Based on a model from a well-known mechanics book, I came across the use of the energetic approach, here are two tables, one double scissors and the other simple, the work proposed by this person is very dense but well handled. By graphic statics it is long and tedious, here we quickly determine the effort exerted. It remains to manage the reactions in the pivots, through the simulation Solidworks can provide estimates let's say in a simple way like determining the buckling by Euler. Thank you in advance, have a good day.
If it is a question of determining the actions in the different links of the mechanism, graphical statics is probably the most suitable solution, if you want to stay in the SolidWorks environment. Energy methods make it possible to quickly find the input/output relationship(s) in a mechanism from the point of view of effort. They can also be applied to determine a particular binding effort, provided that the "good" subsets are considered. And because of this, it is not simpler than the use of statics.
If, after determining the forces, it is a question of studying the buckling or bending resistance of the different elements, it is necessary to know their geometry to use SolidWorks' finite element simulation tools. And in this case, your diagrams are not enough...
You are in the case of a multi with double scissors and from my point of view, there is a bone in your cinematic as it appears in your SW sketches. (see the set)
If you are in the case of a single with double scissors it's ok.
Without adding to @m.blt's remarks, from my most critical point of view are the axes and their supports for this type of table. They must be the subject of a specific calculation at all points of the kinematics.
Following your advice, I will finish my integral modeling with the axes of the pivot connections and the rollers for the two slides and the structure. I understand that my sketch is insufficient, my idea at the base is to do a design study to have an exit instruction here the height of the table according to the stroke of the next cylinder without implantation, which is already a good entry, in a second time it is the direction of my approach anchoring the cylinder that will be the least penalizing during its operating cycle. With my first sketch, the load of the cylinder is variable according to the transitions of the kinematics and that's normal. Can we supervise in design simulation by pilot sketch (with appropriate terminals, rough out a design optimum and a maximum cylinder load to choose the appropriate cylinder), this is the primary meaning of my question which was not well formulated I admit. Thank you for your remarks, I will finish a design of my scissors and deposit my advances on the forum.
I'm going to stay on a simple one, my goal is to first determine the cylinder adapted to the load to be lifted, I want to know the ratio between the load and the force of the cylinder. By going through a design simulation at the stage of a kinematic sketch, it is possible by selecting the sketches or I have to consider finishing the entire modeling with sheet metal and box elements to stiffen the whole. Thank you for your message and advice.
In the one-ton model I think that using SW simulation is not the best method since the force on the cylinder is not linear with a high force at the beginning and less in the High position. So if you want to do in PEF you won't have a direct reading and in addition you will have to do as much simulation as you have position if you are in Static Simulation.
However, you can achieve your goals by using @m.blt's Méca3D software or by using the attached spreadsheet as an example and adapting it if the dimensional limits are insufficient. You also have to pay attention to the CG of the load in your design because it is not (or never perfectly in the middle, especially because of a sliding load most of the time.
Another point of attention is that even if in your example you have a single chisel vertically, you have in your sketch a multi table (there are two mono-scissors side by side).
So for the choice of the cylinder, saying that it is hydraulic will not be enough to make the project a success. If we stick only to effort and resistance, then working on a single chisel is sufficient. Once you know all the " axes and bars " forces, you can do a simulation on the complete model with all the parts that are fine in volume and in an ASM to see in a few positions the forces closer to reality.
The use of a macro offers another possibility to evaluate the force of the cylinder according to the load and position of the table lifting system. The method is necessarily based on the pilot sketch " Esquisse1 " whose geometry and notations it uses. The other sketches are only there for the dressing of the schematic.
The macro takes as input the maximum and minimum heights of the table (pivot centercenter), and the number of intervals between these extreme positions. For each height of the table, sketch1 is re-evaluated and returns the corresponding length of the actuator. The numerical use of virtual jobs makes it possible to calculate the ratio r between the load P on the table and the thrust Fv of the cylinder: r = Fv / P.
At the end of the calculation, the table displays the list of calculated values. It is possible to save these values in a text file (CSV format recognized by Excel), and to animate the schema. The calculation of the binding forces would be possible, at the cost of an analytical static study and a few additional lines of code...
Thank you this corresponds to my initial request, I had exploited manually by changing on my modeling and rebuilding the model to validate an imposed setpoint, but not an automation by managing intervals. Your help is invaluable, I will take the time to study your macro. Happy holidays. Kind regards.
I noticed the problem on the load of the cylinder which is not linear. I will take your point into account by adding the center of mass. Thank you for all your remarks and for the advice given, I will archive the EXCEL table and use it. Kind regards.
Hello @tous There is also solidworks motion which allows you to evaluate in real time the strength of the cylinders For the simu I think that a design study could be useful (personally, I don't use, a track to explore)
Hello For my part, in addition to Meca3D or SW motion, I sometimes make sketches of graphic statics. For an expert report, I have sometimes found that " seeing the forces " adds credibility to the results of a calculation made with the software (for " plan " or " quasi-plan " problems). I make these sketches with blocks in a drawing when I don't have the 3D modelled parts. I enclose the study of the balance of a basket
PDF of a slideshow presenting with videos the method
Graphical statics does provide a direct reading of the values for a given position, this is very clear in your document, by associating the virtual work (you copy your sketch with an initial dimension of the stroke of the cylinder studied, you delete your dimension, you move according to the height of 1 mm and you have the dimension of the stroke of this new current position), then, by making a sketch and entering the formula, you obtain the force of your cylinder; Thank you for the example of a boom lift with 3 actuators.
