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Actually, no body can complete a project in only one method TD, BU. Every time u must use both, at assembly level, at part level or sometimes use both in one part as well. anyway, I am using both methods, but I had saved my own templates and I use that for locate default datums too. mostly what I do is I create a part with my template and save it empty, just datums and veiws. I assemble those on appropriate location in assy, activate the part and start modeling.
mostly what I do is I create a part with my template and save it empty, just datums and veiws. I assemble those on appropriate location in assy, activate the part and start modeling.
Gotta agree with Zaki on this one. There is no 'best' approach.
Following on ffrom the quote above, one bugbear of mine that I always think is worth mentioning are ext refs. As a rule I always delete any ext refs that the above design methodology creates (they are usually the sketched refs that are developed from the assembly itself in the part that you are creating). Spending the extra 2 minutes to open the part and redefine your sketches is well worth the effort, especially if you use DBM systems to control your ProE files. Ext Refs and circ refs cause retrival times to go thru the roof with some DBM's (Teamcenter being a good example of this.
1) Create a design reference part with no features other than datum curves ( similar to a layout, which I also use in some cases).The curves are for those features that I know will be used in one or more of the parts like screw boss locations, perimeters, major component outlines. All are simple shapes.
2) Make a design assembly and place the design reference part with datum curves as the first part, in default position.
3) Assemble new major parts such as a top and bottom housing in default position with no features.
3) In assembly mode I make copies of the pertinent datum curves into each part that I want to use them with. I may or may not use the actual values. Sometimes I just offset from the curves or pick up a center point.
4) I then open each part individually and build what I want it to be which helps me avoid references to other part features or circular references.
5) If I need to make a significant change to one major part, I copy the first edition and revise it. I can then place the new revision into default position so it automatically fits the rest of the assembly. I can also make changes to the design reference part datum curves and migrate that change to all the parts I copied the curves into.
6) For any specific parts like an electronic component or screw, I build those as individual parts on their own.
7) When the design is ready I then build a production assembly and place all the parts, as they would be assembled for real, to make sure the spaces really work, and so that there is no unintended interference that "default position" was hiding.
8) In some cases I will lock the design reference curve features in each part so that a tool maker cannot change them.(nothing like a screw boss suddenly in the middle of a major feature because they thought it was ok to move it)
For me this works great. i can make many revisions of major housings or adjust the whole assembly by simply shifting a few dimensions in my design reference part. I anticipate what might conflict and leave certain features like rounds and drafts until after thise phase to minimize the crashes due to lost references. I think it is important to understand the purpose and value of each set of design features. I am not afraid to have external references as long as I control them. When I check an assembly global reference view, I want to only see those design control curves. Anything else will be redefined to break that undesireable reference. I find that most people have problems with circular references because they build somewhat carelessly in the assembly.
After all, the software is intended to be parametric so I would say it is best to utilize those functions and not neglect them by understanding the risks.
just my thoughts on the matter...still revising my own procedures to streamline the use of parametrics and relations to make design a more fluid process.
magne...sounds interesting i'm going to give it a try!! what type of datum curves are in your start part?? a rectangle and a circle???
i just refineda technique of mine....
1. create part in assy mode selecting copy from existing (my start part has no geom just datums)
2. define the placement buy only mating or aligning the datum that will be used for sketcher...then move the other datums to a position that "looks right"...fix to position
3. create first feature
4.Redefine part placement using geometry of first feature
5. modify the dimension that relate the first features geom to the datums... this will effectifly allow you to position the datums where you want them with respect to the part with out moving the part around in the assembly (if you did step 4).
its pretty fast...but again... a lot of post process modifying / redefining... Edited by: TWINTURBOTOM
Usually i use the methodology that magneplanar describes but i would like to add the following;<?:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" />
I alwaysplace new part on a default location,In thisway it
in my design reference I make simple curves like you described. It all depends on how much I want controlled and plan to modify. Actually, this is what "layout" is intended for, but this is a way to do the same process if you do not have that advanced extension available.
mdias,
default placement is nice for making it easy to drop a new part in, especially if you do some automatic placement. I find that I can build in some target references in the part and place it quickly enough as well. I do not have to deal with the part being at some distance from the assembly coordinate system and I can reuse parts in other assemblies, such as electronic components. Go with whatever works though since ultimately you just want a method to make the design process flow smoothly. I do not trust default enough when it comes to tolerance stack up and interference checks though.
When I have a customer in the office I have a "show and tell" model that has many housing variations in one assembly in the default positions. I cycle through the simplified reports and they get a nice range of ideas for what the final model could look like.
Twinturbo, if you sometimes like to use the other methods but miss your start part features like parameters, views etc. may I suggest you create mapkeys to generate standard parameters and view setups etc.
I have this setup for when I use the geometry creation methods other than 'copy from existing' and also for when Irecieve 'foreign' files and wish to standardise themit works well. Alternatively modelCheck will do the same job for you.
cad_eng.... not a bad idea!! i'll tell you how it works out
guys i've also noticed when i Restructre parts to new assy, even though I have redefined the part to the new sub assy references, when i first open up the sub assy (with the new parts that were restructred in after i redefined the part to assy references) the items are not fully constrained... i then basically redo what I did, which is redfining the part before the restructure.....what are good ways around this type of problem?
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