newby - weird radii - how to create for cnc cutting  1-20  21-27

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 From:  GarBob (GARY-MOI)
3970.1 
I have worked on this very simple piece for most of today trying pretty much everything I can think of to get this to the point of usability but so far no go.

This is a wine bottle balancer which will be carved from oak or walnut with a brass plaque embedded in it.

I want all of the edges to be filleted, except for the whole of the pointy end that is the base. The fillets will be a little less that an eighth of an inch, probably 0.1".

I am totally uninterested in correcting this piece. I just have to know what is the proper method of creating it? Obviously the origianal block of wood will be larger than the finished product. The balancer is 9 by 2 by 1 inches thick. The product will be cut from a larger piece with several other copies. There will be at lease 2 inches around all perimeters for bridges or tabs connected to the leftover material to be cut away later.

I hope that my explanation is complete and I look forward to a solution that just isn't contained in my head.

Thanks in advance!

Gary

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 From:  Michael Gibson
3970.2 In reply to 3970.1 
Hi Gary, well right off the bat I can't see how a fillet of 0.1 is going to fit in some areas.

For example this little line right here:





Is only 0.06 units long, so there's no way for a fillet of 0.1 units to fit in that space.

I would normally start trying to find which areas are causing fillet problems by going through and filleting some smaller isolated pieces of the model first, but the first area that I looked to do was that little piece where the fillet just would not fit.

Aside from that, there may be some problems with MoI's fillet engine trying to handle the sort of concave corners that you've got here. I'll keeping looking at some other areas here...

- Michael

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 From:  Michael Gibson
3970.3 In reply to 3970.1 
Hi Gary, then some other problems are that some of the pieces that look like they should be tangent are actually a bit off.

Do you have your original curves that you used to create this object? If I could check those out that may help me to give you some tips.

For example this area here:



That is not smooth at that juncture there - the curved arc piece on the right-hand side does not come to a full flat tangent, it has an ending tangent that looks like this:



That kind of thing where you've got 2 pieces that are are not smooth but coming within 5 degrees or so of being smoother are difficult for filleting to handle. It's a lot better for such things to be more accurate to be tangent where they meet. Anyway, that's probably what is causing some fillet problems in that particular area.

- Michael

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 From:  Michael Gibson
3970.4 In reply to 3970.1 
There are also some other areas where things are not meeting up with a whole lot of accuracy:





There is a gap of about 0.002 units between those edges, which is getting a bit large - it seems that the curve used to cut that sunken in area was maybe not quite aligned very tightly and that's causing enough little irregularities to cause problems.

Maybe instead of trying to sink in a cut for that area you should instead try to do a boolean union between 2 pieces instead.

- Michael

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 From:  Michael Gibson
3970.5 In reply to 3970.1 
Hi Gary, so some boolean union steps might go something like this - start with a block in the middle (maybe a bit longer than what is shown here actually, but you get the idea):



Then extrude these 2 parts out to make separate pieces for them:



Then boolean union those 3 pieces together, and then cut the hole with boolean difference:



These steps could be easier to control the shapes since you are building each of those end pieces as a whole individual piece, so you can focus a lot of attention on making the curves that are being extruded there to be high quality, like all curves tangent to one another, not any more segments than needed (like make 1 line and not 2 or 3 little lines where you only need 1, etc...).

It's a bit easier to focus on initial curve quality when building one component at a time like that.

- Michael

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 From:  Michael Gibson
3970.6 In reply to 3970.1 
Hi Gary, here is another area of the model that has that "not tangent" problem, you can see this one just by eyeballing it:





That's a sharp area where those pieces meet, there's about a 12 degree difference - you want these arc pieces to be a full 90 degree arc for such things so that the top of it has a flat horizontal tangent so it will be smooth where it touches the top line.

These little creased areas are much more difficult for filleting to process, it will actually have to try to fillet that little crease as well and try to put in corner patches in the pieces around it and stuff like that.

If you can get those arc pieces to be smooth where they touch the lines that would help out for filleting a lot.

- Michael

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 From:  GarBob (GARY-MOI)
3970.7 In reply to 3970.2 
Hi Michael,

I'm sorry not to have said that that area won't be radiused at all as a brass plate fits in there.

