Wanting to 'pad' a part (solved)

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ajoeiam
Posts: 147
Joined: Sun Mar 03, 2019 9:36 pm

Wanting to 'pad' a part (solved)

Postby ajoeiam » Mon Mar 23, 2020 2:55 pm

Greetings

OS: Debian GNU/Linux bullseye/sid (LXQt/lightdm-xsession)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.19758 (Git) AppImage
Build type: Release
Branch: master
Hash: c165edd52c7f06ac09f992e5b5bf1d37661a8c0f
Python version: 3.8.2
Qt version: 5.12.5
Coin version: 4.0.0
OCC version: 7.4.0

I am 'trying' to model a circular saw blade. The actual number of teeth and the placement are not important so I have avoided trying to include that.
Found a forum question for just this but am stymied over and over again by one simple, I think, problem.

Sketch, to point, attached.
Trying to change the X:Y sketch into a 3D 'Body'.
When only including the OD and the arbor - - - easy.
How does one do this when one wants to have the greater thickness of the teeth shown, and the thickness of the body of the blade and also the arbor?

'Pad' in part design - - - - when I can get there - - - - asks if I want to create a cylinder - - - - not quite.
Rather its 2 concentric cylinders with the outer one being centered on the inner one.
Yet its not that either.

I've used 'sketcher' to 'do' this about 35 times as I've always managed to mess things up in trying to find a way to add the third dimension.
(Tried to 'sketcher' something to give what I want the 3rd dimension to 'look like' but when some of the lengths are 0.215 mm - -- - well there is no way that I can find to enlarge things so that one can actually 'see' things so that they can be selected and constrained.)

I can't find a way to add the third dimension (likely the X:Z plane) to the X:Y plane - - - - how do I do that?

Anyone have a list of steps (please include right or left or center mouse button) on how to achieve my 'design'?
Attachments
saw_blade_184mmc.FCStd
(12.54 KiB) Downloaded 15 times
Last edited by ajoeiam on Mon Mar 30, 2020 11:34 pm, edited 1 time in total.
kisolre
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Re: Wanting to 'pad' a part

Postby kisolre » Mon Mar 23, 2020 3:16 pm

Your sketch contains only construction geometry. It is only visible in sketch edit mode and can not be used to generate solids. You have to convert what you want to real geometry (which will be visible out of sketch edit mode) and use that to pad.
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Willem
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Re: Wanting to 'pad' a part

Postby Willem » Mon Mar 23, 2020 3:26 pm

Kisoire is right. Converting all three circles to normal lines will also give problems. It is better to give the center of the circles a coincedent constraint instead of giving a lot of dimensions of "0" mm.
Here is a model of a saw
Attachments
saw_blade_184mmc-Willem.FCStd
(95.8 KiB) Downloaded 9 times
Bance
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Location: London

Re: Wanting to 'pad' a part

Postby Bance » Mon Mar 23, 2020 3:29 pm

You can have a look at this model...

EDIT Willem beat me to it :D
Attachments
tct.jpeg
tct.jpeg (57.82 KiB) Viewed 327 times
TCTSawBlade.FCStd
(159.55 KiB) Downloaded 11 times
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papyblaise
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Re: Wanting to 'pad' a part

Postby papyblaise » Mon Mar 23, 2020 3:51 pm

Qweely I do it with bended tooths
First : we do a sketch wyth plein line (white) not in constructive (bleue)
2cd don't use 0mm of constraints but commun dot
Attachments
circular saw_blade.PNG
circular saw_blade.PNG (29.49 KiB) Viewed 312 times
circular saw_blade.FCStd
(512.9 KiB) Downloaded 7 times
drmacro
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Re: Wanting to 'pad' a part

Postby drmacro » Mon Mar 23, 2020 4:05 pm

Well, first issue is all the geometry in the sketch is construction mode circles. So, nothing to pad. See attached.

sawblade.png
sawblade.png (27.55 KiB) Viewed 308 times
Attachments
Sawblade-mac.FCStd
(289.15 KiB) Downloaded 6 times
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

My beginners, written treatise: Learning FreeCAD
ajoeiam
Posts: 147
Joined: Sun Mar 03, 2019 9:36 pm

