Mollart takes 5-axis machining into its deep hole drilling subcontract service

Mollart Engineering's, managing director Guy Mollart outlines how a full range of deep hole machining solutions for subcontract production has now been developed at the Chessington plant. He said: "We have progressively moved from standard deep hole drilling to an added-value process and machining services operation. Following our development for providing very fine micro-drilled holes as small as 0.5 mm diameter by 50 mm deep, we have also expanded into off-set hole and extremely close pitch hole drilling technology enabling very thin wall sections to be produced." He follows on to describe how the installation of the five-face and single- cycle ability of the groundbreaking Mollart Centeplex has added a further capability to the subcontract operations. With its ability to produce inclined holes up to + 15 deg by 2,000 mm deep via a programmable tilting axis to the spindle, the automated production of these features is now combined into a fully integrated machining centre process. Normally to machine inclined to a centreline features, such as compound angle holes, would require relocation and resetting of the component with all the problems associated with fixturing, positioning, additional programming, handling, inspection and measurement - all elements compounding the possibility of error. The Centeplex overcomes these problems with the added bonus of shorter lead and therefore delivery times. The five-axis, five-face capability Centeplex absorbed some £750,000 of development and build budget at Mollart and stands on the shopfloor alongside other specific Mollart machining developments such as the four-axis Mollart Prismabore, a six-axis FMC that incorporates automatic gundrill tool exchange and an Omnisprint three-axis, knee-type deep hole drilling machine. When combined with its in-house application and tool expertise, this range of machines available for subcontract machining of customer components takes Mollart Engineering to the top of the leader board in precision machining that incorporates any form of hole and especially deep hole requirements. The Mollart Centeplex is designed for medium to large workpieces with a table that is 2,000 mm by 2,740 mm and has a 16 tonne load capacity as well as having a full CNC rotary positioning axis. The table has axis strokes of 1,800 mm in X and 1,325 mm in Y. A totally novel combined over and under (shotgun style) spindle axis having a 22 kW, ISO 50 taper drive to the upper deep hole drilling spindle can provide a drill penetration depth of 2,000 mm while the lower milling spindle, with its 60 tool conventional magazine, is able to carry out normal production processes in the same setting. Centeplex has already initiated new orders for machining components for the oil and gas and mould plate industries due to the flexibility and cost competitive solution it can provide. Combined milling operations with the drilling of holes between 4 mm and 100 mm diameter have been carried out. For instance, due to the exceptionally long stroke available, Mollart Engineering was able to produce four holes 9.5 mm diameter in a 360 diameter stainless steel shaft that was 3,750 mm long. The shaft had a counterbore 950 mm deep in one end from which the holes were started and produced on a 110 mm PCD. In order to guide the deep hole drill, Mollart's application team developed a special fixture that was located in the counterbore with two opposed guide bushes to support the 3,400 mm long double carbide tipped drill. Following datuming using a Renishaw probe in the spindle, the Centeplex was able to position and initially part drill each hole true to centreline to a depth of 1,080 mm. The table was then indexed 180 deg, the part reset to its datum and each 9.5 mm hole was drilled from the opposite end to breakthrough into each original hole. The spindle was run at 1,800 revs/min and the penetration rate in the stainless steel material was 13 mm/min.