Star of the April Open House at the Haas Automation (01603 760539) Midlands Technical Centre near Leicester was the UMC-750, a recently-launched vertical machining centre capable of 3+2 or 5-axis simultaneous machining.
It is not the company's largest VMC; with traverses of 762 by 508 by 508 mm in X, Y and Z, its machining envelope is smaller than all but two of the VF Series of vertical machining centres.
Nor is the UMC-750 the first dedicated 5-axis machine from the US manufacturer; it joins three VF models adapted to incorporate a powered A- and B-axis trunnion (VF-2TR, VF-4TR and VF-6TR), supporting 3+2 or 5-axis simultaneous movement. On the VF-2TR, the removeable trunnion mounts on the table; on the other, larger models, the trunnion mounts on bearing trucks in place of the table. And, trunnions and rotary tables can also be inserted into Haas 3-axis CNCs to perform 3+2 and simultaneous 5-axis machining. The largest of three models of trunnion available, TR310, has 310 mm diameter circular platter and 787 mm maximum diameter component swing.
Still, the UMC-750 is Haas's most serious entrant in the world of 5-axis machining so far. To that end, it has a much larger swivel table than the VF TRs, 630 by 500 mm, which is mounted to tilt in the B-axis, perpendicular to the door opening, rather than the A-axis trunnion on the VF TR machines. Table capacity, 660 kg, is also super-sized; it is three times greater than on the VF-6TR, and the spindle above it offers speeds and feeds to match. And rapids on all three axes are more than twice as fast on the UMC-750, up to 30.5 m/min.
Another key difference from other Haas vertical machining centres is its processing intelligence. First, the Haas proprietary CNC control is beefed up to handle the demands of simultaneous 5-axis machining: processing speed is 1,000 blocks/sec and maximum contouring speeds are 30.5 m/min "without risk of distortion to the programme path", Haas says. Extra memory and a high speed machining option are also available (see box).
Second, new control software compensates automatically for varying part set-ups in both 3+2 axis machining (using 'Dynamic Work Offset') or 5-axis continuous machining (using 'Tool Centre Point Control'). Similar software is offered by control manufacturers Heidenhain (tool centre point management and preset tables) and Fanuc (G68.2). TCPC enables an operator to send the same program to any Haas 5-axis UMC, regardless of minor disparities between the actual and programmed part position on the table. After performing a probing cycle (and a wireless Renishaw-made probe comes included with the machine), it automatically adjusts, and then starts machining.
PART-SPECIFIC PROGRAMMING
Says technical sales manager Adam Cole: "On the old trunnion machines, I would have to write a program relative to [a particular] machine and [its] set-up. That's been the big move forward for us, that the program is now specific to a part, as opposed to a machine." He continues: "Previously, if I didn't have the exact same fixture, but one that was slightly higher, I would have had to rewrite the code."
With 5-axis work, it is all about the program. Pat Fenn, Haas Automation commercial director, says that although programs for 3+2 machining are not so very difficult to write manually, as they consist of sequential movements of spindle (in three axes) and table (in two), simultaneous 5-axis programs are virtually impossible to generate without CADCAM software.
A CHANGING MARKET
CADCAM's purchase cost has been a major barrier to the adoption of 5-axis machines among subcontractors, Fenn believes. But as its price has fallen in the last few years, CADCAM has come within the reach of many subcontractors, making 5-axis machines more attractive, too. One big benefit of 5-axis for subcontract work is fewer fixture changes, which decreases part cycle time: instead of having to manually reposition a workpiece multiple times, the operator can just leave the part inside the machine, and let the swivel table move it around.
In any case, the launch of the UMC-750 marks an attack on a new sector for the American machine tool brand. One market targeted by the UMC-750 is existing Haas customers that haven't tried 5-axis. Here the standard Haas interface and sales and service support helps grease the wheels of transition. States Cole: "For the subcontractor that has got Haas already, it's the perfect step into 5-axis, with the same Haas controls, the same everything".
Another group of potential customers are those already familiar with 5-axis machines. For this market, the machine's low price (base spec machine is £120,000) is a big selling point, as are its control and the availability of options such as through-tool coolant (see box). Some 15 machines have been sold in the UK since the first order was received after the MACH exhibition in April 2014.
Technical specifications and options
Base spec, including 8,100 rpm 40-taper spindle, comes in at a price of £120,000. Trunnion table B axis tilt is -35º to +110º, which is markedly asymmetrical to avoid the risk of collisions with the 40 tool automatic toolchanger that takes tools from a left-hand side-mounted rotary magazine. Table C axis rotation is 360º.
As exhibited in Leicester, the UMC-750 had a belt-type chip conveyor, 12,000 rpm spindle, through-tool coolant and software enhancements, and is offered at a price of £142,000.
A 'Superspeed' version of the UMC-750 also launched in 2014. For an additional £20,000, buyers get a 15,000 rpm spindle, faster toolchanges and rotary speeds three times faster thanks to a rollercam-based table that replaces the standard worm-and-wheel drive. One superspeed unit, designated UMC-750SS, has been sold in the UK already.
Alternatives
While not offered by every machine tool manufacturer, relatively simple 5-axis machines do exist. Here are five examples, entry level and beyond.
-Hurco VMX series (01494 442222). Sample model: VMX30Ui. Five-axis machine with trunnion (traverses: 762 by 510 by 520 mm in X, Y and Z). Table diameter is 248 mm. Twenty-four tools standard. Rapid traverses are 35, 35 and 30 m/min (X, Y and Z). Spindle speeds are 10,000; 12,000; 15,000 rpm.
-Feeler U600 (ETG: 01926 818 418). Five-axis machine with trunnion (traverses: 520 by 460 by 400 mm in X, Y and Z). Table diameter is 600 mm. Thirty tools are standard. Rapid traverses are 30 m/min (X, Y and Z). Spindle speed is 15,000 rpm.
-Doosan VC 630-5AX (Mills CNC: 01926 736736). Five-axis machine (traverses: 650 by 765 by 520 mm in X, Y and Z). Table diameter is 630 mm. Sixty tools are standard. Spindle speed is 12,000 rpm (up to 20,000 as an option).
-DMG Mori Seiki Eco range (0247 651 6120). Sample model: EcoMill 70. 5-axis machine with swivel rotary table (traverses: 750 by 600 by 520 mm in X, Y and Z). Table clamping area is 800 by 600 mm. Thirty-two tools are standard. Rapid traverses are 24 m/min (X, Y and Z). Spindle speed is up to 12,000 rpm.
-Mazak Variaxis range (01905 755 755). Sample model: Variaxis i-500. Five-axis machine (traverses: 350 by 550 by 510 mm in X, Y and Z). Maximum workpiece diameter is 500 mm. Thirty tools are standard. Rapid traverses are 60, 60 and 56 m/min (X, Y and Z). Spindle speed is 12,000 rpm (standard).
