CNC-Fräse: Unterschied zwischen den Versionen

Zeile 328:

=== Aluminium ===

;tldr:

* Cutter diameter should be around 4mm to maximum 6mm on our Machine.

* cutting speed and feed rate per tooth are the important parameters

* Better not use Al99.5, use Aluminium that is designed for milling

* choose higher spindle speed

* Use cooling, but better not isopropanol for longer jobs as you will be drunk afterwards (no joke!)

* Chip removal can be quite a problem

~~Maximum Millheadsize should~~ be 4mm on ~~our Machine!~~

Our machine is not as stiff as we would like to have it for milling aluminium. so larger a_p would not work because the millhead will be bend to much and might break. Also our feed rate and spindle speed is limited.

~~We sucessfully tested a_p =~~ 0.~~25mm with 6mm head~~ - ~~with and without cooling (cooling done~~ by ~~isopropanol)~~

Better use smaller diameter of cutter and higher spindle speed + feed rate.

The reason is, that power is equal to rotation speed times torque (times two pi). The torque of the spindle is almost equal for all rotation speeds, thus the power directly proportional to the rotation speed.

Also the cutting speed for aluminium is quite high. Values of about 200 to 300m/min are common! As rotation speed is proportional to cutting speed divided by the tool diameter, the rotation speed gets smaller for a larger tool.

In the case of our machine, the optimum is about 4mm diameter (as for a cutting speed of 300m/min the rotation speed is about 24k revolutions per minute - the maximum of our spindle).

A too small diameter results in a high rotational speed, which our spindle does not have.

The next issue is the feed rate. You are required to remove a decent sized chip, otherwise the cutter will just rub on the surfaces and melt the material. For aluminium values of 0.03 to 0.07 are reasonable (your results may vary).

Considering a 2 flute 4mm endmill and 24k revolutions per minute, and a f_z of 0.05, we result in 2400mm/min - which is too high for our machine! Better is to design it in the range of 1000mm/min. For example, reducing the number of flutes to just 1 will immediately reduce the feed rate by half.

Another method is to reduce the rotation speed, which lowers the feed rate as well. But it also lowers the cutting speed. A slight larger cutter diameter will counterbalance for that.

~~Spanabfuhr~~ is ~~quite~~ a ~~problem~~ and ~~our machine is not as stiff as we would like to have it~~ for ~~milling aluminium. so larger a_p would not work because~~ the ~~millhead will be bend to much.~~

As you can see, choosing the right parameters is a delicate topic and you should definitively spend some time on researching the right tool for the job!

~~Better use smaller diameter of cutter and higher spindle speed + feed rate.~~

=== MDF ===