Just curious, how would you constrain this and why.
Would you select the edge of the Boss or use Convert Entities first and constrain to that result?
Or would you draw a construction line that is co-linear with the edge and constrain tot hat?
Is it possible to constrain the sketch line to the face rather than the edge?
Sorry if this seems very trivial to you.
I'm trying to get back to basics and understand which approach is most stable.
The best approach is constrain to the edge. Convert entities or the construction line method is just an extra unnecessary step that would be relying on the edge anyway. Best to use the existing geometry instead of repeating yourself. You can't dimension to the face.
Hope this helps
Martin
In 2D sketching you cannot dimension to a 3D entity, but if you are sketching in 3D you can dimensions to a planar face or plane
True ☺️ I had just assumed it was a 2D sketch. But yeah you could dim to the face in 3D. It all depends on your design intent. If you planned on adding a draft to the face then I would still stick with the edge. But I wouldn't add extra unnecessary entities to constrain to.
Personal Account:
.... understand which approach is most stable.
Most stable.
Dimension to the origin.
BORN Technique - Base Orphan Reference Node Technique.
As much as possible create all sketches on origin planes and dimension to the origin or origin planes.
On most of my parts (even fairly complex parts) you could delete all of the solid or surface geometry and still have all (or most) of the information needed to create the part. That is about as basic as it gets.
I disagree with this. I would actually prioritise design intent over stability in this case. If the boss was designed so that whatever mounts to it was always 5mm from the left edge, then it should be dimensioned to that edge as opposed to the origin. So that if the base plate was increased in size for whatever reason, the boss and thus the mounted component would still be positionally correct from the assembly level. If the position of the boss is relevant only to the origin, then by all means dimension it to the origin. This is the whole purpose of parametric modelling.
Modelling to design intent saves manual labour in design checking. I don't like inter-part links due to stability issues and unintended consequences of changes, but for a plate with a boss, I think dimensioning to geometry is fine.
Assuming you want the edges collinear I would just use the convert entities command where it would apply.
I thought about that too.
But it just seemed like an extra step that didn't add any value.
why would you use convert entities over simply constraining to the edge?
This touches on something else I was wondering about.
Would using a 3D sketch and selecting the face be a more stable method?
Earl on, it was drilled into me that sketches are more stable than faces and faces are more stable than edges and edges are more stable that derived edges....and on an on..........
I think you can see why I'm regularly looking to constrain to a face.
So, would using a 3D sketch and selecting the face be a more stable method?
I see what you're referring to J.
I've used something similar in the past. (Delphi's parallel modeling technique)
I create a secondary plane from a primary plane where that secondary plane is co-planar with the face of the box i want to constrain to.
I then constrain to that plane instead of the box.
I've done this on models where i want strict control of the update cycle and I know i'll be swapping out geometry that was created early on in the tree.
...and it allows me to keep design intent.
But, its a lot of extra work; so, i don't use it unless I know i'm really early on in the design phase of a component I know will see a lot of changes.
As others have touched upon, it comes down to design intent. How does the feature that the sketch will create relate to the base feature? It's the answer to that question that will determine how you should constrain the sketch.
I, too, disagree with J. Mather. Design intent overrules stability. While I do make every effort to keep a part symmetrical about the origin, I'll forego symmetry for intent.
Personal Account:
why would you use convert entities over simply constraining to the edge?
I of course can't speak for him, but I believe Bernie was referring to placing a sketch line collinear to an edge and dimensioning to it instead of to the edge itself. If you're going to use that method, then it's probably easier to convert entities than to place a sketch line and make it collinear. I'd personally just dimension to the edge itself instead of creating another line segment with either method, assuming that I would want the dimension to remain constant in relation to the edge in case of future edits.
Personal Account:
This touches on something else I was wondering about.
Would using a 3D sketch and selecting the face be a more stable method?
Earl on, it was drilled into me that sketches are more stable than faces and faces are more stable than edges and edges are more stable that derived edges....and on an on..........
I think you can see why I'm regularly looking to constrain to a face.
So, would using a 3D sketch and selecting the face be a more stable method?
I wouldn't even consider using a 3d sketch in this situation. They are notoriously finicky, and while they're a great feature to use if you need one, I avoid them otherwise. Even to the point of having two or three 2d sketches instead of one 3d sketch.
