Solid Modeling??

[kwolf]

Hi,

 

Is it possible to design a solid in any Solid Modeler (any kernel) with only 3 or 4 simple feature (only protrusion of a rectangle , constant fillet ) and get inconsistent or invalid solid?

If so , then is solid modeling reliable?

 

KWOLF

[cadcam]

Well ,the problem here is you are asking any solid any kernal. I would say I don't know because I do not know them all.

 

Are you saying the issues about a constant fillet that may be bigger the a face, that would remove that intire face so you get one of the errors?

 

I don't no.

 

As for are solids reliable, my answer is yes and vary helpful.

I suggest them to all.

JM2C

[kwolf]

Thanks Jay,

And no the fillet is constant and smaller than the face and do not remove any face at all but the resulting geo was entirely incorrect and if you check it in any cad the software report error.

In fact I tested it with many cad systems from catia and pro/e to solidworks and mastercam.

[kwolf]

Let's try this:

1- create a box 50x50x50 .

2- create a shell with removing top face (1 face)and a value of 1 .

3- create a fillet on 4 edged on bottom face with a value of 5 .

4- voila the geo is incorrect

[kwolf]

I've tested it with many systems

Pro/e Catia UG SolidWorks Solid Edge MDT 6 Mastercam and many more

below the shell is 1 and fillet is 20 for better visualization.

 

[cadcam]

Is this in metric or standerd.

[kwolf]

metric.

[cadcam]

Oh ok this what I made but using what you said in standerd.

 

Example

[kwolf]

Will you look at FTP.

The file is solid-problem.jpg in pic folder.

I send the MC8 file right now.

[cadcam]

the clor 13 one does not look right cant tell about the others.Picture is fuzzy

[Finecut]

Kwolf is right. A 50x50x50 block. Shell the block from the top leaving the top open. use a value of 1. Now fillet the bottom only using 5.0 as a value.

The part should FAIL as the radius extends into the shell.

But it doesnt.

 

Finecut

[kwolf]

Then please check solid-problem in MC8 folder.

i'm sure it's not graphics problem or such a thing rather this is a common kernel error.

[cadcam]

Please get my copy of the file from the Solids folder. same name but added cadcam.

Please look the color 10 model.

[kwolf]

How about color 13 (the right hand side solid)?

I put three solid to show the steps in creating the final invalid solid from left to right.

You can create any solid in any application and see this error.The finecut got the idea.

I first saw this problem long ago and have not found any patch or remedy to it.

However thanks for your attention.

 

[ 02-24-2002, 02:50 PM: Message edited by: kwolf ]

[cadcam]

Did you down load my file?

I am trying to see if this what you wanted.

 

Because if it is then it is like the way solids are,itis in the order in witch you do things.

 

This what i am trying to confirm.

 

Ok i have confirmed it is the oder that you decided to do it in.

 

if I do all in metric the way you want but change the order there is no trouble.

 

So this should help you to understand solids more.

Try different oders some times ,just like the filleting issues in solids.

 

Please view my new file setup just like yours done in metric. solidproblemcadcam1.mc8 in the solids folder.

 

Hope I am being helpful.

 

J

 

[ 02-24-2002, 03:11 PM: Message edited by: cadcam ]

[kwolf]

Thanks for your patience. And I hope this problem can be fixed sometime soon.

KWOLF

[bryan.davis]

I think I understand whats going on here, basically you are creating an invalid solid by filleting the outter edges to a magnitude sogreat that they violate the inner yes???

 

Well this may be possible in MasterCAM, but thats not the case with all CAD packages and kernals. many have the required error checking to prevent this and its probably true to say that soom Mastercam and the parasolids kernal will too.

 

As to making solids drafting unviable then gods no, its the future of CAD, in exactly the same way 2D CAD was the future in the late 70s only more so.

 

Come 20 years time Engineering communication will be totally revolutionised and at the centre of it will be Solids CAD, solid models of the future will not only contain the visual data we have today but also all the material information, hardness, surface finish, tolerance part number you name it will all be embedded in a single solid model.

 

When an engineer designs components he will have the instant ability to produce a photorealistic immage because the modle will have all this information, if he wants to know anything about the components dynamic performace all that info will be ther at the click of a button.

 

OK, so there are a few bugs in it and its got a long way t go, but dont step off the Solids waggon cos its moving fast and if you aint carefull its going to leave a lot of people behind!

[cadcam]

I am sorry folks once again it is the order that you build it that is causing this.

 

So yes it will fail in the others too.

Not just in mastercam.

If I do it in the order that Kwolf did it. you get what he did.

But do one in front of the other and the shape will not fail.

 

Is there some thing I am missing here?

I Kind of feeling like there is.

but I have done the work that tells me other wise for this instence.

 

Gee folks am I haveing a moment or what.

 

[ 02-24-2002, 11:02 PM: Message edited by: cadcam ]

[P_Scott]

kwolf,

 

Jay is entirely correct. I have looked the file over and have tried it out. Your Shell is done before the Fillet and that's why you are getting an incorrect model. Simply drag the Shell below the Fillet and you will not have any error in the model. Shelling in solids is only tricky in that it has to be done in the right order during the modeling process. I could go on all day about this but my boss would want to charge money for this advice.

[Guest CNC Apps Guy 1]

Solid Modeling is very picky in the order of operations. Do something in the wrong order and you end up with a blown out face or any other number of interesting out comes. How do you know what to do first, next and last? Use it! There's no book about this because the possibilities are pretty much endless. There are a few guidelines to follow though.

 

[*]Draw Everything Sharp add the fillets in later.

[*]Shell last

[*]Spend time Solid Modeling different things on your own until you become proficient

JM2C

[rwade]

solids, like surfaces are nice tools but...

...YOU still get to make the part.

[cadcam]

quote:

---

...YOU still get to make the part.

---

Not if your job is drafting.

[bryan.davis]

And rapid prototypes are no more difficult than printing a letter

[d0gFartz]

quote:

---

solids, like surfaces are nice tools but...

...YOU still get to make the part.

---

Good luck with those surfaces when the boss man gives ya a rev change and it says now the fillets are double the size here and half the original size there

[cadcam]

Hey, what's that smell, it smells like a dog farted in here.

 

yes sir you are correct.

(Lets change those fillets fast son we don't have all day for you to redraw the hole part.) Ouch