topic Re: Step file model having trouble with thicken and with shell commands in Inventor Forum

Step file model having trouble with thicken and with shell commands

swissfeed — Fri, 12 Feb 2021 07:43:46 GMT

Hi everyone, first time poster here.

I have used Inventor for about 10 years now, mainly simple machine parts and cast/molded parts but haven't worked using surfaces at all.

I received a step model from an industrial designer for a new housing design. The solid model has some challenging transitions between different surfaces, and I don't know if I can replicate it myself, I'm still working on it. I first tried using the step model trying to get it ready for injection molding. The solid has been shelled already, but the thickness is not enough. Using Inventor thicken tool, works only on a couple surfaces but not all. I also filled in the imported model and tried the shell tool myself, but this also doesn't work at all.

Does anyone have an idea? What do you normally do in a situation like this? Remake the model from scratch in Inventor or try to work around the imported model?

Thanks

Re: Step file model having trouble with thicken and with shell commands

swissfeed — Fri, 12 Feb 2021 07:54:33 GMT

Here is the original and the filled in one plus changes from me.

Re: Step file model having trouble with thicken and with shell commands

WHolzwarth — Fri, 12 Feb 2021 08:34:50 GMT

Hard to say without additional informations.

- What thickness do you want to achieve?

- Are different thicknesses needed?

- Mark the faces to be changed with colors (Each thickness with a different color)

Re: Step file model having trouble with thicken and with shell commands

swissfeed — Fri, 12 Feb 2021 09:44:42 GMT

The model I received has wall thickness 1.4mm. I want 2.4mm thickness uniformly. Now that you ask, I think the "wing" areas might not be able to have 2.4mm as it tapers off toward the tip. Maybe that's a problem. I also derived a surface part from my filled in model, then deleted the back flat surface and tried to thicken the other surfaces, but it didn't work either. Now I'm looking more at building a model from scratch.

Re: Step file model having trouble with thicken and with shell commands

WHolzwarth — Fri, 12 Feb 2021 12:37:01 GMT

This can only be done step by step. The green faces are thickened to the inside of the part.

There' a cavity left near the wings, but no more time by now.

Re: Step file model having trouble with thicken and with shell commands

swissfeed — Fri, 12 Feb 2021 13:31:06 GMT

Wow, Danke! Was this using the thicken tool? I did try smaller sections, but maybe not small enough step by step.

Yes, I still need to fix inside the wings and make it injection mould ready.

Re: Step file model having trouble with thicken and with shell commands

johnsonshiue — Fri, 12 Feb 2021 21:58:33 GMT

Hi Darrell,

I took a look at the part. It is a very nice part. I saw a few places that I would do differently. Inventor is a precise modeler. It is not tolerant to imperfect geometry. Though the imported solid body checks clean, there are tolerant edges which can cause downstream modeling failures.

I would unstitch the body in Repair Environment and restitch them at 0.00001mm to tighten up the tolerance.

The second and third Extrusions and the Delete Faces seem redundant. You can easily create a workplane on the top face. Then use Sculpt to fill the pocket.

For imported model, I would avoid creating new sketch geometry if there is source body geometry readily available. You can use Delete Face -> Heal, Sculpt, Split to manipulate the geometry without having to create Extrusions. Sometimes you do have to create Extrusions, for sure.

Many thanks!

Re: Step file model having trouble with thicken and with shell commands

swissfeed — Mon, 15 Feb 2021 07:41:36 GMT

Hi Johnson,

Thanks for the tips. I'll try that to see how it works. I've actually gotten a pretty satisfactory model built myself without using the imported model.

Thanks again.

Re: Step file model having trouble with thicken and with shell commands

cadman777 — Mon, 15 Feb 2021 21:55:09 GMT

Mind posting your STEP file?
I'd like to have a look at it.

I'm using Inventor 2010, so can't look at any of the posted files.

Re: Step file model having trouble with thicken and with shell commands

swissfeed — Tue, 16 Feb 2021 07:02:12 GMT

Sure, here is what I got from the designer and what I have been working on in step.

cheers

Re: Step file model having trouble with thicken and with shell commands

cadman777 — Tue, 16 Feb 2021 16:20:25 GMT

Excellent, thanx!

Let me see what it looks like in my older version of Inventor (or some other software I have, like Rhino3D)...

OK, I'm back.

Here's what I see:
1. The new part is very different from your original part.

Is this intentional?

Or is the new part supposed to be the same outward shape with the inward features changed?

2. The features that change will determine how you approach this.

3. If the outward features and sizes remain the same, and if the part is LH/RH symmetrical, then I would split the part in half and delete all faces but the faces you that remain unchanged. Then make that a solid and begin reworking it with Inventor native features. I would first make the shelled part, then add the 'unshellable'/'unthickenable' features.

4. The wings appear to have pockets. How can you injection mold them? So, I would delete those pockets and make the wings solids, b/c it doesn't seem like they're doable in an injection mold scenario, right?

So, no point in 'reinventing the wheel' by wasting time on the features and shapes that are already the way you want them. Only change what's new. I may be back with some more suggestions after trying a few things...

Re: Step file model having trouble with thicken and with shell commands

cadman777 — Tue, 16 Feb 2021 23:11:08 GMT

Here's an example of one way to RE this part and work with it (if you want to reuse all the main features). Granted it's complex. But if you want to start from what you have, that's one way to do it. When you get it where you want it, you can save it as a dumdum STEP file and work on it from there (that gets rid of all the work features). But as you can see, there's a few issues (View=Wireframe). Then you have the challenge of adding all the fillets and rounds. But if it's that much trouble, you may as well start from scratch using Inventor features. It's 50/50 whether or not to use Solids, Surfaces or both.

Just my 2 cents worth...

Re: Step file model having trouble with thicken and with shell commands

swissfeed — Wed, 17 Feb 2021 07:32:37 GMT

Thanks for the examples. I've gotten pretty good results with the model I made myself. Some features are not exactly like the sample, but I also have to change some features and add drafts anyway. This is proving to be easier in my native model than with the imported one.

Re: Step file model having trouble with thicken and with shell commands

cadman777 — Wed, 17 Feb 2021 12:43:49 GMT

Glad it's working for you.

Yes, the draft, and then all the fillets/rounds. Same with holes: Knowing when to put them into the model (like the CB holes in this one). They are the tricky parts. When doing molded products like yours, it's a challenge to plan the job so you can get good results without struggling to create the final 'dress-up'.

Incidentally, my example model was a mess of surfaces, which made it difficult to place the Work Points. It was a mess b/c I was trying different things and didn't want to start over. Hope it wasn't confusing! If I did it again, I would split it in 1/2, delete all the internal faces, and then add all the Work Points without doing any trimming or deleting of outer faces. But as you say, if you're going to modify it, you may as well start from scratch using all basic shapes and features. Sometimes creating these molded parts can be like trying to get through a maze!