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scordatura

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Posts posted by scordatura

  1. 3 hours ago, HoGo said:

    Wasn't the fluting carved after the f holes were cut on nearly finished top? We cannot count that as inflection but rather cosmetic treat. I guess before fluting the f hole wing was convex or nearly flat and it looked better to them to carve it concave.

    One needs to remember that the F hole wings are very active at certain frequencies. This has been verified with 3D animation. What may have started as a visual element has a distinct acoustic effect.

    https://www.bormanviolins.com/modalanalysis.html 

  2. 2 hours ago, HoGo said:

    Zebra analysisi is available in RHino as well and it works great to find curvature continuity/tangency problems of your surfaces.

    I think some steps he did in the video are unecessary or at least could be worked out simplier in Rhino (all the stuff with pints and curves in the beginning including removal of the offset line). Perhaps Rhino has better/ more functions for surface creation but I've never worked in Fusion.

    This is the conclusion that I am coming to. Rhino is better for surface creation. As I mentioned above, I am working on a workflow that will allow modeling in Rhino and importing the .3dm  files into Fusion 360 for CAM. I do not like the lack of native CAM in Rhino and am not willing to pay up for the RhinoCAM plugin. That being said I have not tried FreeMill.

  3. 6 hours ago, Geigenbauer said:

    I just came across this interesting discussion on the AUTODESK webpage.

    https://forums.autodesk.com/t5/fusion-360-design-validate/another-small-loft-problem/td-p/9201723

    I found the video at the bottom of the page (posted by TrippyLighting) very interesting. He is demonstrating how he would approach a loft surface with few profiles. Also a lot of practical tips included.

    There are some very good points in the video! The zebra contours is great for visualization.

  4. 10 minutes ago, HoGo said:

     

    I had old distorted instruments in mind when typing. texture of varnish and wood would not make it easy to find it and I guess it would vary wildly around the instrument (the CT scans often show how different arch can be on bass side and treble side). But of course the main schools will have somewhat distinctive placings of the inflection (Amati vs Strad vs Guarneri vs. Stainer)

    Yes this is the problem when working from CT scans. You have to do the arching correction which means bringing down the soundpost/treble side and then mirroring over to the bass side or the opposite if you work from the bass side. It depends on how tight (New York setup) the post has been and the vulnerability of the plates to distort. Splitting the difference between the high treble and low bass seems to make sense to me.

  5. 41 minutes ago, HoGo said:

    sorry, but I consider the ones in picture above a bit odd with very wide channels and inflection almost half way up the arch

    I would suspect that the channel issues are due to the arching from an Andrea Guarneri (Comte Vitale) viola or similar instrument as the Andrea Guarneri violas are particularly revered. Definitely not Strad or del Gesu like. I could be wrong though...

  6. Another element to add to the Rhino 3D story. There is no native CAM in Rhino. You need a plugin to run CAM. RhinoCAM is $1425. Ouch! FreeMill is free but is described as an "entry level" CAM engine.

    So my plan now is:

    Model in Rhino

    Export as .3dm from Rhino and Import into Fusion 360 for CAM. That is provided that the import goes smoothly. I am hoping that there are less steps and issues with working with .stl or .obj files. Converting meshes to a body is tricky. For those who do not know, it is difficult to select faces to generate cutting paths on .stl files. There are Mesh face limitations when converting to BRep in fusion. Sometimes converting to quads from triangles solves the problem but can lose the surface integrity. The other work around is to cut up the body into different pieces.

    Before you say just work in Fusion 360, at this point I am sold on the curve network command in Rhino. I might change my mind though as I just installed Rhino. I'm on the 90 day trial. When that is up, I am educating young musical minds so Rhino would be $150 for a single educator license. 

    Fun isn't it. Most would just say " fool grab the hand tools"!

  7. 12 minutes ago, Don Noon said:

    The chiploads in the linked article are essentially the same as the chart I posted, which again gives recommended feed rates well above the capability of anything other than full-on industrial CNC machines.  

    Us common folks have to use lower feed rates.  The fastest I have cut is 2500 mm/min (~100 in/min) out of the flat-out maximum travel speed of 4000 mm/min (157 IPM), and even that is less than half of the recommended feed rate in the article's example.

    Yes the mega quick feed rates seem to be for commercial production setups that are cranking through milling. No doubt pro level machines that are beyond the reach for most of us. This why when I went from the guestimation formula to a more "evolved" calculation I thought the feed rates are just nuts. As someone I read put put it, when someone is hand routing, they are going by the sound and feel of the process to guide their feed rate not a calculation.

