Product category:
Horizontal machining centres (HMC)
News Release from: Mori Seiki UK | Subject: Horizontal machining center - HMC
Edited by the Manufacturingtalk Editorial
Team on 26 September 2005
Minimised HMC vibrations raise machining
quality
Minimised vibrations effected through dynamic FEM analysis of a horizontal machining centre's components ensure top performance in machining times and surface qualities.
NH8000 DCG is the name of the new horizontal machining center from Mori Seiki that shines forth with top performance in machining times and surface qualities Credit is due to the DCG principle and the components redesigned by dynamic FEM analysis that both serve to minimise vibrations
This article was originally published on Manufacturingtalk on 5 Jun 2001 at 8.00am (UK)
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After its unveiling at the Open House in Paris the NH8000 DCG will be celebrating its trade fair premiere at EMO Hannover 2005.
Presenting a new horizontal machining center means having to gauge the product against high standards.
The machine must have more efficient machining and idle times than the predecessor models, must yield results of greater precision, must occupy less space wherever possible, and must allow simple maintenance - and all that at a favorable price.
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Pollard Mori Seiki's extremely compact CL Series of CNC chucking lathes offer superior rigidity to support continuous high speed machining of production components.
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A substantial three-way guideway system, which supports the longitudinal travel of a moving column, provides theSVL5020 long-bed VMC with plenty rigidity for the high speed milling.
High speed machining centre reduces downtime
Capable of machining workpieces up to 2000kg the Pollard Mori Seiki SH8000 horizontal machining centre offers faster traverses and tool-changing times and shorter pallet changeover cycles.
With the DCG principle and its 'drive at the center of gravity' Mori Seiki has succeeded in revolutionising the evolution of machine design, making it possible for not only the one machine, but for whole machine series to fulfill the specifications.
One example is the new high-precision horizontal machining center NH8000 DCG fitted with a double drive system along all linear axes.
The 'box-in-box' design that supports both sides of the carriage enhances guidance and drive balance, raising speeds and facilitating accelerations in the process.
With traverses of 1400mm along the X, 1200mm along the Y, and 1350mm along the Z axes, the machine is capable of maximum accelerations of 4.2m/s2, 7.4m/s2, and 4.0m/s2 respectively.
The rapid traverse speed is 50m/min along all axes.
* Frame column and double drives - for assured machine stability - together with the double drives along the linear axes, the frame column structure enhances machine stability, so counterbalances are unnecessary.
DCG technology minimises vibrations, therefore improving surface qualities and concentricity.
Along the Z axis the double drives clear the way for unimpeded chip clearance into the chip conveyors arranged between.
It is especially important for minimum lubrication and dry machining that red- or white-hot chips do not come to rest on machine components where heat transfer can impair precision.
As a reliable measure against soiling on guides and ball spindles their covers exhibit neither telescopic nor roll-up designs, but form an integral unit along the Z axis.
* Spindle with sprinter qualities - the NH8000 DCG spindle is fitted with a direct drive that masters all applications from high-speed machining to high-performance cutting.
At the same time it possesses sprinter qualities - needing solely 3.2 seconds from 0 to 10,000 rev/min.
However, vibrations caused by this spindle speed are transferred directly to the tool, so to minimise these to the greatest possible extent, Mori Seiki developed a new chucking system and raised the clamping force to 27kN (BT specifications).
Productivity is also raised by the NH8000 DCG rotary table (B axis).
Unlike conventional designs with a worm gear, a direct drive is used instead that achieves a maximum speed of 100 rev/min.
This has the advantage of rapid side changes during multi-axis machining, with the associated reductions in retooling times and considerable reductions in idle times.
A further advantage of the new table is its precision.
During a pallet change - taking only 14s - the repeat precision of pallet chucking remains less than 5 micron.
Repeated measurements on the machine become superfluous when a zero point system is used for workpiece chucking.
Also retooling is fully committed to minimised vibrations.
The bay magazine, which holds 60 tools as standard and can be expanded for up to 330 tools, is a structure separate from the machine.
This means that the weight does not have any effect on machine precision, and vibrations from the magazine cannot be transferred to the machine.
A long Z axis and the option of inserting very long tools in the magazine help the user to machine through holes up to 800mm deep.
Previously, users had to rotate the workpiece through 180 deg and machine it from both sides - with the associated risks to precision and higher idle times.
Other points are maintenance and repair.
As little time as possible is lost when all important sites allow fast and easy access and all components are designed accordingly.
On horizontal machining centers the main spindle is the most jeopardized site.
In order to minimise replacement times for a damaged spindle, Mori Seiki for example developed a cassette-like system that allows the robot to be detached together with the rear bearing.
This means that the machine is fitted with new components and is ready to operate in only 90 minutes.
High user friendliness is ensured by the new high-performance operating system MAPPS II, which provides dialog programming and visualization options as well as extensive editing functions.
Even when programs have been created externally, it can only be of advantage to machine operators when they can easily check and if necessary modify NC programs on the machine.
Many other advantages lie in the hidden details.
A ball spindle with through cooling bore is nothing unusual.
So that heat from the driving servomotor does not reach the ball spindle at all, Mori Seiki arranged additional cooling ducts in the motor connection on the bearing side - extra work that pays off as consistent precision.
Another example is the clean roller guide that is free of lubricating oil and based on a lubricating system developed by Hitachi Seiki.
Here plastic elements sit on the rails whose pores are filled with grease.
When subjected to friction heat generated by the process they exude minimal quantities of lubricant - a very clean system that has proved itself in the field for ten years now.
Mention must also be made of the pneumatic and hydraulic supply that is mostly realised by the pallet.
When this is not possible, docking stations are integrated in the machine as a preventive measure against disrupted supply.
* About DCG - the recipe for higher speed and quality - above all when accelerating and braking, moving machine parts generate vibrations that have negative effects on machining.
So that these vibrations are avoided to a great extent, Mori Seiki has developed the DCG principle, an abbreviation of 'Driven at the Center of Gravity'.
This development was preceded by considerations on machine dynamics.
Vibrations arise in the first instance when the moved part is not driven at the center of gravity.
Superimposed torques cause small tipping movements that cause the machine to vibrate.
A machine tool, however, does not allow every drive to be installed directly at the center of gravity, so Mori Seiki used a trick to realise the drive at the center of gravity: two parallel drives whose center agrees with the moved parts' center of gravity are used along the linear axes.
This serves to minimise vibrations, which ultimately enhances machining and contour precision as well as surface quality.
Higher accelerations become possible, and therefore shorter machining times.
In addition, tool life increases. Request a free brochure from Mori Seiki UK ...
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