Z-Nano IR improves tool breakage control

Blum Novotest

Z-Nano IR tool probe

The Z-Nano IR tool probe from Blum Novotest has improved tool breakage control at Lindenmaier’s automotive plant.

A broken drill bit in a machine is annoying but not really a problem.

However, if the breakage remains undetected and the downstream tools continue to machine the imperfectly drilled hole, it may well turn out to be very expensive.

This is especially the case with downstream tools such as polycrystalline diamond drills, which cost between GBP800 and GBP1600 depending on the version chosen.

These PDC drills are used in Lindenmaier’s NC machine when large pitches or phase passages have to be drilled in vendor parts destined for the automotive industry.

Hydraulic control blocks are formed from aluminium forging alloy on its horizontal machining centres using up to 60 tools.

These blocks are fitted in the convertible hoods of hardtop cars.

Used in vehicles produced by Volvo, Mercedes and Volkswagen, they contribute to the fully-automatic, smooth opening and closing of hardtops.

A factory in Laupheim produces purely cubic parts, most notably hydraulic control blocks, which are formed applying five-axis machining, for active driving control and driving safety such as ABS and ESP as well as convertible hood controls.

Hans-Dieter Poeschko, head of production for Laupheim, said: ’Compared with steel machining, tools used in aluminium milling are extremely wear-resistant and such tools enjoy a very long life cycle.’ 12 control blocks are clamp-mounted on a pallet for machining, which is the equivalent of one-hour processing time.

If one of the clamped tools breaks during this time, the damage will not be detected until the next change of pallet.

If one of the centre bits breaks right at the beginning, all downstream tools (up to four downstream drill bits) will move into the imperfectly drilled hole and get damaged in the process.

In the case of the PCD drill bits this would inevitably involve high costs.

Tool breakage control is therefore absolutely essential.

New generations of machine tools very often comprise an integrated tool breakage control.

Lindenmaier’s NC machine had to be retrofitted.

What was wanted was a mechanical measuring system able to check tool perfection.

The system had to be cost-efficient and ready for fast retrofitting, adapted to the rough ambient conditions inside the NC machine and offer reliable data transmission to the NC unit.

Blum-Novotest’s Z-Nano IR tool probe provides an accurate repeatability of 0.5 micron, and the mechanical measuring system can be used to monitor tools with a diameter down to about 0.5mm.

In the case of Lindenmaier, tools with a diameter of about 0.6mm are tested with reliable results.

The Z-Nano IR is also safe in respect of robustness.

Fully encased as per IP68, it could theoretically be immersed in coolant without any liquid penetrating the inner workings.

The linear working principle of the probe prevents the generation of transverse forces during the scanning process.

As a result, shearing forces that could affect the tool cannot develop, so that even extremely small tools can be monitored reliably.

The linear working principle is applied to provide protection for fine tools while also providing variation of the contact point on the lip of a tool in case of wear on the measuring surface.

However, it should be mentioned that the measuring surface is extremely wear-resistant.

Even after many months of three-shift operation at Lindenmaier, it is still looking as good as new.

Apart from very small tools, this system is suitable for detecting large tools such as a boring head.

Blum-Novotest effectively guarantees that the measuring principle of the Z-Nano IR is wear-free.

The interior contains a miniature light barrier.

When the probe is deflected a precision pin shades the light barrier, triggering a switch signal.

This non-contact switching signal generation prevents wear and tear.

Two Z-Nano-IR probes have been in action at Lindenmaier’s since spring 2008.

Each pallet is fitted with one probe.

The reason for this is the integrated pallet changeover facility.

While the machine operator is loading a pallet with unfinished parts, work pieces are being machined on the second pallet.

This automatically sets the requirements for signal transmission, making a hardwired execution of the probe impossible for this machine configuration.

The wireless data transmission makes the Z-Nano IR a good solution for machines of this kind.

The switching signal is sent via infrared transmission to IR receiver IC56.

The IR receiver is a standard interface that communicates with other products made by Blum-Novotest, such as the workpiece probes.

At Lindenmaier the probe is operated in ’dual mode’, allowing the two measuring systems to be clock-triggered by only one IR receiver, saving the expense of a second IC56.

A Lindenmaier employee is typically responsible for six to 10 machines.

He takes 10mins to load a pallet with parts and machining each part takes between 30 and 60mins.

Prior to the introduction of the Z-Nano IR, it was standard practice to program a stop when critical tools (prone to breakage) were used so that the NC machine stopped after the cycle of such a tool.

The fitter then checked whether the tool was undamaged and afterwards released the machine.

As a result the NC machine remained idle for up to 10mins until a member of staff was ready to continue with the program.

Now, such a critical tool will be scanned by the probe and the NC program only stops for actual breakages.

As Poeschko outlined, the savings potential for cost of tools is up to 75 per cent, dependent on the number of tools used in a row.

The Z-Nano IR was used effectively from the start of the project with hydraulic control blocks.

Therefore a before/after comparison does not apply.

Previously it was quite common that the first tool in a machining chain was broken but the NC program continued as before.

This usually resulted not only in broken tools but also damaged workpieces.

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