When renovating railway lines there are generally two preferred options; grinding or dynamic milling…
Compared to grinding, the high-speed re-profiling of a line represents significant time and financial savings. Specially designed trains, operating at a constant speed of 700 meters per hour, machine the existing track profile. By removing millimetres of metal from the damaged surface, the track is restored to its original condition. With each application, the first cutter roughens the surface, the second one finishes it, and the two units act on both rails simultaneously.
The operation provides a high-quality surface finish, while metal chips produced during the milling stage are transferred to a nearby container, ensuring no debris is left on the track. This ‘on the-move’ application requires specialised equipment to achieve optimum results, such as ‘train machine tools’ designed to carry dynamic rail milling cutters and inserts. An increasing number of these are being produced by leading global manufacturers as demand from railway organisations and government bodies for track maintenance increases.
Global cutting tool manufacturer Dormer Pramet works in partnership with several high-speed milling machine manufacturers to delivery key projects around the world. One of these projects included the milling of three different rail profiles for a customer in the Netherlands.
Dormer Pramet’s 600mm diameter dynamic rail milling cutter was able to machine the combined profile (60E1, 54E1, 46E3 1:40) and another profile 54E5 1:40, without having to change the inserts. Using the same cutting tools across several profiles is hugely beneficial as it saves both time and costs, reducing the number of tool change-overs.
Tomas Hantek, Application Manager for railway at Dormer Pramet, said: ‘As with all railway projects, each application is different from the next, so we regularly tailor our products to meet the need of the customer.
‘It is very important we work closely with the machine tool manufacturer and rail organisation to identify where adaptions need to be made to achieve the desired results.’
The development of new rail technology is constantly taking place and modifications are needed on both sides to optimize the match between the machine and cutting tool. Dormer Pramet has adapted its popular dynamic milling cutter in various sizes, from 300mm to 900mm, with plans to develop a 1,400mm diameter version in the future.
Tomas added: ‘We recently delivered a 300mm diameter dynamic rail milling cutter to a customer for testing. This has been custom made to specifically fit their new machine. In the first trial, they discovered that the cutter profile was as they required. However, they realized their new machine was not strong or rigid enough to cope with the demands of the application. We are now working with them to make some changes and help move the project forward.’
At present, Dormer Pramet has more than 50 dynamic rail milling cutters out in the market, including in the Netherlands, Germany and Poland. This is an indication of the international nature of the railway segment, with tool suppliers, machine tool builders and customers from different parts of the world, working together on applications which often take place in different countries.
This not only requires precise logistical management, but an understanding of different standards and accreditations between countries. Many projects involve large international organizations, as well as support from government agencies and administrations, along with affiliated transport associations.
Another example where Dormer Pramet provides support to the railway segment is in wheel returning. This too can see standard tools being modified to become custom-made specials, unique to the requirement of the application.
Its assortment of rectangular LNMT and round ROEX inserts, for example, have proven a big hit with customers in North America, with the range available from its distribution center in Hebron, Kentucky.
A customer in Philadelphia was having issues with its previous LNMT inserts as they were not able to break chips during a wheel turning operation. The resultant long, continuous swarf congested the area around the workpiece. The process to clear the chips is not only time consuming but can also be hazardous.
Dormer Pramet put forward its standard LNMT inserts, but during tests, found these too did not break the chips as required. Following further feedback and discussions with the customer, the company was able to make two key changes to its insert. First it added a corner radius chip breaker to relieve some of the pressure on the tool. It then tailored the geometry and design of the insert to prevent nesting at high depths of cut.
The end user wanted to make one pass, so the LNMT insert needed to be able to achieve a staggering .700 inches (18mm) depth of cut at the first attempt. Following the changes, the insert was put in for further testing.
Not only did this new design fix the chip control problem, but it consistently outperformed all other inserts tested. The customer now orders from Dormer Pramet. In addition, the company has started to use their RCMX, RCMT and TNMG inserts on a variety of operations, such as the turning down of axles. This has allowed them to reduce cycle time by an average of 30 per cent, saving more than US$30,000 in the first year, with greater operational efficiency and improved performance.
Railway wheel turning is an area Dormer Pramet is looking to expand its assortment further. Where the LNMT can support large depths of cut, the company is now working on a new insert for delivering small depths of cut, around 1mm.
A popular trend with customers when machining railway wheels is to perform the operation with a low depth of cut. This is still completed in one pass, but the reconditioning will be required more often between uses. This new product will support those applications. It is currently in the testing phase, with the aim to launch the insert in 2020.
Dormer Pramet is a global manufacturer and supplier of tools for the metal cutting industry. Its comprehensive product program encompasses both rotary and indexable drilling, milling, threading and turning tools for use in a wide variety of production environments. An extensive sales and technical support service operate from 21 offices, serving more than one hundred markets worldwide. These are assisted by dedicated production facilities in Europe and South America and a highly developed distribution and logistics network.
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