CNC Mill for small run injection molds

[awerby]

When you're cutting aluminum, chip evacuation is important, but a little lubrication really helps avoid the "welding" of chips to the tool. A good coolant will perform both functions.

[G59]

When you're cutting aluminum, chip evacuation is important, but a little lubrication really helps avoid the "welding" of chips to the tool. A good coolant will perform both functions.

+1

[mc_n_g]

I have a CNC Sherline and have used it for over 10 years to make many things to include small 4.5" x 4.5" plastic injection mold for small hundreds up to thousands of polyethylene and polypropylene parts. The smallest cutter I have use was a 1/32" and with very small cutting rate. The most consistent cutters I have used were 3/32 up to 3/8. The Sherline has held up well as long as I used the proper feed and speed. Many times I purchased carbide rather than HSS for longevity and rigidity. I have cut 6061, 7075 and 2024 and O1 tool steel.
Like G59 has suggested I have layered or made inserts to get 'square' corners on parts. Draft on your parts will be the hardest thing to get. The second major part to deal with is air in the mold. I don't know how you plan on venting but it is going to be troublesome depending upon how you feed. Be prepared for the expense of cutters and a learning curve. This is not something you can easily look up because the you need to match what your CNC machine is capable of.
You will need to have a good CAD/CAM setup and know how to plan out what you will cut. Plan on some long cutting times with small cutters. You will also have to deal with polishing after to help with finish and ejection.
I would second the suggestion that your 'fins' need to be cut with an EDM machine. Some parts are not economically made by endmilling. You have a LOT of decisions to make.