Joint Animation Freezes When Using Tangent Relationships On A Fit Point Spline

[theartofthecraft.eric]

Hello, I am having trouble getting these joints to animate properly, If I rotate the cam without the "pin slot" joint it will animate all the way around the cam. However as soon as they are both active it will freeze or skip over the section of the cam that is the a spline point. The goal is to have the last link(Blade Profile) to stay fixed at 10 degrees. I have tried motion links, contact sets instead of tangent relationships and all seem to run up against the same issue where it stalls or skips part of the cam. Perhaps I am trying to achieve it the wrong way? Any thoughts or suggestions would be much appreciated. Thanks  

[namehelp06]

Hi @theartofthecraft.eric , Would it be possible for you to share a video of the final motion you want to achieve.

[davebYYPCU]

Do you have the cart before the horse?

Pull the timeline marker back 3 steps from the end.  The lever arm 1 runs on the cam lobe as expected, and as you say.

The yellow pushrod, according to the sketch, apparently needs to push the Blade guide, 1 step per revolution?

However, it is not currently aligned with the rachet surface.  You have a tangent relationship, with the end of the pushrod working at the moment, doesn't push anything.

Separate to this arrangement, how can the Wheel Profile remain 10 degrees from vertical, and align to the point of the rachet when Lever 2 would be rotating?

Can you explain the intended result?

[theartofthecraft.eric]

Thank you for the replies, I will attach a video both of the problem and how I intend it to work. davebYYPCU you are correct in your assessment however it is not necessary for me to have that part animated in this project. The pushrod is out of the way of the wheel profile in reality, this is just a simpler way to design the lobe and the pushrod allows me to see when the blade will be advancing and stationary. I will be tackling that part "IF" I can get the lobe to rotate smoothly 360 degrees while the wheel profile stays fixed at 10 degrees through the whole range. The wheel profile, (which will be a grinding wheel) will only lift around the height of the tooth, however the cam needs to rotate 360 degrees and I will adjust the lobe profile to give me a smooth entry and exit into the grind. I should have clarified it is a sharpener. Please excuse the messy timeline, it became that way after trying to achieve the same motion using different methods such as contacts and constraints.  Technically the pin slot joint is not a true 10 degrees across it range, I did have an angle constraint initially referencing the face of the tooth, however I realize the joint needs that degree of freedom to move, again the pin slot is an attempt to solve the freezing cam once it hits the flattened part.  Perhaps I am running into a fusion computation limitation in the animation portion?  

[davebYYPCU]

Contact Sets and Tangent relationships are very computationally expensive.  The pushrod system is contributing to that expense, and if required later, dissolve it now.  However without the Sharpening wheel phase introduced, both were working as expected.

If a rocking motion is required, why are there 2 levers?  Rigid joining them makes a pair into a single arm.

Seems to me that you need the Sharpening wheel, and it would use a temporary tangent relationship, to the face of the tooth, not any of your Pin slots.  When you extract the pivot angle with the lever, convert it to a Motion Link value and dissolve this tangent relationship as well.

Might help….

[theartofthecraft.eric]

Thank you for the input, taking your advice I deleted the push rod and any associated joints to reduce the expense and it responds the same. The motion link was an experiment to see if it would animate. I originally tried the rigid group and am back to that for simplicity. As you correctly stated, it animates properly until the wheel profile is constrained to ten degrees, either with a motion link, pin slot joint, or tangent relationship. 10 degrees being the angle the wheel has to enter the cut and will always be in that plane. That has been the only reason I reached out here because after spending hours trying all the different ways to animate it, I have yet to have any success and yet there are no errors and it seems like it should animate. I believe it is a computation problem but was hoping for a solution I have not tried. Again I appreciate your input!  Perhaps I need to rethink and further simplify the model, the lever arm lengths and lobe diameters are important so as always I turned to fusion to solve a complex geometry problem and ran into a rare limitation. Are there any other ways to constrain a pivot to an angle while allowing the slight arc movement that I have not discovered? 

[davebYYPCU]

Ok, with a bit more understanding of the problem, 

in this file I filleted the Wheel Profile.  (too big)

The Pin Slot works, when you offset to the radius' centre point.  I can keep the fillet attached to the face of the tooth.

But I currently can only click drag the wheel profile to show the movement.  Edit pin slot slider joint limit.

Work in progress, but I think this is what you said.

Might help....

[theartofthecraft.eric]

Okay respectfully, I'm not sure how to make the issue I'm having more clear but I'll try, if you watch the video I posted I already have the pin slot working for the wheel profile, that has not been an isolated problem. I also already have the bearing following the lobe, again no problems. When I suppress the connection between the two lever arms, both the pin slot and tangent relationship animate properly. The issue only arises when you connect the two lever arms, whether through motion link or rigid group etc. Then it only follows the  lobe until the lobe narrows. This is a problem because in order to design the correct lobe shape the entire assembly needs to animate together. Unless that can be solved I think we leave this one as a fusion limitation when too many joints are at play along with the tangent relationship it just can't compute the animation. Thanks for the efforts.