Gary
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 From:  GarBob (GARY-MOI)
3970.8 In reply to 3970.5 
Hi Michael,

This method fixed the one area but the area around the hole still doesn't work or at least doesn't wok properly.

I think that the problem is that the rectangular block has to be located exactly at the middle of the hole otherwise it won't line up properly with the hole thingee. Very interesting.

The look that I was going for is a smoothe transition from the high areas to the low areas.

I will try to use the front and top views to draw curved lines to represent the wine balancer!

Gary
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 From:  Michael Gibson
3970.9 In reply to 3970.8 
Hi Gary, so it sounds like you already know what the problem is, but just in case yes it is the block didn't quite go far enough to meet up with the edge from the rounded piece:





So instead of there being one edge there, there are 2 edges that are a very small distance away from each other - that's another thing that is bad for filleting unfortunately.

But your model in this case is a lot closer, I'll see if I can tune up that one spot.

- Michael

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 From:  Michael Gibson
3970.10 In reply to 3970.8 
Hi Gary, I've attached here what I've been able to come up with - there is going to be some difficulty filleting the remaining edges though because the fillet would need to come to a kind of collapsed point which MoI's filleter doesn't handle particularly well.

- Michael
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 From:  Michael Gibson
3970.11 In reply to 3970.8 
Hi Gary, I've attached another version here with some additional partial fillets added - these were done by separating the model into individual surfaces and selecting 2 surfaces at a time to do a surface/surface fillet.

You can kind of see here how there is some difficulty with multiple fillet pieces running into one another and needing to kind of disappear into a single point at the top parts - MoI's filleting engine is not good enough to handle those areas automatically. That means you may need to trim away some portions of the model and construct some surfaces in there manually to patch things together.

- Michael
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 From:  GarBob (GARY-MOI)
3970.12 In reply to 3970.11 
Hi Michael,

As that shape really wasn't what I was after I decided to try a different approach. As I already had the basic outline I ended up just creating a bunch of outlines of it along x and then lofting it. The end cut and the bottle hole were don after.

It looks good except for the end near the bottle hole. Is there a way to get a rounded end without a flat spot as I now have?

I took this model into the trial of cut 3d and it worked! Lots of cutting time. This is just a learning exercise at this point so I know that I wouldn't actually process these using a 3d cutting package! I have already several using just 2d cuts.

Gary

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 From:  Michael Gibson
3970.13 In reply to 3970.12 
Hi Gary,

> Is there a way to get a rounded end without a flat spot as I now have?

You'd probably want to incorporate a rounded end more directly into your original curve structure to get that.

I'd probably try some steps like this:

Start by drawing a 180 degree arc which will give the rounded end shape that you want:



Now draw in a curve for the side shape:



Mirror that and draw a line connecting them:



Now Extrude this to make a solid out of it - extrude it a ways further than what you need for the final shape because we'll cut off a portion of the top piece to give it additional shape:



Now go to an side elevation view, and draw in a new curve that divides the extrusion into 2 pieces and has the additional contour that you want:



Select the extrusion and run the Boolean Difference command, use that side curve as the cutting object, that will slice the extrusion into 2 pieces:



Delete the top piece. Now select these edges:



And fillet:




I've attached a 3DM model here with that result and the curves I used in it if you want to experiment with those.

Hope this helps,
- Michael

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 From:  GarBob (GARY-MOI)
3970.14 In reply to 3970.13 
WOW,

Thanks Michael. If there's a hard way to do something I'll find it.

This is great!

Gary
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 From:  BobK
3970.15 In reply to 3970.14 
Gary,

Mind if I ask you about your setup? I built a "Joe's Hybrid" and I'm using Vectic Cut 3D and Cut 2D for CAM. There are a lot of really creative and generous people on this forum, but I think that most remain in the digital world. I know it's on a case by case basis, but I'd love to hear tips on how best to model for a machining process. For example my first project in MOI (and on my cnc machine) was a simple plate. The 3D machining process was going to take over an hour and the end results really weren't that great. So I ended up making a slightly simplified plate and using curves rather than surfaces I could complete the process just using 2D machining. The job took less than 10 minutes to complete and came out very nice. Looking at your project, I suspect that unless you have a high end CAM program and a very fast machine a 2D process might save you a lot of time.

