Project Strategy: External Parts, Multiple Parts?

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ChipsNChips
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Project Strategy: External Parts, Multiple Parts?

Post by ChipsNChips »

I am trying to organize my mind on how to integrate existing parts/assemblies with the parts needed for my project. In 2D CAD I would use layers. First I would draw any existing parts or assemblies that my project would connect to. That gave me a starting point but those parts/assemblies would not be made in my project since they already existed. Then I would draw new parts, each on a separate layer. By turning layers on and off I could see the relationships between the existing parts and the new ones that had to be made. Kind of like designing a carburetor for an engine. You are not going to make the engine, but you need to draw/model at least part of it where the carburetor will attach in order to have the attachment points for the carburetor.

So now I want to do a project in 3D FreeCAD. I have been told that it is best to draw only one part in a given drawing/model. But that does not let me see how the parts will fit with each other or with existing parts or assemblies. One thing that occurs to me would be to create everything in one master drawing and then make copies of it (the drawing file) where I delete everything except the single part at hand. So one master drawing/model and many individual ones for each part to be produced. One worry would be how to ensure that deleting the other parts would not lead to problems with the one I was trying to keep. And I would like to use parameters. How would I ensure that they would survive that deletion of parts? Is there a better way?

Is this a good plan in FreeCAD? Or is there a better way? The project I presently have in mind would probably be made mostly with 3D printing of plastic parts to prove the concept and then metal parts, which would be more durable, would be machined for the final devices. Can I make just one drawing and them create 3D print files and individual part drawings from it, as needed/

One thing I always had problems with in 2D CAD was the dimensions. A single layer for dimensions would have a tangle of overlapping dimensions, often with slightly different sizes or different tolerances for what would look like the same distance. So either the dimensions were put on the same layer as the part or a separate dimension layer for each part was necessary. Another method I used was to copy the individual parts to another section of the drawing plane and do the dimensions there. No overlap on a single dimension layer. In FreeCAD I would need to handle dimensions for each of several parts in some sensible manner. But how? What is a good overall strategy?
Bance
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Re: Project Strategy: External Parts, Multiple Parts?

Post by Bance »

First thing to do is forget everything you think you know about CAD.

In 3D cad one creates a model, drawings are 2D extractions used only for manufacture, and these days are often not required (FDM,CNC.)

FC offers a number of assembly workbeches (WB) or if one prefers a top down or insitu workflow.

There are methods for importing geometry to use as reference.

Dimensions are inherent and are not normally shown explicitly.
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onekk
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Re: Project Strategy: External Parts, Multiple Parts?

Post by onekk »

Most reliable and manageable way is to organize your mind and your files in a directory tree.

You model parts one per file, name it accordingly and store in a "per project" directory.

In this directory youncoukd make as example a STP subdir where to store step files (eventually exported from models) for parts that coukd be reused many times.

And use maybe a master file to have a centralized place where to place as example a spreadsheet with common dimensions or a "master sketch".

Each "model" file will refer to common data stored in the "master file".

To join things use an Assembly WB, asm4 is decent and easy enough to be used without too much additional learning.

But the main concept is organisations, too much things in an unique file is the way to have problems.

Regards

Carlo D.
GitHub page: https://github.com/onekk/freecad-doc.
- In deep articles on FreeCAD.
- Learning how to model with scripting.
- Various other stuffs.

Blog: https://okkmkblog.wordpress.com/
ChipsNChips
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Re: Project Strategy: External Parts, Multiple Parts?

Post by ChipsNChips »

That is all well and good, but it does not address my question. At least, I don't see how.


Bance wrote: Fri Feb 03, 2023 10:38 am First thing to do is forget everything you think you know about CAD.

In 3D cad one creates a model, drawings are 2D extractions used only for manufacture, and these days are often not required (FDM,CNC.)

FC offers a number of assembly workbeches (WB) or if one prefers a top down or insitu workflow.

There are methods for importing geometry to use as reference.

Dimensions are inherent and are not normally shown explicitly.
ChipsNChips
Posts: 36
Joined: Sat Dec 25, 2021 10:51 am

Re: Project Strategy: External Parts, Multiple Parts?

Post by ChipsNChips »

Carlo,

Thanks! That looks like what I need to know. I am going to print it to have it handy while I work. I am sure I will have more questions, but I am going to get started.

Thanks again!

Paul A.


onekk wrote: Fri Feb 03, 2023 10:47 am Most reliable and manageable way is to organize your mind and your files in a directory tree.

You model parts one per file, name it accordingly and store in a "per project" directory.

In this directory youncoukd make as example a STP subdir where to store step files (eventually exported from models) for parts that coukd be reused many times.

