I don't know what to title it, but I think there is obviously something I'm getting wrong.
I'm trying to design a fairly complicated case. I 3d printed it out, and have to tweak the design. Basically, I use the part menu, add and subtract various shapes to get the design I want. However, trying to revisit the design, I find I cannot readily alter it, and moving items around, although the coordinates show the correct locations, the drawing does not redraw showing the new locations. Also, I find that subtracting shapes do not work on areas with perhaps overlapping regions. I could happily post the code, but I know it is a mess, if anyone was brave enough to try to fix it. There would be a bit of to-ing and fro-ing, as I would try to explain what I was attempting.
OS: Windows 10 (10.0)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.22665 (Git)
Build type: Release
Branch: master
Hash: b0d7850406e046f3b7a8cd5da261e7d54df6bd99
Python version: 3.8.6
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.4.0
Locale: English/United Kingdom (en_GB)
fundamental
Forum rules
and Helpful information
and Helpful information
IMPORTANT: Please click here and read this first, before asking for help
Also, be nice to others! Read the FreeCAD code of conduct!
Also, be nice to others! Read the FreeCAD code of conduct!
Re: fundamental
I'm sorry but I fail to see the point of this post.
Re: fundamental
The point of the post, was asking for suggestions on how to organise a fairly lengthy design, so that later on alterations can be made. I thought that was the benefit of parametric design. Now, if all your designs work as you think they should, and you can't understand that others may have problems that can not be adequately described, then that's OK. It may be something fundamental that I am missing, or accumulation of bugs/whatever. For example, adding and subtracting various shapes may fail for everyone after maybe six or seven booleans, maybe no-body can move things around which were included earlier ion the tree?
Re: fundamental
You didn't ask any questions, it was simply a set of statements.
There is no mention of which WB is being referred to.
There is mention of drawings and of being unable to alter the design.
But no questions, but then this is the wrong place to ask for help.
There is no mention of which WB is being referred to.
There is mention of drawings and of being unable to alter the design.
But no questions, but then this is the wrong place to ask for help.
Re: fundamental
I must be missing something about this fora, then. The general heading for this section is open discussion. I mentioned the part menu. And, there are numerous questions here. I'm quite happy to argue, if that is what you want. However, it would help me if you explained how you overcome the sort of problems to which I allude, or maybe you're so clever all your designs work perfectly?
Re: fundamental
Aha, a philosophical question 
Just an opinion in the ether.
Is this an adequate exaggeration of your question?
I made a parametric car on 4 wheels, an electric one (of the typical shape of a regular car).
Can I parametrically change that to become a jet fighter, 3 wheels and 2 jet engines.
Maybe, but no, not really in any cad software no matter how much money you spend on it.
Well, you could cheat, and call your top assembly "anything" and have a drop down that is car/jetfigher and replace the assembly "parametric".
After all computers are quite simplistic in their ways of working - when it comes to rendering everything is about polygons (i.e. triangles with 3 points to describe an outer shape, so it´s really just a point cloud with a skin). Points are easy to change (and is not so resource demanding mathematically), which is why all 3d rendering programs works with meshes, where one can morph the point cloud to change shapes as one example. But what happens if you need more points? Or start to collapse surfaces so that they disappear and are no longer needed?
That is really the dilemma here in changing shapes drastically. If you are looking for morphing things, then you should use blender instead of fc.
Cad is generally created to support the "boring" area of manufacturing, and has evolved for those needs.
Those needs are to describe boundaries of bodies, being able to dimension them, assemble into multi component products, run simulations etc.
The approach in cad is to create mathematical descriptions of boundaries, like a box, or a sphere in the simplest cases. With sweep you drag a line along another line to create a mathematically described surface.
So you cannot by will power just change a mathematically build up boundary or the "features" you have used to make it. You have to change it in a way which still preserves the mathematical solvability. Sure one can replace a box with a pyramid, if all consequential bodies/operations still work. Or if it crashes, one can spend time on trying to repair the crashing steps (like remap etc).
