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Old 21st April 2012, 02:45 PM   #641
tomlang is offline tomlang  United States
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Quote:
Originally Posted by planet10 View Post
On request i can supply -- and have done -- DWG or DXF of any specific page. Do note that unless you have a 5-axis CNC, a CNC is only useful for doing the sides and the baffle rebates.

dave
Hi, I just joined this thread and the CNC part of this piqued my interest. Can you explain the above statement? I have found a way to cut virtually any miter angle on the plywood edge on my 3-axis machine if that is what you are talking about and would be happy to share.

For example, I plan on cutting all the pieces on my machine for the DecWare Corner horn:

DecWare Corner Horns
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Old 21st April 2012, 05:11 PM   #642
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I'd love to know how you plan to cut the mitres on your 3-axis CNC.

dave
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Old 21st April 2012, 05:30 PM   #643
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Are there some 45 degree cuts on some of the panels? That's not hard to do with a 45 degree cutter.

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Old 21st April 2012, 05:37 PM   #644
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Mostly 5 or 85 degrees. And 2 ends have round overs (at least as we do the flat-paks)

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Old 21st April 2012, 06:31 PM   #645
tomlang is offline tomlang  United States
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I made some stands to match the University Dean speakers I previously made on the CNC machine. They used the same 62.5 degree miter on the outer edges as the Deans themselves but this time I cut the miters on my Shopbot CNC.

Here is the link to the Dean construction but that was prior to me knowing how to cut miters on the plywood edges. University Speaker "Dean" similar to "Classic" 3D Model and Build - AudioKarma.org Home Audio Stereo Discussion Forums

The Shopbot comes with versatile software called PartWorks. In it is a command "Create Fluting Toolpath". Flutes are cuts that start at a given height in the material and end at a lower level (think drainage grooves on a cutting board). In this case the flutes are not very long and they plunge quickly (rate determines angle). They are also spaced really close together.

The pics show one of the sides of the speaker stand, a piece about 18 inches high.

I used the same 1/4" flat endmill bit as I usually cut the parts out with. What you do is start the flutes (I made mine .15" apart) at the top of the material and have the tool go down an "incline" ---which of course is specified by the user -- till it reaches the bottom. You have to be careful with your layout to make sure you start and stop the bit at the correct place, taking into account bit diameter. At .15 spacing the "cut" has noticeable teeth but if you shift the adjacent part's fluting vectors by half that distance it fits together really nice. If you want virtually no teeth, go with .075 but of course that takes twice as long to machine. These teeth are not stair steps but lengthwise from the top of the material to the bottom. For example, one of these vectors (flutes) cutting a 45 degree angle on 1 inch thick material would be 1.414 inches long. To machine the 18 inch long miter with .15 spacing took 10 minutes.

If anyone wants the PartWorks file I will supply it or attach it here if interest.

Any miter can be cut this way; some Trig calcs are usually necessary to input the Fluting commmand.

The stands are completed and unfortunately I cleaned up too good as I can't find any scraps I tested the miters on.
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Last edited by tomlang; 21st April 2012 at 06:35 PM.
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Old 21st April 2012, 08:00 PM   #646
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Originally Posted by tomlang View Post
The Shopbot comes with versatile software called PartWorks. In it is a command "Create Fluting Toolpath". Flutes are cuts that start at a given height in the material and end at a lower level (think drainage grooves on a cutting board). In this case the flutes are not very long and they plunge quickly (rate determines angle). They are also spaced really close together.
This type of machining was once very common in shops that didn't have anything more than the typical 3-axis mill. With a ball end mill, you could do some quite complex shapes.

jeff
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Old 21st April 2012, 08:41 PM   #647
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I'm no expert, but i'm gonna guess that you may end up spending more time sanding out the teeth than it would take to make many sets of panels on the tablesaw. And the time to program even more.

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Old 21st April 2012, 09:09 PM   #648
tomlang is offline tomlang  United States
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No need to sand out the teeth, especially if you index the adjacent teeth to fit into each other. Also, if you machine these at .07 apart you can barely even see, let alone feel, any teeth.

As far as programming, you just program one flute and then repeat it for the length of the cut, takes seconds really. Well worth it in my opinion, when you can simply lift the finished piece off the machine with no extra attention to it required.
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Old 7th July 2012, 06:34 AM   #649
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I am feeling like a pain in the *** after all the hook up wire post's but after wading thru all the posts in this thread my kids want me to give them some attn, so...
What is the definitive "polyfill" ratio for MH 7.3 drivers? Specifically what are u all using
In the "v"?
Behind the driver?
Underneath the driver behind the front baffle?
I wish i had read the post and used a removable top but that was 20 minutes ago! Murphy's law i guess
I have read the latest plans but its a bit opaque to me. I would just like a bit of clarification
This is my build on the IKEA work bench/dinner table.No wife, wonder why
Now i know why the leaves come out the middle
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Old 7th July 2012, 06:47 AM   #650
zman01 is offline zman01  Bangladesh
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This might help:

Frugal or Frugel Horn Mk3 Do It Yourself high end horn loaded loudspeaker DIY FH Mk 3

I suggest you fix some netting roughly 60% the way down from top, so that as gravity brings the polyfill down it doesn't fall to the bottom.

The density level is suggested in the plans - but probably you will need a bit of experimenting with the stuffing depending on room, amp, listening position.

Also you need to line the areas around the drivers to absorb early reflections from the cone. Jim (the builder's thread referred above) has done it with jute carpet underlay.
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