Been sort of stalling. Trying to prepare, to move on with the project. I am trying to wrap my head around the feed rate, spindle speed, dry cut aluminum game. Going from ideas in my head to the finished product, there are still some weak links. The first project thats been getting focus, is a heat sink for a Luxeon Star. This is a 3 watt tri-color led that dissipates some heat when working. The heat sink is a simple milling operation, chunk of aluminum, holes for the star, holes for mounting. This is something that I would normally cut out with a saw, and drill with a hand drill. It seemed like a good first CNC trial, start to finish in aluminum. The first step was tracking down the material. Lots of aluminum alloys to choose from. I ended up with a stack of surplus 6105-T5 aluminum alloy. This is from 80/20 surplus on ebay, each piece is about 3″ x 5″ x .180 thick, total price about $1.50 a sheet including shipping.

This alloy is harder then 6160, still don’t know if this was a wise choice or not. There are conflicting views on hardness and its ability to be machined, some say harder alloys are easier, some claim softer. It seems to be a very confusing mix of machine rigidity, type of cutter, spindle speed, coolant and feed rate. All the variables work together to machine the aluminum, and unfortunately, for all my reading, studying etc… it seems like its going to be a trial and error pursuit. Its taken me rather a long while to get this drawn up and out to CAM. Partly due, to waiting on material, in order to accurately judge the depth of cut. Partly as a result of oscillating between various pieces of software, in attempts to find the “right” combination. A couple of interesting articles have turned up in the research:

MadVac info on machining aluminum for molds to a high luster. This guys site is great, nice info on software and etc…

CNCZone post on machining 6061 aluminum with a taig mill. Links to cheap sources of cutters, hints and tips on feedrate etc…

Mach3 Mill manual for the artsoft software, but a really good reference for general machine setup and understanding.

Guerrillla CNC this is so good it almost deserves a post of its own, this is a really well done overview of the CNC process. The first of 3 articles, it has some insteresting ideas on using the CNC mill to produce molds and then cast parts using resins and mold agents. Very worth reading. Be sure to check out the photos of the finished parts, amazing detail.

Freeman Supply a place to get the prototype board mentioned in the above literature and machinable wax, this stuff seems expensive, still have to weigh the cost benifit ratio. Be sure to check out the machine videos for the wax, pretty neat!

Milling Cutter info on Wikipedia including explanation of Conventional vs Climb milling techniques

Hopefully in the next post, I will be able to report on a finished aluminum part, and not a pile of broken bits 😉


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