Hi,

I'm trying to create a mount for 3D printing, but I'm having trouble turning it into a solid object so I can apply fillets/chamfers to some of the hard edges. There are some naked edges I can't seem to get rid of, and as far as I understand, they're what's preventing the solid from forming properly.

Any tips or suggestions on how to fix this would be much appreciated. My model is attached.

Thanks,
Frederik

Here is a new version of the model. It's just a SWEEP between 3 profile curves (closed curves). I can't close the bottom hole using "Planar" or "Network" (Yellow selection in the screenshot).

This is probably very simple to do, but I can't figure out how to make this a SOLID?

Hi Fredrick,
the problem I found was the bottom face is not flat so started with outer shape and offset 3mm and sweep outer and inner shapes with 2 rails
Boolean 4m of inner bottom then boolean inner from outer.
Cheers
Barry

Hi Frederik, also another way you could close this would be to slice off the end with a line so you have a planar opening. Then select the object and run Construct > Planar to fill in the planar ends.

I've attached a version with that done.

- Michael

Hi Barry,

Many thanks for helping me out with the model! I'm trying to re-create what you did, just to make sure I understand how it works. Does this sound about right? (And of course, anyone else is welcome to jump in and help too!)

I've attached my clean 3DM curves again.

1. I offset the profile curve at the top, so now I have both an inner and an outer profile curve.

2. Then I Sweep each of these profile curves using the same two rail curves (see vertical ones in my screenshot).

3. That gives me both an outer and an inner surface — with or without Caps on the ends.
3a. If I enable "Cap Ends", then Moi3D only adds a Cap at the top. The bottom is still open. Is there a way to cap both ends automatically?
3b. Maybe related to the above, but I can't seem to manually cap the bottom hole after the Sweep. Any idea why?

4. I noticed you added those double lines at the bottom. How were they used in your process?

5. And from here I'm kind of stuck again.

Hi Frederik, there is a little issue with the rails, they are made up of multiple segments that are just a couple of degrees off from being smooth.

But even without tuning that up I can't seem to repeat the bottom cap failing over here.

Here's what I'm doing, using the v5 beta (https://moi3d.com/beta.htm):

I select the outer curve:



Run Construct > Sweep and pick these as the rails:



That makes this result:



I then repeated that with the inner profile which made a second solid and then boolean differenced them to get the attached model.

Maybe the sharp point in the rails is having some strange effect, I'll post a tuned version of that in a moment.

- Michael

Hi Fredrick,
Your process is correct only I had outer and inner as solids ie with capped ends.
The fact you showed the bottom thickness as 4mm and the side walls as 3mm was the reason for making an inner.
So the 2 lines at the bottom are showing the bottom angle and then offset 4mm this line is used to Boolean difference the inner to give the bottom 4mm thickness.
Boolean difference inner from outer and you have your part.
Hope that’s helpful
Cheers Barry

Hi Fredrick, here is a version with the rails fully smooth, does it behave better for you?

- Michael

Hey again,

I think I’ve solved the first problems now! Turns out my inner profile curve had fewer points than the outer one. So instead, I offset the inner curve to create the outer — that way they matched. After that, I could run the Sweep operation, and I got caps on both ends. From there, it was easy to create the inner and outer solid surfaces, and then I used a Boolean to cut out the inner solid. So I guess the initial problem was the mismatch between the profile curves.

Now I’ve run into some new issues while adding fillets. See my screenshots!

1. I added a few more details to the model.
2. When I selected all the inner edges and applied a fillet, it seemed to work — but when I looked closer, the fillet corners don’t align properly.
3. I also noticed that the fillet on the outer top edge doesn’t match up with the side surface.

Could someone please take a look at my 3DM file again and help me figure out why this is happening? The file includes some layers (styles) showing the model in different stages.

Thanks again — really appreciate the help!

Thanks Barry,

"So the 2 lines at the bottom are showing the bottom angle and then offset 4mm this line is used to Boolean difference the inner to give the bottom 4mm thickness."

I don't fully understand this part. I used the upper line (marked yellow in my screenshot) to Trim off 4mm from the inner Solid. Then I ran the Boolean Difference operation to create the thickness. Is there an easier way of using the lines when working with Booleans?