Bob
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 From:  BurrMan
3970.16 In reply to 3970.15 
Hi Bob...
When looking at your machining job, you will "prefer" to use 2d machining jobs, as it is a much simpler and faster process.. 3d toolpath strategies are reserved for a 3d surface that a "tool" cant make, though the cut time goes up and higher end packages are required for various results in different ways.... Although, "higher end" would be for jobs like a "Z-Level convex finish"... Most jobs like this can be a simple "slice planar" or raster type job... There are even free programs that will do this well (Although you both mention you already have vectric ) MoI has recently created a partnership with Alibre, that offers a simple rastering 3d toolpather for free.... :o

"1 hour" for a cut is not really very long ( maybe for your needs, but not in general) We regularly run 14 hour jobs, sometimes extending into the next day...
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 From:  BobK
3970.17 In reply to 3970.16 
Thanks Burr. I'll check out that Allibre program. As you suggest, I've learned to reserve 3D cutting for shapes that cannot be created with a 2D toolpath or a special router bit. As a hobbyist with virtually zero CAD and absolutely no prior CAM or CNC experience it's taken me quite a while to develop my techniques. I also won't try to hide my disappointment in learning that making a model in MOI might not be the most difficult step in the production process. I was a bit naive as to the capabilities of CNC machine and how the whole process worked. Still, it's been a great experience. Re: machining time, I've done some longer projects but an hour for anything made of MDF is too long :) - but I understand what you're saying.

Thanks again.

Bob
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 From:  Gary (CUTITOUT)
3970.18 In reply to 3970.15 
Hi BobK,

>Mind if I ask you about your setup? I built a "Joe's Hybrid" and I'm using Vectic Cut 3D and Cut 2D for CAM

I have a very elderly Shopbot PRT96 from 2000 AD, actually one of the first of these models. I now use Vectric's VcarvePro v5.5 for 2d cutting out and 2 1/2d v carving.

I have been trying to get into 3d cutting for years but I am absolutely stupid when it comes to cadd and all other 3d packages including silo and McNeels stuff. I had pretty much given up on ever being able to use 3d design software and therefore couldn't do 3d cutting. I have a current version of Alibre Standard and just bought a whole whack of training materials but I have since given up. Then last year I found MOI3d but couldn't believe that it would work as advertised or that I would be able to learn it. Since I spent some time on the v2 trial and Michael has help me I bought the package and it's great.

The latest wine bottle balancer was just an exercise to learn how to use moi3d - for this piece I would only use 3d cutting to create a master. The cutting time was 1 hour 45 minutes. I am planning on buying cut3d as soon as I learn moi3d. Iy seems that if you are dealing with well of people, cost isn'y so important if the product is a one of a kind.

How do you like the cut 3d?

I find that Vectric's products are amazing especially Photo Vcareve.

Gotta go battery is dyingggggggggggg

Gary
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 From:  BurrMan
3970.19 In reply to 3970.18 
Hay Bob,
I realized last night I was in error with the cnc software... "Alibre" is a CAD package, and has a CAM system as a third party add-on.. The CAM software ( and the free 3d rasterer I had mentioned ) is "VisualMill" and they have a product called freemill... They are here: http://www.mecsoft.com

Anyway, correction posted.
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 From:  BobK
3970.20 
Gary,

Cut 3D works very well. The tutorials do a good job of explaining the software and the tool paths are fine. It is not as advanced as a package like Visual Mill though. You can't select different machining strategies for different areas of your part. It does a good job with models made in MOI. Simply save your model as a .stl file and import it into Cut3D. Make a few choices about your material and how you want to machine it (similar to V-Carve) and within a minute or so you'll have a set of roughing and finishing tool paths. You might want to give the demo a try and also check out FreeMill as Burr suggests. It doesn't have as many bells and whistles as Cut 3D but it works just fine.

Thanks Burr. I learned about FreeMill after I bought Cut 3D. I tried it a few months ago and it works as advertised.

Bob
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