Can the precision for angularity red reduced when using mate connectors?

Reece_Isaac

I know my question title doesn't explain at all so I shall try to expand.

I have been having great trouble with an assembly trying to connect several parts that involves 3 revolute and 1 cylindrical mate connectors. Which invariably fail.  I have tried different types and combinations of mate connectors and came to a conclusion that something wasn't inline.  Today I replaced a fasten mate with a planer mate (with some limitations on some axis) and lo and behold the assembly doesn't fail and can be manipulated.  To try and see why this worked I picked two parts to see what the measurement was.  These should be parallel.  It seems that they are at and angle of 0.004 degrees!  This is a ridiculous degree of accuracy to cause a mate to fail. I have attached two screens of the problem, the top image is with the Planer connector the bottom with the fasten connector.  Note the the revolute connectors fail with the part fastened and the misalignment is 0.004deg. 

NeilCooke

You probably already know this, but it’s the blue part that is at fault. I couldn’t open (or find) the linked document. Is it private? Looks to me like an imported part? I think the shafts are not coaxial and certainly the ends of the shafts are not parallel. Creating a mate connector in the part that uses the shaft axis rather than the end of the shaft will probably fix this. 

NeilCooke

I just measured a ton of faces to try to find where the angle came from. I may not have found it so quick without the tip from you. 

NeilCooke

Hi @Reece_Isaac can you share the doc? Mates are very accurate and the best rule of thumb I can offer is to try and not let the mates fight each other (for example a closed loop of revolutes may fail but changing one to a cylindrical will usually let it solve). I can take a look and possibly offer a better solution than planar. 

Reece_Isaac

No worries Neal it's been shared to you.  What permissions do you need for it?  The mechanism involves three bearing points and a screw jack.  The axis of the bearings should all be parallel and the screw should be perpendicular to them.  I have at other times on other models experienced  the same type of angularity of models that have been designed to have parallel faces.   I have tried various types of mates including ball to get this to work.  It was only today that I managed to get any idea where the error was that caused the failures.  I thought the whole idea of animating to so checks on clearances and range of movement would work OK. Although working out where the root error is is not so easy.

NeilCooke

You probably already know this, but it’s the blue part that is at fault. I couldn’t open (or find) the linked document. Is it private? Looks to me like an imported part? I think the shafts are not coaxial and certainly the ends of the shafts are not parallel. Creating a mate connector in the part that uses the shaft axis rather than the end of the shaft will probably fix this. 

owen_sparks

I've had a bunch of similar vendor CAD.  Either there are a lot of sloppy engineers out there or many companies are deliberately mildly sabotaging their parts before releasing the files to customers!

Owen S.

Reece_Isaac

Thanks Neil, I discovered the blue part issue after starting query.  I thought I had sorted something similar some time ago.  How did you determine so quickly what part was faulty?  The part was generated in another document that I trashed because it had become unwieldy.  The other document hadn't deleted from trash yet so I'll try and sort it out.  Thanks. 

NeilCooke

I just measured a ton of faces to try to find where the angle came from. I may not have found it so quick without the tip from you. 

Reece_Isaac

I don't understand how I managed to make the part untrue. Oh well, live and learn.