N the past, a dedicated or special tool was in many cases the only efficient solution for many applications, especially as batches were large.
Today, when more flexibility in production is needed, new milling cutter concepts are providing both broadly capable tools.
Modern tool-design and -manufacturing have made it possible to realise sophisticated tool concepts that utilise CNC machine tools, increase production output and make the machining process more reliable.
Standards
Standardisations in technology are of course crucial to manufacturing because, through them, we speak the same language and know the limits that apply.
But there are instances when standards actually brake the pace of development. It then becomes necessary to escape from the constraints that hinder the introduction of better solutions.
One such instance is the development of milling tools.
Milling cutters and inserts used to be defined by ISO standards offered users interchangeable tools from different tool suppliers. But having to comply to standards impose limitations on the milling cutters and inserts.
ISO codes prescribe shape, thickness, and inscribed circle of cutting inserts as well as indicating the size of insert-holding cartridges and wedge clamps, along with the tool bodies that hold them.
With only a limited scope in insert grade, hone and chip-breaker design, tool suppliers and users adhering to ISO standards faced serious technological and performance limitations.
In contrast to ISO-style milling tools, today‘s milling tool concepts provide tool developers with the freedom to use new cutter and insert designs, where these can be optimised to provide better all-round capability for CNC machining.
Machining security, accuracy, surface finish, capability for different cutting paths, removal rates, tool overhang and high speed machining are issues that can be tackled better through new cutter concepts.
Today’s concept milling tools, such as cutters, are optimised for operations and materials of today and are widely accepted throughout industry. These remove metal several times faster and with smaller and more suitably directed cutting forces than would be possible with any ISO-standard cutter.
With only a fraction of the typical runout of ISO cutters, concept cutters consistently hold closer component-tolerances and also develop less and more favourable cutting edge wear.
Axial and radial runout is at a minimum and this means better cutting edge accuracy for improved surface finish, tighter part tolerances and longer tool-life. They also distribute machining loads evenly to cut faster with less noise, vibration, and wear.
These modern concept tools also provide the technology for high spindle speeds, fast-feed milling and hard part machining, as well as expanding opportunities for dry milling.
Design features make the concept tool leaner in design, needing a minimum of setting and maintenance. Rigid and accurate cutter bodies are machined from pre-hardened steel with inserts located accurately in milling cutters that provide choices of different teeth-pitches to suit applications.
The importance of upgrading
The consequences of using out-dated milling tools can be substantial to the machining economics as well as production security.
Machine shops that carry on using milling cutters that are not part of more recent concept developments are losing out.
Investing in sophisticated machining centres and other rotating-spindle machinery for milling but not continually updating the milling tools and inserts, is only going half the distance.
With the advance in cutting tool technology and CNC machining capability, there is a growing potential for manufacturers who have up to now been using out-dated dedicated milling cutters, boring tools or special tools.
Often, these tools are specifically designed or applied for certain cuts on a component or a family of components. This has meant that when it comes to rotating tools in machining centres a separate tool is needed for each dimension on a component.
The use of specifically-dimensioned tools goes back partly to when milling and boring operations were all performed in milling machines or special-purpose machinery with limited axis-capacity.
Particularly when it came to internal machining, a tool had to be made available for each diameter, face, chamfer and groove - even when the variation was only a matter of a few mm. Some limited flexibility could sometimes be built in through the use of adjustable insert seats in cartridges.
With the wider availability of multi-axis CNC machining centres, tool movement is no longer a limitation. In effect, it provides the possibility of using one tool for several, if not all of the different cuts needed.
The ease of programming various tool paths, and using methods such as ramping and circular interpolation, means that a flexible, more widely capable tool, can be applied with dimensional variations on the component only being a simple programme adjustment.
Less time with fewer tools
A European off-road vehicle manufacturer has benefited through the application of modern concept milling cutters in an FMS-line consisting of horizontal machining centres. The line machines different types of housings for axles for wheel loaders.
As part of a major efficiency project, aimed at improving performance in the manufacture of components for power train assemblies, one particular objective was to improve machining of side-housings through increased productivity.
Previously, the FMS-line used special boring tools to machine the various sizes of the cast-iron side-housings. Each component has several different internal diameters and faces that are machined.
In the machining analysis that took place, it was recognised that concept cutters could replace several of the previous boring tools by not being specific to bore sizes.
A smaller-diameter long edge cutter could, for instance, be used to interpolate and thus machine a range of bore sizes. All that is needed for a different dimension to be machined is a programme change. The cutters are as such universal for various dimensions and operations.
Operators also see the new level of process security as a big advantage in their work as well as the ease and reliability with which tool setting and maintenance is carried out.
The results of the machining upgrade with concept milling cutters included a reduction in machining cycle time of 25%, reduction of the number of tools by 50% and a higher process security level. The new machining method has also reduced component set-ups in the machine.
It is reckoned that another 10% of production time has been made available through the machining improvements.
New concept cutters
The modern long edge milling cutter, with several inserts in cut, is a very effective metal remover relative to available machine power.
Previous versions of this type of cutter have been heavy-cutting mainly because of negative insert geometry and have thus been limited in their application.
The development of the 390 long edge concept cutter has provided a tool with very smooth machining characteristics, to allow high table feeds with a minimum of power consumption.
A new generation of concept cutters is available for applications varying from mass production in the automotive industry to demanding operations in the aerospace industry. Roughing to super-finishing can be carried out.
For aluminium milling these cutters provide a new means to raise performance, process security and quality consistency when milling various aluminium alloy components.
Designed also to be used in high speed machining applications, spindle speeds of up to 40,000rpm can be used.
*Christer.Richt is technical editor with Sandvik Coromant 1300 360 938.