  8. Spindle speeds during CAM seem to have two schools of thought. The fastest for the cleanest cut or slowest for heat and wear. I realize that the feed rate is the other variable and the two are interrelated. I find the calculators that are available (e.g.http://www.cutter-shop.com/information/speed-and-feeds-calculator.html) are fairly aggressive in terms of feed rate...My feeling is to have a higher spindle speed (mine goes to 21K) and slowish feed rate. That being said one is supposed to take into account the chip clearing rate for each bit. One can hear when the machine is cutting if everything sounds happy. Far less calculated but seems to verify if you are on the right direction. Thoughts?

  9. 2 hours ago, Marty Kasprzyk said:

    There seems to have been at least four different ways of duplicating wood plate arch shapes that have been used:

    1.  Hand carving using arching templets as guides.

    2.  Duplicating router machines using patterns.

    3.  Pressing thin plates into molds.

    4. CNC machining.

    5.  In the future we might see 3D printing if suitable materials/designs can be found

     

     

    Each of these has some disadvantages so I make my plates flat.

    I would also add carbon fiber which would be laying material in a mold. I have played the Luis and Clark instruments. They are good but for the discerning player have an unusual tonal characteristic.

    Being a formula 1 fan, I am amazed what they and aerospace are doing with these materials. I also have a few carbon fiber bows that are pretty good. My favorite being the Rolland Spiccato. 

  10. 53 minutes ago, David Burgess said:

    "Recovery" can be quite a challenge. Recently, When I presented at a Michigan Violin Maker's meeting, some woman told me,

    "From what I'd read, I thought you were going to be much bigger and badasser".

    I responded, "What? Ya mean I'm not"?  :lol:

    Hey you are in good company. That is what Aaron Rodgers and Drew Brees hear when fans meet them. :)

  11. 29 minutes ago, David Burgess said:

    I don't use any magnetized tool holders. Too many problems, including what Bill has mentioned. The strips you are seeing are Velcro. Yes, the Velcro can wear out in twenty years or so of intensive use, so might need to be replaced something like once per two decades.

    Very cool idea as I have outgrown the number of slots on my wooden holder. I am verging on being a gouge and chisel junkie. They say the first step to recovery is recognizing the problem.

  12. 2 hours ago, Michael_Molnar said:

    This is a great thread. I too wonder about the advantage of these expensive packages. It pretty much depends on the detail you want the CNC to achieve. It’s a matter of how much time and money you want to spend on this addition to your shop.

    Yes and yes. I am hooked on this stuff now. It comes from my days with Illustrator, photoshop, and all of my other digital endeavors. I feel that it will be time well spent. I also tend to be a perfectionist. 

  13. 1 hour ago, Fiddlemaker5224 said:

    . One thing I like about the v carve and Aspire, is you can get the probe attachment.

    Just for the record you can also probe with Fusion 360.

     

    45 minutes ago, Geigenbauer said:

    I tried to capture the outside arching in Fusion 360 by placing the arching templates from the poster at the respective positions of the back. It worked pretty well but it took me a while to get this set up and scaled. Hope you can see this in the picture below.

    Post2.thumb.jpg.2ccc44bb2a95c25d1d58805ef64a30ce.jpg

     

    That is how I am doing mine. I am matching arching templates as canvases perpendicular to the outline. Then creating new planes that have a 1 mm rise in the arching from the outline up. A topography or layer cake  of sorts. This verifies that I am on  the right track. 

  14. I feel that it would be good to have a discussion regarding CAD/CAM software. There are a number of options out there. As I get deeper into this area two programs seem to be prominent. Rhino and Fusion 360. 

    Fusion 360  - free for hobbyists and education

    Rhino 3D - 90 day free trial $995 to buy $495 for educators

    There is also VCarve pro that is free. Windows only. Even though I have only used it a bit, it does not seem to be as powerful as Fusion 360. For simple projects it seems like it would be fine. 

    Fusion 360 seems to be the obvious choice due to it being free. There is something that Rhino has that is not in Fusion 360-- a curve network command. To me there is a difference between using loft with rails and the curve network. Modeling the surface for tops and backs can be challenging. The question is whether it is worth the expenditure.  

     

  15. I had a friend that owned a Storioni. It had one of the best E strings I have ever played. Everything was there--power, flexibility, color. Peter Prier (or someone in the shop) had to do a major restoration on the top as one of his children sat on it! Really cool violin.

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