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Simple 3D carving on C-Beam

Discussion in 'CNC Mills/Routers' started by Bruce Fenstermacher, May 15, 2017.

  1. Bruce Fenstermacher

    Bruce Fenstermacher Journeyman
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    Folks,

    For the second time since finishing my C-Beam I have a project that requires a form cut into MDF. I do not need to cut intricate designs. The first project involved forming a foam sheet to a airfoil for a model wing. I wanted to carve this airfoil in both positive and negative forms into MDF then heat a sheet of foam in between them. I engineered another solution though I'd love to pursue this again.

    My latest project is a negative sphere form cut out of MDF about the size of 1/8th of a tennis ball. I will use the form to hand form soft aluminum sheet into the relief forming a dimple for relief in the final product.

    I envisioned a ball nose bit carving out the sphere in a ever deepening but decreasing diameter hole. I don't even need it to be that smooth that I couldn't know down the edges with some sand paper.

    I'm finding that 3D seems to be a whole new can of worms requiring more than SketchUP and SketchUCam I'm using. Of course I'm looking for free or extremely inexpensive. These projects are hobbies and I don't need to use my C-Beam but I'd like to.

    Any ideas on simple 3D software capable of generating simple relief cuts and generate the gcode. Or maybe the SketchUCam gurus can give me a clue about how I might fake what I need using SketchUCam.

    Thanks

    Bruce
     
  2. Bruce Fenstermacher

    Bruce Fenstermacher Journeyman
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    Thanks. Tried my hand at creating simple 3D with SketchUCam. Created a half sphere and placed it on a box. Inserted a pocket cut as that is what I assume would be the correct tool. You can see this in the first picture in ISO, the red is the pocket cut path. This generated a tool path you can see in the OpenScam image. Hey this just might work after I fool around with material depth and so forth. However what I want is the opposite of what is shown, I want the sphere cut into the block, not left on top.

    I flipped the objects so the sphere would be below. Removed the center hole of the flat revealing the sphere below. But hard as I try I can not get the pocket tool to work on the resulting box. Can't seem to get a face on it. Tried the trick of drawing a line on it to get it to fill but no dice. What might I be missing Sketchup experts? I've included the sketchup file if you have time to play with it. Would love to get this to work.

    Thanks
    Bruce
    Screen Shot 2017-05-16 at 7.56.43 AM.png Screen Shot 2017-05-16 at 7.58.20 AM.png Screen Shot 2017-05-16 at 8.21.13 AM.png
     

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  3. David the swarfer

    David the swarfer OpenBuilds Team
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    You need a drawing like the attached.
    you do not add any cutlines to it, just tick 'generate 3d' and then generate Gcode.

    There is a 'how to use 3D' in the Sketchucam help, please read it. (big blue question mark in the toolbar).

    Cut the attached Gcode in a block of foam. It is expecting a 3mm bit and will cut multiple passes at 3mm deep at 100" a minute.

    To get a good toolpath you will need to use something like Fusion360. If I get time later I will try to generate this drawing in Fusion, just learning it myself.

    Can you tell me the actual tool shape and size you are using? Fusion is very sensitive to tool shape.
     

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  4. Bruce Fenstermacher

    Bruce Fenstermacher Journeyman
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    Justin and David,

    Thank you for your time and effort. This looks very promising for what I want to do.

    I had read the SketchUCam instructions. And I even viewed the videos. There are 3 simple instructions. Create the object. Put it in the cut area. Click Generate 3D code.

    However, as I have never cut anything with SketchUCam without including a tool path of some sort why would I realize there was no instruction to include one in those 3 steps and that none is required? When people can't get instructions to work, often they miss a step or include a step not required because they think it necessary. Writing flawless instructions is an art form of the highest degree of which I have failed many times. As no tool paths are required, it would help if the author should ever revisit these instructions to add a note that no tool paths are required.

    David, as I'm just moving into and learning this area of 3D carving I don't actually have a suitable bit to give you shape and size. Might you suggest a bit that has worked well for you?

    Thanks
     
  5. David the swarfer

    David the swarfer OpenBuilds Team
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    I was experimenting last night with a half inch round nose bit in a 100mm wide hole. I think your hole is smaller so maybe use a 1/4" round nose bit? 1/8" may be too flexible when it is long enough, we always want to use the shortest and fattest bit possible.

    The result of my experimenting was that Fusion can do it but it can also generate some pretty funky toolpaths (-: I ended up doing it as 3 paths, first a roughing pass, then a 'steep wall finishing;' and then a 'shallow bottom finishing' pass. I forget the real names so don't look for those in Fusion.
     
  6. Bruce Fenstermacher

    Bruce Fenstermacher Journeyman
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    Thanks again David. I have a 1/4 bull nose wood bit I hadn't thought about I might try to cut some examples. The shape I sent was only representative. The sphere recess I need is only 1/4 deep, about 2.5 in diameter at the upper surface but the diameter of the spherical cut mush be about 5 inch in diameter. I'm only guessing about the last diameter. I'm after a shallow dome. I'd use the finished form block to hammer aluminum sheet into to form a dome. The finish of the block does not have to be polished.

    This particular project I've already completed using another method so I'm not in a rush to figure it out. I'm really busy right now but I'm excited to try some of this out ASAP so that I have the knowledge to work with next time I need the technic for another project.

    You guys stepping up so far as to actually try to cut something. This is way over and above but much appreciated.

    Bruce
     

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