Guess what? Here in the Houston area of Texas, we’re having our first 100 degree day this year! I’m sure there’s more to come! 
Fusion is not that great for editing meshes, especially complex ones. Meshmixer is a good editor for STL and OBJ meshes. Autodesk based the mesh editing tools in Fusion off of Meshmixer, but they work much better in Meshmixer. Autodesk has stopped updating it, but it’s still a very usable tool.
In Meshmixer, it would be easy to thicken the sea turtle’s fins or whatever is needed to make it easier to machine.
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I will try that. Agreed Fusion doesn’t edit mesh data very well.
I did create face groups and offset that Cam paths from the thin features to simulate additional thickness to the fins. Great education, but fixing the original mesh would in the end be better.
I will try it tonight
Is version 3.5 the latest/last version ?
Where in MeshMixer do I thinken the mesh ?
Is this part of the push/pull ?
In order to thicken the fins and not the body I am using tool offsets per feature.
I updated the design model in that I added Face groups ( 4 fins and the body ).
I am trying to get a resultant additional .1 inches of thickness ( 0.050) a side.
I also changed some step over and DOC settings trading abuse for time.
I created a mold model to hold the part on the second side. I have MDF for the mold.
@CrookedWoodTex
The spray foam works, but I wanted to try this approach.
@rowiac suggested Meshmixer, which I installed, that maybe the next derivative attempt.
Here is the in-process part that fits in the mold.
I am going to cut the mold +0.010 " so it fits with out issue. Hopefully it will not be sloppy.
Suggestions ??
A lot of firsts for me on this project.
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I’ve used +0.010” before, but I’ve never had such a complex model. Usually, I’m allowing more room due to accuracy and/or “swelling” since I’m usually using cheap MDF.
I have MDF of unknown quality ( I don’t care ) from a good shops scrap pile.
I am making the paths now. Wondering if it is worth going to 1/8 bits for some of the nooks and crannies.
BTW 65 degrees and raining. Perfect days up next.
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The fins where they connect to the body seem to be very thin, so here is a procedure I used to modify the model using Meshmixer. This is just one example of what Meshmixer can be used for on organic shaped meshes like this one.
First, the controls in Meshmixer are different than Fusion: RMB to rotate the view; scroll wheel zooms in/out; hold scroll wheel to pan the view.
W turns on the mesh view which is handy for this kind of editing.
Sculpt–>Brushes–>Inflate is the tool we will use the thicken the area where the fins connect to the body.
Use [ and ] keys to adjust the size of the sculpting brush. This also affects the mesh density of the sculpted area. A smaller brush will give you a denser mesh and thus more detail, but also a larger file size.
Since this model is symmetrical we can tick the Symmetry check box so that any edits we do on one side will be duplicated on the other. The symmetry line appears down the center of the model. This can be adjusted if necessary, but for this model it’s fine where it is.
Use the Inflate tool to thicken the area. If it’s a little lumpy we will fix that in the next step. Holding Crtl while using the tool will reverse its effect. Ctrl-Z to undo if you make a mistake.
To smooth the sculpted area, use Sculpt–>Brushes–>BubbleSmooth and go over the edited area as needed.
This is what it looks like after smoothing:
Here’s the modified file if anyone wants it.
seaTurtle_thickened fins.stl (878.8 KB)
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Thank you ! I will be checking it out tonight.
I appreciate the education
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Day 5 - today is my grand daughters birthday and I missed the due date .
No whistle no foul.
Decisions:
I used the tool offset as the basis of attempt number 3.
This thickens all fins and left the body alone.
Thanks to @rowiac for the mesh lesson. I am sure I will be using that.
I am going to use foam again because it’s simple, the part cross sections are min 3 times thicker and the tool paths are less aggressive.
For a Mold I have 3/4 " MDF and need at least 3 sheets to get there, and I should use 4. I would have to cut each individually in order to get to the small details with smaller bits Too much effort and time for this guy.
I rough cut the bottom today.
Progress, that’s what matters. We are awaiting the final product and appreciate the learnings you have shared.
I am considering Bondo instead of foam per @Tod1d suggestion.
Advertised Dry time is reasonable, doesn’t shrink, maybe more predictable to handle.
Cost about the same
Not sure a thick blob will cure very fast, that maybe a consideration.
I did find some foam urethane had gotten on the previous attempt. It showed when I put some shellac on it. Need to be more careful.
If you’re using bondo, cut a block of wood to cover the bottom surface of the fin and a bit taller than the stock. Tape the bottom of the fin and squeeze the block onto the fin with a thinner layer of bondo. Now machine the block level with your base.
Another option would be to extend your base under the fins. ?
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Day 6 yesterday. Cut the bottom.
Day 7 Prepped for the top cut
Warming up the spindle.
Hopefully no firewood when done
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Sh.t.
3/4 in ball end mill scallop cut .
The bit grabbed the fin, pulled it away.
The other fin hopefully will survive.
Looks like a little hand sanding and glue on the horizon.
The area @rowiac pointed out was/still is the weak link
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Keep at it!
Is it possible to use several dowels to help glue the fin back on? Glue the fin back on and then drill a few dowel holes in and insert them as deep as you can, that should help stiffen the fin up for finishing the milling.
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Glued the fin back. It’s going to be hard to get the surface finish correct ( I sanded it some )
The balance of the part looks great, at least to me.
I think I am going to ship it.
I warned my granddaughter it’s going to be fragile.
Let’s see how long it lasts.
Learned a lot. Still smarting after this one.
Looks great Jim, I’m sure she will appreciate it.
Thanks.
After pondering what happened, I could have avoided it.
I use ncviewer and I had noticed that the fins were processed independently once it got down to a certain elevation.
I forgot that when I was watching.
The tool was a 3/4 ball mill, I was running at 50 ipm.
I was standing there when it happened. As soon as it got 30% along the first cut on that wing it started to vibrate, by the time I reacted it was a projectile.
Oops.
She will appreciate it.
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