shift1313 Posted November 5, 2009 Share Posted November 5, 2009 chris, i dont have anything in my email. can you attach a screen shot of your design tree with all the joints and grounded components in it? Which components does it say are over constrained? Quote Link to comment Share on other sites More sharing options...
shift1313 Posted November 5, 2009 Share Posted November 5, 2009 When i open the file up in dynamic simulation it says it is over constrained by 1. The issue is the sliding on plane joint. The problem is when you create this joint(or its auto-created) you are not telling the roller that it can only slide in that groove. You are telling it that it can slide anywhere in that plane. Well the redundancy is the fact that your geometry only lets it be in that plane to start with so you are not accomplishing anything by placing this joint. If you simulate this, then suppress the joint and simulate again it will be an identical scenario. I think one of the issues came about with your Mate for part7 to part 11. It appears as though you picked the center point of the circle rather than the face. This lets your "roller" spin around as long as its center point is located on that face. I suppress this mate and created another one in its place. When you go back into dynamic simulation this should take care of the issue with this component. Is there another component that is having problems? Quote Link to comment Share on other sites More sharing options...
chris44 Posted November 6, 2009 Author Share Posted November 6, 2009 hai matt, actually i updated the model....i am giving the rapidshare link....in this model...it says there are 3 unconstrained dof's.... can u please check on the model and give me some suggestions http://rapidshare.com/files/303047697/New_WinRAR_ZIP_archive.zip.html thanks a lot matt, chris Quote Link to comment Share on other sites More sharing options...
shift1313 Posted November 6, 2009 Share Posted November 6, 2009 okay chris, its the same problem I stated above. Planning out constraints and joints needs a lot of attention. Its an interesting problem because you dont always need the same amount in the model as you do in real life. For instance when you bolt a part together, in real life you may have 8 bolts holding something together, but in the model, two insert constraints and one mate will accurately define the realtionship between the two. The problem in you model is the same as with the last revision. The grey link in the image below is one of the issues. Its giving you an over constrained condition because the insert constraint for the pivot was created by selecting two edges. This selection makes both of these edges both concentric and planar. The "roller" has a tangent constraint with the bottom plane which is fine, but the mate between the side of the "roller" and the track is where the issue comes up. Now because the insert constraint gave this entire link a planar constraint, this mate between the roller and side of the track is not needed. Another thing you need to be careful with is your selection for things like circular edges. If you select a circle with a green center point, you are actually selecting the center of the circle. If you right click or hover over the joint the "select other" will appear. this is a little icon with a green box in the middle and two arrows. the arrows let you select between different edges and the green box lets you finalize the selection. one of your joints was created with this which created an issue. Basically I removed your constraints in the assembly and started from scratch. When you are in Dynamic simulation and you hover over a joint with a ! it will tell you the link that has issues. This doesnt mean you need to remove this joint, but some other joint is causing an issue for that one. If you look at the second image you will see the mates i have in the model. I suppressed part C1 because it wasnt needed and was only adding joints to the model. The insert joint between the two components there i added a .15" offset which is how wide your part is. Learning what joints you need is something you just have to look at and figure out unfortunately. This is why you should start with simple models first. Keep in mind the orientation of each part and what each mate does to it. In the assembly environment you can manually move things around and its a good idea to add a mate, move the model around to see how many degrees of freedom is still has. Play around with the selection process. edges vs faces vs points and so on. Hopefully this answered your question. Quote Link to comment Share on other sites More sharing options...
chris44 Posted November 7, 2009 Author Share Posted November 7, 2009 thanks a lot matt, as u said, i removed the mate constraint between the roller and the slider...now its working great....i need to put more practice on placing constraints....and need to be really careful Quote Link to comment Share on other sites More sharing options...
shift1313 Posted November 8, 2009 Share Posted November 8, 2009 it just takes some practice chris. Building your models as you did is the way to go. Simple geometry without over-complicating things. Let me know if you need any more help. Quote Link to comment Share on other sites More sharing options...
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