Product category:
Toolholders
News Release from: Haimer, Franz | Subject: Tool Dynamic tool balancing system
Edited by the Manufacturingtalk Editorial
Team on 26 September 2001
Everyone should have a tool balancing
system
Tool balancing was regarded as a science, which nobody really tried to conquer. The Haimer balancing system, Tool Dynamic, makes balancing as simple as operating a coffee machine.
When high-speed machining came into use in mechanical shops precisely balanced tools became a requirement But balancing was for a long time regarded as a sort of science, which nobody really tried to conquer
This article was originally published on Manufacturingtalk on 26 Sep 2001 at 8.00am (UK)
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The Haimer balancing system Tool Dynamic, specifically designed for tool-holders, makes balancing as simple as operating a coffee machine.
The machine is switched on, the tool is put into the adapter.
Following a menu-controlled input of parameters the measuring run is started.
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After that the computer will tell you where material needs to be removed or added.
That's it.
Balancing, which was in former times disrespected as extremely complicated, has lost its bad reputation after the Haimer balancing system Tool Dynamic had been introduced.
This introduction was urgently required.
Due to the high speeds of modern HSC-machines the tools need to be precision-balanced together with its tool-holders.
Otherwise the precision as to surface, specified by the machine manufacturer, can not be obtained and the tools will reach a markedly lower life and - this is the largest detriment.
The high-speed spindles, costing an enormous amount of money, will suffer from bearing failures and they become useless in next to nothing.
Therefore more and more customers are coming to Haimer, the specialist for tool-holders, to raise the requirement for balanced tools.
As, however, the offer in the market place is too complicated, too expensive or simply not adequate for tool-holders, the Igenhausen specialists decided to close the gap in the marketplace by introducing a specific balancing system for tools and tool-holders.
Dipl.-Ing.
Franz Ziegltrum, responsible at Haimer for Engineering, refers specifically to the main differentiating criterion: "A predominant feature of our balancing system is the adapter system specifically designed and patented for this purpose.
In designing we have profited from our know-how as a manufacturer of clamping tools and have prevented a serious weakness of other balancing machines.
In order to achieve exact and reproducible results, the tools to be balanced need to be retained as if on a machine tool." Consequently an adapter system had been devised that can easily be exchanged in the balancing spindle.
Four bolts are sufficient to rig the system for taper-tool-holders or HSK of varying sizes.
The adapters are built in a similar way as a machine tool.
Tension is applied via a spring pack which is operated pneumatically for slackening.
This is implemented very fast by pressing a button and it will achieve a very exact clamping of appropriate tool-holder.
Already during the development phase for the spindle and the adapter system an out-of-balance-condition had been prevented.
C.E.O.
Claudia Haimer is convinced: "Especially for balancing of tools we have the most exact machine presently on the market." Precision, however, is only one criterion which distinguishes the balancing system Tool Dynamic.
Just as important is an easy handling.
The concept provides for any shop-operator, who knows how to operate machine tools, to be able to handle the machine without a specific prior training effort.
The balancing know-how is vested in the computer which will, if fed with the necessary data, carry out all necessary calculations.
You will immediately see from the software that it was specifically developed for tool-holders.
So it is showing features in order to store tool data.
This is saving time, because if a tool had already been balanced, the necessary data are available.
The operator enters the type of tool and the diameter and the system provides the data set where information on the balancing level of the tool is stored and where which diameter needs to be drilled.
Handling of Tool Dynamic is simple.
Nevertheless Haimer is offering a one-day course together with the balancing equipment, which Franz Ziegltrum is warmly suggesting.
"He who operates the balancing system needs practically to know nothing, because all the know-how is included in the balancing system.
But if he needs to decide how a tool-holder should be balanced - in one level or in two - i.e statically or dynamically - he should have a background knowledge which we impart during this one-day-course." So you should know that the total unbalance of a milling spindle is composed of many aspects.
