How to construct a [curved] plane through 4 points?

[harry.doldersum]

In order to repair an old machine, we need to machine some non-flat (is that even a expression?) "wearplates".  And I can't seem to figure out how to construct the uneven surface in these? I'm sure it's possible - I just don't know how to do it yet & I'd really appreciate a guiding hand here...  

In the attached model, I've set up 4 plates - as in 2 pairs. 

Wearplates 1 & 2 have a distance between them of 50mm and as such form a single surface going between the 4 points on their respective corners. The same goes for wearplates 3 & 4.

I think, I'd need to construct 2 planes, based on the 2 respective sets of 4 points each - if that's possible - so that I could use the Split Body to take the flat top off...

But how to do that?  Model is attached. 

[TrippyLighting]

You cannot construct a plane through 4 points as there is no guarantee that the 4 points are coplanar.

Even if they are coplanar, you are save with only using three of those.

[davebYYPCU]

From a limited thumbnail view, 

if you want flat on top, covering all of each plate, 

Offset Plane at the shortest corner dimension.

Might need four of them, can’t tell.

Might help....

[harry.doldersum]

Hi Peter,

Good point - I had a look in the model & the 4 points aren't coplanar. And when I make a plane through only 3 points, I'm coming out wrong on 1 of the corners.

So, I'd need to make a curved plane, utilizing the 4 points? Is that possible?

[davebYYPCU]

Loft opposing edges as a Surface. Ok, connect points with lines, to make the surface for cutting.

When you invert a curved plane you will make squillions.

Might help.....

[harry.doldersum]

@davebYYPCU Thanks, but I can't get this method to work - I seem to be stuck with a single height result in this approach, not the 4 different ones I'd need for this task....

[davebYYPCU]

I wasn’t sure of your needed result.  

Each plate top to be trimmed down to this surface?  Top offcut Removed, leaving a slightly twisted top, result?

You have dimensions at front and back corners, making the twisted plate (straight edges - not curved) using a front and then a back line, to provide the dimension that are not on the inside channel.  If you have dimension for each corner of each plate, they are not provided, so I went from front to back, on each pair of plates.

Are you saying you could not split body with this plate?  Your two bodies on the right were hidden to show the second plate size and position.  I did not press ok, after the photo. 

A second technique would be a Solid > Loft > Cut, Using the top profile my sketch provided.  Select region above the line, front to back, and the excess material is cut off.  One process, 

that said, I may have it all wrong.

Might help.....

[harry.doldersum]

Hi @davebYYPCU,

First of all, I really appreciate everyone's effort, to help me out with these questions: thank you!

In the original model are 4 plates, as in 2 sets of 2 each.  One set was switched off, in an attempt to focus the discussion on the construction of a (curved) plane that would connect on the 4 indicated height points for that set of plates. The idea was, that if I have a solution for one set, I can apply the same to the second set.

I see your screenshot, but I can't fully understand it - for which I apologize - and I haven't been able to reproduce it to a level where I have a plate with the curved surface as a product result.

I'm hoping to see a solution for this question in the near future - but in order to proceed with the repair, we decided to use a more crude approach....  I drew triangles between the height points - since those form valid surfaces - and used those to cut the top portion off.

It's not ideal, but we trust it'll get the job done, for now. And hopefully, I will have learned a better procedure, next time something like this comes up. 😊

[davebYYPCU]

Step by step.

Turn the sketches on, Hide the bodies.

Edit the sketch on the front face, you have a blue profile, and two dimensioned points, on the face of the block.  Connect a line to those points. Repeat for the other block, repeat for the rear sketches.  Finish sketch edits.

Start (Solid) Loft command.  Select the top profile (above the line) for a front sketch.  Select same for a back sketch, preview will show a red cutting result, Press Ok.

Same for the second pair.

My earlier suggestion was using a Surface Loft, Selecting the lines you drew.  Gives a twisted plate, for using in a split body, but the solid Loft method is more efficient.

Might help.....

[MichaelT_123]

Hi Mr HarryDoldersrum,

Consider looking at the following:

https://forums.autodesk.com/t5/fusion-360-design-validate/how-do-i-start-drawing-design-a-pringles-s...

It seems ... you are having a saddle problem. 🏇

Regards

MichaelT

[davebYYPCU · Accepted solution]

Your sketches with added lines.

Select the top sliver front to back, this shows after the cut and before the cut.

Cut the top with solid > Loft .Cut.  Pressed Ok this time.

Might help.....

[harry.doldersum]

Thanks for these extra details, everyone!

I'm away for the weekend, but I'll certainly look into this next week. Much appreciated!

[harry.doldersum]

Many thanks, @davebYYPCU !

While going through the edited model, the coin finally dropped - loft from the side profiles!  I *totally* missed that, works like a charm. 

Quite happy with this solution, it's really appreciated! 😊