Really depends on the design intent and if you're copying an existing design or your doing a brand new product, to me that is what makes this question go both ways, there are guys that copy designs and guys that create the next new widgit.
Here is my rule of thumb;
1. Copying an existing design; then what you did above is perfectly fine, providing it is the base plate and all that changes is the dimensions, w x d x h
2. Brand new product; this is where I agree with J Mather 100% - because the inventor or designer may want the base plate oval or round, now what, I think you know what will happen, all dimensions, all sketches and features tied to the base will be screwed up. I do a fair share of "Brand New" products/designs here, that are brought to us by outside designers and in most cases have no concept of the manufacturing process, so if I were to start a project like Personal posted, a lot of times I would have been screwed.. My best success has been using the Skeleton Sketch Part and each part is tied to a sketch within the Skeleton Sketch, so if I have to change from square to round the issues down stream are much easier to handle and change..
So everyone is right in their own world, and again it's design intent guys.....
A little portfolio of the New Designs that were done in the last year;
http://keystonecollections.com/products/new
I know it's not machinery or cars etc... but the start of the design is just as critical
The scenerio pictured looks like constrain to edge would work best. I have gotten away from using convert as much as possible except for reverse calculations. That being said if I was building for most stable design immune to design changes I would create a layout sketch, create the boss sketch based on the layout sketch and constrain to the layout. I think this is considered "top-down." Overkill, but I have made some models using this technique when designing from concept to print simultaneously.
Edit: John beat me to it
Convert Entities automatically Constrains. Offset entities also implies a Constraint. Why not let the automation built into SW work for you and eliminate steps.
I guess i'm wonder "Why convert at all?"
If there is no convert entities command, there is no need to make two elements co-linear.
"They are notoriously finicky"
Now that is interesting.
This is the first I hear of this.
Why do they fail?
Is it that the 3D sketch method isn't written correctly?
Or is it that the user might tend to be a bit sloppy in element selection when using 3D sketches?
(I've experienced creating rats nests of links when using more advanced functionality - but, that was poor practice on my part.)
Personal Account:
Why do they fail?
Is it that the 3D sketch method isn't written correctly?
Or is it that the user might tend to be a bit sloppy in element selection when using 3D sketches?
(I've experienced creating rats nests of links when using more advanced functionality - but, that was poor practice on my part.)
It's not that they fail. They're just more difficult and slower to work with. I seem to have more problems with unintended relations, and applying relations that I do want.
When doing a 3D sketch there is a lot more involved for me, only because I try to cram everything in too few sketches. To keep the proper perspective in 3D sketches it is good practice to make a temporary 3D model, that way you can get the proper orientation and perspective.
I agree with Glenn - I also don't think the 3D sketches fail, it just takes more planning and a complete different approach from 2D sketches
John Stoltzfus:
"I agree with Glenn - I also don't think the 3D sketches fail, it just takes more planning and a complete different approach from 2D sketches"
Here is one of my failed 3d sketches. Don't ask me what happened......
Granted, this was relatively complex geometry, creating a 3d sketch at the intersection of two bodies, but did it really have to go through all this?
Sorry Mike - but I couldn't stop laughing right away, looks like the Sun is still shining on your end.. But I'm sure it was doubly frustrating......
I see we have reached the design intent vs. stability discussion. Good one. I've come across models that should be a 5 second change, but end up being a couple hour change, since stability sucked. Then I've come across models that should be a 5 second change, but became a couple hour change, since I couldn't figure out what changed what, so sort of design intent.
Design intent, is good if it is for the part, but awesome if stable too. Stability, wish we did not have to model for this one... Good thing I do simple blocky parts 90% of the time. Would need more coffee.
Mark you can learn a lot if you work with people that are continuously tweeking and expect a simple change to take 5 minutes - However the good news is design intent and more coffee..........
Laughter was certainly not my initial reaction........
All hail Ctrl+Z, has gotten me out of a few of those
The best approach is constrain to the edge. Convert entities or the construction line method is just an extra unnecessary step that would be relying on the edge anyway. Best to use the existing geometry instead of repeating yourself. You can't dimension to the face.
Hope this helps
Martin