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Rear 45* panels cutting angle issue (Read 3157 times)
dwight202
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Rear 45* panels cutting angle issue
03/11/16 at 10:16:23
 
In writing the code to cut these panels on my CNC router I ran into an issue with the top and bottom angles of the panels. The plans call for an 8* angle at the top and bottom but that would not angle the panels 8* to the rear but 8*at a 45* angle out from the cabinet. Shouldn't they be a compound cut to angle the panels backward only which would entail cutting an angle of about 4* perpendicular to the panel in each direction to get the panel to rake toward the rear at 8*. It is really hard to explain this in verbiage. I cut a scrap at 8* and when placing it at 45* it does exactly as I described and did not rake straight back but at a 45* angle out from the speaker at 8*. I cut a scrap with a 4* compound angle cut and it raked back close to 8*. That is cut 4* toward the back and 4* toward the outside. If the panel would be installed as described in the plans there would only be a point at the top and a point at the bottom touching  the top and bottom panels if the panel raked back at 8*. Maybe I am missing something but cutting a panel as described does not make it rake straight back at 8*. Same goes for the braces as I see it. I am hoping that there is a previous builder that can enlighten me on this. It has been years since I have used the math to figure out exactly what the compound angle cut should be but cutting the scrap piece from what I remember seemed to do get me close. Maybe I don't quite understand how this goes together but I don't think that is the case. Thank you for your help.
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ZYGI
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Re: Rear 45* panels cutting angle issue
Reply #1 - 03/12/16 at 20:44:19
 
Dwight'

Welcome to the forum….

We as you figured  out it isn't an 8 degree angle, and I assumed the same thing, that it would be a 4 degree, and it isn't. Seems its somewhere around a 5.8 to  degrees. Easy way to do it, cut them long and whack  them off once you've installed them.

Thats what I've done for years as I didn't have a compound saw that would swing both ways.

Good luck with your build.
Zygi
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Donnie
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Re: Rear 45* panels cutting angle issue
Reply #2 - 03/12/16 at 22:34:29
 
If you wanted to know exactly what it is, shoot me a PDF of it and I will have one of my CAD Monkeys draw it up and tell us exactly what it is.
Not one of them could make anything, but they are handy for stuff like that.
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dwight202
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Re: Rear 45* panels cutting angle issue
Reply #3 - 03/13/16 at 06:42:48
 
Thank you for the responses. I drew it up in CAD and was not able to get it to measure the angles that were drawn. Always wanted to use a different plane of reference for measurement. I have a dual radial arm saw table(2 side by side) that would be perfect to cut these but I came to the conclusion that just cutting them long and then cutting them as Zygi suggested was the best option. I'll post some pics next week as I get building on this. I just changed the code on the router to cut an inch longer on each of the parts. I will also measure the angle once I get it cut exact with one of the machinist protractors and see what it comes out to.

Donnie, thanks for the offer. I'll send you a drawing and if your guys could get it exact that would be great. Be a few days. This looks like a fun build. Kind of like making a curved corner shelving unit that gets smaller as it gets taller.

I thought a crown molding calculator would do it but that was a complete exercise in futility.
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dwight202
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Re: Rear 45* panels cutting angle issue
Reply #4 - 03/17/16 at 17:02:15
 
Finally cutting the pieces. The angle turns out to be 5.65* each way. Tuned up the table saw and put on a new blade and the angle cuts within 1/2 a degree. Super tight fit.  There is a question about an internal duct piece mentioned on figure 25 that is 1.5 x 4 inches on the drawing. Can't quite figure out what this excadctly is or how it installs. Looking at all the transparent drawings I can't see it or figure out what it does or where it goes. All that is mentioned is to cut the pieces that make the internal ducts and dry fit them before glueing in place. Can you shed some light on this?? Thanks.

This is a very interesting build. The CNC router is really making it easy to rough cut the pieces within a 1/16 and then cut the precise angles on the table saw. Still getting the radial arm saws dialed right in and that will make these funky angles a breeze to cut. As soon as I figure out how to do it I will post some pictures of how I am building these. This seems to be a somewhat obscure project as there does not seem to be much activity or recent builds of these.
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Donnie
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Re: Rear 45* panels cutting angle issue
Reply #5 - 03/17/16 at 18:55:01
 
Dwight,
Does your CNC router have a programmable Z?
If so, there are ways to cut the angles on the machine and not have to saw them.
For your 5.65 degree angle take multiple .010" depth of cut and add .00098 in your X every pass until you get to your depth( I'm assuming that you would orientate it with the cut being made to the x sides of the machine). I don't know how advanced you are at programming machines, but I would just set myself up a sub routine with a variable in it to knock it out pretty quickly.
You would want a bit with a very small radius, .032" or so.
With that step over, the scallop height is less than .0005, you wouldn't even notice it.
Now if the angle is coming up from the bottom there are some fixturing and tooling issues we would have to address, but the concept is the same.
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dwight202
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Re: Rear 45* panels cutting angle issue
Reply #6 - 03/21/16 at 00:57:46
 
Donnie,

Yes it has programmable Z. I have max Z travel of 8". I thought about doing it like this, but for a one-off build it just  seemed like more work than a table saw cut within 1/2 degree. I'm very adept at programming as I also have a mill I converted to CNC. I think once I complete this build I will spend the time to program the routine. If for no other reason than it would be a good exercise and if I like this box I will build more. There is nothing like a CNC machine to make life easier when fabricating. I already have the complete Decware car sub-woofer line programmed and tested and have build one of each as proof of concept. I'll post some pictures soon of what I have done. On the WO series I CNC slot cut the walls into the top and bottom an 1/8 and then set the panel into the slot with glue and press clamp the box together. Unbelievably strong and rigid. Thinking of doing the same on the home speakers. Everything is in perfect alignment and really speeds up assembly time.

