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Request for help with constraints in arbor press simulation

Question asked by Julian Leland on Nov 6, 2011
Latest reply on Nov 8, 2011 by Jerry Steiger

Hi all,

 

I'm trying to simulate stresses developed in a simple arbor press as part of a class project. The arbor press consists of three parts: the frame, the "spindle" (basically a 1.75" dia. rod, flattened in one section with a 12-pitch, 25 deg. pressure angle rack cut into the flat section), and a pinion to drive the spindle. I have successfully modeled all three components, and have been able to simulate them with SW Motion. However, I'd like to examine the stresses that develop throughout the entire assembly: I've tried a couple of times to set up a simulation using SW Simulation, but haven't had any luck.

 

What I'd like to do is apply a torque to the pinion with the end of the spindle fixed, as though I placed a solid block in the press and applied pressure. I'd like to have the gears mesh together, and then get the stresses in the frame as well as in both the spindle and the pinion reported. Historically, I've set up the simulation as follows:

  1. Assembly set-up: I've set up the assembly with standard mates (concentric, parallel, distance) to position the spindle and pinion within the frame. I have NOT included a rack and pinion mate between the spindle and pinion, but I have made a point of positioning the pinion such that its teeth do not interfere with any of the rack teeth.
  2. Fixtures: I define both the base of the frame as well as the end of the spindle (the part that applies the pressure in an arbor press) as fixed.
  3. Loads: I apply a 1 N-m torque to the pinion
  4. Connections (this is where I think I'm going wrong): I define a no-penetration component contact between the rack and the pinion. I've also noticed that a "bonded" global contact is defined at some point in this process: this didn't make sense to me (why would I want all the components to be defined as bonded together?), so I deleted it. Was this the wrong thing to do?
  5. Meshing: Nothing fancy here - I just let SW set up a fairly coarse mesh, and ran the simulation.

 

Results thus far have been pretty odd - I've gotten a number of error messages during simulation (I neglected to write them down, sorry), and the final simulation plot showed no variance in either deflection or von Mises stress across the model, even though the spindle had distorted WILDLY (stretched out enormously, through the frame of the arbor press). If anyone has any suggestions for what I'm doing wrong, or how I could better approach this problem, I'd appreciate them greatly. I'm using SW 2011, with Motion and Simulation.

 

JL

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