Lifting part with gravity

[gpeetersem]

Hey Guys,

I'm creating a kind of lift at the moment and want to do this with mechanisms, to see if everything will work fine.

But now I don't know which kind of mechanism I need to use...

I've created a simple assembly to show you what I like to do.

- The green part is the lifting device which can go up and down

- The blue part is the load which will be lifted when the lifting device is on a certain hight (when the lifting device will touch the part).

- When the green part is going down, the blue part is going down too, untill it will touch the ground.

I thought that this would be a kind of cam with lift-off, but I don't know how to create this.

In attachment you can find my assembly.

[skunks]

att.

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[gpeetersem]

Hi Skunks,

thanks for the quick reply.

Is there also a chance to do this without adding some rounds? Because I cannot change the design of the lift and the load.

And is thare also a feature to add some gravity? Because now when I pull the lifting device down, the load isn't following.

[skunks]

please run the dynamic analysis

[SweetPeasHub]

We would love to help you further with this model.  Can you please clarify your statement "everything will work fine".  What are the expected inputs and outputs?  Do you just need it to animate or move correctly and are not obtaining engineering data from the mechanism?  There are many ways to get it to look like it moves correctly but there are fewer ways to obtain certain engineering data.  Why cannot the rounds be added?  Often simulations require slight modifications to models or even additional parts added to an  assembly for simulation purposes.

Finally, just to check, do you have the Creo mechanism dynamics option that is required to be able to model gravity? (or any force)

[gpeetersem]

Hi SweetPeasHub,

I will try to explain the design I'm making:

- we have a pallet (green) on a conveyor (red) with a lift in between (blue)

- when the lift with rollers (blue) is going up, the pallet (green) will be lifted when the rollers are touching the pallet.

I've done this with 2 sets of mechanisms on the pallet, but this isn't working as it should be...

We don't have the Creo mechanism dynamics option .

[SweetPeasHub]

You will not be able to simulate gravity without the mechanism dynamics option. 

Also drag will not work with gravity regardless of the options, since drag is kinematic only.

I think we would all love to see PTC add the ability for some type of spring bias or gravity bias during drag such that movements like this lift you want are more correct without doing a full dynamic simulation. 

The best I can suggest specifically for you is maybe you need another translation constraint before the "25mm pallet to lift".

Keep your "test" assembly as-is then

Redefine and add a 2nd general connection of the pallet.

Coincident  Test02:Front to Test01:Front (Align)

Translation Axis 1  Test02:Right  Test01:Right (-120mm)

Translation Axis 2 Test02:Top Test01:Top  (minimum -20 maximum 0)

Also, you can generate the CAM of Skunks with dummy reference surfaces so you would not need to modify your master CAD.  Fillets are just needed there for reference because of restrictions with CAM.  I often add dummy reference geometry to get things working right.