Probing for productivity

With quality control in the production environment now standard practice, integrating probes with CNC machines is becoming more widely accepted by Australian manufacturers. Katherine Crichton reports.

With quality control in the production environment now standard practice, integrating probes with CNC machines is becoming more widely accepted by Australian manufacturers. Katherine Crichton reports.

DESPITE offering significant productivity improvements by reducing the downtime associated with manual set-up of tools, fixtures and work pieces, as well as increased inspection accuracy of first-off components, Australian machine-tool users have been reticent to using probing in their manufacturing operations.

However, advances in probing technology, combined with improvements in machine-tool usability, has seen the increased application of probes to the set-up of CNC machine tools.

Paul Frecker, GM of IS Tecnik, believes local industry is on the cusp of wider adoption of probes, bringing Australian manufacturers in line with their overseas counterparts.

“Initially it takes a while for new technologies to be taken up in Australia because of our lack of exposure to what is out there.

“Significantly smaller production runs and uncertainty about where the next job is coming from also makes the investment into new technologies or process developments a lot harder to justify, but there is a shift of thinking driven by increased confidence in new probing systems,” Frecker explained to Manufacturers’ Monthly.

With probes for CNC machines now available that can operate substantially faster than traditional probing systems, Frecker says this has helped to eliminate one of the prime concerns about using probes on machine tools – speed of measurement.

“Modern probe technology uses an optical switch mechanism rather than a mechanical switch inside the probe.

“Processes are able to be performed much faster because the optical probers are much more resistant to false triggers such as acceleration and vibration and won’t engage until it touches something.

“Being able to measure tools at operating speeds is a very powerful advantage for machine tool users.

“This has a huge impact when you are measuring something on a production machine, as the user is essentially tying the machine up doing a non-productive process (measuring) and time is money.”

High speed probing

Advances in probe technology, such as using laser measurement systems, is seeing probes used in a wider range of manufacturing processes such as high speed machining (HSM) applications.

“When measuring tool edges it is important to minimise or eliminate the need to touch them as this tends to damage the tool,” Frecker explains.

“The laser allows you to measure the edges while they are actually spinning and some probes allow you to measure them at full revs so that means you can measure the path the tool is actually going to cut other than the static size of the tool.

“This is particularly useful in HSM as when you turn the spindle on it could be up to 30/30/50 microns in terms of size because the spindle isn’t perfectly balanced and it cuts a different circle and bearings actually deflect a little bit from the speed of rotation.

“Probes in HSM operations can provide improved process control and reduce scrap by ensuring final cuts have optimum tool wear offset values, error-proof work offset, tool geometry offset and tool wear offset data entry.”

Like when implementing any new technology, Frecker says it is important to be aware that many of the new probing systems now available overcome many of the old constraints of existing systems.

“Some probes need to be calibrated every time before use. This is a double-step process as you have to do a referencing measurement and before performing the ‘real’ measurement.

“However there is new technology available that enables users to calibrate the probe only once so this saves time.

“Probes may look the same but can work quite differently. Potential probe users need to do a careful analysis of what you want the probe to do.”

Frecker advises to really get the full benefits of a probing system, it is important to examine it at a system level.

“The whole production system needs to be configured to look at the productivity gain. Also look at the practical use the probe – do you have to calibrate it every time you want to use it? Look at battery life; also if when you change direction will you get a different reading?

“There are a whole range of performance issues that are fundamental to what you are trying to do. As probe technology continues to improve and development, such as the creation of modular probing systems, the usability and functionality and hence the use of systems will widen.”

Finding the right frequency

With probes getting faster and more accurate due to less chance of interference with the workpiece, they are also becoming more agile and adaptable.

According to Paul Fowler, MD of Dimac Tooling, the development of Radio Frequency (RF) probes is opening up a wider range of applications for probes.

“Today, the operation of an optical transmission touch probe typically involves the delivery of infrared signals from the probe to the receiver, which in turn communicates with a CNC machine.

“This system works great except when the probe and receiver are out of visual contact, as when the probe is deep within a bore or other depression within a work piece.

“This line-of-sight restriction isn’t an issue with RF probes. RF technology also eliminates the restrictions associated with hard-wired touch probes,” Fowler told Manufacturers’ Monthly.

The technology also enables the use of probes on larger machines as RF can cover greater distances than traditional probe technology.

“If a company is doing forging or castings in a machining centre this lends itself quite well to probing because of the variable nature of the work piece. Because of the core movement on casting boxes it’s very nice to go down and probe the bore and clean it up a little bit.

“Also when working with very large work pieces, using the probes you can check it before you take them out of the machine, saving the hassle of re-setting if the parts are not to size.”

However Fowler doesn’t believe RF will replace infrared technology as for it to work well, the frequency has to be set at the right time for the measurement to be accurate.

“You have to set the radio frequency range for each probe, but this also allows you to have several probes set to different ranges in the same factory and they won’t interfere with each other.”

Fowler also points out that operator skill level also has an impact on the accuracy of probing systems.

“One operator may be able to get a lot of value out of it, then another one comes along and can’t. It is a matter of on-going training and education.

“Probing isn’t the answer to everything so you have to look at each application.

“Do a cost-benefit analysis: probably two or three times out of ten you are probably not going to get a huge benefit out of using probes, but on the other hand most applications will gain significant benefit and payback within 12 months.

“Look and see if the numbers make sense. Often when people do implement a probe on their machine tool, they wonder how they managed without one before.”

Dimac Tooling 03 9561 6155, sales@dimac.com.au

IS tecnik 1300 699 176, info@istecnik.com.au

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