Setup on a ceiling of 5-axis-Machining Centres - how it is correct

Problem:
A DMG MORI 5-axis-Machining Centre of DECKEL-MAHO-GILDEMEISTER, weight approx. 130 kN, had been causing problems for 4 years at a large and well-known manufacturer of cleaning devices in Baden-Wurttemberg, Germany. The machine was standing exactly in the centre of a ceiling between two bearers. It was positioned on wedge mounts that were supplied together with the machine. The partly considerable vibrations, depending on the set values, were shown to isoloc. Obviously, they were close to maximum values of the admissible ceiling loads. Because of this, it was run so far with max. 50 % of the possible feeds and velocities. Already during start-up, but also during the following weeks, disproportionately frequent service of a technician from DMG was required on site in order to be even able to operate the machine. During the 4 years the situation has not changed. The expenses were substantial for both sides.

Solution approaches:
“Different elements were tested” in order to solve the problem. E. g. a competitor of isoloc submitted an offer for an extremely low tuning (mounting natural frequency) with an air spring system that would have costed approx. 30,000.-- €. Before, a measurement for the determination of the natural frequencies of the ceiling on which the machine was standing was carried out. As the customer did not want to realise this costly (air spring) solution the results of the measurement were not disclosed.

Thereupon isoloc was engaged.

Isoloc solution, step 1:
Without exact examination of the situation and knowledge of the basic conditions only a pragmatic first approach to the problem was possible for isoloc. 5 pieces Universal Precision Machine Shoes UMS, equipped with isoloc high-performance elastomers, were chosen that had achieved very good results in similar cases.

Total costs: 775.-- €

Results:
(A) Technical
The supplied isoloc Machine Shoes UMS18-ASF/I improved immediately the situation and provided enormous benefits. An increase of the values (feeds and velocities) by 30 % was achieved. The customer was contented for a start, especially because of the long history.

(B) Economic
By the decision for the isoloc solution instead of the suggested air spring solution of the competitor, 29,225.-- € were saved. The costs of the reduced production and the hours of the technician of the machine manufacturer are not included in the calculation.

Isoloc solution, step 2:
Asked for more optimisations, isoloc proposed a more elastic setup. This was accomplished by an additional layer of the Vibration Insulation Panel IPL I beneath the steel plates positioned at the mounting points on which the machine shoes were standing. These had moved slightly on the floor as no slipping protection between steel plate and floor was existing. Thanks to the excellent static friction characteristics of the isoloc IPL panels also this problem could be solved as additional effect, independent from the elastic setup of the machine. The results of the second test are still pending (status: 2017/06/26).

Summary:
This example shows that not always the complex and expensive solutions with air spring systems are necessary for difficult setup situations in vibration engineering terms if the communication between supplier and customer is good and experts are entrusted with the analysis. Due to the low rigidity and damping of air springs the operation of machining centres with the desired accelerations and speeds is highly questionable as large vibration amplitudes are to be expected. On the other hand, this case shows that common wedge mounts are in the end more expensive, too, for the machine-tool manufacturer. Presumed cost savings by cheap mounting elements are out of proportion with the risk of getting into trouble by such problems and high subsequent costs  - not to mention the damage to the reputation.

How it is correct:
Some months ago, the customer bought a new HERMLE Machine C400 and installed it on the same storey ceiling. In spite of similar local installation conditions and of the machine type, the start-up of the HERMLE machine, which was already standing as standard on isoloc Machine Mounting Systems, could be completed in only one day by the technician from HERMLE. Moreover, no limitations of the machine performance could be perceived.

DMG MORI 5-axis-Machining Centre DMU 60 eVo on isoloc UMS Machine Shoes
HERMLE 5-axis-Machining Centre C400 on isoloc Machine Mounting Systems

Setup of a CHIRON Machining Centre

Setup of a CHIRON Machining Centre on a ceiling with unknown natural frequency

Machine:

CHIRON FZ 08 W Machining Centre
Total mass: 2800 kg
Moved mass: 60 kg
Max. speed of moved mass: 40 m/min
Number of setup points: 5 pieces

Isoloc used “only” 4 of the setup points, contrary to the setup guidelines of CHIRON. The existing levelling discs were removed.

The setup was carried out on an upper floor on a ceiling with unknown 1st bending natural frequency which was calculated by isoloc.

Solution:

For setup point 1 and setup point 3:
Machine Mounting System MULTIDAM® 4-axis MD4-8LP/UMS5-ASF/20 (pat.)
Vibration Insulation Panel IPL20, 40 x 40 x 15 mm

For setup point 2 and setup point 4:
Machine Mounting System MULTIDAM® 4-axis MD4-8LP/UMS5-ASF/20 (pat.)
Vibration Insulation Panel IPL20, 35 x 35 x 15 mm

Result:

In fact, vibrations are perceptible, but - due to the local conditions and the high machine dynamics - a more elastic setup of the machine was not possible because larger vibration amplitudes of the machine were expected. The current compromise is completely adequate for the customer.

 

Machine Setup System MULTIDAM® MD4-8LP/UMS5-ASF/20

Machining centres ultra-precision manufacturing

Ultra-precision machining centre on high damping UMS Machine Shoes

Machine:

Pyramid Nano milling machine
Weight: 81 kN
Traverse speed: 25 m/min
Acceleration: 10 m/s²

Solution:

3 pieces isoloc Universal Precision Machine Shoes UMS8-ASF/20-2

Result:

 

The KERN Pyramid Nano stands on isoloc UMS8-ASF/20-2. The vibration behaviour and the specific characteristics of these machine shoes fit best this high-precision CNC-machine which was confirmed by tests in the company Kern. The use of optimized vibration dampers has, not least, a positive effect on the quality of the manufactured workpieces and the service life of the tools.

