Best to get the correct tool balance

2022-08-03
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Getting the correct tool balance

design engineers have a thankless job. They never stop spending energy to restrict tolerances and improve accuracy to fight against failure and downtime. They have been improving the design accuracy to about 1 micron for years. They are perfectionists

however, when the cutters are not properly balanced, their thoroughness and close attention to details are wasted. Machining parts with unbalanced cutters is similar to shooting your own feet. The tool will wear normally after performing the design task. However, the tools designed to perform that task are assumed to be well balanced. If you do this with an unbalanced tool, you are introducing new wear levels, not only for the tool and spindle but also for the parts to be executed. Unbalance can have several effects: it can introduce additional vibration of the spindle and its components, it will wear the tool irregularly, it can reduce the service life of the tool and reduce the quality of the finished product

correction imbalance

the main causes of tool handle imbalance are: defects in the tool body, asymmetric tool design, and all adjustments on the tool. In fact, every time you adjust the tool, no matter how small the adjustment amount is, you must balance it again before using it

properly balanced tools can significantly reduce noise and vibration, which increases tool life and better part accuracy consistency. The centrifugal force amplifies the vibration caused by the unbalance in proportion to the square of the velocity. The resulting increase in vibration minimizes the life of bearings, bushings, shafts, spindles, and gears. In addition, if you do not balance the tool, you will risk invalidation of the spindle manufacturer's warranty. Many warranties specifically state that the warranty is only valid if there is sufficient evidence that the tools used on the machine tool are correctly balanced. In this respect, tool balancing can lead to significant savings

before balancing the tool, you need to measure the magnitude of the unbalance and the angular position of each selected correction plane. These variables are measured on two general types of balancing machines: the non rotating or gravity machine is used to measure single plane (static) unbalance, and the rotating or centrifuge is used to measure single plane and/or two plane (dynamic) unbalance

after measuring the size and angle of unbalance on the correct plane, you can correct it by adding or removing materials from the workpiece. For components that are not tools, the most widely used method of material addition is to weld counterweights on the components. For components with slight unbalance, other methods include adding solder to the component body or adding weight in pre drilling

for the tool, when the measured unbalance determines that the material must be removed to obtain the correct balance, the easiest and most effective method is drilling. This is a quick adjustment and the amount of material removed can be accurately controlled. Another option is milling, which is most effective for balancing thin-walled tools or forcing shallow cutting

theoretically, perfect balance can be obtained when balancing the tool. In practical applications, due to the consideration of cost and the limitation of cutting tools, the perfect balance can only be achieved when we are very lucky. Therefore, the accuracy level must be set to allow a certain amount of residual imbalance to control harmful effects at an acceptable level. The accuracy given in iso1940 usually produces satisfactory results, but make sure that the standard you implement is suitable for the tool to be balanced. For example, machine tools will obviously use different values than rigid loaded propellers

tool selection and maintenance

tool balance is not just measuring the unbalance and adding or removing weight. Tool selection is very important. Short and light-weight tools are easy to balance to good accuracy, while large and heavy tools are much more difficult and tend to produce great vibration. You can also save time and cut costs by choosing a tool handle that has been pre balanced or pre machined to a minimum, Kirkby added

furthermore, you can reduce the quantity that must be balanced through routine maintenance and careful research at home and abroad. Any surface damage to the shank will affect balance and concentricity. Why? When the rotation speed climbs, the influence of the tool handle defect is amplified. If your instrument detects a force that can be ignored at 1000 revolutions per minute, the force will increase 100 times at 10000 revolutions per minute and 400 times at 20000 revolutions per minute

excellent concentricity is also more important under the high-speed spindle, because if the tool does not rotate on the spindle centerline, it becomes the primary factor of additional imbalance. However, the effect of unbalanced tool handle is also obvious at lower speeds. Small imbalance according to the report in the aluminiumtimes, feb2015, p.12; october/november2015p.8: the micromillr of Alcoa can produce the second generation of automotive aluminum strip, which can cause high force to damage the spindle bearing of your machining center, and the continuous large radial force will lead to early bearing failure and expensive machine tool maintenance costs

also, keep in mind that any adjustment (installing or removing the tool assembly, tightening the nut, or any slight twisting or remelting) requires some degree of balance. Even if the adjustment interferes with the tool balance only a few grams × A few millimeters, this imbalance is converted into an increase in vibration, resulting in accelerated tool wear, deterioration of surface finish and decline of part shape and position accuracy (such as the loss of roundness or straightness during boring in the next 10 years)

proper accuracy = better balance

in addition to the correct maintenance and handling of high-quality tool handles, it is important that the tool components are correctly installed on the machine tool spindle. In order to obtain a firm and stable connection, the spindle taper hole should be matched as accurately as possible. The difference between good fit and poor fit is especially obvious at high speeds. You may have the best balanced tool in the world, but if it is not connected to the spindle correctly, you are asking for trouble

when you think that many machining centers sold today are equipped with spindles with a maximum speed of 10000 rpm or more, you have to infer that the quality of the tool handle must be the same as the performance of the spindle. They must be firm, centered, properly balanced, and free from surface damage and contamination. If not, Ken

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