Stave-constructed woodturning application questions

david_delker

Background information:

I am learning Onshape as a tool to model segmented woodturning sculptures. My Onscape design work is in my “bowl 12 – copy” document:

https://cad.onshape.com/documents/942bac19e715a4c0d38031f6/w/bb1095573b5a6fa3923009d4/e/90aebd897e09093e8fa9c9b6

Basically, my sculpture is comprised of 8 “bowls” that are assembled into the shape shown in Figure 1 (see the “Assembled 8 bowls” assembly file). 

Figure 1: Finished sculpture

Each bowl begins as 12 staves (see figure 2) glued together (see Figure 3) that I turn on my woodturning lathe (see Assembled 12 staves” assembly file).

Figure 2: Stave

Figure 3: 12-stave "bowl"

 I then “disassemble” the turned bowls by cutting them on my bandsaw to create “3/4 bowls,” as shown in Figure 4 (see the “Finished ¾ bowl” Parts Studio): 

Figure 4: A "3/4 bowl"

Those “¾ bowls” are then reoriented and glued together into the final sculpture shape shown previously in Figure 1.

I am using variables to experiment with the stave dimensions to tweak the design geometry, particularly the critical slope angle of the bowl walls. That being the case, I made an assembly of 12 staves (Figure 3) that are “glued” together using tangent mate connectors (see the “Assembled 12 staves” assembly file for details).

My Onshape questions:

What I have modeled so far works fine, but I would like to take my design a bit farther by intersecting the bowl profile (Figure 4 or similar) with the stave assembly (Figure 3) so I can “cut away” the unwanted “wood,” much as I would on the lathe. Why? Because I want to vary the color of staves (think walnut and maple), perhaps alternating them to create a pattern that I can visualize in Onshape. Here's a photo of a previous project showing two colors of wood:

1.  My Onshape problem is that I need to use some of the drawing tools (revolve, sweep, etc.) from the Part Studio in the assembly file (where the Figure 3 assembly lives). Any suggestions as to how I could achieve that? I don’t see a good way to connect individual staves to make a “bowl” while still in the Parts Studio, but I don’t see how to do the revolve or sweep operation in the Assembly environment.

2.  I attached the 12 segments together using tangent mates on three corners on faces of two staves to “snap” the staves together, as shown in Figure 3 (see the “Assembled 12 staves” assembly file). That works OK, but is there a better way to do that?

Let me know if you need additional information to understand what I am trying to do. Thanks in advance for taking the time to read this post (my first one) and offer any suggestions!

David

S1mon

Using tangent mates is not ideal for either of your assemblies. If you find yourself using more than one mate to join two parts, you're most likely making things more complicated than they need to be. 

I would create your bowl in a part studio with a stave. I would also create a part which is the boolean intersection of the bowl and the stock stave. You can relate the raw block to the finished shape and make sure that you have enough stock to glue and turn into the finished shape. I would create a mate connector at the vertex of the cone of your bowl and use that as an assembly reference. You can use a radial pattern in the assembly to add the pieces.

Creating the finished sculpture may be more complex, but you should be able to mate the rectangular faces from one 3/4 to another with a simple fasten mate at the centroid of the face. Definitely not tangent mates.

You can vary the colors of pieces of would by configuring the appearance of the parts, or configuring decals with wood grain pictures.

S1mon

I couldn't help myself. I modeled the start of a solution to some of your issues.

https://cad.onshape.com/documents/9a67fa10e9a35e9c156b7f5e/w/452e6f52cc89da90cb9fc715/e/e6bf34e3d769609daf32a2af

The part studio has 3 parts. The finished sector, and two steps to making the pieces.

Assembly 1 is the 3/4 bowl.

Assembly 2 is a start of a finished sculpture. 



There's also a variable table which has "sectors" in it. You can modify that to any multiple of 4 and hopefully get intelligent results.

Assembly 2 will need a lot more work to allow this sort of parametric play as it get more complex because right now I'm mating the first sector to the first sector.

I started to play with configurations of wood colors, but making that work with patterns in the finished bowl will take more work.

david_delker

Thanks for your prompt response, S1mon! Wow! You really gave me some good suggestions. I played with your model a bit to reverse engineer how you made those parts and assemblies. I think I can follow those steps to achieve my design goals. (Be patient with me - I only started using Onshape 2 weeks ago. The only other 3D CAD work I've done was with SketchUp...

I'm still trying to figure out how to align two bowl faces correctly. I figured out how to use one fasten mate on each face, as you suggested. While I can flip the primary axis and rotate the pieces in 90 degree increments, I still can't align them. What am I missing?


