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'Unusual use' of CMM cuts set-up times

Mould maker combines a CMM with CAM system and customised software

Posted on 26 Jun 2020 and read 1871 times
'Unusual use' of CMM cuts set-up timesBurnley-based mould maker Kavia Tooling Ltd is using a Hexagon co-ordinate measuring machine to create an offline Zero Transfer system ahead of the manufacturing process for parts and electrodes; in doing so, it is considerably reducing down-time on its CNC and EDM machines when setting up new jobs.

According to production director Mark Cole, some components can be particularly time-consuming to set up on machines using ‘traditional’ methods, “and even simple parts mean that the machines are idle during set-up”.

However, Kavia’s ‘unusual use’ of the Hexagon CMM means that the machines are cutting a job while the set-up for the next one is being carried out.

Mr Cole said: “Hexagon customised the flexible PC-DMIS software, which comes as standard with their measurement devices, to enable us to use it to find offsets at the beginning of the operation.

“Instead of having to put each part on the machine and then set it, we set it on the CMM, which gives us the X, Y, Z and U orientation.

“We only have to put the Zero Transfer plate, which is micron-accurate, into position on the machine, and it knows exactly where the part is.”

This can be done with any number of components, thanks to another piece of customised software, which Kavia Tooling devised itself and which engineers for its CAM system — Edgecam (www.edgecam.com) from Hexagon’s Manufacturing Intelligence division — developed for the company.

This software drives seven high-speed CNC mills (with spindle speeds varying from 12,000 to 30,000rev/min) and a Sodick EDM machine.

Kavia 1Mr Cole said: “However, it is no ordinary machining process, thanks to the customised software, which we call Merge. It collates data from all programs for the job and merges them into a single file, many at 36MB and containing around 1.5 million lines of code.

“It includes the Edgecam NC code, datums to set the parts on, Zero Transfer, and cutter tool heights.”

He cites an example when Kavia was working on two cavity plates on one side of the machine, and four inserts on the other.

“We put the individual Edgcam CNC programs for each component together into one file, and it all went to the machine as one large program. The software also keeps cutting tools to a minimum, by looking at information such as duplication, length and the quality of the tools in all programs.

“If there are two repeating cutting tools in the individually merged program, it selects the best one for the manufacturing process. Indeed, it goes through every single NC program and re-arranges all the tools accordingly.”

The end result of using Merge with the Zero Transfer fixture plates created on the CMM is a CNC program that can machine several parts at a time without the need to use the machine as a set-up station, as all preparatory operations are carried out offline.

“If we were setting up a component to be square, directly on the CNC machine tool without the CMM, we’d have to ensure that it’s perfectly in line with the machine’s axis.

“Doing that for 10 components considerably increases the risk of error, especially where there are overhangs. However, setting them on the CMM means that everything is automatically correct, because it tells the machine the angle of each part.

“To set up six fairly difficult components directly on the machine may take one day, during which time it’s not running, but it only takes about an hour on the CMM — and we can be confident that they will all be absolutely accurate.

Kavia 2“Furthermore, while the Merge software and the CMM Zero Transfer system get the best out of our CNC mills, they offer even greater benefits when used on our Sodick EDM.

“This machine used to be our biggest bottleneck, as we had to set the electrodes and the part on the machine and program it by hand, typing figures directly into it.

“This led to errors and was an absolute nightmare, but with the Merge software, it went from being the largest bottleneck to the fastest machine in the factory, and it’s all mistake-proof.

“There is no typing, as — dimensionally — everything is done from the CAD; and because all the offsets are set on the CMM, there is no setting on the machine.”

The Merge software collates all the programs, Zero Transfers and information about the spark positioning. It works with up to 12 electrodes at a time, bringing all the CNC programs together and identifying the X, Y, Z and U orientation, putting everything together in a format that runs on the Sodick to the correct datum, automatically adjusts the tank height, and provides a setting sheet.

In fact, Merge is proving to be so beneficial for both simplifying and speeding up the work on the Sodick EDM that Kavia is now developing the software commercially for those machines.

Mr Cole said:“It is currently being trialled in the field, and we’re aiming to start marketing it shortly.”