Wanting to 'pad' a part (solved)

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drmacro
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Joined: Sun Mar 02, 2014 4:35 pm

Re: Wanting to 'pad' a part

Postby drmacro » Thu Mar 26, 2020 1:42 pm

Bance wrote: Wed Mar 25, 2020 9:29 pm ... try to pad a sketch that contains just one, then try two!
I second this motion. ;)
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

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ajoeiam
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Re: Wanting to 'pad' a part

Postby ajoeiam » Thu Mar 26, 2020 2:14 pm

Bance wrote: Wed Mar 25, 2020 9:29 pm I think you have already been told that it is not possible to create a solid from three concentric circles..... try to pad a sketch that contains just one, then try two!
That was done a long time ago - - - - - the problem is that a saw blade is really well illustrated using 3 concentric circles.
In increasing diameter:
1. arbor
2. ID of the carbide teeth
3. OD of the blade

The teeth themselves a nice option but not near as necessary (imo anyway!).
The challenge is that the blade body is one thickness.
The carbide teeth are NOT that thickness.
So to somewhat more accurately model the blade the thickness needs to be DIFFERENT from the OD of the blade to the ID of the carbide teeth - - - - that's what I've been trying to do.

I re-read the previous responses - - - - someone could have told me that what I was trying to do is impossible.
My question now is why isn't it possible?
ajoeiam
Posts: 147
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Re: Wanting to 'pad' a part

Postby ajoeiam » Thu Mar 26, 2020 2:16 pm

drmacro wrote: Thu Mar 26, 2020 1:42 pm
Bance wrote: Wed Mar 25, 2020 9:29 pm ... try to pad a sketch that contains just one, then try two!
I second this motion. ;)
Neither of those options leads to a solution.

Had done the doughnut model a long time ago - - - - hadn't asked about that either.

Interesting - - - - seems like no one that has offered a solution has ever tried to do what I would like to do.
A couple individuals offered what they had modeled and those options are interesting and I looked at them very carefully.
Large thanks to those that have offered their own solutions.

Over and out.
Bance
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Location: London

Re: Wanting to 'pad' a part

Postby Bance » Thu Mar 26, 2020 2:39 pm

Willem wrote: Mon Mar 23, 2020 3:26 pm Converting all three circles to normal lines will also give problems.
If you were manufacturing the blade from a single square billet, you would machine it in stages wouldn't you?
CAD is no different, create a pad that represents the plate, pocket an arbour into it, then pad the teeth thickness.
Does that sound simple?
ajoeiam wrote: Thu Mar 26, 2020 2:14 pm My question now is why isn't it possible?
If you did as I asked with a single circle sketch, followed by a sketch containing two concentric circles, you might've realised that it is impossible for the software to know what is solid and what is not if there are three concentric circles!

HTH Steve
drmacro
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Re: Wanting to 'pad' a part

Postby drmacro » Thu Mar 26, 2020 2:44 pm

I guess I still don't get what the problem is.

Three concentric circles can't be modeled from one sketch. How doe the modeling engine know which circle represent solid and which represents hole?

The carbide teeth are different shape altogether than the thickness of the blade. That's a given and they need to model as such. And modeled at a position where they intersect with the blade.

I'm truly trying to understand what I'm clearly missing...I'm going to reread this thread from the start. :?
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

My beginners, written treatise: Learning FreeCAD
Bance
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Location: London

Re: Wanting to 'pad' a part

Postby Bance » Thu Mar 26, 2020 3:03 pm

To save you some learning please accept this file, it is parametric. To change the parameters to suit your needs, select sketch in the tree view, scroll down to data view, expand 'constraints' and then change the dimensions as required.
Attachments
SawBladeBlank.FCStd
(17.25 KiB) Downloaded 5 times
ajoeiam
Posts: 147
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Re: Wanting to 'pad' a part

Postby ajoeiam » Thu Mar 26, 2020 5:20 pm

Bance wrote: Thu Mar 26, 2020 2:39 pm
Willem wrote: Mon Mar 23, 2020 3:26 pm Converting all three circles to normal lines will also give problems.
If you were manufacturing the blade from a single square billet, you would machine it in stages wouldn't you?
CAD is no different, create a pad that represents the plate, pocket an arbour into it, then pad the teeth thickness.
Does that sound simple?
ajoeiam wrote: Thu Mar 26, 2020 2:14 pm My question now is why isn't it possible?
If you did as I asked with a single circle sketch, followed by a sketch containing two concentric circles, you might've realised that it is impossible for the software to know what is solid and what is not if there are three concentric circles!

HTH Steve
To manufacture the blade:
1. sheet product cut to size
2. arbor likely cut at the same time as the OD but dunno
3. tooth supports are cut (means that the gullets are cut but there is still a flat product)
4. product is either trued (center ground) here or after the carbide teeth are attached
5. carbide teeth blanks are attached
6. carbide teeth are sharpened
dunno if there is a balancing step in there somewhat but highly likely

I wasn't trying to tell the software that everything was a solid. I was trying to tell the software that there were two different 'pads' trying to space them vertically concentric (no way to specify that either). Can NOT do that. (Don't know why, its illogical that its not possible but it is what it is.)
ajoeiam
Posts: 147
Joined: Sun Mar 03, 2019 9:36 pm

Re: Wanting to 'pad' a part

Postby ajoeiam » Thu Mar 26, 2020 5:26 pm

Bance wrote: Thu Mar 26, 2020 3:03 pm To save you some learning please accept this file, it is parametric. To change the parameters to suit your needs, select sketch in the tree view, scroll down to data view, expand 'constraints' and then change the dimensions as required.
Thank you very much.

A question (hope that's allowed)?
It seems that the 'pad' function only works when there are 2 'geometries' described.
Am I understanding that correctly?

(I'm not sure that I'm 'avoiding some learning' seems more like I'm being directed around the aspects of the software that I'm not aware of and aren't clear .)

A useful option - - - - thank you very much for your assistance.
Bance
Posts: 2030
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Location: London

Re: Wanting to 'pad' a part

Postby Bance » Thu Mar 26, 2020 5:39 pm

No that is not correct, you may have many geometries described, but you may only have one level of nesting. In other words a plate with half a dozen holes is fine, because it clear what is solid and what is space, and the outcome of the operation results in a single contiguous solid. Three concentric circles is not OK because the outcome of a pad would result in two solids which is not allowed.

To examine someone else's file expand the entire tree and make everything invisible (using the space bar), then make each step visible in turn starting from the top..... sketch,sketch001,Pad etc.
drmacro
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Joined: Sun Mar 02, 2014 4:35 pm

Re: Wanting to 'pad' a part

Postby drmacro » Thu Mar 26, 2020 6:09 pm

ajoeiam wrote: Thu Mar 26, 2020 5:20 pm
I wasn't trying to tell the software that everything was a solid. I was trying to tell the software that there were two different 'pads' trying to space them vertically concentric (no way to specify that either). Can NOT do that. (Don't know why, its illogical that its not possible but it is what it is.)
It is possible, the technique you describe is just the wrong way to do it. ;)
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

My beginners, written treatise: Learning FreeCAD