Interview How much measurement do you need on the shop floor?
Opinions vary on what die and mould makers require from metrology and quality control. Geoff McFarland, group engineering director at Renishaw, says toolmakers should use the latest measurement technologies to keep up with machining and other advancements.
ETMM: What are some of the most recent developments in measurement that can help die and mould producers?
Geoff McFarland: The much wider adoption of 5-axis machines in recent years has led to the development of a number of metrology products that enable manufacturers to fully benefit from the capabilities of the machines and to ensure that those machines are also functioning with operating parameters.
ETMM: What has the effect of this been?
McFarland: For example, with ever more complex free-form shapes, it is imperative that touch probe systems used to verify the dimensions of expensive moulds and dies both during and post machining cycles have a true 3D capability and also include robust methods for transmitting measurement data to the machine controller. To meet such requirements manufacturers can now source a wider range of probes that contain highly accurate strain gauge mechanisms which are able to handle data acquisition from complex 3D parts and also have the capability to carry long styli used to probe features deep within the tool without introducing measurement errors.
ETMM: Are there any additional changes?
McFarland: The other trend that we have seen is for tool manufacturers wanting to carry out inspection of the finished tool at the machine tool, rather than remove it to a co-ordinate measuring machine (CMM), especially where the tool is large. This also has the advantage of allowing adjustments to be made more easily to the tool should there be some tolerance issues.
ETMM: How has the industry responded to these shifts?
McFarland: Reacting to such challenges, metrology companies have introduced software that allows large volumes of data to be captured by probe systems on the machine tool and then for complex data analysis and subsequent part compensation to be carried out – Delcam’s Power Inspect and Renishaw’s OMV Pro software are examples of such products. The OMV Pro software incorporates advanced CMM style functionality including constructed features and geometric dimensioning and tolerancing (GD&T).
ETMM: And for the rise of machining that exceeds three axes?
McFarland: With ever more machine tools incorporating 4th and 5th axes, the accurate alignment of a machine’s axes is ever more important to ensure the quality of a finished part, both dimensionally and surface finish. A wide range of tools are therefore now available to manufacturers to check the positioning performance of their machines long before they actually cut metal, especially critical where cycle times are long and materials to be used are expensive. Scrap simply isn’t an option! You will therefore see more companies either owning or using the services of calibration companies with an arsenal of tools to help this process, including laser interferometer systems for measuring linear and rotary axis positioning, wireless ballbars for fast machine tool performance checks, and touch probe based systems that can be used to check rotary axis alignment.
ETMM: Can we expect any new introductions or breakthroughs from the industry over the next year?
McFarland: In the near future we are likely to see further advances in software including improved data handling and more user-friendly interfaces, more suited to the production environment, plus the development of more application specific software for a new generation of contact scanning probe system that have recently been introduced for machine tools.
ETMM: What type of quality control and measurement technologies does every die and mould shop need? What type should they have?
McFarland: Really no shop should still be carrying out manual setting tasks on machine tools – either the setting of tool length and diameter, or clocking the position of billets, and yet surprisingly many are! Contact and laser based probe systems have been available for many years to carry out these tasks automatically, eliminating the errors that creep into manual processes, either when establishing offsets or manually keying these into the machine’s controller.
ETMM: What are the advantages for shops by adding metrology equipment?
McFarland: Tools are expensive items to manufacture and being able to eliminate the risk of scrap and better control the machining process is a fundamental requirement for modern manufacturing processes. Introducing probe systems also gives producers the ability to introduce better process control regimes, checking for drift in part dimensions during the machining process and also tool wear and breakage, especially key when machining smaller features.
ETMM: What type of devices should shops have?
McFarland: As mentioned earlier, the same measurement probe systems can also be used to validate part dimensions on the machine without the need for removal to a CMM, which may be impractical due to size. Such validation is credible with the right controls on the machine tool including the use of reference artefacts and ensuring that the machine tool has been checked with suitable calibration tools to ensure a sound geometric framework. Such modern measurement probe options have in most cases removed the need for manual gauges in more complex machining facilities.
ETMM: Has your company worked with a toolmaker to help with its problems?
McFarland: We have worked with the toolmaking community for many years, supplying measurement probes to control machining processes and also tools such as reverse engineering systems to aid in tool design.
ETMM: Were there any specific solutions to the problems the shops faced?
McFarland: Surface finish of the tool is critical for many and this has led to a number of developments and challenges to be met. For example we have introduced a surface finish probe for our Revo head used for five-axis measurement on CMMs. Furthermore, as many will know, we are also a supplier of additive manufacturing (AM) systems and last year acquired the assets of the highly respected German company LBC which works very closely with the mould and die community, and is seen as an expert in the optimisation of mould tool design. They have perfected the use of AM technology to create conformal cooling channels that follow the surface of complex tools, meeting the requirement for faster cooling and the elimination of part distortion caused by uneven cooling.
ETMM: What areas is your company currently working on? When can we expect results?
McFarland: We are currently investigating powerful optical based systems that will aid in the rapid measurement of parts produced on 5-axis machines and will also eliminate the issues of inspecting finished tools with contact systems that may in some cases cause surface blemishes. The latter issue has led some toolmakers to look at laser tracking and other non-contact systems, but we believe that our new system will be a better integrated solution to this challenge.
ETMM: Were there any other recent developments for the die and mould industry?
McFarland: At EMO 2013 we also introduced our new Sprint contact scanning probe system (see Oct. 2013, p 57.) for complex machine tools which records a constant stream of highly accurate 3D points across a part surface and then enables the analysis of this data in real-time on the machine’s controller. This allows a step-change in automated in-process control on machine tools, including the rapid measurement of prismatic parts and also the ability to verify the capability of a complex multi-axis machine in less than a minute with checks for linear and rotary axis errors.