can not thickness this helmet@@

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chrisb
Posts: 25175
Joined: Tue Mar 17, 2015 9:14 am

Re: can not thickness this helmet@@

Postby chrisb » Thu May 17, 2018 6:06 am

I found an error in Sketch: The symmetry implies the point-on-object constraint, making it overconstraint. Delete one of the point-on-object constraints.
Bildschirmfoto 2018-05-17 um 07.54.28.png
Bildschirmfoto 2018-05-17 um 07.54.28.png (11.42 KiB) Viewed 420 times
However it doesn't help with the thickness, nor with the non-symmetry in Sketch001.
Time is short, someone else may look into this. If not, I'll return later.
chrisb
Posts: 25175
Joined: Tue Mar 17, 2015 9:14 am

Re: can not thickness this helmet@@

Postby chrisb » Thu May 17, 2018 6:24 am

last-minute find: the dependency graph shows errors (in red):
Attachments
Bildschirmfoto 2018-05-17 um 08.22.39.png
Bildschirmfoto 2018-05-17 um 08.22.39.png (30.99 KiB) Viewed 416 times
emills2
Posts: 631
Joined: Tue Apr 28, 2015 11:23 pm

Re: can not thickness this helmet@@

Postby emills2 » Thu May 17, 2018 6:32 am

got it, but it's an empty victory for me, because that sharp edge won't take a fillet (Part fillet anyways...maybe if put into a Part Design Part Body?)
Helmet_thickness_16.PNG
Helmet_thickness_16.PNG (238.96 KiB) Viewed 414 times
emills2
Posts: 631
Joined: Tue Apr 28, 2015 11:23 pm

Re: can not thickness this helmet@@

Postby emills2 » Thu May 17, 2018 6:38 am

chrisb wrote:
Thu May 17, 2018 6:06 am
Time is short, someone else may look into this. If not, I'll return later.
i have a solution screenshotted, but it'll take a while to write up. in short:
-fixing the sketch so edges are tangent and truly symmetric
-the extruded profile was based off of an independent sketch copy! big no no. deleted, re-extruded
-at this point i deleted all possible conflict sources, rebuilt the surface>cap>shell> solid
-tried to thickness the solid: failed!
-union to extrusion to fillet the hard edge: fillet fails!
-thickness the union??? works for 1 mm, fails for 5 mm. this is my 'empty victory' mentioned in the post above.
-tried to fillet after thickness, fail! stuck
-subtracted the other body to get final shape (i did not modify anything in that shape)

but remember, my spline version worked much better than this multiple arc business.
emills2
Posts: 631
Joined: Tue Apr 28, 2015 11:23 pm

Re: can not thickness this helmet@@

Postby emills2 » Thu May 17, 2018 6:49 am

delete the 65 dimension, drag lower arc center points to Y axis
Helmet_thickness_03.PNG
Helmet_thickness_03.PNG (80.31 KiB) Viewed 410 times
delete the 74 dimension, drag upper arc center points to Y axis
Helmet_thickness_04.PNG
Helmet_thickness_04.PNG (76.5 KiB) Viewed 410 times
Just found the duplicate sketch as basis for the extrusion!!!! forked data will be nuked from orbit
Helmet_thickness_05.PNG
Helmet_thickness_05.PNG (91.43 KiB) Viewed 410 times
the document tree after thorough cleaning (i didn't touch body 001 because it doesn't affect the feature we're trying to fix)
Helmet_thickness_06.PNG
Helmet_thickness_06.PNG (79.66 KiB) Viewed 410 times
rebuild extrusion, change color and line size to distinguish from sketch lines. turn off main profile sketch, we wont directly refer to it anymore.
Helmet_thickness_07.PNG
Helmet_thickness_07.PNG (213.09 KiB) Viewed 410 times
notice that you can highlight an edge and read the name of the edge in the bottom left: Extrude.Edge3 in the picture above

since the front of the top rib hits at an angle, we won't be able to set G1 to all surrounding faces, that would be contradictory. make a list of edge that should be G1 to surrounding faces of the extrusion
emills2
Posts: 631
Joined: Tue Apr 28, 2015 11:23 pm

Re: can not thickness this helmet@@

Postby emills2 » Thu May 17, 2018 7:00 am

this is what i settled on:
edges 23, 3, 6, and 9 will be set G1 (tangent) to faces 8, 1, 2, and 3 (you need to know the face number as well to select it right in the surface tool)

we could pick the next two edges towards the front as well, but i don't want to. the above is sufficient to make the surface vertical in the ear area, and will allow a gentler 'break off' towards the sharp corner up front. i believe this gentle break helped me obtain the thickness.