This is on one side the out-of-balance condition of the spindle as a single part where the unbalance due to concentricity deviations need to be added.
Concentricity and out-of-balance of accessories, e.g a drilled hole for coolant, adds to the total unbalance.
In addition the lateral distortion of the clamping system upon clamping or using spring forces of a tie-rod, may possibly also be added.
The versatile origins may also lead to various types of unbalances.
We are differentiating between static and moment unbalance as well as the dynamic unbalance which is a combination of both.
In the static unbalance the centre of gravity of the rotor is located outside the rotary axis; it can also be measured in the stationary condition and it will provoke a centrifugal force upon rotating perpendicular to the rotating axis.
This unbalance can be removed by balancing in one level.
It is different with the moment unbalance where the centre of gravity of the rotor is in effect on the rotating axis, however, existing unbalances upon rotation may result in a torque.
This moment unbalance can be eliminated by balancing dynamically in two levels.
So far upon balancing tool-holders everybody thinks mostly only of balancing in one level.
Even the balancing qualities quoted by machine manufacturers (e.g G2.5 at 20,000 r.p.m.) refer only to static unbalances.
This will, however, not achieve in many cases the intended purpose and the dynamic unbalance will nevertheless provoke unwanted vibrations.
The balancing system Tool Dynamic offers an option to balance in a simple manner also in two levels.
This makes sense in particular for long, asymmetric tools where two sources of out-of-balance exist which provoke a big moment of flexure.
In short tools no high moment may occur.
Therefore in this case it is sufficient to carry out balancing in one level only.
In order to obtain results which are as far as possible exact, Tool Dynamic offers various measuring methods.
The most exact one is measuring by rotating by 180deg, where a second measuring run needs to be implemented.
The tool is inserted and a measuring run is carried out.
For the second run the tool is rotated by 180deg.
As the spindle and the adapter had remained in the same position, the computer can calculate the residual unbalance from both results.
A compensation run is slightly faster where the unbalance of the spindle and adapter are determined.
This unbalance is saved and it will be compensated by calculation during the subsequent measuring runs with the tool and the adapter.
A third possibility is a simple measuring operation without compensation, where the unbalance of the spindle, adapter and tool-holder is incorporated.
This method is good enough in order to compensate a rough unbalance.
The subsequent precision balancing needs to be implemented using one of the previous methods.
Whatever method had been selected, the operator is always getting an optimum support by the software.
During a measuring run the tool-holder is clamped into the balancing spindle and then it is rotated.
The unbalance will produce centrifugal forces which can be measured on the balancing spindle using force sensors.
The software will evaluate the measuring signal and it will show the operator where and how much material needs to be removed or added.
Finally he can decide how the unbalance will be removed.
There are various options: he can drill a hole or remove material by milling, both methods are taking relatively much effort, because the tool-holder needs to be brought from the balancing machine to a machine tool and back again for inspection.
Franz Ziegltrum explains: ,This is useful upon initial balancing, e.g when balancing tool-holders which need subsequently not to be balanced any more.
If the customer intends to re-balance tool-holders and tools after every change of tools, then this is too much of a work".
For this purpose we have more sophisticated solutions, e.g the use of what we call balancing rings.
These are composite rings with a specified unbalance.
They are clamped on a cylindrical portion of the tool.
This allows compensation of the unbalance of the tool.
For this case the software will specify exact angular degrees indicating how the rings shall be rotated.
An extremely practical option is the line laser which shows the position to be set directly on the tool.
This process can also be used for the other balancing methods.
Balancing will by no means take very long.
Measuring will not take longer than one minute and if balancing rings are used, the whole method will be finalised within two minutes.
If a drilling machine needs to be used for achieving a mass compensation of the tool, it will of course take slightly longer.
But if you consider the possible damage which an unbalanced tool can provoke, these times are of no relevance.
The purchasing price too is relatively moderate.
An amortisation of the balancing system Tool Dynamic is already achieved, if you can only prevent one spindle failure.
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