A mild steel chamber that requires 24 hours of almost continuous milling is being produced by Paragon Engineering more consistently, faster and at lower cost, following intervention by applications engineers from tooling supplier, Iscar.

The medical industry component, which weighs nearly one tonne, is machined by the subcontractor on a Haas VF8 vertical machining centre. Previously, extensive use was made of costly solid carbide cutters that did not give particularly good service life and had to be scrapped if the cutting edges became chipped. These have been largely replaced by indexable insert tools from Iscar, following consultation and cutting trials with the machine supplier and the customer to optimise the process.

Paragon moved to its current premises in Ely, Cambridgeshire in 2002 and specialises in work for the medical and hi-fi sectors and also makes parts for astronomical telescopes, cameras and satellites.

Joint owner and managing director, John Kent, comments: “We have used Iscar cutting tools for more than a decade for prismatic machining and turning a wide variety of materials from aluminium and plastics through most types of steel to titanium, ceramics and composites. They are one of several regular suppliers of tooling to our machine shop.

“Their local sales engineer, Phil Ginn, who keeps in regular contact, visited us at about the same time as we received a request from an existing medical customer to machine a series of large prototype chambers. Phil could see that the tooling we were using for the job was not ideal so he set about analysing the best way to machine the part using Iscar cutters.”

The improvement has been dramatic, as not only have tooling costs been reduced, but also surface finish is improved, saving the customer a considerable amount of time when subsequently hand polishing the component. In addition, the noise generated during cutting is lower, improving the working environment for all of Paragon’s machine operators.

Most significant, however, has been a reduction of 60% in the time needed to complete the part using the latest technology tools and carbide inserts from Iscar.

Mr Kent continues: “The job was previously taking far too long, making it difficult to make any profit on the work. Whereas we could charge £50 per hour for our capacity a few years ago, the recession and continuing loss of work to low wage countries overseas means that the going rate now is nearer to £35 per hour.

“Being able to reduce machining times as dramatically as in this case by changing the tooling has made a big difference to the bottom line. We moved to 24 hour running in February this year to extract maximum benefit from our capital investment in machines on the shopfloor, which is also helping us to remain competitive.”

Around 75% of material volume is removed during machining of the steel chamber on the Haas 3-axis VMC, which has a 14.9kW, 7,500rpm, 40 taper spindle and 1,626mm x 1,016mm x 762mm axis travels. The component is machined dry, with air blast to remove chips from the cutting area instead of coolant. General tolerance is ±0.2mm, although some features are tied down to 30µm.

There are three main areas where Iscar tooling has made a significant improvement: one is the use of high feed, extra long-reach Helido end mills for face milling, ramping and interpolation.

The tools have double sided, TiAlN PVD coated SumoTec inserts with six cutting edges and take successive 1mm cuts using a 2,300rpm spindle speed and 4,250mm/minute feed rate.

After the component has been refixtured, Iscar’s Multi Master milling system is deployed, using the company’s new chatter free, interchangeable solid carbide end mill heads. Using a 2,000 rpm spindle speed and 1,000mm/minute feed, the 15.2mm diameter, 120mm long tools go down in10mm steps to rough out the bulk of the material efficiently. The same type of tool then finish machines the chamber, leaving deep side walls with a good surface finish.

The third area where Iscar tools make a big difference in machining efficiency is during one of the last operations, where a significant amount of undercutting is needed. A 100mm diameter slitting cutter is mounted on a long extension arbour for both roughing and finishing.

The tool has six carbide inserts comprising a fine grain substrate coated using Iscar’s SumoTec TiAlN PVD process, which exhibits good resistance to chipping and wear. Paragon’s setter/operator, Melvyn Cornwall, confirmed that four hours of continuous machining are achieved before tip change is necessary.

Iscar
www.iscar.co.uk