Closing the loop on boring adjustment

Posted on 24 Oct 2018 and read 602 times
Closing the loop on boring adjustmentWhile the automatic adjustment of offsets for turning and milling is commonplace and straight-forward, this has not been the case with fine-boring tools. However, with its development of Zenith, Cornwall-based Rigibore Ltd ( says it has eliminated the need for manual intervention and machine down-time to achieve micron-level adjustments.

Moreover, the Industry 4.0-compliant closed-loop system works seamlessly with in-process gauging and a machine tool’s control system.

In the past, making minute adjustments to fine boring tools required the tool to be removed from the machine and adjusted manually in a pre-setter — interrupting production with a time-consuming operation that required a skilled person to be involved.

However, having developed its ActiveEdge wirelessly adjustable boring bars, Rigibore’s next step was to “close the loop” on this semi-automatic system and make it fully autonomous. Now, Zenith can automatically compensate for insert wear, temperature drift and material inconsistency.

Rigibore says that with Zenith, tolerance bands can be narrowed to maintain bores as close to nominal size as possible; and while this may increase the number of times a boring bar needs adjustment — sometimes 1µm at a time — there is no loss of production.

Zenith makes use of Rigibore’s ActiveEdge boring tools, which feature boring cartridges that can be wirelessly adjusted.

This wireless capability is powered by batteries in the tool’s ‘yoke’, which means that the system can make adjustments to the boring tools wherever they are in the machine — in the spindle or in the tool carousel.

The ActiveEdge interface closes the loop between the tools, CNC system and the in-process measurements needed to calculate the adjustment offsets.

Once a bore has been machined, the part is automatically measured and its dimensional data is fed back to the machine’s CNC, which in turn uses macros to communicate with the ActiveEdge interface.

If the measurement falls outside process-defined limits, the interface calculates the adjustment required, transfers this to the tool and the offset is made automatically; this capability eliminates scrap (or greatly reduces it), reduces cycle times and cuts machine down-time. It also allows 24hr ‘lights out’ capability with zero human interaction.

An ultimate finish

For the machining of high-value components, Rigibore has developed its ‘two-cut finish’ solution, where the Zenith system backs off the tool from its pre-set size before an initial semi-finish cut is taken.

The bore is then measured, and the tool is adjusted by the precise amount needed to accurately achieve the specified size, thereby giving 100% confidence that the final bore will be correct.

Key to this process is ensuring that the in-process gauging is precisely calibrated — particularly where spindle probing is being used.

Here, Rigibore has partnered with Metrology Software Products (MSP), a Renishaw-associate company that guarantees spindle probe accuracy.

RigiboreRigibore’s chairman, Roger Bassett, said: “Tight control of the measurement process is critical. Zenith uses upper and lower limits to calculate and trigger any adjustments, so the accuracy of in-process measurement data is vital.

“Probes can easily go out of calibration, so it is essential that they are regularly calibrated against a known standard.

However, using Zenith and the two-cut approach gave significant savings to a customer producing high-value landing-gear assemblies, to the extent that the reduction in cycle time on one component alone paid back the cost of the Zenith installation.”

Mr Bassett says that Zenith also delivers significant benefits in high-volume manufacturing situations.

Making use of in-process gauging to feed data to the machine control and ActiveEdge interface, tool adjustments (up to seven boring cartridges per bar can be independently controlled) are made while the boring bar is in the tool carousel.

This means no interruption of machining cycles, no operator intervention and an Industry 4.0-compliant system — and all adjustments are logged on Rigibore’s ActiveNet PC software.

Moreover, in these high-volume environments, process capability (Cpk) is significantly improved through the use of Zenith, leading to an overall business performance benefit through a reduction in scrap and machine down-time.

In an example from an automotive company producing some 2 million aluminium con-rods a year, Cpk performance went from 1.17 to 1.97 after installing Zenith.

In conclusion, Mr Bassett says Rigibore is so confident in the capabilities of Zenith that, subject to carrying out a survey and analysis of a company’s current manufacturing requirements, it will install and make all necessary changes to the machine’s control free of charge.

The customer then has two options: pay for the system in full after a one-month trial period, or pay six monthly instalments calculated to allow customers to cover the entire cost by the savings generated by Zenith.

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