Making it black and white from a user perspective, parametric just means that if you put in 10 mm length, in order to make it 20 mm, you don't have to start a new model from scratch, you can change 10 to 20 and be done with it (well assuming that it does not crash, which btw all 3d modellers do - there is always a way to make a model crash - no matter how much money you spend on your software - might be that it tries to hide the crash with suggestions of what to repair - but the underlying crash is still there).
Regardless of these limitations cad as it works today is really useful for the purpose it is intended.
At last, you would probably be surprised if you really knew how much remodelling from scratch that is going on out there (including industry), it can be as simple as someone created a topology which others just don't understand, or you thought that one dimension was the one going to be change, but it turns out that the dimension that needs to be changed is somewhere else, or a version update makes features unusable, change of file formats corrupts models etc, you name it, it's all out there (of different degrees).
If you are in a corner, it is often just better to scrap the old and remake it for better "edit-ability", which has the benefit that you are probably going to make a more fit for purpose model the 2nd time around.... 3d cad modelling is really a skill and something that takes practice, as well as upfront knowledge of how one wants to modify in the future (if one wants to modify at all).
Just an opinion in the ether.
Is this an adequate exaggeration of your question?
I made a parametric car on 4 wheels, an electric one (of the typical shape of a regular car).
Can I parametrically change that to become a jet fighter, 3 wheels and 2 jet engines.
Maybe, but no, not really in any cad software no matter how much money you spend on it.
Well, you could cheat, and call your top assembly "anything" and have a drop down that is car/jetfigher and replace the assembly "parametric".
After all computers are quite simplistic in their ways of working - when it comes to rendering everything is about polygons (i.e. triangles with 3 points to describe an outer shape, so it´s really just a point cloud with a skin). Points are easy to change (and is not so resource demanding mathematically), which is why all 3d rendering programs works with meshes, where one can morph the point cloud to change shapes as one example. But what happens if you need more points? Or start to collapse surfaces so that they disappear and are no longer needed?
That is really the dilemma here in changing shapes drastically. If you are looking for morphing things, then you should use blender instead of fc.
Cad is generally created to support the "boring" area of manufacturing, and has evolved for those needs.
Those needs are to describe boundaries of bodies, being able to dimension them, assemble into multi component products, run simulations etc.
The approach in cad is to create mathematical descriptions of boundaries, like a box, or a sphere in the simplest cases. With sweep you drag a line along another line to create a mathematically described surface.
So you cannot by will power just change a mathematically build up boundary or the "features" you have used to make it. You have to change it in a way which still preserves the mathematical solvability. Sure one can replace a box with a pyramid, if all consequential bodies/operations still work. Or if it crashes, one can spend time on trying to repair the crashing steps (like remap etc).
Making it black and white from a user perspective, parametric just means that if you put in 10 mm length, in order to make it 20 mm, you don't have to start a new model from scratch, you can change 10 to 20 and be done with it (well assuming that it does not crash, which btw all 3d modellers do - there is always a way to make a model crash - no matter how much money you spend on your software - might be that it tries to hide the crash with suggestions of what to repair - but the underlying crash is still there).
Regardless of these limitations cad as it works today is really useful for the purpose it is intended.
At last, you would probably be surprised if you really knew how much remodelling from scratch that is going on out there (including industry), it can be as simple as someone created a topology which others just don't understand, or you thought that one dimension was the one going to be change, but it turns out that the dimension that needs to be changed is somewhere else, or a version update makes features unusable, change of file formats corrupts models etc, you name it, it's all out there (of different degrees).
If you are in a corner, it is often just better to scrap the old and remake it for better "edit-ability", which has the benefit that you are probably going to make a more fit for purpose model the 2nd time around.... 3d cad modelling is really a skill and something that takes practice, as well as upfront knowledge of how one wants to modify in the future (if one wants to modify at all).
Re: fundamental
Using Part workbench means primarily that you can later change the parameters of the objects involved. Change dimensions, turn them, move them. But it doesn't mean to change the structure.
There are nevertheless possibilities to change the structure as well, but you should be familiar with the basics before. OpenSCAD workbench provides possibilities to exchange objects nested in a tree, or to remove complete subtrees. Fusion provides a Shape property which you can change. Cut provides Base and Tool properties to change the main part and what is subtracted.
