topic Re: How would you design Hilbert Curve Marble Run? in Fusion Design, Validate & Document Forum

How would you design Hilbert Curve Marble Run?

bizilux — Fri, 14 Feb 2020 11:52:18 GMT

Hey all, im trying to design a marble run very similar to this one:

link: https://www.thingiverse.com/thing:3031891/makes

it's a Hilbert curve, similar to how brains look like 🙂

The problem is I don't even know where to even begin. Main issue that I first need to overcome is that the path needs to have a constant downward trajectory, but its constantly changing directions

I found an addon here: but it's only for AutoCAD: https://apps.autodesk.com/ACD/en/Detail/Index?id=3508769894832884425&appLang=en&os=Win32_64&autostart=true and googling for help didn't produce anything

Re: How would you design Hilbert Curve Marble Run?

TheCADWhisperer — Fri, 14 Feb 2020 12:08:31 GMT

Hint: Imagine stretching this out in a straight line inclined plane and then folding the bends.

Re: How would you design Hilbert Curve Marble Run?

bizilux — Fri, 14 Feb 2020 12:22:09 GMT

okaaay that is a good hint.

Okay, let's forget that it needs to be a channel for marbles, that is easy to achieve with sweep command once you have the path.

so let's just focus on a path right now:

here is where I'm at so far:

start with a plane at an angle of 5 degrees
draw, for example, 52 sections of straight lines in a sketch, one after another holding points together
what then? how would you go around making a path (folding the bends) without manually needing to move all points with 3D sketching?

Re: How would you design Hilbert Curve Marble Run?

TheCADWhisperer — Fri, 14 Feb 2020 13:57:38 GMT

Whisper #2

Re: How would you design Hilbert Curve Marble Run?

MRWakefield — Fri, 14 Feb 2020 13:55:56 GMT

I've quickly knocked up the attached spreadsheet which calculates a Z value given an X and Y coordinate and a slope angle. As I said, it's just something I put together quickly and just has a few rows which you'll need to expand but it might give you a starting point. Put your X and Y coordinates in the first two columns and the slope on Sheet2. Once you've entered your data export it as a CSV and use the 'ImportCSVPoints' add-in in fusion to get your sweep path.

I hope this helps.

Re: How would you design Hilbert Curve Marble Run?

bizilux — Fri, 14 Feb 2020 14:23:20 GMT

I tried using this script: https://github.com/hanskellner/Fusion360ImportCSVPoints

it just wont work with the numbers that you supplied? it says that points are invalid... it did however worked if i copied his points in

1,1,1
2,2,2
3,3,3

2,8,0
4,6,1
6,4,0
8,2,1

so thats strange...

and yeh i never worked in sheet metal environment before, so got to see how that goes 🙂

Re: How would you design Hilbert Curve Marble Run?

MRWakefield — Fri, 14 Feb 2020 15:18:57 GMT

Yes, that is strange as it works for me. I've attached the csv file exported from Excel so you can compare it to yours.

Re: How would you design Hilbert Curve Marble Run?

chrisplyler — Fri, 14 Feb 2020 18:14:34 GMT

This kind of thing is a pain in the rump.

I established the 3D path like this:

Then, with a little surfacing, filleting, sweeping, extruding and revolving, you can end up with something like this:

Please note that sweeping will NOT give you corners as shown in your picture, where the outside radius is different than the inside radius, making them look kinda squared off. But my version is actually contant-width, and constant-slope along the middle.

Yes, it's a pain, but you're going to discover it's a lot MORE of a pain to do it with sheet metal as @TheCADWhisperer has hinted towards. You're going to have to teach yourself all about K-factor and bend allowance and bend reduction to have ANY hope of using the Bend tool and ending up with nice, symmetrical geometry. Even if you already know all that stuff, it's still going to be a pain.

Re: How would you design Hilbert Curve Marble Run?

TheCADWhisperer — Fri, 14 Feb 2020 18:34:45 GMT

My plan was only to use sheet metal bend to get a path for Pipe or Sweep from edge of the part.

Re: How would you design Hilbert Curve Marble Run?

chrisplyler — Fri, 14 Feb 2020 18:41:41 GMT

Understood. It's still going to be a giant pain to get your bend lines in the right places.

Re: How would you design Hilbert Curve Marble Run?

bizilux — Fri, 14 Feb 2020 19:43:42 GMT

Hey, chris how did you make that? Can you share the path or how did you create the path?

