18 October 2002
Modern CNCs orchestrate new product
manufacturing
The in-built flexibility of each of two eight-axis universal mill/turning centres, a five-axis VMC and a hard turning centre paid dividends in a hydraulics product manufacturing change.
The in-built flexibility of each of the two Traub TNC 65 DGY eight-axis universal mill/turning centres, a Hermle C800U five-axis vertical machining centre and a Traub TNE 300 hard turning centre paid dividends when Havant-based hydraulic component manufacturer Eaton Fluid Power had to change its product design and production methods The machines were all originally configured into a machining cell turn-keyed by Traub Heckert UK of Brackley
This article was originally published on Manufacturingtalk on 22 May 2001 at 8.00am (UK)
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As production engineer Barry Ingles explains: "Since then we have produced two ranges of pump component kits on the three Traub lathes and the Hermle vertical machining centre.
It was the flexibility of the machines that gave us a smooth transition between product types, especially when we had to produce old and new in parallel." The Havant site produces a variety of hydraulic pump and control valves used on industrial machinery, off-highway vehicles and construction equipment.
Components produced in the Traub Heckert cell include a rotor body/ring, two end and two wafer plates.
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These are used in four different sizes of pump which are then exported to the United States for final assembly.
Whereas the current range of components involves a fairly complex design of rotor, previous pump versions had very complicated machining requirements especially for the end plates.
Components are produced to extremely tight tolerances while the high surface finish specification is mainly achieved through CNC grinding.
However, although the level of final process machining is high, it can only be effectively attained due to the consistency achieved on the metal cutting operations.
Of the cell produced components, the rotor is manufactured from heat treatable carbon steel, the ring from bearing quality steel and the two end plates from castings.
The initial specification of the Traub and Hermle machines was based on Traub Heckert's capability to supply a turnkey package that met Eaton's tough productivity and quality requirements.
However, the track record of Traub machines utilised elsewhere in the factory was an important confidence factor in the selection.
As Barry Ingles recalls: "On this project Traub Heckert was able to achieve the cycle times that we required while meeting six sigma SPC capability on three key features per component." He follows on to describe the involved production sequence of the rotor.
The billet is first machined in the soft stage on one of the Traub TNC 65 DGY machines in an operation which turns the outside diameter, faces the end, produces the main bore to a 20 micron process tolerance and generates internal grooves while the part is held in the opposed spindle.
It is the opposed spindle configuration of the TNC 65 DGY that allows the component to be completely machined in a seamless operation and once completed, the fully turned part is removed from the chuck by a pick-off unit mounted on the lower turret.
The next part, completed in the main spindle, is then transferred to the opposed spindle.
As a result, when the operator opens the door he can load the next billet into the main spindle and retrieve a finish turned part.
The rotor component is then loaded to the five-axis Hermle C800U vertical machining centre for slot milling which also has to engrave an arrow onto the periphery of the component.
A round profile at the bottom of the slots is then produced by broaching and the component is then heat treated as an intermediate operational process.
Following heat treatment, the component faces are ground parallel and then reset on the Hermle for precision drilling of 12 pin holes at the base of the slots.
These are locations for pins that activate the vanes of the pump and must also accommodate any up-down movement of the vanes.
Following a final heat treatment process, which takes the material hardness up to HRC63, the faces and slots are finish ground and the parts then transferred for hard turning on the Traub TNE 300.
This machine finish bores a non-splined portion of the main bore to a tolerance of 10 microns.
Says Barry Ingles: "We normally process rotors in batches of around 100 and changeover between different rotors is fairly straightforward.
On the Traub TNC 65 DGY, for instance, it is simply a case of changing chuck jaws and four tools which takes less than 15 minutes.
Similarly, the Hermle C800U needs very little adjustment between jobs because the machine was originally specified to accommodate flexibility of positioning through its five axes of motion, rather than for complex machining." The ring component follows a similar production path except that the powered turret tooling on the Traub TNC 65DGY machine is used to finish bore a pair of dowel holes.
The outside diameter and end faces are also turned before this component too is transferred to the Hermle C800U for boring two ports on the outside periphery of the ring as well as two bolt holes.
Originally, the Hermle was used to rough machine a cam profile on the inner diameter of the ring to a 0.1mm tolerance.
The component was then heat treated and the faces ground prior to finish turning in the hardened condition of the outside diameter to a 25 micron tolerance on the Traub TNE 300.
"We need a fairly tight tolerance on the outside diameter because it is doweled and bolted into a housing as part of the final assembly process," Barry Ingles explains and follows on to praise the effectiveness of the process.
"Hard turning on the Traub TNE 300 is faster than grinding and the machine is capable of combining dimensional stability with very acceptable levels of finish.
We mount the component on a special chuck type fixture which enables the complete periphery to be turned in a single set-up." The cast iron end plates are also finish turned on one of the Traub TNC 65 DGY machines.
While the latest component is much simpler in design than the previous type, which featured a dual 'kidney' profile on one end and a 'dart' type groove on the other.
Says Barry Ingles: "The generation of these profiles and grooves made full use of the machine's X, Z and Y axis milling capability." He then concludes: "All four of the Traub Heckert supplied machines have performed well, have proven to be very flexible and reliable.
On the Traub lathes, in particular, we have found tool setting using the ATC patented setting scope is far more straightforward than using a touch trigger probe," he maintains.
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