[done] Developing a spreadsheet based loaf pan

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user1234
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Re: Developing a spreadsheet based loaf pan

Post by user1234 »

Ulicad wrote: Thu Mar 16, 2023 6:27 pm - how can a beginner be prompted to use expressions without sweating ..
- accordingly edit the other topic (above)
The conception of expression, formula, or whatever they called, is a general CAD feature in many CADs. If someone use calculators like excel or have some (even small) programming experience, expressions is almost self explaining. What is not self explaining is, what can be accessed. For that is try and error and the wiki. But when you know a part of it, then you figure out the rest almost complete.


Ulicad wrote: Thu Mar 16, 2023 6:27 pm - continue on the loaf pan along your suggestion
That is up to you. But to be brutally honest, if you have no CAD experience, and have really nothing with sheet metal (or generally with machining of steel) till yet, creating a full parametric sheet metal CAD, which is also produceable, is a damn hard task. If you are a hobby technical enthusiast, then maybe yes, but you seems to underestimate the complexity, in CAD and machining/producing, even on a very simple part like this.


And general according CAD, i sound like a broken record, but CAD is no fast just plaything, just because it is (an easy accessible in the case of FreeCAD) program. I always compare it with machines, like a lathe or milling machine. Even they conception of the machines are similar or mostly the same, you must know the machine specific and environment, else you only produce cull. Example a fit 100 +/- 0.02 mm, if write a CNC program (or do it manually) and you position the machine in that coordinate and make the fit, will not be in most cases 100 +/- 0.02 mm , because of the stiffness the machine, scale arrangement, cutting edge, material, temperature, infeed, axis arrangement .... . You must know many details, and that case is also in CAD. And like machines, even brand new, have quirks, CAD also have them.


Greetings
user1234
Ulicad
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Re: Developing a spreadsheet based loaf pan

Post by Ulicad »

Thanks for your honest and frank post - it helped a lot to work on my communication skills here in the forum. These are are very meager due to various factors :roll: ...

However, we are on the same page, regarding the issues raised by you.

To speak on a more practical level:
I am not at all worried of taking care of tolerances in the order of ±5 µm for instance. Neither in theory, designing small machinery, nor practically in machining. And I definitely like it (if the task is small..).

Nor am I afraid of entering into CAD or FC to the point required. This may take more efforts and time than hoped for. That's the point where some underestimation may get into the matter...

Regarding further points:
Agreed on the issue of using some formulae - this can be taken as granted to start with.

But, as you said:
user1234 wrote: Fri Mar 17, 2023 4:33 pm ... What is not self explaining is, what can be accessed ...
I definitely would add: and how it can be accessed in FC. This matters even more so, while we are talking about beginners to FC or beginners to CAD in general.

This clearly is bothering me the most in this conntext.

Regarding the complexity and 'strangeness' of CAD in general and FC specifically (for a beginner), I am very much aware - this can be horrible...

Regarding the choices which had to be made in my paths and which was triggering your words:
user1234 wrote: Fri Mar 17, 2023 4:33 pm ... That is up to you. ...
In the given case (to avoid TNPs), either I could follow drmacros suggestion above (high level, minimised dependency tree, not on beginners-level) or for instance the path you were suggesting (the use of expressions), the only alternative I know of by now.

And the choice went to the expressions for both targets: personal use and Mini-HowTos for beginners.

That's why I am following this path (using expressions) for these two interdependent little projects now.

Greetings
Uli
Regards, Ulicad / Uli
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Ulicad
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Re: Developing a spreadsheet based loaf pan

Post by Ulicad »

Hi all,
in my trials to add the sketch for a cutout (to be multiplied later on), I firstly added a datum plane and ran into problems therafter, not to be mentioned here.

Still very uncertain about how a datum plane is attached safely avoiding TNP, I show this here.

attachment-of-a-datum-plane.png
attachment-of-a-datum-plane.png (91.32 KiB) Viewed 1083 times

This way, the plane can be offset by using the parameters to the desired position rather easily.

Since I am still very uncertain: Would this be a 'good' cornerstone to build upon?

Especially, I can't sufficiently understand the 'Solid' | 'Pad' in the panel.

