Product category:
Machining centres - all types
News Release from: Chiron Werke UK | Subject: High speed machining
Edited by the Manufacturingtalk Editorial
Team on 13 February 2001
High-speed machining is in vogue.
Does high-speed machining always result in high-speed manufacturing? Chron Werke examines the phenomenon and suggests work handling and fast tool change times constribute more to HSM.
Everywhere you look - in magazines, at exhibitions and even on your own shopfloors - it seems that everyone is talking about it But the big question is, does high-speed machining always result in high-speed manufacturing? High-speed manufacturing is often wrongly used to describe the application of fast spindle speeds and feed rates to reduce 'in-cut' times, with the aim of achieving higher output
This article was originally published on Manufacturingtalk on 29 May 2001 at 8.00am (UK)
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But users are finding that the application of these two developments in isolation not only reduces machine reliability and tool life, increasing downtime, but can also actually add to cycle and lead times while never achieving the desired higher output! This is due to a number of causes including the fact that in-cut times as a proportion of overall machining times are short when other operations such as axis or spindle ramp-up times, or tool and pallet change cycles, are considered.
Many machines that boast high spindle speeds may take several seconds to reach maximum speed or decelerate in order to change tools.
This dead time effectively reduces, and sometimes even eliminates, any potential gain that might be achieved from these so-called high-speed machines.
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Chiron, on the other hand, has traditionally always focused on the implementation of proven, all-round high-speed machining technologies, balanced with other time saving features, to eliminate all the non-cutting time that surrounds a production process.
Crucially, these technologies and processes are considered - and applied - simultaneously by Chiron to enable its machines to consistently deliver reliable higher output at the lowest capital and labour cost.
But first, why is high-speed manufacturing in such demand? In the past, special-purpose and rotary transfer machines were the first choices to satisfy the twin demands of high-volume production at low piece part cost.
Today, however, shorter product lifespans and increased product variety has created the need for smaller batch work - while consumers are driving up standards of product quality and reliability! Considering these factors alongside developments in 'standard' machine tools in terms of operational speeds and the ease at which they can be quickly adapted (in terms of fixturing, tooling and programming), then the benefits of modern machines in many cases far outweigh the inflexibility of special-purpose units.
To increase the output of standard machines, some users have opted for complex multi-part fixturing to help amortise the machines' slow tool and pallet change times.
But complex fixturing makes process capability much more difficult to achieve - and we all know what impact the micron has had on quality expectations.
Effective process capability is the only way to satisfy customer demands for consistent high-quality parts.
And while this means that the machine must cut metal quickly, it also requires improved traceability and easier targeting - in other words, lean production based on the use of simplified processes.
Improving traceability means being able to identify which machine and which part of a fixture produced a certain component.
And easier targeting means being able to quickly adjust the process if components are moving out of tolerance through, say, tool wear.
The concept of simplicity and single-piece flow can only be achieved with the maximum utilisation of the spindle increasing in-the-cut time as a proportion of the overall cycle time.
With that as a backdrop, it is clear that high-speed manufacturing is not the same as high speed machining.
Chiron has successfully applied a number of proven ground rules that enable its high-speed machines to be able to deliver true high speed manufacturing.
These include: [] A simplified process that is easily re-targeted to match SPC requirements; [] Higher spindle utilisation featuring minimal delay for spindle acceleration and deceleration; [] High speed cutting capability (for both spindle speed and contouring); [] Efficient swarf removal; [] Fast in-cycle load/unload - with options for automatic load/unload and part positioning; [] Improved process management; [] Fast set-up and prove-out; and [] High machine availability via low maintenance demands.
With 45 kW motors producing spindle speeds of 20,000 revs/min as standard (27,000 revs/min option), Chiron machines are able to accelerate and decelerate in 2.2 secs.
They also boast ramp up speeds of 1.3G for both spindle rotation (maximum speed in just 0.7 sec) and positioning in all axes at an impressive 60 m/min.
In addition, the machines are characterised by fast tool change (less than 0.5 sec on one model) taking place over the workpiece at minimum height (no redundant movements to a zero position), and super quick pallet change times of only two secs chip-to-chip.
A number of other factors are also embraced by Chiron's high-speed manufacturing equation - all designed to eliminate dead time and hoist product quality.
The Chiron policy, utilising travelling column machines where the tool is taken to the workpiece, is based on minimum parts per fixture (simple 'throw-on' fixtures) and completing the part at one spindle and in a single clamping.
Part quality is also ensured by, for example, temperature control (in the machining area and coolant supply) coupled with, for example, hydraulic/pneumatic workpiece clamping and air sensing for part location.
Control technology should also be considered, so that contouring (using Look Ahead functions) is fast and efficient to ensure maximum metal removal coupled with accurate surface finishing.
Swarf removal, too, is another important aspect.
All swarf-trapping points on both fixturing and the machine itself have been designed-out.
Even the pallet table design has been tackled, having less moving parts than traditional designs and no trailing cables.
These factors lead to more efficient fixture clamping with minimal component damage or part misalignment, while minimising the possibility of breakdowns and easing coolant provision.
Combined with auto tool monitoring and management, in-process tool measuring, and fixture/part location by probe, the result is a high level of machine utilisation, less manual involvement, reduced consumables, less maintenance and the flexibility to adapt to frequent batch changes.
Chiron is proud to say that, in most cases, it can prove that a Chiron machine will pay back quicker and generate a higher hourly income than a competing product!.
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