Calculating Kerf cuts for bending wood/mdf 1

[baniels]

Howdy folks,

I'm hoping there is a way to leverage SW to help with calculating the location and number of kerf cuts for bending some MDF panels. The cabinet shown will be CNC cut, and I will use the horizontal braces to guide the curves of the panels (left and right sides). An example of what I mean by kerfing can be found here.

The curved are created with splines, and as such the only read I can get on them is the minimum radius. With constant arcs, I could figure it out using this formula. With splines it isn't so simple. And because these curves vary from one design to the next, I'd prefer to not experiment each time to find the minimum kerf count and their placement for each version.

I'm looking for ideas. Even long-shot simple ones that you think I may have considered already!

Some pictures of the drawing, and curvature.

 

[Eltron]

This isn't something that SW can help with. You can definitely flatten the piece to determine its stating layout, but you won't be able to determine the kerfing. Can you just kerf it similar to bendy-ply?

Dan

http://www.eltronresearch.com

Dan's Blog

 

[ShaggyPE]

Your bends seem much more gentle than the bend in the example. Have you considered "wiggle board" a.k.a "bender board"?

Essentially it is plywood where all of the plys are layered such that their grain directions are aligned... instead of crossed.

-Dustin
Professional Engineer
Pretty good with SolidWorks

 

[Eltron]

Dustin, that's what I was thinking, but I could swear there used to be a thicker product that was pre-kerfed. Guess I'm getting old.

Dan

http://www.eltronresearch.com

Dan's Blog

 

[baniels]

Yes, my bends are more gentle - but still need the same treatment, though to a lesser degree. I have looked at bendy mdf, kerfkore, etc. Those are not cheap products. I would be more inclined to just recreate them myself. I could experiment and find an optimal kerf count and placement for this curve, but if the curve changes, or for another design, I'd be back at square one again. I was hoping there would be something w/in SW that I could leverage. Heck, even if I could create construction lines from the curvature combs that would be a good start... essentially segmenting the arcs and providing lines perpendicular to the curve at each point.

FWIW, this part is 1" thick.

I assume to flatten, I would need to convert to sheet metal, yes?

 

[rstupplebeen]

Looking at your link I would measure the outside length of the curve and the inside length of the curve and use this information to determine the density of the slices based on the length disparity and the kerf of the blade. Since your case is a spline I would create a bunch of examples with constant radii and thicknesses and create a best fit equation from this data and then apply this density based on the local curvature of the part. My guess is that you do not need to be spot on since you have the forming braces. FEA could be useful to make sure that the part doesn't split when you bend it and could be a sanity check that your density is appropriate. I hope this helps.

Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/

 

[baniels]

That was a good suggestion, Rob. This minimum radius on this design is 16". Using that as a starting point, following the formula I found, with a 1/8" blade, the kerfs should be very close to 1" apart.

With an arbitrary 7/8" depth of cut, this is the result on a 16" OD, 14" ID circle. There's probably no getting around a test to see how smooth the result is.

I'm going to hunt and peck a little more. I'm still unclear as to how I would create this first as a flat stock and then bend to the shape. My current approach is to draw the curve in 2D and extrude upward.

 

[Eltron]

If you want to flatten it out you will need to convert it to sheet metal. Also, you can insert face curves by going to Tool/Sketch Tools/Face Curves.

Dan

http://www.eltronresearch.com

Dan's Blog

 

[baniels]

Thanks.

Unfortunately I swapped the radius for diameter in the above example.

 

[baniels]

I have a working calculator now - feed in variables (saw blade thickness, material thickness, radius of outside edge), and it spits out the spacing. Next will be to test it. It seems to put the kerfs awfully far apart. In the example above, my error meant that the kerfs displayed would be cut in half. Probably better off assuming a smaller blade thickness than I actually use, at least with MDF.