Sectional arc

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degarb
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Joined: Fri Apr 16, 2021 7:49 pm

Sectional arc

Post by degarb »

I want to draw an arc and have it sectioned in 18 equal parts. I wonder how I can do it?
chrisb
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Re: Sectional arc

Post by chrisb »

degarb wrote: Sun Apr 18, 2021 4:43 am I want to draw an arc and have it sectioned in 18 equal parts. I wonder how I can do it?
Do it the other way round: draw 1/18th of the arc, and use a polar array to multiply it.

I have the very strong feeling that you are doing something rather weird. You are giving us quite some work here with your posts of small snippets like small pieces of pizza. Helping is usually much easier if you show us the whole thing. So what should your final result really be?
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
heda
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Re: Sectional arc

Post by heda »

next time around, can you please limit yourself to making one post per "project",
what we see here is you getting acquainted with the software - which is perfectly fine,
but the forum becomes less cluttered if that type of learning is bundled posts covering one "learning project" per post.

let's try and keep it simple.
the following file is made without a single click in the 3d view,
it is also made without entering a single digit anywhere, the scroll wheel is used to change the numbers,
it does require hitting enter key 3 times when creating the arc (for the radius, start angle and aperture angle).
the rest is clicking buttons either in toolbar or "task view" ("Enter point" is one example of a useful button in task view),
duplicate is located in edit menu
wheel.png
wheel.png (48.93 KiB) Viewed 916 times
here is what to do:
- create one horizontal line (0,0) to (10,0)
- duplicate it
- select it in treeview, go to placement (in data view) and change angle to 20 deg
- click "create arc", center in (0,0), radius 10, start angle 0, aperture angle 20
- select the last line and last arc in treeview, duplicate those
- take (select) the last created line and change placement angle (in data view) so that it is increased by 20 degrees
- take (select) the last arc and change placement angle (in data view) so that it is increased by 20 degrees
- repeat the last 3 steps until you have the full circle

this takes me a couple of minutes to do, sure it is cumbersome, but it is really simple and easy to understand.
of course there are faster and smarter ways to do this, but that requires actually learning
a bit more about the software and concepts around modelling - which typically takes weeks/months

to export, in treeview, select all and go to file menu and export as dxf - you now have a dxf file to use in other software

an example of concept to learn is what crisb pointed out, rather than thinking in a circle that is sectioned, you should (actually must) think as arcs that are "multiplied", then one can ask oneself why - simply because the entities in the software is either a full circle or an arc, so to "section" a full circle to 18 arcs, you need 18 unique entities, ergo better to use an arc and multiply that one to begin with.
Attachments
wheel.dxf
(5.67 KiB) Downloaded 25 times
wheel.FCStd
(39.27 KiB) Downloaded 22 times
mario52
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Joined: Wed May 16, 2012 2:13 pm

Re: Sectional arc

Post by mario52 »

Hi

try Macro_Cut_Circle (paste the complete macro in FreeCAD Python console and type:)

Code: Select all

cutCircle(6, 1)  # here with 6 arcs and coloured

Image

mario
Maybe you need a special feature, go into Macros_recipes and Code_snippets, Topological_data_scripting.
My macros on Gist.github here complete macros Wiki and forum.
Olav
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Location: Netherlands

Re: Sectional arc

Post by Olav »

heda wrote: Sun Apr 18, 2021 8:59 am next time around, can you please limit yourself to making one post per "project",
what we see here is you getting acquainted with the software - which is perfectly fine,
but the forum becomes less cluttered if that type of learning is bundled posts covering one "learning project" per post.
A project can (and usually does) consist of many different operations. I think it's perfectly reasonable to ask separate questions about them.
chrisb
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Re: Sectional arc

Post by chrisb »

Olav wrote: Sun Apr 18, 2021 1:53 pm A project can (and usually does) consist of many different operations. I think it's perfectly reasonable to ask separate questions about them.
You are right in general, but did you have a look at the other questions? The first post was ...
degarb wrote: Fri Apr 16, 2021 7:56 pm I downloaded cad, basically to draw a pizza slice with pepperoni. 2 D only. This is the part that the machine must cut, a pizza slice.
... where the current topic would have perfectly fit. :roll:
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
degarb
Posts: 58
Joined: Fri Apr 16, 2021 7:49 pm

Re: Sectional arc

Post by degarb »

Sorry, I am just getting started, and am focused on a specific problem in my life that I need to solve by learning freecad. Most forums want you to break up different problems into different threads, which makes future googling to find answers much more easy for future people.

I have been mining search engines and forums for answers since 1998, at least. What I always find is that if I post more than one question per thread, most of my questions are ignored by answering one of the questions, then the thread is closed as solved when it is not. The most frustrating thing about googling forum answers is reading hundreds of Google forum thread results where people are asking my question, but are getting shut down because there is some old, poorly indexed, single case solution sometime in the past. Fortunately, I am currently impressed with the helpful community here. I might take up learning freecad as a hobby, after getting my dwg, dwf file to the machine shop for the part cutout, because of the community, and so far, I have been enjoying learning how to do really useful stuff while laying out my drawing.

I only need 2D for now, with a background graph. I have 9 sticking to draft workbench, because it appears to do what I want to do.

On a side note, I think autohotkey, an open source macro and basic like programming language, is the best example of a easy to use help file and community. It is only windows based, and is the main reason I won't use Linux. I am impressed with this community in comparison to autohotkey. Autohotkey has a killer chm. The chm is so well done and searchable, in a few minutes of searching and reading, a person can easily write incredibly complex exe programs that solve computer problems and tasks that cannot be found otherwise. ... I currently do not have the time to learn how to do things unrelated to my 2D drawing. But at my leisure, I want to come back and learn how to do other things. I am getting lots of good text answers to my question. I am surprised how little I could follow on most of the youtu.be videos. I think it is because I need to fish through a 45 minute video to find the 30 second answer to my question. Also, many of videos aren't narrarated. Also, when they go up to select a menu item it clicks so quickly that I can't tell what they clicked. Also, many of the video quality freecad videos are slightly blurred which makes it hard to see what they are doing exactly. I am sure there is a freecad Rockstar channel I should be subscribed to (for a beginner to watch) and any suggestions are welcome.
chrisb
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Re: Sectional arc

Post by chrisb »

You are very right with the videos. And even worse: I have seen so many videos doing things wrong! But as a newbie you have no possibility to judge this. To really benefit from the videos you have to have reached already a minimum level. That's why I rather recommend to start with the written Tutorials.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
Bance
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Location: London

Re: Sectional arc

Post by Bance »

To add to what chris has said, FC is not suited (designed) for use as 2D cad.

If you just want 2D cad use libreCad or some other. There is less to learn, and is less difficult to learn.

3D cad is not trivial, it takes time and practice and lots of FAILS.
mario52
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Re: Sectional arc

Post by mario52 »

Hi

FC Daft and the super Sketcher are sufficient to work in 2d

if you want special line you have also Macro_FC_Convert_Lines Image (and cut line by number or by length)
if you want convert dxf wire to Line Arc or Circle you have Macro_Compound_Plus Image

and other litlle macrossss

and the forum for other special feature

PS:have you tried cutcircle

mario
Maybe you need a special feature, go into Macros_recipes and Code_snippets, Topological_data_scripting.
My macros on Gist.github here complete macros Wiki and forum.
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