Constraints/Dimensions or No Constraints/Dimensions in 3D Modeling

Jasonb said:

So Pat I can't see why you say DON'T use constraints and dimensions when they make managing your sketches so much more predictable. I suspect you are actually using constraints and dimensions but don't know it.

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This is entirely possible.
I am a self-taught Solidworks user, and so like a blind man walking down the street, it may look like he can see perfectly well since he is walking straight down the sidewalk, but when in actuality he is tapping his way along, feeling as he goes.

I am not aware of any 3D modeling engine design classes that one can take, so I make it up as I go.
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Check your local library. They may provide access to digital learning services that contains e-training videos on all kinds of software. Out of all the stupid things my property taxes are wasted on, this is the one good deal because I recall it was 300-400 USD? I use mine extensively & have benefitted a lot. My library card cost $10 back in the day & they are subscribed to LinkedIn Learning (formerly Lynda.com) so I just access through library portal. I have some friends who use it for Fusion. All kinds of software, Adobe, Microsoft... just have a look. There are other e-training sites too, its getting to be a competitive business for people wanting to upgrade & remote working thanks to pandemic or whatever. My employer came to similar realization. It was cheaper to pay for a company membership & allow employees to choose from hundreds of titles at their own pace & time vs in-house or paid courses. For software, personally I find videos the best way to absorb because its a collection of menus & screen interaction. Textbooks are kind of dry & they cost money too. Unfortunately software that is less well known (typically in industry) is less supported in this way, which doesn't help matters learning something new. I guess from that perspective I personally would rather have a hobby/community/cloud (choose your buzzword) version of more established software purely for the associated training content. But its a personal choice & everyone has a different perspective.

https://www.linkedin.com/learning/courses

I am in the "JasonB" school of 3Dology.

At this point, I have probably learned more about 3D from JasonB than anyone.

Edit: And that goes for engine design too; JasonB has it going on for sure.

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Jasonb said:

So Pat I can't see why you say DON'T use constraints and dimensions when they make managing your sketches so much more predictable. I suspect you are actually using constraints and dimensions but don't know it.

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Great video, and great explanation.

The answer is simple, I don't use constraints and dimensions because most of my sketch work is done in AutoCad, and then imported into Solidworks.

I have used AutoCad for 30 year, and have the keyboard programmed so that I use the mouse and the left hand, at the same time.
So I can literally fly in AutoCad, and I have to be extremely efficient, since I do all of my own engineering drawings for work.
My sketch speed in Solidworks is perhaps 1/10th fo the speed in AutoCad, if that much.
I could never earn a living using Solidworks, but I actually do earn a living using AutoCad.

My engine design is a pretty free-lance approach, but I don't pick random sizes typically, but rather try to match the exact dimensions of a real engine, or at least meet the design intent of the real engine.

At this point, I don't have the time to stop and learn the functionality of sketching in Solidworks, but I can see the advantages of using all of the features available in the 3D modeling program, especially with regards to sketching.

And I guess one reason I don't spend any time working out contraints, dimensions, etc. is that very often, when I start sketching out a part, I really don't know what method will work, and I don't know what approach is best.
So I just try something, and sometimes I have to discard the part and start over, so all that dimensioning and constraining was totally wasted time.

Generally speaking, I don't know a good method for modeling some random part until I actually create a 3D model for it, and then look back and say "How could I have made this model easier/better/more accurate?".
Hindsight is often 20/20.
Forward sight is often looking at a fog bank. Which way do I go?

Edit:
Another consideration is how often you change your sketches.
I work out the basic engine geometry in AutoCad, and so by the time I import the sketches into Solidworks, the design is final, and I seldom have to modify a sketch in Solidworks.
Sometimes if I have to modify a complex sketch in Solidworks, I just modify it in AutoCad, and then import it into Solidworks again, writing over the sketch in Solidworks (or actually deleting the sketch in Solidworks, and pasting in the revised sketch, maintaining the same origin point).

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But you are constraining and dimensioning the part you produce in Autocad you have said yourself you enter a radius or use the rectangle tool etc.

Just because it's then imported into Solid works does not stop the original sketch being constrained and dimensioned elsewhere.

What you describe is a bit like me producing a 3D part in Alibre all dimensioned and constrained and then importing it into F360 for CAM. I don't add any more constraints or dimensions as they were all entered in Alibre.

I think it is a matter of terminology, and the terminology in 3D modeling is very confusing for me, and confusing for others too I think.

3D modeling is a database.

If I draw a line on a sketch in a 3D modeling program, the program creates a set of data for that line, which is start point, end point, length, and angle.
Also perhaps color.

