Hanging-spindle VTLs up machining productivity

The installation at the end of 2002 of two hanging-spindle vertical turning lathes has brought substantial productivity benefits at an Abingdon, UK-based contract machinist.

The installation at the end of last year (2002) of two Hitachi Seiki hanging-spindle CS25 vertical turning lathes has resulted in substantial productivity benefits at Abingdon-based contract machinist, Holifields, 75 per cent of whose business is directly or indirectly in the medical sector.

One of the lathes is equipped with live tooling and a turnover station for complete machining of complex work.

An example of a medical job going through in February 2003 was a cylindrical copper part that starts as a 100mm diameter by 20mm thick billet and is face milled, drilled, counterbored and tapped.

Loading of raw material and subsequent un-loading of components is carried out within the machine cycle by the spindle, minimising idle time.

Says Roy Marshall, Sales Manager, "These machines produce parts continuously and do not stop until the batch is finished.

Contrast this with a manually loaded lathe whose operator cannot be present all the time; even a bar-fed lathe has to have the magazine periodically restocked.

The VTLs do not even stop for worn tool changeover, depending on batch size, as load monitoring warns if a cutter is near the end of its life and sister tooling is normally held in the turrets." The result, he says, is two self-loading production centres that can each operate at a much higher efficiency level than the equivalent horizontal-spindle machine with a dedicated operative.

In this way, Holifields is able to keep production costs down and stay competitive on price.

In addition, as a VTL stocked with raw billets works completely automatically, one operator can look after other machines at the same time, contributing further to minimising unit production costs.

The VTL programmer offers an insight into the user-friendliness of the machines.

During the first operation, the copper medical component has a large, central hole drilled through it so when the part is turned over, there is a risk of distortion if the chuck pressure is too great.

He comments that the machines offer a wide range of clamping pressures that can be adjusted precisely and automatically during the machining cycle to hold the part securely at all times without causing any dimensional movement.

Concluded Marshall, "Both VTLs are DNC-linked to our programming office, as are all our machines including the water jet profilers, so machine downtime for program changeover is short.

Combined with all the other areas where spindle idle time has been reduced or eliminated, these lathes have proved a big advantage to our business and have exceeded all our expectations.".

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