i only made the lines thick for the highlight picture (it is easier to work with 1 point lines on bodies and surfaces in general)
Helmet_thickness_08.PNG
Helmet_thickness_08.PNG (155.58 KiB) Viewed 408 times
circled in red: the edge to double click for G1 AFTER adding the unbound edges of the top rib
Helmet_thickness_09.PNG
Helmet_thickness_09.PNG (185.34 KiB) Viewed 408 times
G1 in the back, sharp up front
Helmet_thickness_10.PNG
Helmet_thickness_10.PNG (127.97 KiB) Viewed 408 times
straight up the sides
Helmet_thickness_11.PNG
Helmet_thickness_11.PNG (84.33 KiB) Viewed 408 times
Helmet_thickness_12.PNG
Helmet_thickness_12.PNG (184.59 KiB) Viewed 408 times
emills2
Posts: 631
Joined: Tue Apr 28, 2015 11:23 pm

Re: can not thickness this helmet@@

Postby emills2 » Thu May 17, 2018 7:13 am

make the cap. from the surface, not from the sketch or extrusion, keep data connection as short as possible!
Helmet_thickness_13.PNG
Helmet_thickness_13.PNG (158.82 KiB) Viewed 405 times
the goddamn son of a @%#^%$#*%^$#@^%$$@%$^ solid still won't take a thickness!!!!!! :lol: :oops:
Helmet_thickness_14.PNG
Helmet_thickness_14.PNG (144.18 KiB) Viewed 405 times
i don't know what is up, the zebra on that surface is gorgeous, i can't detect any flaws that could grow into problems...and i looked!
Helmet_thickness_15.PNG
Helmet_thickness_15.PNG (493.71 KiB) Viewed 405 times
so we have to resort to lying. tell FreeCAD you're going to the bathroom, and when it thinks you're gone, fusion to the extrusion and apply thickness.

i only got it to work with 1 mm. take it and run!
Helmet_thickness_16.PNG
Helmet_thickness_16.PNG (238.96 KiB) Viewed 405 times
this model cannot be filleted on the front sharp break. this is a show stopper. anything that goes to production needs a realistic fillet, or it is just a graphic.

remember: sketcher splines would let you model the sharp plane, AND a very small rounding to vertical in one curve. this method makes a manufacturable object right off the bat.

remember2: this model is ultra vulnerable to topological bombs. i tried adding a construction line to one of the sketches, and the profiles turned into a criss cross mess. deleting the construction lines did NOT fix it. that model was toast, had to redo it from the earliest sketches. i am very used to this, but it is a very fine line to walk, and can be really frustrating. if you build a big model without being aware of this, you could end up getting very mad at FreeCAD.
emills2
Posts: 631
Joined: Tue Apr 28, 2015 11:23 pm

Re: can not thickness this helmet@@

Postby emills2 » Thu May 17, 2018 8:10 am

here's my version with sketcher splines. i don't think it's a better design, but i do think it's better CAD technology
Helmet_03_01.PNG
Helmet_03_01.PNG (240.92 KiB) Viewed 394 times
Helmet_03_04.PNG
Helmet_03_04.PNG (245.7 KiB) Viewed 394 times
Attachments
Helmet_03.FCStd
(328.58 KiB) Downloaded 18 times
ethan0124
Posts: 5
Joined: Tue May 15, 2018 1:45 pm

Re: can not thickness this helmet@@

Postby ethan0124 » Thu May 17, 2018 3:12 pm

thanks for everyone especially for emills2 ^^

thank you very much ^^
oldmachine
Posts: 241
Joined: Wed May 31, 2017 11:49 pm

Re: can not thickness this helmet@@

Postby oldmachine » Thu May 17, 2018 8:18 pm

I spent a bit of time trying to do a 5-minute SolidWorks model using FreeCad. Learned a bit about 4-ways to create surfaces in FreeCad and, though having varying results on different aspects, in the end, I was not able to do it completely with surfaces and, certainly not quickly. I keep my SolidWorks loaded for real consulting projects but, push myself toward FreeCad and it's getting better...

To that end, the best approach I can use for something like the helmet, is construction without surfaces. With more time, I imagine a result more closely like the desired shape.

My final attempt is below - using simple Pads and Pockets, along with Thickness and Fillet... Basically 6 steps...

[FILE ADDED]
MAC OSX Sierra
3D Parts & Links (made using FreeCad and Solidworks): https://www.thingiverse.com/Still_Breathing/designs
Android App & Links: https://play.google.com/store/apps/deta ... .bestknots