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  1. #11
    Quote Originally Posted by JAZZCNC View Post
    So what do you want STL file or G-code file.?

    For G-code we will need more details like Cutter type and diameter, # of flutes, Material.
    STL code would be the best as DeskCNC can create G-code from the STL file. I can set up tool paths.

    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.

    Mike

  2. #12
    Quote Originally Posted by Rufe0 View Post
    RE: JAZZCNC

    It looks pretty concave to me, I guess if you had your machine set with the Z low at the top and high at the bottom then it would be, anyway it's a simple task to do file>replace the G2>G3 and vise versa.
    Hey!! Think you'll have to explain that one to me.? Only way that code would cut concave is if machine was upside down . . . But like you say to get it concave is easy fix but still not correct because like Jon points out there's no tool height Comp.


    Quote Originally Posted by Jonathan View Post
    I'm not sure that the code Jazz has linked to does this either?
    Think it does Jon because he's got tool dia in one of the params and does some maths with it but I haven't checked it so could be wrong.!! . . . Terry isn't a muppet so would have took the easy route I'm sure if not.?
    Last edited by JAZZCNC; 20-11-2015 at 05:19 PM.

  3. #13
    Quote Originally Posted by JAZZCNC View Post
    Think it does Jon because he's got tool dia in one of the params and does some maths with it but I haven't checked it so could be wrong.!! . . . Terry isn't a muppet so would have took the easy route I'm sure if not.?
    To cut the correct concave profile, you need to cut along a diameter which is the tool diameter subtracted from the diameter of the surface you wish to cut. Having looked more carefully, I can confirm that Terry has done this (the line #1000=[#1040-#1030]), so barring other errors, he is not a muppet, at least in this case.

    I plotted a graph to demonstrate. The blue line represents the desired surface, red line is the toolpath (so an arc of radius [r_surface-r_tool]), and the red circles represent the tool. You can see it touches nicely at a tangent.

    Click image for larger version. 

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    So, sorry Rufe0, but in Jazz's words, you apparently are a muppet!
    Last edited by Jonathan; 20-11-2015 at 06:20 PM. Reason: spelling
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  4. #14
    question here:

    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?

    Thanks

  5. #15
    Quote Originally Posted by Jonathan View Post
    So, sorry Rufe0, but in Jazz's words, you apparently are a muppet!
    Ah ah you shit stirring little Geek I wasn't calling anyone a Muppet or having a go at Rufe0 so bugger off and twiddle some wires. .

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  7. #16
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 9 Hours Ago Has been a member for 4-5 years. Has a total post count of 1,000. Received thanks 170 times, giving thanks to others 5 times.
    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?

  8. #17
    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.

  9. #18
    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.

    Quote Originally Posted by JAZZCNC View Post
    Ah ah you shit stirring little Geek I wasn't calling anyone a Muppet or having a go at Rufe0 so bugger off and twiddle some wires. .
    Bit of a struggle to twiddle the wires I'm using to be honest:

    Click image for larger version. 

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  10. #19
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 9 Hours Ago Has been a member for 4-5 years. Has a total post count of 1,000. Received thanks 170 times, giving thanks to others 5 times.
    Quote Originally Posted by Jonathan View Post

    Bit of a struggle to twiddle the wires I'm using to be honest
    You won't do much of a lap if your mains lead is only that long...

    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!

  11. #20
    Quote Originally Posted by JAZZCNC View Post
    Hey!! Think you'll have to explain that one to me.? Only way that code would cut concave is if machine was upside down . . . But like you say to get it concave is easy fix but still not correct because like Jon points out there's no tool height Comp.
    Ah I think I've figured out the confusion, in mach 3 it's convex but I was using quick and dirty toolpath simulator. Tried it in a couple other simulators I had when you questioned it and they where all concave. I think it's the G18 XZ axis designation, in Mach3 the CW/CCW circular interpolation is in respect to the back elevation whereas everything else it's the front.

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