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Old 12-16-2020, 09:25 PM
afish afish is offline
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Default How do I...

OK, i have been trying to figure out how to take a spiral ramp and then basically unfold/flatten it so it can be cut on a cnc router. To better explain, I am messing around and drawing up a cyclone dust extractor. Right now mostly as an exercise to brush up on my rusty CAD skills. I can unflod and flatten the cone in SketchUp but cant get the spiral ramp to do it. Basically I want to make a piece with an outside Dia of 18-22 inches and inside Dia. of around 8" and have it rise about 8-10" in one 360 revolution. I can draw it in 3d in Sketchup and Corel CAD using the helical tool but cant flatten it. I can do a "flatshot" but that only gives me a shot looking straight down but doesnt actually "flatten" it, best I can tell. Based on my experience I should be having some variation of a french curve, Euler spiral, or clothoid curve , whatever you want to call it when this thing is flattened out. Can some one explain how I might go about this, I really only have free sketch up and corel cad at my disposal which is a lot like auto cad so if you can tell me auto cad commands I can usually get corel cad to do the same but I havent pushed it into the more complicated areas yet.
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Old 12-17-2020, 12:23 PM
NorthernWI NorthernWI is offline
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I don't know what you're ultimately trying to create so my solution and its simplistic approach might not be acceptable. I'll share a photo and my process and maybe you can build on it to find a solution that works for you.

The goal was to create a working auger from baltic birch plywood. I don't have the recoil accessory so I'm limited to routing flat pieces.

My solution ended up being a series of 30 degree stacking segments. To avoid having a sharp step on the leading edge (thickness of the material), I used a 120 degree v-bit to create a chamfer. This softened the edge and with a little more math / testing I could probably get a smoother transition between the segments.

This is not an elegant solution by any stretch of the imagination but it did achieve the goal of creating an auger. For my intended purpose - moving baseballs up an incline - this will work.

In the future, I might try double-siding machine to chamfer the top and bottom surfaces. I might also look at ways to play off the layered design elements to make it look more artistic and less utilitarian.
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File Type: jpg auger.jpg (13.4 KB, 51 views)
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  #3  
Old 12-17-2020, 12:36 PM
Charlie_L Charlie_L is offline
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Does this post in the Vectric forum help in any way?
Are you wanting the CNC to cut from wood or metal?

https://forum.vectric.com/viewtopic.php?p=264665
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  #4  
Old 12-17-2020, 10:49 PM
afish afish is offline
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Thanks guys, I know my description was probably confusing.
Here is a picture of basically what im trying to draw.It goes inside a cyclone dust collector to help direct the dust down into the cone.
Im only looking to do one revolution.
I may be overthinking it but I dont think I can simply cut the inside and outside diameters once I put it at an angle its going to change the radius.
If its stiil not clear I will try and post a screen shot of what I have drawn thus far. As I said I was able to unfold and flatten the cone portion but for some reason I cant seem to flatten the spiral ramp.
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File Type: jpg spiral ramp.jpg (68.9 KB, 21 views)

Last edited by afish; 12-17-2020 at 11:03 PM.
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  #5  
Old 12-18-2020, 07:07 AM
afish afish is offline
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here is a better pic of what I am experimenting on. The spiral ramp I am having trouble with is the internal piece. The other two main components I was able to unfold and flatten
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File Type: jpg cyclone spiral ramp.jpg (91.3 KB, 14 views)
File Type: jpg flattened cone.jpg (74.4 KB, 14 views)
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  #6  
Old 12-18-2020, 04:20 PM
tb1472000 tb1472000 is offline
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Default Bill Pentz's Site All About Cyclones and Dust Collection

Have you looked at http://http://billpentz.com/woodworking/cyclone/cyclone_plan.php#my_cyclone_solution
His plans figure the size. The part looks like a donut when flattened.
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  #7  
Old 12-18-2020, 07:41 PM
afish afish is offline
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Yes, I am familiar with bill pentz, and thats mostly what I was doing but from what I remember he had trouble computing the air ramp too and confessed it wasnt a perfect fit. I figured there was a way to do it in cad and was more of an exercise in figuring out a way to do it.
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