Dog-bone Fillet excessive overcutting

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charlesbur
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Dog-bone Fillet excessive overcutting

Post by charlesbur »

Hey guys,

recently I had to mill a hexagon pocket and wanted to overcut into the corners. First I used SolidWorks to sketch the hexagon including the overcutting arcs, then I realised this was a lot of work I wouldn't want to do every time. So I tried out Aspire's "Dog-bone Fillet" and noticed immediately that the overcutting was more than what I had drawn in SolidWorks and more than actually necessary to free the corners. After a bit of investigation it looks like the algorithm Aspire uses is not "perfect" in that sense - check out the attached picture. To make it clear to see, I duplicated the vectors before using the feature, to have the sharp original corner as a reference.
As you can see there is too much material being removed when the angle is larger than 90 degrees (as in my case of the hexagon). I can't think of why one would cut further other than that the programmer couldn't come up with a better algorithm :lol:. Maybe this could be improved?

Also, I find it a bit inconvenient having to apply these fillets manually in the sketching stage (and hence having to know the tool diameter in advance). It would make much more sense to have this as an option for the toolpath and would also make it much easier when changing the tool diameter - simply recalculating the toolpaths, instead of having to go back to the drawing and redoing all the fillets... Even some less expensive software already offers this type of automatic overcutting internal corners through an option.

Thanks!
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ohiolyons
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Re: Dog-bone Fillet excessive overcutting

Post by ohiolyons »

I am not the creator of the Dog bone gadget nor am I a menember of Vectric's staff. Until I read your post I hadn't run the dog bone gadget before.

Several things come to mind.

1) Did you watch the dog bone tutorial?

2) Since you did not talk about any of the settings did you add or subtract any inner or outer allowances? It might be that you can make your non 90 degree joints more acceptable by tweaking those dog bone allowances.

3) I did a google search on "dog bone cnc joints" and all I got was surfaces being joined perpendicular to each other. I did not see any exotic angles you are trying (doesn't mean they aren't out there).

4) I am uncertain what you are talking about "... I find it a bit inconvenient having to apply these fillets manually in the sketching stage ...". When I ran the gadget it did all the work for me, I didn't have to manually apply anything.

5) The gadget is creating a new toolpath so it has to know the tool diameter before it can calculate that new toolpath. So your comments about having to know the tool diameter ahead of time seems odd to me.


When the person who wrote the gadget responds I think you will find it was never intended for the angles you are trying to use it on.

All this being said gadgets are quick and dirty extensions to vectric software some written by vectric some written by users like us.

They are not as robust or versatile as the stand alone vectric software. Gadgets don't get all the bells and whistles incorporated.

BTW there is a separate Gadget forum area this should have been submitted there.


Just my opinion
John
John Lyons
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Adrian
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Re: Dog-bone Fillet excessive overcutting

Post by Adrian »

I don't think he's talking about the dog-bone gadget rather the dog-bone option on the standard fillet tool.

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ohiolyons
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Re: Dog-bone Fillet excessive overcutting

Post by ohiolyons »

My mistake as usual Adrian you are right!

Maybe the gadget would resolve his issues?

John
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Gundawg
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Re: Dog-bone Fillet excessive overcutting

Post by Gundawg »

I have noticed this myself so I make them myself and use the trim tool. I make a few parts and use a pocket to hold a hex bolt. Here is what I do I make the hex the proper size I then create a circle the diameter of the hex so I have a hex inside a circle I then draw a circle slightly larger than the bit I am using .128" for a .125" bit. I set the hex up so the tip of one of the points is at X0 and center of the circle. I use the move to make my small circle edge at X0. I copy the small circle rotate and rotate everything 60* paste the small circle rotate again until you have circles at all points then use the trim tool. I will post a picture that should make sense of my description.

I included some I keep for my own use feel free to use them. I used this method with earlier versions that did not have a good fillet tool. The one with the big circles is what you get with the fillet tool the last one is from my method.

Mike
New.pdf
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New - 1.pdf
(6.29 KiB) Downloaded 94 times
Bolt heads.dxf
(162.2 KiB) Downloaded 165 times

Gundawg
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Re: Dog-bone Fillet excessive overcutting

Post by Gundawg »

Here is a picture that shows the process and also shows what I get using the fillet tool the first image is using the fillet tool the last one is the result I get using my method.
New.jpg

charlesbur
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Re: Dog-bone Fillet excessive overcutting

Post by charlesbur »

Thanks guys, I will try out the gadget. Gundawgs method is more or less the same effort as what I did in SolidWorks, only there I can update the tool diameter and everything later on and have it rebuild the sketch. Still hoping Vectric will add this as a proper feature for the toolpaths some day... :|

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