June 10, 2021 at 8:46 pm
don't worry about the response time due to the time zone. Having the opportunity to talk to you on a daily basis, even if only once a day, is already a great help! But thanks for your concern As seen from the figure above, I notice that this pin and shaft (PS) system is going to rotate with the help of electric motor, now my question is:
1) If the WP is rotating continuously or just momentarily till you rotate it by a small angle?
Let's say it is more the second case. The WP will have to rotate until it sequentially reaches four desired positions with an increment of rotation of 90 ┬░ with respect to each other. The WP must be worked by a laser in all four positions that will follow. Consequently, the service of the electric motor will be of the intermittent type with running phases (rotation of 90 ┬░) and stop to allow processing (which can last even a few minutes) which are repeated alternately until a full revolution is completed.
2) Also the shaft in your PS system seems like a flange or a coupling between the Pin and the WP (to transfer rotation from motor to pin to WP) ? Or is the shaft part of the WP which is mounted over the pin with the help of linear actuators ?
Yes, itÔÇÖs the first one you said. As you have rightly noted "the shaft" acts as a flange to connect the real rotation shaft (which is an integrated part of the WP) to the pin, to transfer rotation from motor to pin to WP.
(Also assuming its a balanced WP system, if its unbalanced you will have to balance it before doing fatigue analysis or calculations which ever you prefer)
What do you mean when you talk about balanced / unbalanced system? I thought that to conduct an analysis in the "static structural" environment the system had to be necessarily balanced. Otherwise it would not be solvable. Or is there something I'm missing?
Also in the second case, that of intermittent rotation with 90 ┬░ angles, should I still carry out a fatigue analysis of the PS system? Or would the effect of fatigue be negligible in this case?
If the angles are fixed, do a static loading at 90┬░ rotation (which is worst case scenario in my opinion).
Yes, the angular rotations are fixed, and even I actually thought of considering the most disadvantaged case the one with static load at 90 ┬░ (i.e. when the moment arm is at its maximum)
I feel like yours is a static case and then centrifugal force need not be worried about. You can transfer the Weight force (F=mg) from CG to WP end of the shaft. All you have to do is shift it parallel and add the moment at the WP end of the shaft to make it statically equivalent system.
I have a question about this simplification of the problem. If I eliminate the point mass, how can I then insert the centrifugal force in the model?
I also have a practical question. When do you say that I have to add the moment at the WP end of the shaft, at what point of the shaft are you referring to in particular? In other words, which area should I select as the area of application of the moment? The more external surface of the shaft / flange?
So basically your focus is to design a holding mechanism for the WP and rotate it by some angle to work on WP maybe
Exactly, I have to design a holding and centering mechanism for the WP and rotate it by some angle
So basically your focus is to design a holding mechanism for the WP and rotate it by some angle to work on WP maybe. I still think there won't be an axial thrust on the base of the turrets, unless you bring the actuators very close that the WP is applying force on the top end of the turret via the Pin (IDK if this explanation is clear or not) All you actually need to worry about is the moment (which is also a kind of force on turret base if you think about it)
Actually, a first prototype of the system has already been built and, through empirical observation, I can tell you that if the turrets are not held in position by the actuation force of the linear actuators placed at their base, they tend to be pushed away by the shaft which therefore tends to slide off the two pins.
However, this axial force that we are experimenting empirically, could actually be due to the presence of the tilting moment you are talking about.
Also, could you be so kind as to explain to me what you mean by the following sentence? :
"I still think there won't be an axial thrust on the base of the turrets, unless you bring the actuators very close that the WP is applying force on the top end of the turret via the Pin"