Not really applicable to speaker building, but I'm adding a 4th  rotary axis for turning and carving on a radius. Have it on the mill on the rotary table and I can see some interest things that could be done on the router. Horn profiles is one that could get very creative.

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Donnie
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Re: Rear 45* panels cutting angle issue
Reply #7 - 03/21/16 at 17:30:06
 
Dwight,
4th and 5th axis are fun! Most of the machines I mess with are at least 4 axis.
The thing that I'm getting really wrapped up in now is 3D printing.
I tell my CAD Monkeys what I see in my head and the next day it is sitting on my desk.
Pretty soon no one will need my expertise in machining, everything will be printed.
Thank about it, you will have a printer in your home and all you will buy is the file from the designer and print it out yourself. PFM
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dwight202
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Re: Rear 45* panels cutting angle issue
Reply #8 - 03/31/16 at 12:41:36
 
Well after rebuilding the transmission on my Suburban it's time to get back to speaker building. I wrote variable code to cut the 5.65* angles in a sub-routine I can insert wherever I need it and just give it start coordinates and length of the opposite side. Trial run made a perfect angle and smooth as glass. Did not change tools, just used the 1/4" upspiral I use for cutting. Lowered Z .005 each pass which I may go bigger. As I suspected it took a long time to cut the angle but it sure looks nice. If my phone had not slid off the center console into my coffee cup and drown while test driving the Suburban I would post pictures Angry Angry. Nokia 1020 with the 41 MP camera. Got it dried out and cleaned. Tested it out with the screen hanging loose and was fine Smiley, then I started to put the screen back in the case and of course with the way things have been going Embarrassed I cracked it in half pushing it onto the locks Cry. So Amazon just got more of my money.

The time to cut these angles on the CNC router is considerable compared to closest guess on table saw, but the router cuts it so perfect. It will be one of those load and hit start then go build something while it does its thing. When I built the router I chose accuracy and repeatability over speed so while I can cut to .001 my fastest speed doing it is 80 FPM. Rapids are at 120 so you can see it is not a speed demon but very exact. When the phone gets fixed so I can pull out the pics I'll start a new thread on one of the other general forums on CNC routing/machining. I'm sure there are others who run and/or own one on these boards. Always a fun and interesting discussion. Kind of off topic here except as it relates to how I am building these speakers using it.

More to come.
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Donnie
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Re: Rear 45* panels cutting angle issue
Reply #9 - 03/31/16 at 17:39:43
 
dwight202,
When I did the calculations on .010" depth of cut the scallops came out at less than .0005", no one will ever notice. You can cut your cycle time in half by stepping it down .010"
You are right about letting the machine do the work while you do something else, I recommend staring out the window and wishing that I wasn't at work!
Wow 80 FPM, 960 ipm sounds pretty fast to me, but I work in metal most of the time anymore.
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dwight202
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Re: Rear 45* panels cutting angle issue
Reply #10 - 04/02/16 at 06:02:47
 
Oops, That would be extreme in the speed department. Should be IPM, not feet. I'm rethinking the accuracy thing for wood, though. Really no need for that tolerance but everything is so tight when gluing up.
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dwight202
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Re: Rear 45* panels cutting angle issue
Reply #11 - 05/24/16 at 01:05:10
 
Well finally got things cut and am in the fit-up stages. Got a little side-tracked building a WO32. Wrote the G-code to cut the angles and tried it out. As I found out from a test cut I had done earlier I get exact perfect angles, but the time hit is not worth it to do this for every angle in the design. Can do almost as good on the table saw that I keep dialed in. So far fit has been good. Knock on wood  ::)but thus far I have not had to scrap any parts. I have been a little remiss in posting any pictures of this so I'll make it a point to get some up prior to glue-up. This is a mind warping design but actually fun to build. Don't get to use the math very often to figure out how to make a design fit together and get cut correctly. Most projects are just straight cuts with a few radiuses.  

The subroutine calls to make the angles works great, it's just the time it takes to do 50 or so passes to get a perfect angle. I can cut every one on the table saw in the time it takes the router to cut a few of them.

Zygi, How have you been gluing these up. Do you use dowels or biscuits or do you just glue and clamp?? Seems it would be stronger with a mechanical fastener and hold the angle while the glue sets up. Or is just a brad nailer good enough. I would imagine this is a pretty inert box with respect to internal pressures and vibration. I'm still a little confused on the duct design and bracing but but I think I got it figured out. The last problem I'm trying to solve is locating those crazy foam balls. They are very elusive. The place mentioned in the plans does not appear to carry these and locally all I can find is hard styrofoam or small diameters of the "nerf" type balls. Any ideas?? Thanks  
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