 

 

Optimization of machining centres (1)

Highly dynamic machining centers with simultaneous 5 axes- / 5 sides-processing are setup on special isoloc Original Machine Bearing Systems and Machine Shoes for many years.

This kind of setup offers the following advantages:

  • Optimization of the dynamic behaviour of the machine during the processing by vibration insulation

  • Noise reduction by structure-borne sound insulation

  • Easier setup by fast and precise levelling

Optimization of machining centres (2)

Besides the insulation of vibrations and structure-borne noise of machining centres, the optimization of the dynamic behaviour of machining centres, e.g. for the processing of aluminum, steel and titan, is another focus of isoloc. By installing isoloc original machine bearing systems in a free and unanchored way, processing with very high cutting forces becomes possible. This results in reduced processing times and reduced unit costs.
Compared with fixed, anchored setups on the often used fixators, considerably higher Kv and jerk values are attained with isoloc.

Improvements were achieved at three different 5-axis horizontal machining centres.

weight: 150 kN
max. 30,000 rpm
spindle power: max. 125 kW
max. torque: 1,010 Nm

Comparison:

fixed setup         isoloc setup

Kv = 1.5                               Kv = 5
jerk j(t) < 25 m/s³              jerk j(t) up to 125 m/s³

                                           -reduced processing times
                                              -reduced unit costs
                                             - reduced setup costs

Optimization of machining centres (3)

Optimization of a machining centre of 190 kN
(7 points bearing, put on wedge mounts so far).

The layout of isoloc machine bearing systems was realized after a modal analysis on-site. The setup of the machine showed a lower flexibility at the resonance frequency of 94-96 Hz compared with the setup on the wedge mounts used so far. Measurements of the vibration accelerations at the measuring points M1 and M2 (spindle adapter and tower) during impact excitations show that it leads to lower excitation of the structure-inherent frequency, or to less maximum values of the vibration acceleration, when the machine is positioned on isoloc elements. Less relative motions between the spindle adapter and the workpiece were measured, too, after the isoloc setup. Further measurements carried out with vibration acceleration sensors proved, as expected in the case of a setup with isoloc elements extremely better absorption characteristics compared with the setup on wedge mounts. 

image: vibration acceleration in x-direction at measuring point M1 (red) and at measuring point M2 (blue) during shock in x-direction
image: used machine bearing system

Better workpieces from rotation / milling centres

Integration of rotating / milling centres at production lines

During the integration of rotating / milling centres at production lines of a machine park of more than 180 machine tools, a receiver insulation had to be realized. Because of environmental influences or vibration immissions frequencies occurred which disturbed the production process. The required quality of the surface of the workpieces at the rotating / milling centres could not be reached.

Solution:

isoloc Machine Bearing Systems of the type MULTIDAM MD+UMS8-ASF/17-2 

Result:

  • Protection of the machines against vibration immissions of the rotating / milling centres by receiver insulation
  • Reduction of the vibration movements between tool and workpiece
  • Complete elimination of the grinding process which was necessary and which usually followed. The improvement of the roughness of the surface [Ra Value] of the workpieces amounted to up to 0.2.
  • Savings potential > 100,000.- €

 

Machines on mineral cast beds

Machines on mineral cast beds

Mineral cast beds have a higher damping compared with machine beds which are made of steel/grey cast iron, but they do not absorb all vibrations as it is often falsely stated.

 

At a damping rate of 1%, the resonance elevation of mineral cast beds is still fifty times higher!  

 

Therefore an additional setup on highly absorbing [D >> 20 %] UMS machine shoes of isoloc becomes necessary to attain a really effective vibration damping and vibration insulation.

 

Advantages:

  • The machine beds can be delivered to the machine manufacturer, already pre-installed with UMS Machine Shoes and ready for final setup.
  • Increase of the damping of the mineral cast bed and thus an enhancement of the natural vibration behaviour of the machine.
  • Improvement of the vibration properties of the machine and of its production results.
  • Simple, precise and quick setup of the machine.

 

image: comparison steel vs. mineral cast vs. isoloc

Setup of machine tools on upper floors

A Gildemeister lathe CTX410 was to be reinstalled in a production building on a ceiling (1st floor) with a very vibration-sensitive fine processing operation (gears for watches etc.). The bearing ceiling structure consists of steel girders, on which a relatively thin concrete-floor is located.

During the operation of the Gildemeister lathe impact-like vibrations would have occurred, which would have been transmitted over the floor of the ceiling to the fine processing and which would have disturbed it.

Data:
Total mass of the machine approx. 6,000kg
Natural frequency of the ceiling ƒ0z = 10 Hz

Based upon the results of a vibration measurement run on-site by isoloc measurement engineers the lathe was installed with the specially laid out isoloc Machine Bearing Systems on that floor.

Solution:

Machine Bearing System type B8
Horizontal supports type HOAW 3 with UMSD35-ASF/IPK68

Natural frequency of the system ƒ0v approx. 5-7 Hz
Natural frequency of the system ƒ0h approx. 1-3 Hz
Static deflection approx. 20-25mm

Result:

The elastic bearing lead to a very good vibration insulation (source insulation) which reduced the annoying vibrations significantly. The production is not disturbed by the operation of the Gildemeister machine.

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image: CTX410 elastically mounted
image: fine production
image: size comparison of the produced gear wheels
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