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Cut thin aluminum, almost

cut thin aluminum

My first attempt to cut thin aluminum almost worked. But not quite.

The picture above shows my first try to cut thin aluminum on my CNC machine. The 8” wide aluminum sheet is 0.025” thick. It is clamped down to the spoiler board and held securely. The cutting tool is an end-mill of 1/8” diameter held by a rotary tool serving as a spindle. The tool was programmed to cut holes and profiles to a depth of 0.03 inches in four passes, each of which set to around 0.0075 inch. The cutting tool was programmed to feed across the material at 15 inches per minute.

Before cutting, the tool was set level with the top of the material. I used my digital multi-meter to emit a tone when the tool touched the metal, completing an electrical circuit. The cutting path started in the lower left of the picture.

The cut failed, but came close. There were two problems.

The first problem was caused by the apparent difference in level across the cutting surface. As you can see in the lower cut (a stator plate for a capacitor) the tool cut all the way through on the right hand side, but not on the left.

Lifting caused failure to properly cut thin aluminum

But I think that the second and more serious problem was that the cutting action caused the center of the aluminum sheet to lift as it was being cut. While the clamps were holding down the aluminum at the edges, there was no clamping at the center of the sheet. This thin aluminum has some flex, and as the tool engaged, it’s up-cutting design caused the aluminum to lift slightly.

By the way, I used some WD-40 as coolant sprayed onto the aluminum surface. I also used a hair dryer, on cold, to blow air across the surface while I cut.

As the aluminum edge lifted, it bent. You can see the distortion in the cut on the right hand side of the upper cut, the rotor plate for the butterfly capacitor. Mid way through cutting the right hand side of the rotor, the end mill got stuck in the aluminum twist. Time to hit the “kill” switch.

On my next attempt to cut thin aluminum, I will use some double sided tape to hold down the bottom of the sheet. Hopefully this will stop the lifting. As a result, the cutting bit did not get too hot and does not appear to have been damaged, even after it got stuck as described above.

Before I try again, I will get some strong double-sided tape, and also make sure that my CNC machine is properly level.

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