However, to answer your question, we plan on using a ball nose end mill, 1/4" wide, 2 flutes. The final material
will be aluminum, probably 6061 type aluminum. We would do a prototype in wood though just for practice.
Last edited by JAZZCNC; 20-11-2015 at 04:19 PM.
Last edited by Jonathan; 20-11-2015 at 05:20 PM. Reason: spelling
How would I find out the maximum depth (the center portion of the cut) of the curve?
I know that from simple trig that a^2 + b^2 = c^2
b in this case is half of the 4 inches, so b is 2. c can be approximated to be the segment between the two tangents of the block (the center part and one of the
ends) which is tangent alpha = 2 / 5.53125
the length of the arc of the curve is the diameter x pi x (alpha/360)
I am still befuddled as to the true value of c, not the approximated one.
Can someone help me out here?
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So, at risk of prolonging the Muppet show. how would other people do this? In wood, I would probably throw a quick CAD model together in something like Fusion360, produce an STL model from it, then throw it at Vectric Cut3D to produce toolpaths. Rough with flat-ended cutters, then finish with whatever largest radius ball-end milling cutter I could find in the box. F360 could probably produce the toolpaths as well but I haven't played with the CAM stuff in it yet. Depending on finish required, probably end up with sandpaper wrapped round a dowel...
In aluminium, depends on what it's going to be used for. Clearance? Finish not so important so might do similar to above. Bearing surface? Try to rig up something on the vertical mill and use a large-radius boring bar of some kind. Not CAD but geometrically better? Good finish needed for cosmetic reasons but accuracy not so important? Maybe use "wood" technique and then find a way to file/polish out the ridges?
The Muppet show....love it!!
Anyways, the wood prototype is basically that...a prototype, to prove that the part can be made. The aluminum part will basically "hug" the outside of a round metal pot
which will allow the other side to conduct heat from a peltier cooling/heating device. That is the reason for the curved part. I somewhat agree with you regarding the vertical mill and using a boring bar. We just cannot visualize it. We do have a Grizzly Mill....with indexing: G0619 6x21 vertical mill. We've never done anything with a boring bar...an idea to possibly try. Our finish required is not super important...just can't have a real rough finish or the part will not have great contact with the pot and the conductivity will not be as efficient.
Regarding the surface finish in aluminium, if aesthetics are important then I'd use a small step over (maybe 0.1mm) which should be adequate to then sand/polish it in a reasonable amount of time.
To get good thermal conductivity you do want it really smooth. I wouldn't polish it though as you could easily inadvertently leave dips which wont make contact over a relatively large area.
Having heard what the end product is going to do, I would go back to the milling machine/boring bar/boring head setup if I were doing it in my own workshop. Clamp the work to an angle plate (tapped holes into the back of the work?), get a tool rotating with the right radius (I would use my boring head with the tool sticking out the side) and feed very slowly down. Slow spindle speed!
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