Hi Frederick,

re:
> So I guess the initial problem was the mismatch between the profile curves.

It shouldn't be that... Were you trying to use both the inner and outer profile curves in just one single sweep?


I'm having some difficulty finding the locations you show in your screenshots. Could you maybe save a separate file for each question with the view showing the area where you did the snapshot? It seems like the posted model is slightly different than the screenshots.

It's a normal thing for CAD fillets to have different widths where they meet up, it's how a "rolling ball" fillet functions. It's focused on keeping a constant radius value and it's only when all neighboring surfaces are at the same angle to each other that they will have the same widths.

So for example something like this:


When you fillet it, you will get a result like this which is how CAD fillets are intended to work:


If you include all edges that meet at a point then the fillet surfaces will still be like that but they will be cut back and have a corner juncture patch where they come together:





- Michael

Hi Michael,

Thank you so much for helping me figure this out! I'm not sure what was wrong with my original rail splines — how did you make them fully smooth?

I'm starting to understand how I can use different objects to build and cut surfaces... but I'm still running into some issues when adding fillets to my solid objects. See my latest posts for details.

Hi Frederick,

re:
> how did you make them fully smooth?

I turned on their control points and used Transform > Align to make these points all exactly in line:




> but I'm still running into some issues when adding fillets to my solid objects. See my latest posts for details.

I posted a reply above, but I'm having a hard time finding the location that matches your screenshots.

Like where is this one for example:



I think I found your #1 which is a normal result and I thought your #2 is here but your screenshot has a sharp corner while the model has a juncture patch:





It kind of makes it hard to answer your questions when the file is different than your screenshot.

- Michael

Michael,

Thanks for explaining how CAD fillets work. I'm more used to polygon modeling, where I always expect bevels (fillets) to line up evenly. As long as the fillets I created are considered normal in CAD, that makes sense. I'll make sure to save separate 3DM files with the correct views for any future questions.

The only thing I still don’t understand is the fillet on the top outer edge of the model. It seems to align correctly in the Front view, but not in the Right view. I fixed it by cutting and deleting a portion of the outer side surface, then closing it off again using a Loft between the top fillet curve and the open curve on the bottom side.

I’ve attached a 3DM file with the camera focused on the problem area. It should match the screenshot I posted earlier.

Thanks again,
Frederik

Hi Frederick,

re:
> The only thing I still don’t understand is the fillet on the top outer edge of the model. It seems to
> align correctly in the Front view, but not in the Right view

Looks like a cosmetic display artifact with the display mesher not generating enough triangles in that area to make it look nice.

The display mesher is focused on doing things fast, when you do an export the export mesher is more tuned towards higher quality.

So it's just something to ignore, it doesn't need to be fixed:



At export, it looks like this:



- Michael

For the fillet widths not matching, the fillet width is purely a function of the angle between the 2 surfaces being filleted:


When each of those is filleted with a radius 1 fillet, it will make this:


So each of those fillets is made up of a radius 1 arc but with a longer or shorter length of the arc:


- Michael

Thanks again, Michael — good to know! I'm making some progress now. There are still a few bumps, but I’m getting there.

Hi again,

I've built a backplate for my holder, and now that I'm nearly finished, I feel like the base is a bit too long. Is it possible to just select and move "the lip" of the model, or is rebuilding the shape the only way to go?

I've attached the two 3DM models shown in the screenshots.

Thanks,
Frederik

Hi Frederik, in general it can be difficult to edit pieces by dragging when you've got fillets and shelling applied.

For your case here though you can use construction techniques to edit it - draw in a rectangle like this:



Select the object and run Construct > Boolean > Difference and then select the rectangle as the cutting object which will make this:



Drag the end piece over:



And then select both pieces and run Construct > Boolean > Union:



- Michael

For your blue object, it is possible to remove that edge using boolean union which will merge faces that are coplanar.

Select this face:


Use Edit > Separate to break it off as a separate object, then select the 2 pieces and run Construct > Boolean > Union.

Or another way - you could delete those 2 faces and prepare a selection like this and use Construct > Planar:





- Michael