Resize a STL File For Me

[CatalinaWOW]

That is fine if you stop there.  But now imagine that you want to add cleats to the U.  By just padding a rectangle and merging it with the U.  Now the faces are different and it might make the reference go away.  But a different set of follow up operations would foul up a sketch tied to the base plane.


Again, I am a fumbler, not an expert, but the only way I see to know which way to go is to plan out the entire model, understanding all the pitfalls and decide then how to start.  Recognizing that if you change your plan in the middle you might need to go back and start over.  I am not proficient enough to do this so I do a lot of messing around a finding out, with quit a few dead ends and a few mysteries that have never been solved.

[MarkF]

There is no right or wrong here.

What you did is a correct thing to do.  What we are pointing out is that if, after the fact, you want to go back to an earlier step and make some change.  That change may break what you did in referencing the face.  There are ways to mitigate the risk of breaking the model while doing a modification.

You can reference one of the XYZ planes instead of a face.  However, this also has risks of breaking when editing older steps.

Only experience will determine which is best in any one situation.
Later, you will discover you can create custom reference planes in addition to the XYZ planes.

[bostonman]

I fully agree more than one way exists to do something; not just with 3D modeling.

Hopefully I wasn't coming off as asking for the 1-2-3 step process. Obviously the way I approached this design worked and various ways to create this exist. When the design "broke", I was unable to understand the reason(s) why and that was the more frustrating part.

I can always delete everything and return to just a single 'sketch', but I always look at such problems knowing a time will come when something is more complex, greater precision is needed, etc... and question the correct way to do it now before I'm confronted with such issues.

[MarkF]

I didn't think you were asking for a 1-2-3 step process.
And, I still don't know why your design broke.  Mostly, just guesses.

We're just pointing some of the pitfalls we have run across in our own designs and alternatives that may help you in the future.  I most cases it doesn't matter how you do the design.  The trouble starts raising its ugly head when you need to tweak the model.  Over simplified examples are your knobs and adjusting the dimensions of the hole for the D-shaft to correct for tolerances in the encoder and your 3D printer.  It's much easier to break a model if you need to add a hole or change a shape.

[bostonman]

It's nice to know that my confusion isn't just me.

I'll tinker with it more just for fun, but think the fillets is what added a layer of complexity and why things break when I tweak. I thought my foundation was enough to build on, but, after watching some of those FreeCAD videos, I learned lots exist I never imagined.

It's a comforting feeling though knowing something can be created and printed which makes 3D modeling so much fun.

[MarkF]

I was just sharing some new 3D designs for my model railroad.
Thought you might enjoy some more complex FreeCAD model examples:
(All the walls, roof, and furniture are their own 'body' in FreeCAD.)
   https://www.eevblog.com/forum/chat/model-trains/msg5697955/#msg5697955

[bostonman]

Wow, those are some great designs. Maybe you know FreeCAD better than you think.

[bostonman]

I have another design that went off into left field.

Attached is something I made for a project. The larger square began as 3.55" and the width of the two forks were 1.5" along with two ovals on the sides with pockets.

I wanted to increase the square to 3.6" and decrease the width of the forks to 1.4". After about three-hours of trying to accomplish this due to constraints getting in the way, I was successful, but realized one of the ovals went off into left field.

After I went back to the original design to tinker with the pockets. I discovered if I made pocket two 0" depth and pocket one "through", then it made pocket two a hole too.

My first question: why is pocket one affecting pocket two?

My other question: why did the oval go off into left field and how to get it back?

I thought trying to map it to a sketch would help or switching planes, but I don't understand what is going on.

As always, I'm trying to understand things rather than have it done for me.

[MarkF]

• In your "I'm More Lost" file you once again discovered what happens when you wipe-out a sketches reference.  I suspect FreeCAD changed the sketches name while you were making changes.  Sometimes it's easier to redraw a simple sketch rather than fixing its reference.  You can make this model by only referencing one of the axis planes.  I've attached an example.
  
  
• When making pockets, the sketch does NOT have to be on the surface.  It can be out in space as I demonstrated here.  Try changing the pocket to various distances instead of through all.  Also in your "I'm More Lost" file, you can see that your pocket is cutting into both forks.
  
