Problems with constraints in Autodesk Inventor 2012

Hello all, just coming to see if you can help me out with an issue i’ve been having with my CAD mockups…

The main problem is certain parts not allowing more than one constraint active at a time. The two parts i’ve noticed so far having this issue are the 393 Motor, without the wire, and the standard delrin bearing. I’ve been getting around this with suppressing the other constraints, but this is a bit time consuming.

If it helps, i’m using Super Sonic Spark’s CAD library (Which is very nice :D), but i’ve noticed people mentioning problems even with the default parts.

Thanks in advance,

I have had no problems with motors in my CAD Library. I use tangent contraints right now along with a mate constraint. Like I said I have no problems with those… However Bearing blocks are a big pain in my rear when it comes to CADding with them. I tend to design around even having them in the design as much as possible. Do the tangents first then the mate constraint, otherwise you’ll get an error.

  • Andrew

Can you elaborate a bit, how are you trying to constrain?

For motors I use three constraints. A mate constraint between between the center motor post and the surface the motor is being connected to. Two constraints between the axis in the center of each motor post and work axis in the center of the (usually square) holes that the motor is being attached to.

Here’s an example, it’s hard top see what’s going on but this is the second constraint between two axis. There may be a better way to do this but I’ve found three constraints are nearly always needed to properly constrain parts.

Three is usually the number I find are needed as well. (for larger parts, at least)

Yoder: What are you trying to constrain and finding problems? (What faces/axis on the parts?)


P.S. Thanks for the compliment on the CAD library – I’m glad you like it and are finding it useful.

You can get away with two for things like screws and nuts but they will still be able to rotate on their axis which obviously doesn’t matter.

  I'll try some more with using the work axes. The way i was doing it was just eye balling it with a mate and a flush to the sides of a chassis rail and the motor, after mating the motor post and the surface. 

  This might just be me, but when i was constraining the bearings the "lazy" way, just eyeballing it, I could only have one constrain editable at a time, while with other parts I could have as many as I wanted (Screws/Standoffs mainly)

  The tangents will also be something to try, thanks AndrewRemmers. Oh, and thanks again MindstormsManiac, but just a quick question on it-With the chassis rails what are the dots surrounding it for?

You cannot constrain the sides of the motor using a flush to the chassis as they are not perpendicular to the base. Look at the motor from the end and you will see the housing is not rectangular but has a slight angle to it. Do the constraint using the two work axis, it takes just a few seconds to do it this way.

The dots that are not on the actual faces of the part were made when I created the Sketches on the parts. Just ignore them, or you could try to get rid of them if you wanted. They serve no purpose, really.


this is a kind of off topic question, so sorry about it but i have a question about grounded components in inventor.
I am building a square bot in inventor and i need to move the grounded component…how do i do that. i think you can, even though it is ground, i just dont know how.

Also, what do you use as you grounded component that you cant move?

You can unground the component by right-clicking on it, the in the context menu, uncheck grounded.

You simply need to turn off the Grounded setting. Right-click on the part, and on the list that pops up you should see “Grounded” and it should be checked. Click on it to un-check it, and the piece will no longer be Grounded. If you want to ground a different part you can do it the same way, just turn on Grounded.



Thanks too!

also , this is a question for anyone but what is the point of a grounded component? is it so you dont get lost? i know i got lost in sketchup once or twice lol

It really just means that all 6 degrees of movement (position XYZ, rotation XYZ) are locked without any constraints. You can ground a part anywhere in space so it doesn’t help with getting lost. You can have more that one grounded component but it’s not necessary.

I found using a grounded component helpful when creating individual assemblies of axles…

Jpear, i tried using the constraint to an axis and it worked perfectly! (for the motor) I would assume it might work much of the same way with a bearing, although i haven’t worked with it. it’s just three constraints, first a mate to the metal and then through the axes. (which were easy to create thanks to the drawings on the face of the metal pieces :D)

thank you for the clarififcation!