First US showing of innovative two-channel CNC system for machine tools with up to five axes

NUM is showing its new two-channel CNC kernel for the first time in the US at IMTS. Designed specifically for developers of small to medium sized machine tools with four or five axes, the Flexium+ 8 CNC provides an exceptionally cost-effective control solution that in many cases eliminates the need for a second CNC kernel. NUM is also launching a new version of its 3D simulation software which now includes kinematic equations to support advanced 5-axis machining applications.

The Flexium+ 8 CNC kernel offers two CNC channels and accommodates up to five axes, four of which can be interpolated. At any one time, either CNC channel can be used to control a spindle motor and four axes, instead of the full complement of five axes. This control flexibility helps designers to lower the cost of machines with complex synchronisation requirements. For example, on a grinding machine, one channel could control two X/Z axes and a spindle to perform the grinding functions while the other channel controls two rear mounted U/W dressing axes. Each channel can either run its own part program asynchronously and operate autonomously – much as if it had a dedicated CNC kernel – or the two channels can be synchronised. Control of one to five axes, or a spindle, can be passed on-the-fly from one channel to the other, to maximise use of available hardware resources.

Like all NUM CNC systems, the Flexium+ 8 firmware includes RTCP (rotation around tool centre point) and Inclined Plane functions. Pioneered by NUM, the RTCP function provides enormous advantages for precision 5-axis machining applications. By very accurately controlling the machine’s rotary axes, such as a dual rotary tool-head or a table and cradle holding the part, the function enables the tool to be held in contact with the part, and at a constant angle, throughout the machining process. The RTCP function is even more beneficial if the part is not flat; it automatically computes all the offsets due to factors such as tool head mechanics and tool length that are needed to maintain accurate tool contact.

As its name implies, the reference point for all RTCP calculations is the tool’s centre, or contact point – and not the tool-head position, which would require the contact point to be determined mechanically. The difference between these two methods has a major impact on machining. For example, if the distance between the tool tip and the centre of the rotary head is 600 mm, a head positioning error of just one-hundredth of a degree will cause a tool tip error of 0.1 mm; without the RTCP function, this can result in tool or part damage. Another significant advantage of the RTCP function is that the programmed coordinates are those of the part contour, not the machine, which makes the programs machine independent and means that tool offsets can be applied without program modification. The RTCP function is implemented as part of the Flexium+ CNC post-processor, which further helps to ensure part program portability.

NUM recently integrated the complex coordinate transformation algorithms of the RTCP function into its Flexium+ 3D simulation software. Users can now analyse and optimise the kinematic performance of part programs for 4- and 5-axis machines easily and accurately by employing advanced 3D visualisation techniques. The software includes comprehensive collision monitoring and detection to guard against tool, part or machine damage.

For maximum flexibility, NUM offers two versions of Flexium+ 3D simulation software. One is designed for standalone use without a CNC system, as a production planning tool for verifying part programs. The other is fully integrated with the Flexium+ HMI (human machine interface) and is connected to the machine’s CNC system. Unlike many competitive CAD/CAM visualisation systems, this uses the NC code that is being processed by the CNC interpolator to create a true real-time representation of machine operation. Part programs can be simulated at the same time that other programs are being executed on the machine, and the same part program can be executed and simulated simultaneously. The simulator visualises the tools, the machine’s kinematic properties and the work piece blank as 3D volumes, and shows the TCP (tool centre point) and material removal as the tool moves along the machining path defined by the part program.

The Flexium+ 8 CNC kernel can be used with various NUM drives. For optimum performance it is best teamed with the company’s latest NUMDrive X digital servo drive modules. These drives are some of the smallest on the market and offer numerous configuration options to help designers minimise machine build costs through use of axis-appropriate technology. The drives use advanced DSP control techniques to maximise the CNC kernel-to-drive servo bus speed, and feature high loop bandwidths and special acceleration algorithms for uncompromised speed and positioning accuracy. A numerical processor in the CNC kernel, together with the precision number-handling capabilities of Flexium+ software, helps to ensure a high overall CNC resolution and facilitates ‘sub nano’ interpolation between axes.

Flexium+ 8 also features an inherently scalable safety architecture known as NUMSafe. A safety PLC built into the CNC system oversees all critical operations; in conjunction with NUM’s safe I/O modules and the safe motion monitoring circuits in NUMDrive X servo drives, this enables machine designers to implement high-integrity safety functions using minimal additional components. The safety architecture complies with the EN ISO 13849-1 machinery safety standard up to PL e, as well as the EN 61800-5-2 functional safety standard for variable speed drives, up to SIL 3.

NUM’s Flexium+ CNC platform now includes three CNC kernels, all of which are on display at IMTS, enabling machine designers to configure cost- and performance-optimised control systems for a wide range of automation. The product series comprises the Flexium+ 6, which is also on show for the first time in the US, the Flexium+ 8 and the Flexium+ 68. Flexium+ 6 has a single CNC channel, can control four interpolated axes and a spindle, and is designed for small to medium size machines. Flexium+ 68 is designed for larger and more complex machine control applications. Offering up to eight CNC channels, each accommodating up to nine interpolated axes and as many as 32 spindles, it provides an excellent foundation for multi-spindle applications such as transfer machines.

The Flexium+ platform is backed by powerful software. All CNC, servo drive, I/O, automation PLC and safety PLC functions are programmed using a single unified toolset. A fully customisable HMI allows users to add value to their machines, through improved ergonomics and touch-sensitive controls. NUM’s application support software covers a broad range of machining functions such as grinding, tool grinding, turning, milling, gear hobbing, shaping and finishing, as well as water-jet, laser and plasma cutting. Many of these software packages are regarded by machine tool manufacturers – and users – as industry standards.