Basic innitial criteria

As stated in the previous post I wish for this machine to be able to machine MDF and 6063 T6 aluminum.

Ive found some information in regards to the mechanical properties of MDF on this web page:
http://www.makeitfrom.com/material-data/?for=Medium-Density-Fiberboard-MDF

Ive also found some information about 6063 T6 Aluminum from these web pages:
http://www.makeitfrom.com/material-data/?for=6063-T6-Aluminum

http://en.wikipedia.org/wiki/6061_aluminium_alloy#6061-T6
Ive decided that I wish for a minimum of 300cc/minute material removal rate in MDF and 100cc/minute in 6063 T6.

The reason for this is I only wish to design and build this machine once due to its complexity. Thus I don't really want to be feeling the machine is lacking in performance shortly after its been built. Based upon previous research prior to starting this project it seems that for a fairly strong and well designed machine this is achievable.

So from this I think its best to get a rough idea of the kind of forces involved when cutting at those rates.

Because most of the cutting done will on two dimensional shapes the tool that will primarily be used will be an end mill type cutter.

Cutter choice will be a 10mm end mill made from carbide. I don't wish to go much bigger because components will be nested together and cut from one sheet, thus going much bigger will start to waste material. However going to small will mean the cutter will not be strong enough. I think 10mm is a good compromise between cut width and rigidity. Cutting speed is a result of the material interaction between the cutter material and the workpiece material. Carbide tools can run much faster than their high speed steel counterparts.

Cutters can come with coatings, Aluminum Chromium Nitride is one of the best coating available. It improves tool life as a result of it being very hard. It also has good heat retention properties.


MDF generally requires single flute cutters due to the way it produces chips. It requires only single flute cutters because more time is required to evacuate chips whilst cutting. So a single flute cutter ideally made from carbide.

Thus the cutter used in these calculations will be a single flute 10mm carbide end mill with an AlCrN coating.

According to the CNCCookbook feeds and speeds wizard it dictates a surface speed at the outside tool edge of 630meters per minute with ALCrN coated tools in MDF.

I plan to use a low depth of cut high feed speed type cutting strategy with this machine, this will reduce tool and machine deflection resulting in better accuracy.

If i take my 300cc/minute MRR value I can use this to calculate speeds and feeds with a nominal value of feed per revolotion taken from the CNCCookbook feeds and speeds. This is quite a high figure but it ensures the tool cuts rather than rubs the material before cutting as the tool is coming around to take another bite. This improved tool life and surface finish.

So:

MRR value: 300cc/minute

Chip load: 0.5 mm/revolution per tooth.
Cutter speed = surface speed/cutter circumference
                      = 630000/(pi*10)=20000rpm (5SF)

Feed rate= 20000*0.5=10000 mm/minute.

Thus cut depth = mrr/cutter diameter/feed rate.                           =300 000/10/10000=3mm


Summarized speeds and feeds for MDF with a 10mm slot cut: 20,000rpm 10,000mm feed, 3mm depth of cut.