Roundover on Knob


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I'm creating a roundover along the edge of wooden knob using the "Follow-Me" tool. However, I have not been successful for a couple days. Attached is my screenshot of the knob with roundover. Noticed some "holes" at the rounded corners of the knob after using the "Follow Me" tool. Advice on resolving these "holes"? Step-by-step or video greatly appreciated.


5 Point Knob.JPG

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There are no dimensions shown in your model but I'm guessing it's pretty small. SketchUp has trouble creating faces that are very small in situations like this, especially where curves are involved.  The best solution is to work at a larger scale, then shrink your model down to size after you do the roundover.  Before you do the roundover, do this:

1. Draw a 1" long line, off somewhere separate from your model.  A 1x1x1 cube works too if you prefer.  But it has to be exactly 1", or some other known dimension.

2. Use the tape measure tool to measure the line.  Immediately after seeing the 1" measurement appear in the status bar area in the bottom right of the screen, type in a new dimension like 100 and hit enter.  SketchUp will ask if you want to rescale your model, answer yes.  Note that this will rescale everything in the model, not just the line.

3.  You've just resized your entire model by a factor of 100, so that 1" line is now 100" long, and your knob is 100 times bigger also.

4.  Do your roundovers with the follow me tool, using your preferred method.  They should not have gaps.

5.  Repeat step 2 to shrink the model back to it's original size.  Measure the 100" line with the tape measure tool and immediately type 1 and hit enter.

6. Save!

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My posted model is based on 3" diameter knob with 1/4" roundovers. Following your suggestion, I created a test piece and got similar result as shown below. First, I created a large circle with 100" radius (with 100s applied) and inserted smaller radius of ~25" (with 100s applied) at the intersection of red axis. Deleted lines to create a notch in bigger circle. Added ~15" roundover at the intersection. Extruded the surface to desired thickness. Applied smooting tool to the model. Created rectangle along green/blue axes and then created ~15" roundover. Applied follow-me tool along top edge. As you can see, it's still producing holes. I've tried several methods I can think of, but no luck.

My goal is to create a knob and scale it to various sizes ranging from 1" to 6" for 3D printing.


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Wow, I would have bet that it was an issue with scale.  I need to experiment a bit on this one.  Quite an advanced modeling technique too, you must be familiar with other packages.  Occasionally I run into these types of models where the desired outcome seems to expose limitations in SketchUp.  I hate to resort to manual intervention, drawing lines to heal the surfaces, but occasionally this is needed.  You could fix one "corner" then copy and paste the correct geometry onto the remaining areas, with precise control of rotate tool.

Another possible idea would be to create multiple extruded shapes for each of your circles (main body, inset cutout, rounded corner) and round each of them over with the deisred radius, then finally merge and explode them, then delete the unwanted areas.  If doing this, consider making one "bay" of the design only as a component, then assemble a whole knob out of a series of identical segments.

When I get back to a computer I'll do some further experiments.

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Best advice, in my opinion, for the follow me tool?  Don't use it unless you have to. 

Get the fredo6 "round corners" plug in.   In simplest terms, it's like applying a roundover router bit of what ever radius you want.  You can apply a roundover to any single edge in your object, so you can easily apply a roundover to a table top for example. 

I've made a LOT of rounded over knobs for 3d printing.  There's lots of ways to skin this cat, but here's how I do it.   But from experience, items like this are easiest to make by getting a complete drawing in 2d first, then extruding into 3d.   



Pick how many knurls you want your knob to have, I went with 4, so make an 8 sided polygon with a radius less than your final max radius.   Make this polygon an object so you can select it later. 


On the perimeter of the polygon, make 2 arcs, one facing out, one facing in.  Size them to get the profile you want.  This one is rather ugly, as I didn't take the time to finesse the edges.    Bigger arcs would have better transitions. 


Select both arcs, and rotate them using the Ctrl-Rotate button.  3.JPG

Type "x3" to finish off the profile. 



Select and erase the Polygon.  Then right click on the lines and "Generate Faces".  See those sharp edges?  That's what I meant about bigger outside arcs having smoother transitions.


Extrude into 3d.




Click the "Round Corner" button in the fredo6 collection. 



Choose the offset you want.   I went with 1/4".  I could easily have gone with more for more rounding. 


Click the top face.  The red lines indicate the edge(s) selected, and the green lines show where the rounding will occur. 


Without clicking outside the object, rotate the object and click the opposite face.   With a little practice selecting and deselecting edges to round is quite easy with fredo6, but initially it's a bit confusing.   You can also double click the entire object to round all faces, but for this example I didn't as the rounding would be hard to see. 



Now click outside the object, that will have the plugin round the edges.  It is reversible by "undo" if necessary.  I recommend make a save before rounding, in case you need to make major edits later. 




Find the axis, draw a circle for the bolt hole, and a hexagon for the bolt head or nut.  13.JPG

And extrude them through.



Voila.  A knob.    It took me longer to type this up than to make the knob. 


Here's a pic showing the hidden geometry so you can see the curves better.  This is the knob I use for most places I need a 1/4"-20 bolt on something.  I've printed so many of these that I actually made a Latex mold of one so I can cast multiple knobs from resin.   This one is listed on Thingiverse, under the same user name I use here if you're interested. 



Using this plugin you can make easily make curved tubes and the like if you want to.  The follow me tool is not the most user friendly, so If I were to say layout 4" pipes in a drawing, I'd make the pipes 4" square, and then use a 2" offset to turn the squares into tubes.  

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@DefZilla, for your C shaped knob, use the same technique.  Make the original circle to size, remove the slice to form the C, extrude to 3d, and then just click the top face to round the edges over. 

With this plugin, I've never had to scale my projects up or down to get results.  I've modeled 2mm bolt knobs before with any issues, aside from the fact that trying to print out a rounded over edge at that scale is really hard to notice. 


If you're going to be using sketchup for 3d printing design, the fredo6 collection is one of my essentials. Not only will it do roundovers, but chamfers and other types of edge effects.  He put out quite a few plugins, some quite complicated but very powerful, check them all out.   Also get "Solid Inspector", this plug in will tell you if your object is manifold or not, if it's not, the slicer may start doing weird things.  


EDIT:  Found a link for ya for the roundover plugin:

Also, during my search, I found a page that lists a bunch of other nifty scripts that you'll probably find useful: 

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