45 Replies Latest reply on Nov 7, 2016 10:30 AM by Roland Schwarz

    Who Fixes Entire Assemblies, and Why?

    S. Casale

      Who Fixes Entire Assemblies, and Why?

      Why not mate the bad boy to be fully defined?

       

      This fixing sounds ridiculous to me, but I read of people doing this all the time. How can someone interrogate an assembly, and truly validate it if they can't verify that it can be put together? The only component in an assembly that ought to be fixed is the base/dominant component (I don't mean the first or initial component).

       

      The only benefit I see of fixing an entire assembly is saving file size, and when the assembly will never be modified again.

       

      What about Design Intent...............?

       

      I once had to rework an entire assembly that was fixed by the person I had replaced at another company I worked with. It was still a WIP. Less than half of the assembly would actually work, and what nearly killed me was a majority of sketch and feature geometry was made by but not linked to other components in the assembly. Parts were being ordered. Hole locations didn't line up, sizes wouldn't have fit, interference was a major problem. No one else noticed. I had this problem with almost everything this guy had touched. [/rant]

        • Re: Who Fixes Entire Assemblies, and Why?
          Jim Steinmeyer

          This sounds more recent that "once at a place I used to work at".

          On the other hand, I agree 110% to the point I usually remove the fix for the first part and mate it to the coordinate planes too.

          • Re: Who Fixes Entire Assemblies, and Why?
            Steve Calvert

            For some, I do Scott, after the design is finished and ready for release.  It speeds up large assemblies and their drawings.  I don't do it for everything, just the large assemblies where we have many subs.

             

            Steve C

            • Re: Who Fixes Entire Assemblies, and Why?
              John Stoltzfus

              S. Casale

               

              I didn't know you work here???    - You missed one item that I see here a lot with one of the old designers, edit the sketch and you don't see any.............any black line, the sketch isn't locked down at all - everything is Blue, with dimensions as an equation that is linked to a non-existent part, because is was saved over or just down right deleted.... Feel the pain

               

              The only reason I would fix the entire assembly is for the simple reason there was external references (equations, planes etc), that were deleted, or disconnected.  -  Having said that if you were to look at my top level models you would find most of my Sub-Assemblies show fixed because of my workflow.  I work in Zones (Sub-Assemblies), and I drag and drop the Sub-Assemblies into the main assembly, this creates a fixed state, if I need to insert more than one, then I would mate the subsequent inserted Sub-Assemblies.

               

              I want my assemblies to move.  Here if we're doing a new bed our starting size is Queen Size, then there are four more sizes that need to be detailed.  I pack & go the Queen for each size from there, replacing part numbers etc, so I edit one sketch which is referring the mattress size, change 2 dimensions, now the basic model has changed/adjusted every part to those new dimensions...

              • Re: Who Fixes Entire Assemblies, and Why?
                Alin Vargatu

                Simple. If you would use the Master Part workflow, the end result is an assembly with all the components fixed.

                 

                The positions of the components is determined by the position of the bodies in the master part.

                  • Re: Who Fixes Entire Assemblies, and Why?
                    S. Casale

                    Master part - same definition as I meant base/dominant component. I like your term better.

                     

                    IMO and when I check the only object to be fixed is that.

                    • Re: Who Fixes Entire Assemblies, and Why?
                      Daen Hendrickson

                      An example of Alin's Master Part workflow is with our aircraft simulator 360° visual displays.

                       

                      We work backwards by defining the surfaces the projected images will ultimately reside on, then the projection light paths (often bent about a mirror), to determine where in space the projectors must be. This information is contained in Master datum / skeleton part(s) that only contains reference geometry - no physical parts. This skeleton part is then referenced in multiple places: the several welded frameworks that physically position the projectors; the structures that make up the individual rear projection screens; the structures that make up the framework that mount those screens, structures to mount the mirrors, structures to mount the structures...

                       

                      When these major sub-assemblies are brought together, they are simply placed in the default location - for future clarity I will often replace the default "fix" with a coincident mate of the origins with axis aligned. I am not sure if there is a difference performance-wise. But in my mind it will help in understanding the intent with any future interrogations of the assembly.

                       

                      How do you qualify the assembly doing this? Since all of the joining parts reference a shared common datum / skeleton part they all  share a common interface. Does this mean we blindly move ahead without cross checks? Well, that would be foolhardy!

                       

                      The up side of the approach is the greatly improved performance in the upper level assemblies with thousands of components. And the greatly improved stability.

                       

                      This approach is not effective for everyone. Its merits and deficiencies are certainly a source of much debate. But this is an example of when "fixing" components is an intended approach in the workflow.

                       

                      All that said, fixing just because poor modeling wont let the assembly go together as intended is NOT a good practice. Except when the boss needs that sales screen shot of... "get 'er done".

