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extrude cut failed

A

alvin164

New member
Hi guys,


I'm trying to cut a hole on the center of the two little V shaped cut circled in red.I recreated a flat surface without the V shape and recreated the V shape and cut the flat surface, but it still failed... anyone know how to solve it??2008-04-17_135047_e3_2.prt.rar
 
[-Skint- said:
]


I have your file, but im not quite sure what you are trying to achieve ?
Click to expand...


I'm trying to create a hole on the center of that mini triangle. That mini triangle is used as a gauge for the shop floor people to drill hole there instead of having to measure a certain distance everytime from the side or the top of the extrusion...


i think unigraphics NX2 and 3 also have this problem... creating a cut with a redius on a hole... Don't know why.... so my solution is to create the hole first and just create the mini triangle without the radius... hahahah since that radius is so small anyway.... it works for now since i have to give the drawing to the production people...


let me know if u have any other solutions...


thanks
 
> Don't know why...


That would drive me buggy (now the secret's out
smiley2.gif
).


How 'bout another pic; a close detail of the original notch with a circle indicating hole position and size (Sketcher screen dump or ...)?
 
My guess is that 'a' cut / hole will work fine.


Some specific hole that interacts in some specific way with existing
edges is having problems. That's why I asked for "position and size".
Long and short; you probably have an accuracy / tolerance problem.
If you want to put a datum sketch on the part representing the cut
profile as you're trying to make it and export a .neu, I'll take a
look at it.
 
I wasn't able to extract your file, the *.rar came over corrupt.


That said, I bet it's an accuracy problem. Remember, the default accuracy is relative. That value (.0012 default) is the allowed ratio between the longest and shortest edge. From the screen shots it seems that your part is pretty long with some fine detail. That usually creates weird problems like this where a simple cut won't work.


These sort of parts benefit from absolute accuracy which is the actual value of the shortest edge allowed. I usually start at .0001 for inch parts, .0024 for millimeter.


Frankly, we never use relative accuracy because of issues like this. We do a lot of injection molded parts which end up having a lot of small edges. It's maddening to get 200+ features into an organic molded plastic part and find you cannot create a rib due to an accuracy problem. That far into it, changing the accuracy is sometimes impossible as other earlier features fail with the new accuracy value. Had this happen just last week using a client start part with relative accuracy. Had to jump through several hoops to finsh the part.
smiley7.gif



Sorry to be so long winded ...
smiley36.gif
 
Hi dgs,


How do i change the accuracy of my part? EDIT->SETUP->ACCURACY-enter 0.0012 for relative accuracy? it's already at 0.0012 by default for mine...











The hole is what i'm trying to create. I managed to create the hole only after i take out the radius in the middle of the "V shape cut" (circled in red). If i have a redius of 0.01 in the middle of the V shape cut and then create the hole, my extrude feature will fail. However, if i create the hole and then the V shape cut, i cannot put the radius back on thev shape cut. The radius is not that important, but it's just bugs me when i can't recreate the radius....so simple, yet so complicated


dgs said:
I wasn't able to extract your file, the *.rar came over corrupt.


That said, I bet it's an accuracy problem. Remember, the default accuracy is relative. That value (.0012 default) is the allowed ratio between the longest and shortest edge. From the screen shots it seems that your part is pretty long with some fine detail. That usually creates weird problems like this where a simple cut won't work.


These sort of parts benefit from absolute accuracy which is the actual value of the shortest edge allowed. I usually start at .0001 for inch parts, .0024 for millimeter.


Frankly, we never use relative accuracy because of issues like this. We do a lot of injection molded parts which end up having a lot of small edges. It's maddening to get 200+ features into an organic molded plastic part and find you cannot create a rib due to an accuracy problem. That far into it, changing the accuracy is sometimes impossible as other earlier features fail with the new accuracy value. Had this happen just last week using a client start part with relative accuracy. Had to jump through several hoops to finsh the part.
smiley7.gif



Sorry to be so long winded ...
smiley36.gif
Click to expand...
 
Alvin,


I believe dgs was suggesting you change your accuracy from the default value of .0012 to a value of .0001.
 
If you create an axis through the round you can use that as a placement reference.


When I first tried it, I still had cut errors (likely due to accuracy as stated).


Then, I started a hole on the back, flat surface referencing the axis and the end of the bar and it worked fine without any change in accuracy.


I started an extrude-cut on the back and it worked fine also.





Note faceting on circular cuts due to poor accuracy.
 
CRang72 said:
Alvin,


I believe dgs was suggesting you change your accuracy from the default value of .0012 to a value of .0001.
Click to expand...


No, my suggestion was to change from relative accuracy to absolute. When you go to edit -> setup -> accuracy it will ask for a value right away. Accept the default and then go to the menu on the right and pick absolute instead of relative. It will then ask for a value again. I'd start with the default and only change it if you have regeneration problems.


The value will default to .0001, but the value is less important than the accuracy type. Absolute is needed on large parts with small edges. You can't createsmall edgeson a large part (orjust a part with long edges)with relative accuracy because of the way it's defined. Aluminum extrusions, sheetmetal and injection molded parts tend to benefit from absolute accuracy.


Frankly we use absolute in everything we do to avoid problems like this.
 
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