Problems with Chamfer and Sweep

[xeddog]

I am a very newb to Fusion 360 and I am trying to make cookie cutters for my daughter.  The problem (this time) is that when trying to make a sharper edge on the cutting edge of the cookie cuter,  I get one of a dozen errors depending on how I go about doing it.  Chamfers seem to fail at different places depending on which way I select paths, but I cannot get a full chamfer.  I have also created a small right triangle profile along the top edge and tried to run a sweep.   I got quite a bit further with the sweep, but not quite all the way around.
The V3 sample below is the cookie cutter I am working on now.  It shows the surface I am wanting to sharpen.   The V4 sample shows how far I got.  I used two profiles and got most of the edge like I want all the way around except for two small points at the top.  I'm guessing that the two places where it did not sweep are just too sharp.  At any rate, I would appreciate suggestions to fix it.

[Phil.E]

Hi,

Great project.

A couple observations:

• The overall size is less than 50mm/2 inches across. That's pretty small for a sugar cookie.
• The bag top, and sleigh corners are currently designed to make cookies that have 2mm features. 
• The wall thickness you are trying to chamfer is only 1mm thick. Is that printable?
• Have you printed one of these and tried it out yet?

Regarding chamfer, sweep (and technically also loft):

1. Whenever the profile of the shape you are making "self-intersects" at sharp corners, the modeling kernel simply cannot compute it.
2. In general, making more gently curving shapes will help commands like this compute the feature.

Good luck,

[Phil.E]

[xeddog]

Thank you for the reply. 

I do realize that the size is very small for cookie cutters, but my daughter needs that size because she is Making Advent Calendars to sell.  The cookies have to be "bagged and tagged" and placed into a 2.5" pocket. When I began making these for her she told me the pocket size was 2", so I might be able to scale them up a little, but not enough to make much difference.   As for the 1mm thick wall, I have printed several larger 4" cookie cutters with the 1mm wall (with the chamfer) and they hold up fine for the small batches she makes.   I doubt they could hold up to making a thousand cookies, but for the maximum of 50 or so that she needs they work well.  One more thing I have started doing with the ones where the chamfer works, is to create an offset plane at the top sharp edge -.3mm, then sketch a rectangle on it that covers the entire cutter, and then do an extrude/cut to flatten the sharp edge just a little.  They print a little better that way.

Back to the problem at hand though, it seems my suspicions are confirmed that the angles are just too tight for either chamfers or sweeps.  Do you know of any alternative methods I might employ?

Wayne

[philpdxthesecond]

To avoid self intersecting geometry, make the curves more gentle, less sharp.

Also, you can apply a 0.5mm chamfer to the inside edge, if that helps.

[PG.Eng2]

Something like this would be possible using a couple of surface lofts and the stitching the surfaces and the body together. At least I think this is what you are aiming to accomplish:

Attached an example of your model with:

 - offset parallel plane from top (bottom?) of cookie cutter

 - sketch project the profile of the cookie cutter

 - sketch offset the inner and outer edge (-0.35mm for outer and -0.25mm for inner in example)

 - use a couple of surface lofts with chaining unselected. Add as many curves to the loft untill Fusion starts complaining, and go 1 back. Then start a new surface loft for the remaining curves. Do this for both the new offset inner and outer profiles to existing inner and outer profiles on body.

 - Use patch command to make the top (sharper) surface

 - unstitch existing model

 - delete old 'top / bottom' surface of cookie cutter

 - stitch all planes to get as attached.

[xeddog]

Thank you for this. It seems like a whole lotta work for a simple cookie cutter, but I am going to give it a shot.  Overkill for this, but it might come in handy for something else down the road. I think I even understood most of what you said.  I will have to figure out the stitching part, but this forum and google can probably help.