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Problem Printing Hollowed Out Object
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* January 11, 2020, 09:38:36 AM
I was cruising along with my 3d drawing/printing, thinking I finally had it under control when I ran into a problem with what seemed like a simple project.  I'm trying to make an object in the form of a hollowed out shell to go over an opening to provide a "bump out" for clearance (drawing attached).  Using TC 2018 and Cura 14.07 with my Anet A8.

The Cura X-Ray view tells me I have some problems with the drawing, which I think I can fix by providing more overlap with the adjoining parts.  However, the big problem I have is that I cannot get the object to print with a hollow interior.  I've tried printing just the shell of the object in solid form, hollowed out (Boolean Subtracted the interior) and tried printing and tried printing the hollowed out version with a variety of Cura settings.  No matter what, my printer insists on filling in the interior - not with support structure, but with infill.

What's the trick to printing the equivalent of an "upside down cup" so that the inside is hollow (after removal of support).

Is it better to use TC to hollow out the object before making the STL version, or, better (feasible?) to make the STL of the object as a solid and somehow (???) use the Cura settings to only print the shell.

I've been printing this with the flange section flat on the bed, thus the "inverted cup" analogy.  I'm assuming the flange section complicates this because I've had a lot of prints where the flange prints detached from the main body of the object.

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January 11, 2020, 02:26:07 PM
#1
While some of us have 3D printers, you may be better served to join the 3D Printing group on Reddit.com.  They're a much larger community of actual makers.


Jeff

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TC Pro Platinum 2019, 2018, 2017, 2016 & 2015 (all with LightWorks & RedSDK) & V21
System: i7-5820K @ 3.30GHz, ASRock X99 Extreme4, 16GB DDR4-2133 RAM, Gigabyte GTX 970, Samsung NVMe SSD 950 (256GB), Windows 7 Pro (64-bit) SP1


* January 11, 2020, 03:29:46 PM
#2
I will do that.  I was thinking that my problem might be in my TC drawing - that would be in the wheelhouse of the folks on here.

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January 11, 2020, 03:34:24 PM
#3
I'd be curious if the reported Volume-- of the "shell'-- is correct. In TurboCAD.

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Alvin Gregorio
Intermittent TurboCAD user since yr. 2000 (ver6.5).  No formal CAD Training.
---TurboCAD: V21PP; V20.2PP; V19DL; V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)


January 11, 2020, 04:41:43 PM
#4
Sorry for the critique, but visually, the part has many issues. Even TC 3D Print Check shows issues. When opened in MakerBot, it cannot be read properly and it shows an inner block of stuff.

Are the large faceted faces part of the design? I think this part needs to be remade using a process other than what was done to ensure a smooth shell-able object.


* January 11, 2020, 06:25:24 PM
#5
Sorry for the critique, but visually, the part has many issues. Even TC 3D Print Check shows issues. When opened in MakerBot, it cannot be read properly and it shows an inner block of stuff.

Are the large faceted faces part of the design? I think this part needs to be remade using a process other than what was done to ensure a smooth shell-able object.
That would explain why it's not printing properly.

The large faced faces are from the cones that formed the rounded ends.  I just used the default number of facets (14, I think).  I can re-do and get a smoother object by upping the number of facets.

My TC 2018 Deluxe doesn't seem to have a 3d Print Check function.  Is that available in newer generations of Deluxe?

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January 11, 2020, 06:52:58 PM
#6
...
The large faced faces are from the cones that formed the rounded ends.  I just used the default number of facets (14, I think).  I can re-do and get a smoother object by upping ...

Murray says to use a multiple of 4 for curved surfaces.  So, 88, I believe would be the highest recommended in Deluxe.

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Alvin Gregorio
Intermittent TurboCAD user since yr. 2000 (ver6.5).  No formal CAD Training.
---TurboCAD: V21PP; V20.2PP; V19DL; V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)


January 11, 2020, 07:19:07 PM
#7
Sorry for the critique, but visually, the part has many issues. Even TC 3D Print Check shows issues. When opened in MakerBot, it cannot be read properly and it shows an inner block of stuff.

Are the large faceted faces part of the design? I think this part needs to be remade using a process other than what was done to ensure a smooth shell-able object.
That would explain why it's not printing properly.

The large faced faces are from the cones that formed the rounded ends.  I just used the default number of facets (14, I think).  I can re-do and get a smoother object by upping the number of facets.

My TC 2018 Deluxe doesn't seem to have a 3d Print Check function.  Is that available in newer generations of Deluxe?

I didn't realize you were using Deluxe. In that case you are limited in how you can approach this and it makes sense now to me why you approached the model the way you did. I don't have Deluxe on my computer so I can't offer much, other than suggest using max segments as much as possible.


* January 13, 2020, 10:16:22 PM
#8
I needed a similar, but much less complicated object (again, think upside down cup).  Basically just a hollow cylinder with a solid top.

Drew it up (used 88 facets on cylinder and plug used to make hollow for smoother surface) and printed it out using pretty much the same Cura settings I used for the previous print.  Came out just as planned.  Only have to remove brim and interior support structure to get finished piece.

So, my analysis of the issue is that I have a problem with my TC 3d object, not a Cura issue.  Fortunately, hanging out on here, I've learned enough about saving layout lines and layer management that it won't be a big job to refine the drawing.

I'll modify the drawing and try again (filament is cheap).

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* February 09, 2020, 06:00:12 PM
#9
Finally, success.  I made a couple of very small and simple (quick to print) objects using the same basic design as the problem one.  They printed out fine with the same Cura settings that caused a "fail" on my project.  That reinforced that the problem was in my drawing.

So, back to the drawing board (keyboard/mouse/screen?).  I found a couple of problem areas in my original object - after a lot of reading/revising I now grasp the concept of "water tight" for 3d printed objects.  I also redid the basic structure of the object.  Took a simpler approach.  Instead of using a couple of truncated cones, with a rectangular section in between, I started with cylinders.  Then was able to do a rail sweep to get the sloped sides and curved top all in one shot.  This made for a much simpler, cleaner approach.

I also got smarter with use of layers.  Kept almost every interim step on a separate layer - made edits/changes much quicker.  I ended up with almost twice as many layers as with the original drawing.

Finally, back to the STL, Cura and printer.  Results attached.  Inside hollow kind of rough, but I was using a 0.6 mm nozzle and kind of a mid-range layer height. 

When I made the cabinet for my printer I squeezed the foot print down as much as I could.  Got carried away and didn't leave clearance for the build plate plug and cable at the rear of the cabinet.  So, made a cutout and the subject object to cover the cutout.  Last photo shows the completed object set in place on the back of the printer cabinet, ready for mounting.  (sorry, now first photo - got confused loading attachments)
« Last Edit: February 09, 2020, 06:03:02 PM by minuteman64 »

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* February 20, 2020, 08:15:30 PM
#10
You can go higher resolution than the 90 or 99 or whatever the circular segment limit is in deluxe by using regular polygons instead of circles and revolving, extruding, coning, prisming them instead of using default circular primitives.  To shell a solid TC primitive or created shape, explode the solid shape down to polylines, give the polylines the thickness you want the shell to be in 3D properties, then 3D add the thickened polylines together.  TC isn't the best with orientation of normals, so you might (probably will!) find that some of the polylines thicken outwards, others inwards.  Make the thickness negative for the contrary ones before you 3D add them.  If you want to omit a face, you can either delete the face's polylines before you add the keepers together, or you can make another object to cut out that face and boolean subtract it.  Whichever method gives the neater result is the one to use.   
« Last Edit: February 20, 2020, 08:19:58 PM by murray dickinson »

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