By the way, your Assembly 2 has the two 3/4 bowls connected incorrectly. The large-diameter of one bowl must connect with the large-diameter edge of the second bowl. Yours has the large-diameter rim of one bowl connecting to the small-diameter rim on the second bowl:


It's very challenging to wrap my brain around which direction each bowl must be oriented for the design to work correctly. That's why I am learning 3D CAD to model this stuff, rather than taking the trial and error approach by cutting pieces of wood!

I'm feeling MUCH better about using Onshape for this project after your helpful contribution!!  Watch out - this woodturning sculpture stuff can be very addictive!

S1mon

I added mate connectors to centers of the rectangular faces of the staves, and I aligned their secondary axis to the long direction of the rectangle. This makes it really easy to mate the ends of the 3/4 bowls. You can just hit the rotation button twice on that mate to get things the right way around. 

S1mon

Using tangent mates is not ideal for either of your assemblies. If you find yourself using more than one mate to join two parts, you're most likely making things more complicated than they need to be. 

I would create your bowl in a part studio with a stave. I would also create a part which is the boolean intersection of the bowl and the stock stave. You can relate the raw block to the finished shape and make sure that you have enough stock to glue and turn into the finished shape. I would create a mate connector at the vertex of the cone of your bowl and use that as an assembly reference. You can use a radial pattern in the assembly to add the pieces.

Creating the finished sculpture may be more complex, but you should be able to mate the rectangular faces from one 3/4 to another with a simple fasten mate at the centroid of the face. Definitely not tangent mates.

You can vary the colors of pieces of would by configuring the appearance of the parts, or configuring decals with wood grain pictures.

S1mon

I couldn't help myself. I modeled the start of a solution to some of your issues.

https://cad.onshape.com/documents/9a67fa10e9a35e9c156b7f5e/w/452e6f52cc89da90cb9fc715/e/e6bf34e3d769609daf32a2af

The part studio has 3 parts. The finished sector, and two steps to making the pieces.

Assembly 1 is the 3/4 bowl.

Assembly 2 is a start of a finished sculpture. 



There's also a variable table which has "sectors" in it. You can modify that to any multiple of 4 and hopefully get intelligent results.

Assembly 2 will need a lot more work to allow this sort of parametric play as it get more complex because right now I'm mating the first sector to the first sector.

I started to play with configurations of wood colors, but making that work with patterns in the finished bowl will take more work.

david_delker

Thanks for your prompt response, S1mon! Wow! You really gave me some good suggestions. I played with your model a bit to reverse engineer how you made those parts and assemblies. I think I can follow those steps to achieve my design goals. (Be patient with me - I only started using Onshape 2 weeks ago. The only other 3D CAD work I've done was with SketchUp...

I'm still trying to figure out how to align two bowl faces correctly. I figured out how to use one fasten mate on each face, as you suggested. While I can flip the primary axis and rotate the pieces in 90 degree increments, I still can't align them. What am I missing?


By the way, your Assembly 2 has the two 3/4 bowls connected incorrectly. The large-diameter of one bowl must connect with the large-diameter edge of the second bowl. Yours has the large-diameter rim of one bowl connecting to the small-diameter rim on the second bowl:


It's very challenging to wrap my brain around which direction each bowl must be oriented for the design to work correctly. That's why I am learning 3D CAD to model this stuff, rather than taking the trial and error approach by cutting pieces of wood!

I'm feeling MUCH better about using Onshape for this project after your helpful contribution!!  Watch out - this woodturning sculpture stuff can be very addictive!

S1mon

I added mate connectors to centers of the rectangular faces of the staves, and I aligned their secondary axis to the long direction of the rectangle. This makes it really easy to mate the ends of the 3/4 bowls. You can just hit the rotation button twice on that mate to get things the right way around. 

david_delker

Excellent idea! I'm beginning to understand this new Onshape world I find myself in! Thanks much for your help!

GregBrown

Here is one of your examples with an alternative approach - it only requires a single mate and a circular pattern in the assembly.

As S1mon said... when you see long lists of mates in Onshape with relatively few components, there's likely to be a better way. The only other things I changed in the Part Studio were to make the revolve symmetric about the plane (for convenience in the next feature), then a sketch to create appropriate construction help for a mate connector which is going to be the axis of the pattern. The key angle dimension in the helper sketch is driven by one of your variables. This construction line drives the Primary axis of the mate connector.

The mate connectors I used to orient the single Fastened mate were aligned as S1mon suggested: with a secondary (red/X) axis long the rectangular edge. 



https://cad.onshape.com/documents/e1e0cb9ed9c47f2c788f7885/w/133ad95c1657a78a150ae0cd/e/c9433efe6ddffdd903ad2dbe

david_delker

Thanks for your suggestion, Greg! I was able to replicate your idea on my own, this time using mate connectors and a circular array. Your help gave me a better understanding of aligning mate connectors with the desired axis. Thanks again!