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In regards to balancing tools, what is worth knowing?
During balancing in accordance with ISO 21940-1, very often, unnecessarily, the aim is to obtain an unbalance meeting the next (better) class in the order (e.g. G 2.5 instead of G 6.3). This is often unnecessary as well as unachieveable and expensive.
For example, when balancing overall systems, i.e. electric motor rotors, the quality requirements specified in ISO 21940-1 for rigid rotors cannot be applied correctly because machine tool spindles, clamping devices and tools have different properties.
The main purpose is to reduce vibration and system loads associated with machine imbalance. The repeatability of balancing conditions can be limited by inaccurate clamping between the tool system and the tool spindle. Requirements for balancing rotating systems must take into account all relevant parameters. ISO 16084:2017 describes the requirements for unbalance tools for rotary applications, taking into account the actual load on the spindle bearings caused by tool unbalance.
The ISO 16084:2017 standard specifies that bearing loads that are caused by unbalance must not exceed 1% of their dynamic load resistance. Permissible residual unbalance is in the standard expressed in (gmm), it is also not assigned to a specific quality class G specified by ISO 21940-1 – Balancing of rigid rotors.
Should we balance woodworking tools?
In Poland, but also in the world, the process of balancing tools after sharpening is often underestimated. Companies that deal with tool sharpening often do not have balancing machines, and, worse, they often use the balancing method after the third sharpening operation. This is a wrong approach, which can cause considerable costs for carpenters or furniture factories
Advantages of balancing after each sharpening:
- increasing the accuracy of surface treatment – better quality elements leading to fewer complaints
- tool life – increased tool life between sharpeners, higher efficiency, lower costs
- bearing durability – no costs for regeneration of electrospindles and replacement of bearings
- no vibrations – ideal surface quality
- increase of rotational speed of tools
What if we don’t balance regularly?
- complaints from the recipient – inferior surface quality
- machine downtime and frequent sharpening are additional costs – shortened tool life
- machine repairs – runout of tools means extra strength for bearings
- repair of electric spindles or engines – repair of electric spindles or engines
- the appearance of a “wave” on the milled element
What causes milling spindle imbalance?
- Unbalance of the tool holder
- Unbalanced accessories for tool holders
- Unbalance of the spindle itself
- Unbalance due to concentric errors in the spindle (the axis of symmetry does not coincide with the real axis of rotation).
- Concentricity errors in the spindle hardware
- Excessive tightening force and deformation of fastening
- Concentric error and slope of the tool holder in the spindle
- Concentricity error in the tool itself