Assembly Creation Questions
Assembly Creation Questions
(OP)
I need to create an assembly consisting of a welded tubular frame with panels and gages, etc. I started building the frame in a file called "frame". Basically rectangular shaped with corner joints mitered, welded, and ground flush. I created the front, back, left end, right end, and cross brace, all as new parts in the same file, and assembled them using mate and flush constraints. I created a scene with explosion factor, but the only part that moved is the cross member. Any suggestions?
Should I create each of the component parts of the frame (there are more pieces to be added) in seperate files? How do I constrain the parts in the assembly so that if the size of one part changes, the affected parts will change with it? For example, lets say the length of the side changes from 30 units to 20 units, then the cross member must also change by 10 units and maintain face to face mating relationship with the front and back rails.
Mike Butts
michaelb@sccoast.net
We are small, and offer CNC machining, Fabrication, reverse engineering, AutoCAD generated documentation in 2D or Solid Models. We look for the challenges that others pass up, working with numerous materials such as Aluminum, Stainless Steel, Inconel, Ha
Should I create each of the component parts of the frame (there are more pieces to be added) in seperate files? How do I constrain the parts in the assembly so that if the size of one part changes, the affected parts will change with it? For example, lets say the length of the side changes from 30 units to 20 units, then the cross member must also change by 10 units and maintain face to face mating relationship with the front and back rails.
Mike Butts
michaelb@sccoast.net
We are small, and offer CNC machining, Fabrication, reverse engineering, AutoCAD generated documentation in 2D or Solid Models. We look for the challenges that others pass up, working with numerous materials such as Aluminum, Stainless Steel, Inconel, Ha





RE: Assembly Creation Questions
When creating assemblies it is always better to create part files and attach these to an assembly file afterwards. I found this out the hard way. The reason is that assemblies with referenced parts use less current memory than an assembly file with parts created internally. One of my files crashed and I had to systematically export each part to a new file and recreate the assembly.
Now, the one thing I have learnt about explosions is that they are dependant upon the current UCS and the way the constraints are produced. Try changing the constraints so that the assembly will explode the way you ant it to. Otherwise use tweaks and trails.
The last part of you quaestion refers to parametric dimensioning. There are two ways of doing this. If you create the parts in the assembly file then you can create paramtric dimensions explicitly. Create the first part, switch the dimension view to show equations (I think), you'll find this by right-clicking in the drawing pane. Here you will notice that the dimensions are labelled d1, d2, d3, etc. When you create a dimension on another part that has to be related simply write d2+10, for example instead of a value.
If you go to the constraints toolbar you'll find parametric dimensions shown, you can create part or global dimensions. Any dimensions you wish to use across parts create as global dimensions (note: part dimensions override global ones so don't have the same names in each section). Here you can call a dimension width, length, etc. Give it a value and then, when you dimension the part call the dimension width or length+10.
You can't use this method if you reference parts. Refrenced parts are locked and can only be edited in the part file. So here's the second method.
If you go to the parametric dimensions on the constraints toolbar you'll notice that you can link an Excel speadsheet.
Create a spreadsheet with all the dimensions you need, follow the rules (these are given in the help files) and then link the speadsheet to the different part files. The basic rules are:
1. The first cell you link to is the top right corner of a matrix that has the first row and column as unit or part references and dimensions names.
2. You cannot duplicate dimension names or part refernces (try not to use d1, d2, etc. as Desktop uses these as default and may throw up an error).
3. You cannot use the letter E as a dimension (don't ask me why, I don't know).
4. You cannot leave cells blank, always enter 0 for cells with no value.
Using the dimesion names in the spreadsheet you can manipulate the dimensions of different parts maintaining assembly and design constraints.
This isn't fool proof, and it does require some user actions. For instance, if you're in the assembly file and you change a dimension in the spreadsheet you have to open each part file, update the Excel link, update the model, save the file, update the referenced part in the assembly and hope that the constraints don't go manic.
Hope this answers your questions.
Fawkes
RE: Assembly Creation Questions
Thank you for the very useful information. I am still trying to get a grasp on how to build my model so that it will explode properly. Until then, Tweaks and trails for now. The spreadsheet info was very interesting, but seems like alot to do to make a simple change. Using the equations will work nicely for me.
Mike Butts
michaelb@sccoast.net
RE: Assembly Creation Questions
Dear Mike;
I had the same problem producing exploded views of industrial brakes. After reading the desktop training material I discovered you must avoid mate plane/plane and insert mates if you are going to be making exploded views that explode correctly on the first try.
According to the manual, you should use flush line and line/line wherever possible. Try to constrain without suing planes. This worked for me. I still had to use the odd tweak but no where near as many as when I started.
Regards Adrian
RE: Assembly Creation Questions
As soon as I read your message I jumped into my drawing and checked my constraints. Sure enough I had mate pl/pl listed on just about all the pieces. I deleted all of them but still had no luck exploding. Must be something else wrong, I'll have to dig deeper. I did a quick model of two parts with a mate ln/ln and created a scene with explosion factor of 4, and activated that scene. No exploded parts. If I pick the edit constraint icon and enter the value in the dialog box, update the scene and it will then offset the amount entered. Perhaps I have some parameter set incorrectly?
Mike Butts
michaelb@sccoast.net
RE: Assembly Creation Questions
Do you know that there are two seperate explosion factors.
The explosion factor for the entire assembly is accesed through Assembly, Exploded Views, Scene Explosion Factor.
The explosion factor for the individual part is accesible by right clicking the part in the browser.
If that is of no help examine system variable AMSCENEUPDATE
It is supposed to be set to 1 for auto update, If it is 0, exploded views wont update without pressing the scene update at the bottom of the browser.
Also I am mistaken in my advice re the constraining of planes, my manual reads as follows;
If no constraints were applied, parts will not move, no matter what explosion factor is applied
Only the insert constraint and Mate constraints that involve planes will move apart when an explode factor is applied.
If you do not want a particular pair of constrained parts to move apart, consider using Flush instead of Mate plane-plane, Flush plus Mate line-line instead of Insert and Angle line-plane instead of Mate line-plane.
Sorry to send you on a wild goose chase, I hope this clears up your problem. Please let me know.
Regards Adrian
RE: Assembly Creation Questions
Your information was most helpful. I used the mate pl/pl on the faces of the mitered corners, and the parts explode nicely. Thanks again.
Mike
Mike Butts
michaelb@sccoast.net