                       

                      Daen

                        • Re: Who Fixes Entire Assemblies, and Why?
                          John Stoltzfus

                          Daen Hendrickson wrote:

                           

                          "When these major sub-assemblies are brought together, they are simply placed in the default location - for future clarity I will often replace the default "fix" with a coincident mate of the origins with axis aligned."

                           

                          I do this at the part level. First part in the Sub-Assembly feature tree is the Master Sketch Part, which is mated to the 3 Main Planes (not Fixed), and every new part is placed in the front plane of the Sub-Assembly. So the process is "Insert" new component and I save the part right away, SW asks for the Insert Plane, I always pick the Front Plane, which opens a sketch and before I draw anything I close the sketch and only then do I pick a plane where the part needs to be developed from...   -  For me it is more important in getting the lowest part in a proper place, then as you develop a higher level sub-assembly it becomes easier, set your foundation and then your tree becomes stable and sits on solid ground....

                            • Re: Who Fixes Entire Assemblies, and Why?
                              Daen Hendrickson

                              John Stoltzfus,

                               

                              Depending on the particular need, I use this even one level deeper. I will insert the datum / skeleton part as a part in part. This is usually the first item in my frame weldment parts. All the frame weldment parts contain the same inserted datum reference part.

                               

                              Our display geometry is a bit peculiar - very few nice angles. I will often add sketch points at the datum part level that will drive hole, bracket, and fastener patterns at part and assembly levels. "...and one ring to rule them all."

                               

                              One downside to this approach is that if you make changes at the datum level, you need to systematically open and force rebuild all the referencing components all the way up the hierarchy in ascending order... THAT can be tedious!

                               

                              Daen

                        • Re: Who Fixes Entire Assemblies, and Why?
                          Chris Saller

                          I don't fix anything unless for some reason it's needed. That's why the feature exists.

                          We have an engineer that will fully dimension and constrain sketches, then delete all of them and fix the sketches!

                          If he needs to change anything, he un-fixes them, adds dimensions, changes them, then removes/fixes again.

                          UGH!!

                          • Re: Who Fixes Entire Assemblies, and Why?
                            Paul Risley

                            As a practice: NO.

                            But like your rant about inheriting previous models from someone else, then yes I usually "fix" the whole assembly and start working on mates from there. As a rule I try not to fix anything as I agree with the philosophy it should be made so it can be made.

                            • Re: Who Fixes Entire Assemblies, and Why?
                              Wayne Schafer

                              We get a lot of solidwork files from a tooling vendor and there mating practices can be poor at best form time to time.  So if we make changes in house some times when we try to move parts in the assembly parts can be moving all over the place because of there poor mating habits.  So we will lock things down (fix) instead of going through the whole large assembly and try to mate parts properly.

                              • Re: Who Fixes Entire Assemblies, and Why?
                                Alin Vargatu

                                Scott Casale wrote:

                                 

                                The only benefit I see of fixing an entire assembly is saving file size, and when the assembly will never be modified again.

                                 

                                 

                                I do not think that fixing components will decrease the file size. Also, eliminating mates will decrease opening and rebuild times.

                                 

                                Also if the file comes from a customer or vendor, that is a "brick" to me. I would be very scared to add mates inside such an assembly, since I would not want to change their model.

                                • Re: Who Fixes Entire Assemblies, and Why?
                                  Deepak Gupta

                                  I have done several assemblies where parts were driven via master part/sketch. So all parts in the assembly were fixed as no mates were needed.

                                  • Re: Who Fixes Entire Assemblies, and Why?
                                    Roark Summerford

                                    Deepak Gupta is where I'm at on the topic. I have been known to work out master part/sketch to the point where if it's right the assembly will work. And I will generate a master "brick" assembly that all the prints and master part files are based upon.

                                     

                                    Having a moving assembly is mostly an executive luxury item as far as my world is concerned. If your design process is under control, there should be little need for a full moving assembly, and it appears solidworks architecture is based on that concept. 

                                     

                                    There are a few cases where I NEED to be able to move the assembly mechanism, but that rarely is going to be the full up detail design assembly... mostly ancillary experiment files to determine how to draw the master part/sketch.

                                     

                                    Last month I flew out to a customer to see the actual physical installation just to see it actually move for the first time. Needless to say the customers management was not privy to the true nature of my visit until dinner after the inspection.

                                    • Re: Who Fixes Entire Assemblies, and Why?
                                      Roland Schwarz

                                      Not everybody lives and works on such a tiny planet. There's an awfully big universe of design out there.

