Creating Indentions To A Semi-Sphere

[Anonymous]

Greetings!  I'm new to Autodesk Inventor and wanted to know what's the most efficient approach for creating a groove/notch at the base edge of a semi-sphere.  The best way for me to describe is for you to envision a tapered sinusoidal wave pattern going around the entire circumference of the semi-sphere's base edge such that the trough of the wave is tapered at the edge (thus you still see a perfect circle when looking down).  I've reviewed various Freeform videos but the closest approach that I've seen is to use sculpting tool to create groove/notch that does not penetrate completely through the edge of the semi-sphere.  Is that possible using the Bridge tool or is there a better way?

Thank you,

Travis

[TheCADWhisperer]

Can you Attach your file here?

[johnsonshiue]

Hi! If I understood your request correctly, you would need to use one of the 3D Sketch Curve types: Curve on Surface or Profile to Face or Project to Nearest Point. I am sorry I cannot seem to visualize what you are trying to do exactly. Do you have a reference picture or a drawing or a model?

Many thanks!

[Anonymous]

Thank you Johnson for the prompt reply.  My internet access on the computer with Inventor is down right now thus unable to send a file at that moment but I'm fairly certain you understand my question which is how to sketch a groove onto the rounded surface of the sphere.  I'm using the Freeform semi-sphere design to create a dome which I wanted to modify further for creating a helmet.  From there I simply wanted to add a groove/notch to the edge of the brim.  From viewing all the other helmet videos, it appears that users implement parametric tools such as guide rails/loft/sculpt to create the helmet design.  I was hoping Freeform would be more efficient for this.

Do you recommend Freeform or parametric to create a basic helmet design?   I'll send a file once internet is back up.

Thank you,

Travis

[swalton]

I've always thought of the Freeform tools as something for quick and dirty concept development, not for modeling the production parts.  This may be a personal limitation, not a limitation of the tool.

So what is your planned manufacturing process for the model you are creating?  Will shape and control you get with the Freeform tools give you a file that meets the requirements for that manufacturing process?  Injection molding has different requirements than FDM printing for example.

[johnsonshiue]

Hi! Indeed, like Steve suggested, Freeform is more for conceptual design purpose. If you want precision, it would be hard to achieve. But, it really depends on what you want. Is this sphere exact? What kind of tolerance do you need? Or, as long as it looks nice, it is fine?

Many thanks!

[Anonymous]

I very much appreciate the responses.  Yes this is just to provide a basic proof of concept that can be 3D printed.  Once I get feedback, then I would modify design.  Based upon what the two of you have said, sounds like Freeform is good for quick approach but then go back and design fresh using parametric tools which can be used to tighten up dimensions for future injection molding.  Would you agree?

Travis

[blandb]

Is this kind of what you are looking for? I know its not perfect, just concept

[Anonymous]

Yes that's basically it.  Did you construct with parametric tools?

Travis

[blandb]

Yes.

[kelly.young]

Hello @Anonymous I see that you are visiting as a new member to the Inventor Forum.
Welcome to the Autodesk Community!

How are you measuring the helmet? Are you trying to do it so that it fits on your head? Do you have access to ReCap Photo? 

You could

• Take a bunch of pictures of your head from different angles
• Load it into ReCap Photo
• Export as a .obj to bring into Inventor
• Draw each 2D Sketch on it's own Work Plane either parallel vertically or along a central axis
• Loft between them
• Or create a Surface offset defined by the .obj points

Might be easier to create the base Solid and then convert to Freeform if it will let you. 

If you can share a screenshot of what you are trying to do or attach the .ipt file so forum experts can comment on further that would be helpful. 

Please select the Accept as Solution button if a post solves your issue or answers your question.

[Anonymous]

Thank you Kelly.  Yes at some point I would like to have the design fit on a head but right now I'm still in the infant stages of using Inventor to create the basic prototype.  That said, I am overly impressed at the amount of feedback that I have received from this forum in assisting me with what I know is an elementary design.  I honestly didn't expect any feedback to my post let alone such professional feedback. 

In regards to a uploading a photo/file, I'm still awaiting internet access at our new house thus having to respond here from work (project file is at my house computer).  I will hopefully be able to upload later this week but you will quickly realize the effort is very basic.  Again my goal is to generate a 3D object from the Inventor design so that I can demonstrate some tangible progress thus I appreciate everyone's inputs.

Also, being new to Inventor and this forum please let me know what is acceptable etiquette as I certainly do not want to flood the forum with excessive questions.  I have already ordered Ascent teaching materials for Inventor and watching the various Youtube videos but still encountering the initial user challenges when learning a new application. 

I do have a follow-on question.  Inserting/creating a hole in the Freefrom model.  I would have anticipated this an easy operation but clearly Inventor uses a logic that is absent from my mind.  Youtube recommends using Work  points/work axis but Inventor is preventing me from selecting an existing point on the semi-sphere.  Any suggestions?

Thank you all again,

Travis

[kelly.young]

@Anonymous your questions are on par with the forum, so not to worry. Adding more detailed documentation (screenshot, attach parts, screencast) would be the only thing I would recommend so forum experts can give you suggestions that pertain to your model, rather than generalized ideas and instructions. 

For the hole, you can create a Work Plane, create a 2D Sketch, draw a circle, Extrude Cut > Through All. You can also create a Work Point and use the Hole command as well. You probably have to exit out of Freeform and just do in the modeling environment. 

When you get your internet up and running post back the part or screenshot for others to comment on further. 

Please select the Accept as Solution button if a post solves your issue or answers your question.

[johnsonshiue]

Hi Guys,

There are multiple ways to do it. It really depends on what construction geometry you have. Here is an example without using 3D Curves. The rounded pentagon is a surface. It was used to split the sphere. Next, I created ruled surface based on the split edges. Then I extended the surface a little bit. Lastly, thicken -> cut was used to create the groove. Please take a look at the attached 2019 file.

Many thanks!

[Anonymous]

Thank you all.  Based upon the comments it sounded like I should use the parameteric tools (rather than freeform) thus I started a 2D sketch last night and did some simple extrusions.  After 30 minutes it became apparent that I should ask you all how best to approach this.  Should I start with 2D sketches to create the helmet's side silhouette and then extruding out?  I originally started with a dome and then a spline curve to create the sinusoidal pattern on the helmet's rim but then started second guessing myself on the proper sequence.  I hope to have internet up today or tomorrow to load up file.

[johnsonshiue · Accepted solution]

Hi! There is nothing wrong with using Freeform. It is best for conceptual study. Without constructing any wires, Freeform lets you manipulate a spline surface with ease. It behaves a little bit like a play dough. You almost have infinite degrees of freedom to play around with. However, when you start doing engineering work and trying to turn the geometry to high-precision geometry to make, you will need to build the curves and reduce the degree of freedom (or reduce the variables).

Many thanks!