Simplified CMM inspection for productive quality control

WLR Precision Engineering is a contract machining specialist in Wilford, Nottinghamshire, and the company was using a pair of 15-year-old coordinate measuring machines (CMMs) in its inspection room. Looking to upgrade the technology, WLR Precision invested in two CMMs manufactured by LK Metrology. Soon, they had largely superseded the older CMMs. 

The machines have been supplied with the LK Launchpad, an icon-driven, touch-screen operator menu, and a network of viewing screens and tablets. Production operators and the quality inspectors who operate the CMMs are provided with easy access to measurement reports as part of the operator menu. 

The operator’s menu lists available inspection programs, and the exact part position on the machine table for inspection, giving operators the ability to perform measurement tasks in just a few clicks. It enhances flexibility and opens the system for use by non-specialist CMM operators. Measured results and automatically generated reports may be shared between screens, tablets and other networked devices for easy access and viewing from any location.

WLR is a full-service provider that manages entire production process. A proportion of the value of each part is metrology, often involving 100% inspection. Contracts are received from the oil and gas, pharmaceutical, medical, laboratory and scientific instrumentation industries, which place great reliance on the accuracy and consistency of parts delivered. The company's sales manager Tom Parr said, "The increasing confidence that our customers have in the accuracy and consistency of components they receive from us has resulted in our winning considerably more business in virtually every sector that we serve."

What has helped in raising that level of confidence was the purchase in 2015 of the first LK CMM, an AlteraS 15.10.8 with a measuring volume of 1,524 x 1,016 x 813 mm. The machine's acquisition was triggered by a steep increase in components ordered by key customers coupled with a requirement for more comprehensive, 100% inspection and detailed reporting. Soon afterward, a customer in the defense sector had a similar requirement for the provision of traceable measurements and certified reports covering the supply of critical, matched components.

A benefit of the CMM is its large table area, approximately 1.0 x 1.5 meters, which can accept up to 12 identical components at a time for batch inspection, instead of just one as on either of the older CMMs. 

After components have been uploaded, an inspector presses a button and every part is measured in a single, automatic cycle, the longest of which is two hours. The operator is freed to work elsewhere on other metrology equipment for most of the day and the time the inspection will take is known exactly. 

With the previous metrology route, preparing reports by hand on 12 inspected parts would typically take three hours. Because of the CAMIO's ability to perform the task automatically, a comprehensive, graphically supported inspection report is generated on an entire batch in a matter of minutes, covering 30 or 40 critical dimensions on each part, complete with color-coded content in the event of any non-conformance. The report data is exported, via a CSV-type file especially formatted by WLR, directly into an Excel spreadsheet.

Launchpad automates inspection

By May 2021, a requirement was also introduced for in-process inspection of a particular family of components for one customer. This time a smaller LK AlteraS 10.10.8 with a working volume of 1,016 x 1,016 x 813 mm was purchased, together with the latest CAMIO 2021 and the additional LK Launchpad software. The unit allows for parts to be loaded singly or in batches of up to six at a time.

Launchpad makes it simple to load the correct program for inspecting a component, which is easily identified from stored data, with details called up via simple graphical menus and icons on a screen positioned by the machine.

The operator can locate the component by selecting the customer by name, via the part category, or by directly calling up the part itself complete with details of the machining process. Set-up on the CMM is straightforward, assisted by 12 mm thick aluminum fixture plates pre-drilled with a grid of holes at a 50 mm pitch fitted across the granite table of the machine. The operator simply places the component in a numbered location on one of the fixture plates, as indicated by the Launchpad graphic, and instigates the measuring program by pressing a button on the touchscreen. Despite being a powerful process, WLR confirms that the software is remarkably flexible and easy to use. 

For convenience, the same inspection results that appear on the screen adjacent to the machine are also available on networked tablets used by machinists on the shop floor and the information may also be shared with other devices. It enables more robust inspection and less downtime as well as creating an environment where machinists become invested in the procedure. The next step will be to include functionality that allows operators to be alerted via their tablet when the measuring cycle is complete, so there will be no need for the person to keep an eye on the time. 

Pre-drilled location plates are a feature on the granite of the larger LK CMM as well, assisting loading of components in batches or individually on that machine too before the inspection. Launchpad software is also used, so both machines may be employed for either batch inspection or for operation inspection by shop floor staff, further increasing the efficiency of the quality control department. 

CMM programming from CAD
Another plus point, introduced at the time the first LK CMM arrived, is the ability to program the machines directly from CAD. Before the new LK CMMs arrived, it was sometimes necessary to produce a first-off component for a customer in up to six operations on a succession of machine tools, then take the part repeatedly to the inspection department to be measured and subsequently corrected if necessary. After it had been finished-machined, the component was used as the basis for teaching a measuring program into one of the older CMMs. Now, in the same way that a metal cutting program is derived directly by a CAD/CAM system from an electronic model of a customer's component, the DMIS inspection cycle for the LK CMM can be created from the same CAD model using LK CAMIO software in advance of the first part being produced. 

All inspection routines for both LK CMMs are now prepared this way in CAMIO, which performs not just programming but also analysis of the captured data and automatic reporting of the results. The measurement program enables the first-off part to be checked immediately on its first visit to the AlteraS 15.10.8. Programming time is quicker than before, but the biggest plus point is that it is completed off-line, so the CMM is not occupied, allowing inspection of components to continue uninterrupted. Together with the benefit of multi-sensor capability, permitting the use of a Renishaw SP25 scanning probe or a Nikon LC15Dx laser scanning head instead of a touch-trigger probe, measuring throughput has been raised dramatically.

On the implementation of the successful metrology upgrade at WLR, Mr Blood commented, "Our new measuring processes can be used by personnel with a wide range of experience levels. The high degree of automation plus the ability to increase speed by scanning as well as touch-probing has helped us save time and remove inspection bottlenecks. 

"Automation and deskilling of operations have also allowed us to enhance inspection efficiency without adding to our headcount. Added to this, every day there is a further economic advantage through the ability to run the CMMs unattended for up to two hours at the end of each day shift due to our strategy of batch loading."

Parr said, "The parts we produce typically range in size from about 5 mm square up to 115 mm in diameter by 250 mm long. 

At one end of the scale they are milled, turned, ground, spark eroded, and diamond lapped from free cutting brass, aluminum and stainless steel, but often they are machined from the toughest of alloys including Inconel 718, Invar or Hastelloy.

"Consistently high precision is the watchword here, with machined tolerances normally of the order of ±25 microns but exceptionally down to ±3 microns, if necessary.

"Nearly all components are inspected on our highly productive LK CMMs. There is enough spare capacity now to provide our customers with an additional service whereby, if required, some components that we do not manufacture for them are also inspected here and certified by us."