Retrofit Using Six-Axis DRO Offers Flexibility

Following a retrofit using Heidenhain's (Schaumburg, Illinois) Positip 880 six-axis readout on a partial machine rebuild of a vertical milling/boring machine, UKAEA Fusion Special Purposes Workshop in England is now benefiting from greater flexibility on existing machinery.

The BOKO WF1 vertical milling machine has been a machine shop favorite because of its integrated rotary table, swiveling head and Z-axis capacity from either the head or quill. This translates to four axes of linear movement and two rotary axes.

Retrofitting an encoder to the rotary table allows the rotary movement of the table to be shown on the readout, which offers greater positional accuracy and ease of positioning. On the BOKO, however, this usually requires the removal and re-engineering of the underside of the table to accept the encoder. When the Special Purposes Workshop of UKAEA Fusion decided to get some rebuild work and have a new five-axis readout fitted to its 20-year-old machine, Eric Clarke from Promtech Services (Milton Keynes, United Kingdom), Heidenhain's regional retrofit distributor in the United Kingdom, suggested a new approach. This approach incorporates an encoder retrofitted to the end of the rotary table's worm gear, combined with some reworking of the existing worm gear to remove excessive backlash.

“We are now positioning the rotary table to within 5 arcseconds, with backlash of less than 10 arcseconds,” comments Dave Langridge, workshop supervisor at UKAEA. “A recent job involved 40 holes around a flange at a nine-degree pitch angle. Having the angular display on the readout made the job much quicker to produce.” Mr. Langridge described the ability to sum both the head and quill movements into one Z-axis display, which allows either the head or the quill to be used without losing the Z-axis display value, as “fantastic.”

Specializing in R&D work for the fusion research program worldwide, the Special Purposes Workshop provides the machining expertise for the UKAEA (Fusion) Special Techniques Group based at the Culham Science Center near Abingdon. Gordon Harrison is the manager of the Special Purposes Workshop.

“Promtech had previously undertaken two Bridgeport Interact CNC upgrades with Heidenhain controls—both with four-axis capability,” Mr. Harrison says. “This gave us the confidence in its ability to undertake the work on the BOKO that has now returned the machine to ‘as good as new' condition with the retrofit, adding more flexibility in the type of work undertaken on the machine. This helps us to be competitive in bidding for work in our specialist field.”