Epoxy aluminium

[hespj]

I've been asked to machine a 3D shape out of epoxy loaded with aluminium (powder) which is to be used as a former for vacuum moulding. It seems mighty hard stuff, almost like stone. Anybody cut anything like this? Got any tips about feed speeds etc?

John

[don]

John,
I haven't cut anything like this with my prt96. But my primary job as a toolgrinder.
We have a customer that cuts something that sounds very simular to this. Don't know what their feeds and speeds were, but they were breaking the corners off, their using .375 4fluted endmills. They need a square bottom. We have since made them some .375 4fluted with a .060 radius endmill.
I think by doing this they are doing 2 operations. We've also polished the inside of the flutes ( look like chomed when we are done) This helps to keep any building up and sticking to the inside of the flutes. I hope this make sense and helps.

Don

[hespj]

Thanks Don. I was going to use round end cutters - the part is being designed with radius's everywhere to allow the vacuum forming.

Good tip about polishing the flutes.

Since posting the above I thought I might ShopBot a female mould a little larger than the finished item, cast the epoxy/ali in this and then just skim off with the SB to the exact shape. This to save large amounts of material removal.

[tomj]

I have looked at this material for some potential products at work. Our distributer recommended using a coolant on the aluminum filled urethane due to the explosive nature of aluminum dust. Just a heads up.

Our sister company cuts mainly aluminum and have had some intances where the dust in the air would arc and ignite from the outlets. They have since put explosive proof outlets in.

[hippo]

I've been actually thinking about the very same thing. I've been avoiding cutting real aluminum molds, and seriously considering the aluminum filled epoxy as an alternative.

Which epoxy/brand are you planning to use? I haven't yet tracked down a good material to machine. I was planning to use ball nose bits also.

[hespj]

Dan, I don't know the brand - I've been given a sample block from the vacuum forming company, and they will supply the epoxy/ali for me to cast when the client has finalised the design. In any case, I'm in the UK where we probably use different brands.

I do know that commonly available epoxies such as WEST sell ali powder too.

Another option would be to ShopBot a male plug and finish to a polish, then take a female mould, then cast the epoxy/ali former in this.

[tomj]

Dan, Freeman manufacturing & supply carries an aluminum filled urethane. Their website is www.freemansupply.com - look under machinable media then tooling/high temp board works.

Their material is kind of spendy but they have good references on there website for use and applications. Also, there are some good tutorial videos for building molds and casting parts as well. We found it pretty useful when we are exploring a project.

[hippo]

Thanks, Tom I'll check it out...