If I add a dimension to that line in 2D Autocad, that dimension is for display only, and no data in the database for that line changes just because I added a dimension to it.

If I add a dimension in the 3D modeling program, I can "drive" the line database using the dimension as an input tool.
The dimension can define and dynamically control the line.
I can delete the dimension, and not change the line's database if I have not used the dimension "drive" function.

There is no need to fully constrain anything in 3D modeling unless you do something that requires a fully constrained sketch.
I have never constrained anything in 3D, as far as doing any additional steps after importing a sketch from Autocad.
You may want to fully constrain a sketch in 3D, but I am living proof that you can also totally ignore constraints as far as adding extras to an initial sketch.

Jasonb said:

Just because it's then imported into Solid works does not stop the original sketch being constrained and dimensioned elsewhere.

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I think you have to think of it in a database format, as I mention above.

Think of it as a spreadsheet.
You can think of the sketches I do in Autocad as just some dumb valve like "A" that has been typed into a spreadsheet cell.
"A" does not do anything, and is not linked to any other cell in the spreadsheet.
I can copy or move "A's" around in other cells, and it does not affect anything.
"A" is just a dumb valve with no links or formulas.

If I type in the number 1, then I can start to program other cells, such as cell #2 equals two times what is in the first cell.

When you start adding driving dimensions and constraints in 3D modeling, you are basically programming the database to say "When I change this, these other things are linked so that things happen automatically".

So the analogy is that I use a spreadsheet with dumb input valves, with no formulas, no links, no programming of any type.
You can't say spreadsheets don't work unless you program all the cells; this is false.
You can just punch numbers and letters into spreadsheet cells, and it is all good; nothing is linked to anything.

I think we are talking circles because of terminology.

Talk about the initial data table created for each line or shape (creating a sketch).

Then talk about automating the optional connections between the various values in the data tables (adding constraints).

Then talk about adding optional driving dimensions to further constrain a sketch, and automate the sketch (like adding forumlas to a spreadsheet cell).

I use the dumb method.
It works very well, it is very simple, and since I design and draw (created sketches) very accurately in Autocad, it is a very fast method for 3D modeling for me.
I rough out the initial overall engine geometry in 2D Autocad before I start any 3D modeling.
I don't try to make things work in 3D modeling, I work out the geometry in 2D first, and then 3D modeling is just a visual representation of the 2D geometry.

If you can get value-added function from using additional constraints, driven dimensions, etc., more power to you, but that slows me down a lot.

In spreadsheets, I get very sophisticated, and use look-up tables, extensive Visual Basic programming, popup dialog boxes; you name it.

How sophisticated I get with any given program depends on what I am trying to do, and what is the fastest and most efficient way for me to do it.

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Pat it is because you don't start your 3D models in a 3D CAD program that you are doing it differently to 99% of people and think you are not using constraints

Most would do the sketching in their 3D program with constraints and dimensions and then extrude that sketch. You import an Autocad sketch that has been constrained and dimensioned and then just extrude that.

Typical example as both Pete and I have tried to explain. You say you use the rectangle tool in Autocad. simply by doing so you constrain the corners to be at 90deg, opposite sides equal length, opposite sides parallel.

So you are constraining a sketch in Autocad and then imported that constrained sketch into SW as SW can't alter that sketch all constraints will be there.

You say you input values into your spreadsheet analogy. Those numbers are dimensions or positions(constraints)

I think your unusual method is not the best to recommend to new users with sweeping statements of "You do not need constraints and dimensions"

petertha said:

Check your local library. They may provide access to digital learning services that contains e-training videos on all kinds of software. Out of all the stupid things my property taxes are wasted on, this is the one good deal because I recall it was 300-400 USD? I use mine extensively & have benefitted a lot. My library card cost $10 back in the day & they are subscribed to LinkedIn Learning (formerly Lynda.com) so I just access through library portal. I have some friends who use it for Fusion. All kinds of software, Adobe, Microsoft... just have a look. There are other e-training sites too, its getting to be a competitive business for people wanting to upgrade & remote working thanks to pandemic or whatever. My employer came to similar realization. It was cheaper to pay for a company membership & allow employees to choose from hundreds of titles at their own pace & time vs in-house or paid courses. For software, personally I find videos the best way to absorb because its a collection of menus & screen interaction. Textbooks are kind of dry & they cost money too. Unfortunately software that is less well known (typically in industry) is less supported in this way, which doesn't help matters learning something new. I guess from that perspective I personally would rather have a hobby/community/cloud (choose your buzzword) version of more established software purely for the associated training content. But its a personal choice & everyone has a different perspective.

https://www.linkedin.com/learning/courses

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Hmmmmmmm - - - interesting - - - - - I find that I can't stand videos - - - - find they are a tremendous amount of waste time.
Webinars - - - - - most of them remind me of some of the poor profs that I had a few of at uni - - - - - took forever to get anything done.
Most of the hour long webinars could have been placed into about 4 pages of text and a few pages of graphs or pics or other visual aids.
Then I can get through those pages of text quickly - - - - with the webinar - - - - I've got to sit there for the whole bleeping time while the presenter farts around all too often trying to 'sound impressive' (and failing too much of the time).

