Creating a Crown Bed Post

[george]

I thought I'd try to throw together a quick model for a friend but it's been more than a month since I've used A360 and my memory cells are failing me. I kind of jumped in and started a sketch and then moved on to models.

I have the basic shape created using a pattern of bodies but now I have the original body and the pattern and I don't want to keep the origin. If I delete the original then the pattern falls apart.

I also just kind of eyeballed the position of the structures of the crown so it looked good but when I created the pattern I should have ended up with a nice hexigon at the top point and I have some gaps.

Would somebody be so kind and take a look at my model and help me fix where I went wrong. The model can be accessed at http://a360.co/1Ryqemd

Thanks a million,

George

[James.Youmatz]

Hi @george,

Sorry for the late response! After taking a peek at your model and playing around with it, I was able to create a screencast showing my workflow (based off of yours) that can create that tight hexagon on the top of the crown. The reason, as you somewhat hinted to in your post, as to why it wasn't lining up was because it wasn't exact. The biggest factors that influenced where the points on the hexagon lined up were the size and distance of the hexagon, as well as the width of the rounded part of the crown. 

What I did to recreate your crown was to first project the scaled body from the .f3d that you attached in your post into a sketch so I had the general outline. (Recreating that by scratch would've been tough!) Also, the reason I projected the body geometry as opposed to using your sketch, was that you scaled the original body to a larger size. This just saved me some steps. Also, your sketch geometry was not perfectly lined up with your plane that the base was created on, so this caused a few overlap problems as well. In my screencast I saved the projected body geometry as a .DXF file and uploaded that as a Fusion Design and opened it. Then I aligned the center of the sketch with the origin (this just makes things easier to visualize in my opinion). Then, I created a new sketch on the plane where the base would be and projected the sketch geometry of the imported sketch (the curved crown part) onto the new sketch plane. This allowed me to see my end points so I could sketch the base. Once the base was sketched I then created my hexagon on the base (this will allow you to manipulate what size you want the inner hexagon to be and from this you can figure out what width the curved crown parts should be.) I know that was probably confusing to read, so please enjoy the screencast!

Hopefully this answered your question! If you have anymore questions, please don't hesitate to let me know. I'm more than happy to help!

Thanks,

[george]

Hi @James.Youmatz,

Thank you very much for looking at this and spending the time to fix my errors. I find that the beauty (and curse) of F360 is there are so many ways to do things and with my light occassional use I end up making more mistakes! By chance did you save your model after you were done? The only thing that I could see that I would want to change is to make the thickness of the pieces 1/2" (12.7mm) as that is the wood I plan to cut this model out of.

I think everything made sense what you did but I wasn't clear how to decided where to place the center point of the base of the circle and then the 250mm hexagon. Ending up with a 500mm wide opening at the top of the crown is also much larger than what I was going after.

Your right, I did screw up and not place things at the center in the beginning which made things more difficult. Once we had the shape of the splines the way we thought looked good we then relaized that they were too small so I did have to scale them. It was after that point that things started to get messed up but I plowed through it just to see if it would end up looking good.

Thanks again,

George

[george]

I just noticed something odd while trying to reproduce your steps. When I take the sketch and save as a DXF when I open that DXF the object has been scaled by 10X. The origin "height" of the spline is 135mm yet when you open the DXF and take the same measurement you get a "height" of 1350mm

[James.Youmatz · Accepted solution]

Hi @george,

That is something that I overlooked completely, good catch! A DXF file imports unitless (and it defaults to CM), therefore that is why it is off by an order of magnitude. I was just exporting the DXF for ease of access, but we could work with your original sketch as well! (We also could scale the sketch/change units appropriately and then export/import the DXF) The biggest concern here (I feel) is how to figure out how to create these posts with only the width of the curve piece as your known variable. I've been working on this answer and knowing that the curved piece is .5 inches in diameter and you want a perfect hexagon at the top, we are going to have to do a little bit of math (on paper or even in Fusion) to figure out the diameter of the hexagon. We know that each edge of the hexagon will be .5 inches, therefore with a little math (which I prove in my screencast below in Fusion) that the diameter of the octagon with a 1/2" edge is 2*sqrt(1/8) + 1/2 = ~1.207 (although we should enter this parameter in fraction form if we want the edges to touch precisely). I calculated this by knowing that each angle was 45 degrees (360/8) and then drawing the octagon. Using pythagorean theorem I could calculate the diameter since the diameter equals two angled edges and a straight edge. Anyways, by knowing this, we can then create our base and our pattern and it should work. Please refer to the screencast I made below. Since I just figured I'd work with the missized imported DXF, what I did was first extrude the sketch symmetrically so that its width was 5". That way, when I scaled it down by a factor of 10 it would be the correct 1/2". 

Screencast Showing Octagon Math:

Screencast Showing Creation of Crown:

Hopefully this helps you get on your way! Let me know if you have anymore questions!

Thanks,

[george]

Sorry I missed your call, I'm around if you wanted to try again. I'll start looking at your latest screen casts now and see if I can make sense of them. The only fixed things in my original design is the shape and size of the spline and then the spacing of the splines which defines how wide the crown will end up. That should define what size the hexagon is on top so that all of the points of the splines touch perfectly when I go to build this. As a side note, I realized that I should change the bas piece from a donut to a circle with a square cut out in the center. That way this crown could slide right over a 4" x 4" post (with actual measurements of 3.5" x 3.5").

Thanks again for helping, I love learning this stuff and hopefully my brain can retain some of these approaches you're using!

[george]

Well thanks to James help I was able to create the crown with proper alignment! Now I'm thinking of the best way to bring this into CAM. I was thinking of saving one of the splines as a component and then bringing that into a new document and arrange 8 of them on a flat sheet so they can be cut. 

[James.Youmatz]

Hi @george,

I'm glad the crown is now how you would like it! Unfortunately, I'm not really anything special when it comes to CAM work so you may want to check our CAM forum as well or maybe create a new post detailing the CAM questions you have!

Thanks,