Re: How would you design Hilbert Curve Marble Run?

bizilux — Fri, 14 Feb 2020 23:58:22 GMT

Okay, new development. I used that excel script, and after quite a long time of fiddling around, I made a path...

and then I used sketch fillet to round the corners.

Now I have a problem where sweep command doesn't produce nice results because the path goes at all different angles.

I also tried pipe command and making it hollow, but then I cant slice it along the middle because its the same problem as above

I know all of these commands have guide rail and guide surface options, but I couldn't get it to work in this case...

Does anyone want a save file to try and make it work?

Re: How would you design Hilbert Curve Marble Run?

bizilux — Sat, 15 Feb 2020 09:47:13 GMT

I've uploaded the file here https://a360.co/2HrrHhi

You can download it using the password: bizilux

If someone can figure out how to get a nice and even marble path across this path, I would be very grateful

In case you are wondering why I want to make this... it will be a module for my marble machine

I'm also uploading data for excel sheet that made the path work, in case someone in the future will need it 🙂

do note that the last two values in C column Hilbert Curve.xlsx are wrong, I don't know why. They are manually fixed inside .csv

Re: How would you design Hilbert Curve Marble Run?

MRWakefield — Sat, 15 Feb 2020 13:12:35 GMT

I'm glad the Excel spreadsheet worked for you in the end. I still don't quite understand why you were having problems with it in the beginning though.

I've had a look at your expanded version and noticed some errors. At line 4 you've transposed a couple of cell references (A instead of B and vice-versa), so you're mixing X and Y values, and from line 17 onward you're referencing the wrong values (you're referencing the next X and Y values rather than the current ones). Although you've only noticed that the last Z value is incorrect, actually all the Z values are incorrect from this line onward.

To guarantee consistency I'd recommend filling-down the formula from C2 all the way down to the last row.

Re: How would you design Hilbert Curve Marble Run?

bizilux — Sat, 15 Feb 2020 14:36:05 GMT

the problem at the start was that when saving as .csv, Z values had , instead of . as decimal punctuation

so csv file had 4 "columns" instead of 3

Yes I was copying around A and B values when I was planning the path, because I made errors a couple of times, and I think that messed up the formula a bit then, and then I deleted a value here and there and it also messed up the rows sometimes 🙂 I don't think I will go back and fix it at this point, because it looks good enough for me, It doesn't need to be exact science 🙂

Now I just need to figure out how to make marble path out of this, that will be consistent

Re: How would you design Hilbert Curve Marble Run?

MRWakefield — Sat, 15 Feb 2020 15:33:50 GMT

Ah, the comma instead of a decimal point might be due to your region settings.

Re: How would you design Hilbert Curve Marble Run?

chrisplyler — Sun, 16 Feb 2020 00:18:55 GMT

I made it the hard way. One sketch to lay out the grid. Eight vertical sketches to control the Z values. Made a parameter for the slope, and manually dimensioned each Z value in turn as an incremented multiple of that slope value.

I'm attaching my file below:

Re: How would you design Hilbert Curve Marble Run?

chrisplyler — Sun, 16 Feb 2020 15:19:56 GMT

When I created the path sketch, I made sure to assign it to this plane...

BECAUSE my next step is to extrude a surface from the path, and I want the direction of the surface extrude to be straight down...

Then I fillet that surface as desired, and make a new sketch (on that same plane), to capture the top edge of it using the Project>Capture-3D-Geometry tool. Start another new sketch and set up the desired sweep elements...

I do the sweep with a path and a guide surface, selecting them appropriately...

That will keep the sweep from twisting around unexpectedly. The sweep starts out perpendicular to that surface, and by using it as a guide, the sweep knows it's supposed to maintain that relationship everywhere along the path.

Then I made ANOTHER sketch on that same plane, and projected in the entire body that was created by the sweep...

Then I switched to the solid toolset, and extruded that last sketch up TO OBJECT, selecting that sweep body as the object. This creates the desired solid body...

You could have just swept a solid profile in the same manner and been done right there, if the shape you wanted is like your later pictures instead of like your first picture...

I know, I know, it's a convoluted approach. But it worked, and it's parametric, so I can adjust dimensions and it updates accordingly.

Re: How would you design Hilbert Curve Marble Run?

bizilux — Sun, 16 Feb 2020 15:15:46 GMT

ahhhhh, very smart with that guide surface. Thats the key part that I was missing... I will try to do it and report back in a bit

Re: How would you design Hilbert Curve Marble Run?

chrisplyler — Sun, 16 Feb 2020 15:30:29 GMT

I edited my last post. Don't know if you saw the last bit about sweeping a solid instead instead of a surface.