We all have our own learning styles. Google CAD text books & compare the price to digital subscriptions. Another factor is software version numbers. If the platform is stable older texts may be applicable for learning or general principles, often times not.

The distinction I'm trying to make is that a CAD course is intended for a target audience, CAD users. Typically companies or individual will pay for them out of pocket to become competent or certified. So if its substandard quality, the ratings will reflect this & they wont sell. So there is a vested interest in delivering something decent. Substandard can be any combination of poorly organized, non-progressive levels, poor choice of example / exercise files (typically downloadable), bad audio / speech.... Even among the good courses some are better than others.

Now if you want to see some prime steaming garbage, just hop on YouTube. Yes its free & there are some good ones too, but you will consume time sorting the gold from the gravel. I've noticed some of what I consider good ones are basically gateway/teaser videos (show 5 titles of what might be a 200 title offering). The problem with many of the Mom's Basement operators is often they don't know what they are doing to begin with, so you are picking up bad habits thinking you are learning. And subscriber count & view hits metrics & hop over to my Patreon.... sometimes sway them with unrelated filler content.

Like any new skill, knowledge absorption is a 2 way connection between student & instructor. I'm just pointing out another potential resource to explore for those who may not be aware. If you don't like it or prefer something else, that's fine, each to their own.

Jasonb said:

I think your unusual method is not the best to recommend to new users with sweeping statements of "You do not need constraints and dimensions"

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Jason-
I have created plenty of sketches in Solidworks, and I have never dimensioned any of them, and this has not caused problems.
So I hear people say "You must dimension every sketch" as an absolute statement, else the program will not work, and this is just patently false.

Obvsiously things will have some sort of constraint on then, whether done automatically or manually.

I also hear over and over again "Your sketch must be fully defined, else the program will not work", and again this is a patently false statement.
I never fully define anything in Soldidworks.

So while you can recommend that folks dimension every sketch, and fully define every sketch, and while this may be good practice, to say that this is an absolute necessity is misleading and outright false.

I don't have a dog in this hunt, but lets be clear; the facts are the facts.

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I've not said "So while you can recommend that folks dimension every sketch, and fully define every sketch" but it is almost impossible to produce a sketch and then extrude that to form a 3D shape without any constraints or dimensions.

You started off by saying you never constrain or dimension and then you have since said you do enter lengths and radii etc and that you use things like arectangle tool or snap to an axis which are constraining things.

How did those plans for your Green twin end up with the dimensions that are on them if not entered at the sketching or extrusion stage? If you did not dimension them how does Solidworks know the diameters and lengths



Part of the reason you may not be doing it in soliworks is because a lot of your sketching is in autocad where again YOU ARE constraining and dimensioning.

Lets take that rectangular cover I did in the video how would you do that in Solidworks, the cover is 30mm x 40mm x 3mm thick 1.25" x 1.5" x 1/8 if you prefer. holes 3mm and 3mm in from corners

Pat you just seem to keep contradicting yourself, you have just siad

"I have created plenty of sketches in Solidworks, and I have never dimensioned any of them"

Yet in the second post in this thread you said

"Lets assume I am sketching in Solidworks:

I pick a plane, either Front, Side, or Top.
Draw a circle on that plane.
Whenever possible, I put the origin of the circle, or at least the origin of the part at the X,Y,Z intersection.

There is a window on the left side of SW, and when you draw a circle, the window will show the circle origin, the circle radius, and some other info.
You can manipulate any of the circle info in the window, but I only change the radius to my desired dimension."

And again

"For a shaft, again draw a circle, and edit the radius in the box on the left.
Extrude the shaft out to some dimension, again controlled by what you type in the box."

And here

"The idea behind the papertrail is to help me remember how I got from the beginning of the model to the end, and also to capture dimensions in the dialog box on the left of the screen, so I can quickly see what dimension I used for any sketch."


