Around 12 months ago, SPP decided to reconfigure its split casing machining process into roughing (on a refurbished Mecof gantry mill) and finishing (on a new Dugard Eagle HBM-4 horizontal borer
). Initially, it was necessary for roughing and finishing operations to be completed on the HBM-4 while refurbishment of the older machine was taking place. Now, with the two machines up and running, SPP has been able to refine the machining process – balancing cycle times and significantly improving throughput.
“The fact is that, when we were first researching our options, everyone we spoke to said that if we were going to continue with shopfloor programming, the Heidenhain control is the most user-friendly,” says SPP’s production engineering manager Gary Hurcombe. “This has proved to be the case because our machinists really like the flexibility and ease-of-use of these new controls.”
Retrofitting of the iTNC 530 control to the Mecof gantry mill was undertaken by Simon Hopkins of SDH Controls & Services of Worcester (an approved Heidenhain TNC
retrofitter), which also fitted a Heidenhain TS 220 touch probe. This probe has an accuracy of ±5 micron, using a standard stylus and a repeatability of ±1 micron at a probing velocity of 1 m/min. Heidenhain applications engineer Martin Lyons then provided the TS probe training, a crucial requirement, as probing of key features on the raw castings determines the optimum set-up for the machining of datum faces, with tighter alignment tolerances being achieved, and also determines the amount of material to be removed from wear ring bores prior to finish machining of the assembled halves of the split casing on the new CNC horizontal borer.
“Martin Lyons, in co-operation with Seco Tools, which supplies around 80 per cent of our tooling, wrote a parametric program that enables us to remove the optimum amount of material from the wear ring bores of all sizes of pump casing using a ball nose cutter,” says Mr Hurcombe. “This new method has eliminated the extreme boring bar overhangs required when machining on the old manual horizontal borer, and will also reduce wear and tear on the new CNC horizontal borer.”
SEARCH AND REBUILD
Another OEM recently requiring a prismatic machining retrofit solution was West Lothian-based Balfour Beatty Rail Track Systems, which produces switches and crossings for the railway industry.
Broadbent Stanley has already supplied four large capacity machines as part of a turnkey project for the company, but on this occasion Balfour Beatty didn’t have a machine to rebuild. The quest was to locate a large capacity plano-mill, rebuild it and retrofit a CNC control system.
Within a short period of time, a 1970s Waldrich model SLP 220 manual plano-mill was sourced, given a full inspection and a detailed report produced on the work required to completely strip the machine, rebuild the slideway systems, add a milling head and convert to CNC.
Once the machine was stripped into component parts, the detailed modifications began. Its two heads were re-engineered and converted to AC drive utilising 60 kW GE Fanuc motors. And while Balfour Beatty wanted to retain the 60 ISO taper vertical spindle drive, the company also needed the flexibility of universal heads. Thus, two new universal heads were sourced, modified, and adapted for ease of removal and replacement by the machine operator.
New slideway systems were provided for the heads, along with the elevating rail, which was redesigned with synchronised re-circulating ballscrews and hydraulic counterbalance, retaining the full 800 mm of vertical travel required. Heidenhain linear scales were also fitted to the cross-rail making it a fully closed-loop system. The table top was re-machined and fitted with hydrostatic slideways driven by a twin pinion anti-backlash system.
The machine required six axes under CNC control, and the GE Fanuc model 31i controller was selected in tandem with the latest high torque digital drives.
Elsewhere, at David Brown Gears and Transmissions of Huddersfield, the management and engineering teams were becoming increasingly frustrated with the reliability of one of the company’s internal grinding machines – a 1970s VEB Berliner manufactured in the former East Germany.
Purchased in the 1980s, the machine has proven a good investment and still performs well mechanically, maintaining tight tolerances. The original PLC of indeterminate manufacture seemed to be the root of the problems, and a call was made to nearby CNC retrofit and rebuild specialists Electronica Mechatronic Systems
has developed a new solution to the replacement of obsolete linear scales on elderly machine tools.
Based on its GS126 glass linear encoder
, which features a 40 micron grating pitch as standard, the new product features 11μA analogue output, making it compatible with existing DROs used on many turret mills.