PartDesign offers more flexibility for changing, but you have to be very careful to build a robust model. Have a look at this page, especially the paragraph about creating stable models.
There are nevertheless possibilities to change the structure as well, but you should be familiar with the basics before. OpenSCAD workbench provides possibilities to exchange objects nested in a tree, or to remove complete subtrees. Fusion provides a Shape property which you can change. Cut provides Base and Tool properties to change the main part and what is subtracted.
PartDesign offers more flexibility for changing, but you have to be very careful to build a robust model. Have a look at this page, especially the paragraph about creating stable models.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
Re: fundamental
The heading for this forum is indeed open discussion, there are questions here, but they are generally not help questions.
Despite having used FC for over 5 years I cannot find a WB called "part menu".
You keep asking if my models work "perfectly," the answer to that is, most of the time a resounding YES.
I say most of the time because the software has it's limitations, and variously I have mine.
Instead of alluding to problems, why don't you head over to the Help forum and ask a bold, direct question, don't forget to include a file or screenshot or some-such that clarifies your problem.
Despite having used FC for over 5 years I cannot find a WB called "part menu".
You keep asking if my models work "perfectly," the answer to that is, most of the time a resounding YES.
I say most of the time because the software has it's limitations, and variously I have mine.
Instead of alluding to problems, why don't you head over to the Help forum and ask a bold, direct question, don't forget to include a file or screenshot or some-such that clarifies your problem.
Re: fundamental
Hopefully the image gives an idea. One of the corrections is to move the fan holes.There is a fan fixing towards back rhs corner in base. I can't undo that, so added a 'patch'. I redrew new fan vents, shown bottom left, they need to be rotated 90 deg wrt x axis, and subtracted from front vertical face. If I do that, the 'fan' disappears, and no holes in the front face. the triangular strip below the box, I can't remove that (but meshlab can in the stl.) I can move the four mounting studs, but the old ones remain in position.
Simpler stuff, no problem, but as it evolves into the lengthy tree of booleans, I lose any concept of what does what. Highlighting the part I'm interested in, does not necessarily show it in the tree. It needs to be more magical. Naming the parts, sometimes the name appears after the item, e.g. cube angle trim 1' other times it overwrites cube, gives 'angle trim 1', which then leaves me trying to get a name for when I do the subtract to actually trim the angle. It's also a lot of jumping around the tree, keyboard and mouse. I've got one pasrt, or it maybe two, with the same name. I can't delete one, both go.
I think all the parts are listed in the tree, I wonder if i can delete all the booleans and start again by recombining the bits. An alternative is just print it as is, and machine the new fan holes, etc. But that sort of defeats the object o9r paranetric design. It is, apart from the new vertical fan, a 2.5 d shape, more or less, so maybe i should have started with sketches and padding. Am I complaining too much...
If I start again, how do I not get into the same mess wrt dozens of booleans, etc.
Simpler stuff, no problem, but as it evolves into the lengthy tree of booleans, I lose any concept of what does what. Highlighting the part I'm interested in, does not necessarily show it in the tree. It needs to be more magical. Naming the parts, sometimes the name appears after the item, e.g. cube angle trim 1' other times it overwrites cube, gives 'angle trim 1', which then leaves me trying to get a name for when I do the subtract to actually trim the angle. It's also a lot of jumping around the tree, keyboard and mouse. I've got one pasrt, or it maybe two, with the same name. I can't delete one, both go.
I think all the parts are listed in the tree, I wonder if i can delete all the booleans and start again by recombining the bits. An alternative is just print it as is, and machine the new fan holes, etc. But that sort of defeats the object o9r paranetric design. It is, apart from the new vertical fan, a 2.5 d shape, more or less, so maybe i should have started with sketches and padding. Am I complaining too much...
If I start again, how do I not get into the same mess wrt dozens of booleans, etc.
- Attachments
-
- case.jpg (356.43 KiB) Viewed 590 times
Re: fundamental
Moved to Help forum.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.