Six-axis readout improves machine control

Edited by the Engineeringtalk editorial team Jun 23, 2004

The retrofit of a Positip 880 six-axis readout and partial machine rebuild on a Boko vertical milling/boring machine gives UKAEA Fusion, Special Purposes Workshop, greater flexibility.

Following the retrofit of Heidenhain's new Positip 880 six-axis readout and partial machine rebuild on its Boko vertical milling/boring machine, UKAEA Fusion, Special Purposes Workshop, is now benefiting from greater flexibility on existing machinery.

The Boko WF1 vertical milling machine has long been a machine shop favourite because of its integrated rotary table, swivelling head and large z-axis capacity from either the head or quill.

This means there are four axes of linear movement and two rotary axes.

Most readouts can only cater for three linear axes; however Heidenhain's new Positip 880 is claimed to be the first machine tool readout that will cater for up to six axes including rotary axes.

Retrofitting an encoder to the rotary table allows the rotary movement of the table to be shown on the readout offering greater positional accuracy and ease of positioning.

However on the Boko this usually requires the removal and re-engineering of the underside of the table to accept the encoder.

This is both expensive and time consuming.

When the Special Purposes Workshop of UKAEA Fusion decided to have some rebuild work and a new five-axis readout fitted to its 20+ year old Boko WF1, Heidenhain's regional retrofit distributor Eric Clarke of Promtech Services (Milton Keynes), suggested a new approach; using an encoder retrofitted to the end of the rotary tables worm gear, combined with some reworking of the existing worm gear to remove excessive backlash.

Promtech Services called on the experience of Barry Lockett from Boxer Machine Tool Services (Milton Keynes) to provide both the machine rebuild and rework of the worm gear.

Dave Langridge (Workshop Supervisor) commented: "We are now positioning the rotary table to within 5arc-sec with backlash of less than 10arc-sec".

"A recent job involved 40 holes around a flange at a 9-degree pitch angle".

"Having the angular display on the readout made the job much quicker to produce".

Another of the features Langridge described as "fantastic" was the ability to sum both the head and quill movements into one z-axis display allowing either the head or quill to be used without losing the z-axis display value.

Specialising in R and D work for the fusion research programme worldwide, the Special Purposes Workshop provides the machining expertise for the UKAEA (Fusion), Special Techniques Group based at the Culham Science Centre near Abingdon.

Gordon Harrison, Manager of the Special Purposes Workshop, is a great advocate of getting the best from the machinery at the facility.

He added: "Promtech had previously undertaken two Bridgeport Interact CNC upgrades with Heidenhain controls - both with 4th axis capability".

"This gave us the confidence in their ability to undertake the work on the Boko".

"This has now returned the machine to 'as good as new' condition with the Positip 880 retrofit adding much greater flexibility in the type of work undertaken on the machine".

"This machine flexibility helps us to be competitive in tendering for work in our specialist field".