Frequently Asked Question

Milling thin walls and webs
Last Updated 3 months ago

The best way is to keep the webs as stiff as possible during milling. The procedure to machine them is explained as follows

1- Tap test the cutter, and obtain chatter free depth of cut, speed and width of cut.

2- Select the spindle speed, depth and width of cut which does not cause chatter.

3- Machine the part layer by layer without leaving any material at any layer. This way, the webs will always be stiff, and the dominant flexibility will come from the cutter.

4- If the top part of the machined web touches the cutter due to forced vibrations, reduce the cutter diameter by 0.15-0.20 mm after two times of the stable depth of cut. You will avoid cutter rubbing against the thin wall and exciting it at tooth passing frequency.

If you need to go far deep when the web is already thin and you are not able to implement the procedure above, follow the process outlined below

1- Tap test the cutter from the tip to the web height along the cutter axis. Select points with 20mm distance.

2- Repeat the process at the thin web which corresponds to the cutter. The web will be stiff at the bottom of the web.

3- Store all measurements from MALTF and export them as FRF files.

4- Use Modal analysis and obtain mode shapes of both cutter and flexible web separately. Save the modal parameters separately.

5- In CUTPRO Milling Module, select the modal parameters of the cutter and modal parameters of the web for the workpiece structure.

6- You need to use time domain simulation to get chatter stability lobes. Therefore select a speed range which is practical. You can use first the cutter at the tip and part at its thin tip and use analytical stability lobe first to get an idea about good speeds. Use the time domain stability later.

7- After you select a good depth and width of cut, and the speed, run time domain simulation of the process to see the vibration amplitudes and frequency.

This is more complicated solution and one needs to be well trained and knowledgeable in milling dynamics of thin webs.

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