  Review this video for "Understanding Pocket Types and Options"
  
  
  
• In both files, the sketch used for padding is not totally constrained.  Although this is okay to through something quickly together, it's a bad habit to get into.  It's also a possible source of things falling apart when later being edited.
  
  
• When constraining a sketch some things I noticed:  set opposite sides equal instead of their dimensions the same, set a line endpoint tangent to the axis instead of setting the distance to zero to attach a line to an axis.
  

[bostonman]

Sorry for the file naming. I was aggravated and named them out of being annoyed.

Am I suppose to select 'map sketch to a face' when I add something (in this case) an oval to make a pocket?

In the video you linked, he just clicked a face and selected 'create a sketch'. Maybe this is causing names/links to get renamed/break?

I never know how much to constrain. Usually I constrain lengths, I try making things equal so two sides move equally, etc... Eventually the design is full of so many constraints that I can't figure out which one is applied to which line(s).

Unless I haven't found it, I think being able to click on a constraint in either the constraint list or the image would help.

One minute I'm trying to change a line length and next minute fillets are giant reversed circles, some line changes length, a line goes off the main axis, etc...

[MarkF]

I couldn't care less what your filenames are.  They just give me a laugh.   

First, there should be a toolbar in sketcher with all the constraints listed.  It may be shrunk a little if all your toolbars are on the same line.  You can re-arrange them to suit.  If the toolbar is not there, go to View -> Toolbars and turn it on.



I tend to avoid mapping a sketch to a face unless it's needed.  It's has been the most likely way I've broken my models.  If you have something selected when you create a sketch, FreeCAD will use the selection as the reference plane.  Otherwise, it asks you which XYZ plane you wish to use.  I have a great deal of difficultly in fixing the reference plane after the fact.

I try to totally constrain my sketches.  Mostly starting with things vertical and horizontal edges.  Then constraining the lengths and diameters.  While dragging points, those large reversed circles and flip-flopping can be minimized by having more constrained prior to dragging a point.  You want to continue until FreeCAD tells you that there is zero DOF's left and the sketch turns green.

[CatalinaWOW]

I tend to use sketches for complex geometry, which means LOTS of constraints.  Naming the constraints can help in keeping track of them.  Also a large, high resolution screen so you you can see and separate them more easily. 

For simple shapes like ovals and circles I tend to use simple geometry from the Part Workbench.  I know many folk recommend not doing that, but it works for me.  As always you have to keep track of the geometry references.  The Body concept in Part Design handles much of this and is the reason that approach is recommended.  So far I haven't done complex stuff like multi-cylinder engines or submarines that really benefit from the recommended approach

[bostonman]

I couldn't care less what your filenames are.  They just give me a laugh.

Good to know, I'll keep up the good work. My PhD friend would name variables and such as 'dog', 'cat', etc... and I thought that was funny. Eventually I adopted it, so when I'm questioning a variable in something like an Excel spreadsheet, I'll use them.

The constraint list is visible on my screen. I do need to practice naming constraints as I go. Being able to click on a constraint and/or a line where it tells you the constraint number would help.

I'll also stop clicking 'map sketch to face' before adding a sketch. The concepts and planes I have an understanding of, but it's when FreeCAD (I assume no 3D modeling software comes without quirks) throws something off into left field, then I can't seem to connect my knowledge of X,Y, and Z planes, and what FreeCAD is torturing me with.

[MarkF]

The constraint list is visible on my screen. I do need to practice naming constraints as I go. Being able to click on a constraint and/or a line where it tells you the constraint number would help.

If I understand what you're saying, FreeCAD does do that.  All the constraints are listed in the 'Tasks' tab (mine is on the left bottom).  You can select one in the tab and it should get highlighted on the model.  The reverse is somewhat true also.  They are numbered at both places and you can delete one from both places.  I find it a little hard to select one on the model sometimes.

I have to check but I think some of them can be hidden.  Haven't really fleshed that out.

[bostonman]

I'll have to check again.

I thought when I click one in the 'tasks' tab, it doesn't highlight the line in the drawing.

All the constraints can be hidden at once by clicking the eye, and believe individual ones too.