And use maybe a master file to have a centralized place where to place as example a spreadsheet with common dimensions or a "master sketch".

Each "model" file will refer to common data stored in the "master file".

To join things use an Assembly WB, asm4 is decent and easy enough to be used without too much additional learning.

But the main concept is organisations, too much things in an unique file is the way to have problems.

Regards

Carlo D.
ChipsNChips
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Joined: Sat Dec 25, 2021 10:51 am

Re: Project Strategy: External Parts, Multiple Parts?

Post by ChipsNChips »

After re-reading Carlo D's post, I have a question.

So first I model an existing object that my parts will fit on. This will be in a file, by itself. And it will be dimensionally accurate.

Now I want to model my first part that will fit that existing object. So I start a new file for that part. Can I see the model of the existing object while modeling my part in this new file? This would help me to work to both the dimensions and the shape of the existing object.

Or do I need to just work from a mental picture for each part I create? And then use the Assembly work bench you refer to to check after creating each part?
ChipsNChips
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Re: Project Strategy: External Parts, Multiple Parts?

Post by ChipsNChips »

While clicking around the board I saw a post by luggw1 where he is modeling a HO scale roundhouse. He seems to be doing all the parts of this model in one file and then, somehow copying them for 3D printing. He even talks about breaking his latest part, a roof, into printable pieces so I would guess that will be several ... several whats? Several files?

viewtopic.php?p=658028#p658028

This looks like what I would like to do with my project. Have all the parts, including pre-existing ones in a single file and then separate out (copy) them for individual 3D prints or model files where I could extract the dimensions for machining them from metal.

Could someone explain the process he is using in more detail? How are the parts kept separate? Is that an automatic thing when you start with new sketches? And then, just how does that copy process work? Is he copying to a new file? Or what?
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onekk
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Re: Project Strategy: External Parts, Multiple Parts?

Post by onekk »

You could have multiple file and then using Links (sort of import) have them in another file.

See on wiki "Basic Attachment Tutorial"
Or you could use a master sketch or a spreadsheet that old some "relevant" lenghts and reuse them across different files as example in Sketch.

Or reuse Sketches "named constraints" across files to model as example mating parts.

For complex models I use a different approach, I "code" my models using Python and then assemble them in an unique file, but this file that could have hundreds of parts, is only a destination file, it will be big if saved on disk and very complex to manage.

However the script file could be very small I have a complex model made by 4 script file with 1200 lines each, but they are very far from reaching 1MB in total of disk space.

But this involve to write code and learn many things.

Changing a dimension is however a matter of modifying a value of a variable and relaunch the script, it will recreate the whole model and eventually will export solids as STL for printing.

I have some happy customers around the world who have printed "model scale" things.

Regards

Carlo D.
GitHub page: https://github.com/onekk/freecad-doc.
- In deep articles on FreeCAD.
- Learning how to model with scripting.
- Various other stuffs.

Blog: https://okkmkblog.wordpress.com/
Bance
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Re: Project Strategy: External Parts, Multiple Parts?

Post by Bance »

ChipsNChips wrote: Sat Feb 04, 2023 4:40 amit does not address my question
The question was general, so was the answer.

The benefit of using FC is that one can work in whichever workflow that suits.

I prefer to work with the top down method, for simple models, and use an assembly WB for more complex projects.
ChipsNChips wrote: Sat Feb 04, 2023 5:05 amAnd it will be dimensionally accurate.
I should hope so! (not much point otherwise.)
ChipsNChips wrote: Sat Feb 04, 2023 5:05 amdo I need to just work from a mental picture for each part I create?
I explained that there are methods to import geometry.....

Here is a link to an assembly:-

viewtopic.php?t=73158

Here is a link to a top down approach:-

viewtopic.php?t=29354
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dprojects
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Re: Project Strategy: External Parts, Multiple Parts?

Post by dprojects »

ChipsNChips wrote: Fri Feb 03, 2023 10:07 am What is a good overall strategy?
There is no such thing. This is the difference between knowledge and skills, or rather the intelligence of an engineer, developer. You can memorize all the books, you can have A grade from all at the university, but the ability to plan a project is more important. You can gain knowledge online, but you can't teach intelligence and coping skills to anyone. Either you have it or you don't.

It is extremely difficult for corporations to deal with unique resources. When corporations hear about unique resources, they immediately go crazy and angry, because they can't do it and manage it. They think that manipulation and psychology will help them, they even invented coaching, but it's a road to nowhere.

So the answer is simple, you need to be smart ;-) or need to get smart engineer to do it in the smart way ;-)

Thanks
Darek
github.com/dprojects

workbench for woodworking is available at: github.com/dprojects/Woodworking
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