Software to Design Machinery Involving Moving Parts

[Alpesh Patel 1]

Designing a machine or a product involving moving parts is common. This kind of design process requires performing motion simulation – also known as rigid body dynamics. Consider a classic Mechanics example of an elliptical trammel used to trace ellipses. A designer can define mates to perform assembly animation in a normal CAD program available today, to see how the components of the trammel mechanism move. 

However, the speed of the motion is irrelevant and timing is arbitrary in this case of assembly animation. In order to find velocities, accelerations, joint reactions, and other details such as power requirements, etc., there is a need to perform motion simulation as well.

Motion simulation provides the designer with all the information related to kinematics such as velocity, acceleration, joint reactions, and forces due to inertia as well as power requirements. To perform the motion simulation, the designer has to define only the speed of the motor, points to be traced and the results he wishes to see in the motion simulation program. 

The program then automatically fetches other information such as material properties from the CAD parts and translates the assembly mating conditions to kinematic joints. The equation for motion is formulated automatically based on these details. This approach is different from FEA where the bodies are considered flexible. 

Rather, in motion simulation, the parts are considered rigid and have only a few degrees of freedom. Thus, the solver is able to solve the motion equations quickly and provides all the information on displacements, velocities, inertial forces, joint reactions, and power required to sustain the motion.

Apart from the above details, the motion simulation study also checks for interferences. This check is different from the one available with CAD assembly animation. Here, the program accurately performs interference checks in real-time and provides spatial and time positions of mechanisms along with exact interfering volumes. Motion simulation thus solves the problems easily, irrespective of any complex mechanisms involved containing a large number of rigid links, springs, dampers, and contact pairs, such as in the case of a CD drive.

The use of motion simulation however is not the last stage of designing a product involving moving parts, since the study considers all the parts as rigid. In reality, however, there are stresses and strains involved due to forces. To identify the behavior, the results obtained from the motion simulation such as inertial forces, joint reactions, etc. can be transferred to the FEA program. Usually, engineers utilize the maximum reaction loads to obtain maximum stresses and deformation in the part or assembly.

The part or the assembly is then assigned elastic properties and is submitted with other boundary conditions in the FEA program to perform structural analysis. The final results obtained can then be observed to perform necessary changes or finalize the design of the product under consideration.

All these phases, i.e. CAD modeling, motion simulation, and FEA can be performed in different programs or in a single integrated environment, such as the one available in SolidWorks. This CAD software includes SolidWorks Simulation (FEA) as well as SolidWorks Motion (motion analysis) as add-ins, providing a fully integrated environment to the user. 

This is beneficial as there is no need to transfer data to a different program to perform motion studies and structural analysis, which would otherwise increase the chances of errors in data transfer and discrepancy in results.

You can approach engineering design services firms like Hitech CADD Services if you are looking for assistance in designing a product involving moving parts. The company provides services like CAD modeling, motion simulation as well as FEA, which can be helpful in finalizing the design for actual manufacturing.

 

[Timothy L Dennison 29]

Was this an advertisement for Solidworks or Hitech CADD Services. It seems to promote those two companies, and no others. 

[aimstorms 0]

The design mechanism has several stages: feasibility, design and analysis, and even allows you to understand the forces involved.