Any hint would be appreciated - thanks in advance!
Attachments
tmp-1.FCStd
(15.42 KiB) Downloaded 23 times
Regards, Ulicad / Uli
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user1234
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Re: Developing a spreadsheet based loaf pan

Post by user1234 »

Ulicad wrote: Sat Mar 18, 2023 10:06 am However, we are on the same page, regarding the issues raised by you.
Sorry, what? Do not interpret in things, were are not things and to not turn the tables.


Ulicad wrote: Sat Mar 18, 2023 10:06 am I am not at all worried of taking care of tolerances in the order of ±5 µm for instance. Neither in theory, designing small machinery, nor practically in machining. And I definitely like it (if the task is small..).
It is not about preciseness, it was a analogy. FreeCAD (and CAD in general) is like a machine, where you have to be trained/experienced to get good and valid outputs. You have to know the environments and consider them, like in a machine.

It is not a "just input, enter, output" plaything, just because it is software, especially when you want to produce something in real life.


But i am now out, this here leads to nothing.


Greetings
user1234
chrisb
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Re: Developing a spreadsheet based loaf pan

Post by chrisb »

The pad as a total has the same cordinate system as the underlying sketch or some generated face. Thus you should not use the pad, but the sketch instead. See also: TNP.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
Ulicad
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Re: Developing a spreadsheet based loaf pan

Post by Ulicad »

user1234 wrote: Wed Mar 22, 2023 9:17 am ... But i am now out, this here leads to nothing. ...
Sorry about that. It is much an issue of language, mixed with my only slowly beginning comprehension.

Regarding the model you showed, I was trying to follow, but was not able to find a way to position the sketch to where it is needed.

Regards

edit: just now I understand that your model and my next trial may be directly linked..
Last edited by Ulicad on Wed Mar 22, 2023 11:57 am, edited 1 time in total.
Regards, Ulicad / Uli
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Ulicad
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Re: Developing a spreadsheet based loaf pan

Post by Ulicad »

chrisb wrote: Wed Mar 22, 2023 9:20 am The pad as a total has the same cordinate system as the underlying sketch or some generated face. Thus you should not use the pad, but the sketch instead. See also: TNP.
This is what I was suspicious of. TNP live!

Having read, that a sketch may be attached and positioned using the global coordinates directly, I hope to find a suitable way. Or a way to attach the datum plane to the coordinate system and move it afterwards.

Thanks
Regards, Ulicad / Uli
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adrianinsaval
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Re: Developing a spreadsheet based loaf pan

Post by adrianinsaval »

Don't attach to the pad, instead attach to one of the base planes inside the body (they are inside the Origin object in the tree)
jeno
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Re: Developing a spreadsheet based loaf pan

Post by jeno »

Ulicad wrote: Wed Mar 22, 2023 8:33 am Hi all,
in my trials to add the sketch for a cutout (to be multiplied later on), I firstly added a datum plane and ran into problems therafter, not to be mentioned here.
Still very uncertain about how a datum plane is attached safely avoiding TNP, I show this here.
...
Attach the datum plane to this edge
edgedatumplane.png
edgedatumplane.png (6.44 KiB) Viewed 923 times
Fix your sketch. The radii aren't coincident
sketch.png
sketch.png (10.66 KiB) Viewed 923 times
the presumed further course of action see attached file

cheers
jeno
Attachments
tmp-1-jeno.FCStd
(25.13 KiB) Downloaded 18 times
Ulicad
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Re: Developing a spreadsheet based loaf pan

Post by Ulicad »

adrianinsaval wrote: Wed Mar 22, 2023 1:46 pm ... attach to one of the base planes inside the body (they are inside the Origin object in the tree) ...
Thanks! Finally I managed to right click one of these planes and click the datum plane button therafter - which great achievement 8-) ;)

jeno wrote: Wed Mar 22, 2023 2:41 pm ... Attach the datum plane to this edgeedgedatumplane.png
Fix your sketch. The radii aren't coincidentsketch.png ...
Hello jeno,
the point you show for attachement would be ideal as an origin for constructing the 1st cutout, but its postition is depending on values in the spreadsheet.
Consequently speaking, would'nt this point then be part of the cross-sections Pad, possibly leading to TNP (and it definitely did before)?

Regarding the fillet:
This still is a workaround which may require manual adjustment in case of changing the values.

Depending on the wishes of mechnical workshops, the inner (and outer) fillet radius may be set to 0mm in the spreadsheet! A generallly functional and suitable expression (based on school geometry) did not occur to me yet.
Regards, Ulicad / Uli
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