Either you are entering dimensions or you are not

Just using ACAD to create the "3D sketches" (If I understand it correctly) & importing them into the 3D CAD program seems very counterproductive & I really don't understand why you would do that. Usually, the sketching tools in the 3D program are quite adequate at creating any sketched feature, dimensions, & constraints.

John

Jasonb said:

How did those plans for your Green twin end up with the dimensions that are on them if not entered at the sketching or extrusion stage? If you did not dimension them how does Solidworks know the diameters and lengths

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The dimensions were added when the 2D drawings were created, not when the models were created.
The dimensions added in 2D are also completely optional, and not necessary, and you can delete them without changing the 2D drawing.

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Jasonb said:

I've not said "So while you can recommend that folks dimension every sketch, and fully define every sketch" but it is almost impossible to produce a sketch and then extrude that to form a 3D shape without any constraints or dimensions.

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Perhaps not, but I have heard that over and over online, and it keeps getting repeated as an absolute dogma, but it is false.

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Jasonb said:

Pat you just seem to keep contradicting yourself, you have just siad

"I have created plenty of sketches in Solidworks, and I have never dimensioned any of them"

Yet in the second post in this thread you said

"Lets assume I am sketching in Solidworks:

I pick a plane, either Front, Side, or Top.
Draw a circle on that plane.
Whenever possible, I put the origin of the circle, or at least the origin of the part at the X,Y,Z intersection.

There is a window on the left side of SW, and when you draw a circle, the window will show the circle origin, the circle radius, and some other info.
You can manipulate any of the circle info in the window, but I only change the radius to my desired dimension."

And again

"For a shaft, again draw a circle, and edit the radius in the box on the left.
Extrude the shaft out to some dimension, again controlled by what you type in the box."

And here

"The idea behind the papertrail is to help me remember how I got from the beginning of the model to the end, and also to capture dimensions in the dialog box on the left of the screen, so I can quickly see what dimension I used for any sketch."


Either you are entering dimensions or you are not

Click to expand...

I think you are confusing defining the radius of a circle in a dialog box with the additional step of picking the "dimension" button and using several more mouse clicks adding the dimension to the sketch, after you have defined the radius in the dialog box.

The extra steps and mouse clicks required to use the "dimension" feature are not required.
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johnmcc69 said:

Just using ACAD to create the "3D sketches" (If I understand it correctly) & importing them into the 3D CAD program seems very counterproductive & I really don't understand why you would do that. Usually, the sketching tools in the 3D program are quite adequate at creating any sketched feature, dimensions, & constraints.

John

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I can only state why this works for me.
It works well for me because I find the sketch tools in 3D programs to be very slow, inefficient, and totally inadequate for what I do, and how I do it.

The sketching tools that come with 3D programs are quite adequate for most folks.
I am not "most folks".
And I can speak from 10 years of using this method (sketching in Autocad and importing to Solidworks) to make a lot of complicated models, so I am not just speculating, but rather speaking from experience.

Everyone should use the method that turns them on, and the method that works for them best, and stop worrying about whether someone else's method is different, or if that method conforms to the norms, or is or is not "like everybody else is doing it".

There are many ways to do everything.
Let the users decide what works best for them.
Tell them all the options, and let them decide.
I don't see the downside to this.
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The other thing I just picked up looking back through Pat's posts is that he takes a series of screen captures so he can go back and look up what dimensions were used on a sketch, this again is very unconventional and counterproductive as you would have to flick between the 3D CAD and the images. and in Pats case Autocad as well

Alibre and I'm sure Solid works has a much better way of doing it simply display the entered dimensions with the sketch, one image below has the dimensions toggled on the other off. So easy to see what dimensions were used when they are toggled on.

GreenTwin said:

I think you are confusing defining the radius of a circle in a dialog box with the additional step of picking the "dimension" button and using several more mouse clicks adding the dimension to the sketch, after you have defined the radius in the dialog box.

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In that case it must be a Solidworks thing, or your admittedly muddled understanding. Maybe one of the other Solidworks users could tell me what is different between entering the diameter of a circle as it's sketched or entering the length a sketch is extruded to using the "dimension button"

Jasonb said:

In that case it must be a Solidworks thing, or your admittedly muddled understanding. Maybe one of the other Solidworks users could tell me what is different between entering the diameter of a circle as it's sketched or entering the length a sketch is extruded to using the "dimension button"

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In Solidworks, you can toggle on and off "auto-dimension" I think, but check me on that.
I never use auto-dimension, because I don't want to enable driven dimensions.

It is critical for users to understand the difference between driven dimensions and non-driven dimensions.

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