                                       

                                      Fixing components works well when doing in-place design. Who's doing in-place design? Nobody you know. Just small time players like GM, Ford, Apple Computer, Palm, HP, GoPro. (It's a small list. Only going by what I've seen with my own eyes.)

                                       

                                      As far as design intent goes, design intent rests with the designer. If this component goes "here", it bloody well goes HERE and stays HERE. Fix. Boom. Because I said so, that's why. I'm the designer.

                                       

                                      Maybe I was born with a superpower other CAD users don't have. I can unfix components and then move them (they call it "float" in my world). I can add constraints when it pleases me. I can even change or delete constraints. The CAD gods have truly blessed me!

                                      • Re: Who Fixes Entire Assemblies, and Why?
                                        Craig Schultz

                                        "I once had to rework an entire assembly that was fixed by the person I had replaced at another company I worked with. It was still a WIP. Less than half of the assembly would actually work, and what nearly killed me was a majority of sketch and feature geometry was made by but not linked to other components in the assembly. Parts were being ordered. Hole locations didn't line up, sizes wouldn't have fit, interference was a major problem. No one else noticed. I had this problem with almost everything this guy had touched. [/rant]"

                                         

                                        Try following a guy at one job, completing his projects in a month when he couldn't figure it out for 2-3 years.  Then at your next job, he works there too! You end up working in a different department, but you still get to fix his screw ups.  Yay!!!!  And of course he doesn't follow the most basic practices to make modeling/assemblies more efficient.

                                        • Re: Who Fixes Entire Assemblies, and Why?
                                          Roland Schwarz

                                          I was once a sheet bender like you. I also lived in Upstate NY (Rock City Falls) and trained at D1G (the "big ball"). It's a big world that moves in small circles.

                                           

                                          If fixing components rocks your world, you would completely lose it if you saw how rapid product development works in the electronics industry. The things that save your bacon in Schenectady will cook your goose in Cupertino.

                                           

                                          Most parts are fixed and in-place. Design is top-down from master sketches and ID-driven surface models. Key components are "tacked" into place and fixed without mates. Mates are more likely to cause conflicts than keep context. "Design intent" is impacted from so many directions that keeping a fully-constrained assembly would kill the model, the timeline, and ultimately the product.

                                           

                                          On NX projects, we don't even keep a feature tree. NX capabilities are such that you can lobotomize a part into a lump and still have better editing capabilities than Creo or SW. SW lets you play. Creo lets you play doctor. NX lets you play god.

                                            • Re: Who Fixes Entire Assemblies, and Why?
                                              S. Casale

                                              Interesting comparison between creo, NX and SW. I haven't used creo.

                                               

                                              I've used NX and was not impressed- perhaps because my role in use became the guy who had to fix the mess of previous users. I liken it to a much be a more powerful keycreator which has no feature history. One thing that blew my mind with NX was the fact that there were something like 6 different ways to create a line (from legacy Unigraphics and NX...) - that wouldn't have bothered me if it were easy to know what type of line was used when interrogating and validating drawings and models.

                                               

                                              I get the fixing and top down construction now, just haven't had a significant use for it. Although, I can see where it would to a benefit in my applications of past. Anyone who ever used it in my application used it  because they couldn't figure out how to work with the program correctly, true story.

                                               

                                              Cupertino? I used to live in San Jose. -should have never left. Was just there on a vacation in June.

                                                • Re: Who Fixes Entire Assemblies, and Why?
                                                  Roland Schwarz

                                                  My home office is in downtown SJ. I recently went back to working in Silicon Valley after returning to the Midwest to raise my kids.

                                                   

                                                  I was a UG-gunslinger at Apple during the original iMac years. In those days, you could get under the hood of UG and do some magical things. UG gave full access to surface definition points. You could adjust knit tolerance on a face-by-face basis. Solids and surfaces could be moved and rotated from one coordinate system to another. You could make a features from raw curves in space, then later move those curves to a sketch and parameterize, and then remove the curves entirely and keep the feature.

                                                   

                                                  You are right that it can be confusing to have so many options. But there are times when you need to get to option 6 of 6 before something works right. With more power comes more choices and fewer defaults.

                                                   

                                                  I went to Pro/E after that. Most of my SW technique for ID projects actually originated in Pro/E. Some UG things also actually work OK in SW.

                                                   

                                                  For instance: if you have a combine (add or subtract) that is giving you trouble, you can turn the solids into surfaces, trim and remove faces as needed, then knit together again. Once solid, nearly all the downstream features retain their original references.

                                                   

                                                  The biggest lesson from all that is that I learned to think topologically, to look at a body as a collection of faces. Edges are intersections of faces. A canned feature like extrude or revolve is just automating the steps. When you learn to see that, then modelling possibilities are nearly unbounded. The SW dogma learned in basic training becomes merely suggestitory.