Re: Wanting to 'pad' a part

Postby ajoeiam » Mon Mar 23, 2020 4:19 pm

kisolre wrote: Mon Mar 23, 2020 3:16 pm Your sketch contains only construction geometry. It is only visible in sketch edit mode and can not be used to generate solids. You have to convert what you want to real geometry (which will be visible out of sketch edit mode) and use that to pad.
So - - - - how does one 'convert' sketcher stuff into 'real geometry'?
ajoeiam
Posts: 147
Joined: Sun Mar 03, 2019 9:36 pm

Re: Wanting to 'pad' a part

Postby ajoeiam » Mon Mar 23, 2020 4:25 pm

Willem wrote: Mon Mar 23, 2020 3:26 pm Kisoire is right. Converting all three circles to normal lines will also give problems. It is better to give the center of the circles a coincedent constraint instead of giving a lot of dimensions of "0" mm.
Here is a model of a saw
OK - - - - noting the suggestion to use coincident constraints (shouldn't have to use such - - - - - thinking that that might even increase the complexity).

Your saw blade is 'flat'. I need to be able to show the difference between the width of the carbide teeth inserts and the body of the blade.
(Needed because I have one set blades for the prototype and am looking at sourcing for production and every company has slightly different values for the kerf, thickness of the carbide blanks (partly as a result of the different angles of attachment and blade tooth style) and the body of the blade. In fact some blades are hollow ground so that the blade is slightly concave when viewed from the side - - - - I haven't worried about that but that would be an issue for spacer dimensioning.)
ajoeiam
Posts: 147
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Re: Wanting to 'pad' a part

Postby ajoeiam » Mon Mar 23, 2020 4:40 pm

drmacro wrote: Mon Mar 23, 2020 4:05 pm Well, first issue is all the geometry in the sketch is construction mode circles. So, nothing to pad. See attached.

sawblade.png
Sorry - - - - disagree with your assertion.
Your blade is flat. The carbide teeth are the same thickness as the blade - - - - - also not true.

(A likely response is going to be 'it doesn't matter' - - - - except my shaft is likely going to have 70 blades on it - - - - that means an overall difference in shaft of some 28 mm if the teeth are 0.40 mm thicker than the blade body.)

Now if only there were an easy way to take your drawing and modify it to have the blade body at thickness x and the tooth thickness y and the number of teeth at z and the o/s dia of a - - - - - well life would be good (things are rarely that easy though - - - - I've just spent some time looking at your drawing - - - - - trying to understand how you did what and in what order and there is so little information so that one could figure out the steps inside each step of the drawing - - - - - this is where I'm quite lost in FreeCad).

(I think I could likely draw, using pencil and paper, an accurate drawing in likely 10% of the time I've already spent trying to figure out how to use the tools. The time was spent in that I want to use all the other tools but so far this has been quite time inefficient.)
drmacro
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Re: Wanting to 'pad' a part

Postby drmacro » Mon Mar 23, 2020 5:01 pm

ajoeiam wrote: Mon Mar 23, 2020 4:40 pm
drmacro wrote: Mon Mar 23, 2020 4:05 pm Well, first issue is all the geometry in the sketch is construction mode circles. So, nothing to pad. See attached.

sawblade.png
Sorry - - - - disagree with your assertion.
Your blade is flat. The carbide teeth are the same thickness as the blade - - - - - also not true.

(A likely response is going to be 'it doesn't matter' - - - - except my shaft is likely going to have 70 blades on it - - - - that means an overall difference in shaft of some 28 mm if the teeth are 0.40 mm thicker than the blade body.)

Now if only there were an easy way to take your drawing and modify it to have the blade body at thickness x and the tooth thickness y and the number of teeth at z and the o/s dia of a - - - - - well life would be good (things are rarely that easy though - - - - I've just spent some time looking at your drawing - - - - - trying to understand how you did what and in what order and there is so little information so that one could figure out the steps inside each step of the drawing - - - - - this is where I'm quite lost in FreeCad).

(I think I could likely draw, using pencil and paper, an accurate drawing in likely 10% of the time I've already spent trying to figure out how to use the tools. The time was spent in that I want to use all the other tools but so far this has been quite time inefficient.)
It was simply meant as an example, as are the others that were offered.

Learning from what others have done or display is how most of us have learned to use various features of FreeCAD.
You complain that the teeth are the same thickness as the blade. Simply edit the pad for the tooth and make it thicker and pad in Two dimensions.
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

My beginners, written treatise: Learning FreeCAD