Frequently Asked Question

How do you select impact hammers and accelerometers?
Last Updated 7 years ago

The frequency range of the machine tools can be listed as follows:

10Hz- 200Hz: Machine tool column, bed, guides, portal frames, spindle housings, tomb-stones have large masses with low natural frequencies. You need to use large hammers which can deliver more than 5000N force. The accelerometer must also be large which can cover this frequency range. CCS1 hammer package, which has large and small hammer sets, is recommended.

200-1500Hz: Machine tool spindles with tool holders or large boring heads typically have the first natural mode at around 500Hz, and higher modes at around 800 Hz, 1200 Hz to 1500Hz. A hammer with a force range of 2000N to 5000N can be used. Higher the force range is, the lower the measurement frequency range will be. If the work material is Titanium or Inconel, it is best to have a hammer which can deliver 5000N force. If the work material is Aluminum and machined at high speeds, 2000N force range with 4000Hz frequency range is sufficient. Miniature accelerometer with a small mass is recommended for the measurement. CCS1 hammer package, which has large and small hammer sets, is recommended.

Above 1500Hz – Typically, the tool holder and end mill modes will be dominant at this frequency range. The end mill diameters are typically less than 25 mm with 75-100mm stick outs. The hammer must be small with a frequency bandwidth up to 5000Hz. Steel tips can be used to widen the frequency range of excitation. The smallest possible hammer set should be used. Hammer set given in Shop-Pro set is sufficient.

Above 5000Hz: If the end mill has a diameter less than 12 mm, the frequency will be higher than 5000 Hz which is difficult to measure with standard hammers. Miniature hammers from DYTRAN and PCB are recommended. If possible, the displacement must be measured with laser vibrometers. Note that the measurement of such high frequencies is rather difficult in practice, and any equipment purchase must be consulted with experienced users or MAL Technical Personnel.

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