Lead Screw model in Creo and calculations

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Discussion Overview

The discussion revolves around the design and analysis of a lead screw mechanism in Creo, specifically for moving a 400lb load. Participants explore the relationship between torque, speed, and the structural integrity of the supporting components, including the lead screw and lever system.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Experimental/applied

Main Points Raised

  • One participant describes the initial setup of a lead screw with a major diameter of 1 1/4 inches and calculates the torque required to move the load as approximately 36.70 lb-in.
  • Another participant emphasizes the importance of the screw thread pitch over the diameter for determining linear movement per crank turn and suggests that the speed of the crank affects the load's movement speed.
  • A participant mentions using a TPI of 4 to relate RPM to linear velocity and seeks guidance on determining failure conditions for the support structure holding the lead screw and lever.
  • One participant discusses the deflection of the vertical part of the mount under axial force and its implications for screw alignment.
  • A later reply indicates a shift to using Workbench for analysis instead of Creo, suggesting progress in the investigation.

Areas of Agreement / Disagreement

Participants generally agree on the importance of the screw thread pitch and the relationship between crank speed and load movement. However, there is no consensus on the specific failure conditions for the support structure, as this remains a point of inquiry.

Contextual Notes

Participants have not fully resolved the mathematical steps involved in analyzing the failure conditions or the specific stresses and strains to consider in the support structure.

Who May Find This Useful

Individuals interested in mechanical design, particularly those working with lead screw mechanisms, structural analysis, or simulations in CAD software may find this discussion relevant.

inamukak
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Hi

I'm trying to make a lead screw in Creo which would be used to move a 400lb load linearly along the ground. This would be turned manually using a lever as shown in the pic (not the complete model). I have used a lead screw with a major diameter of 1 1/4 and determined the torque to move the load would be around 36.70 lb-in. What I'm unable to determine is the speed at which this would move the load a total distance of 3 feet, and if it would be possible to change this speed so that the lever doesn't have to be turned for quite a lot of time. Any help would be appreciated.

Thanks in advance!
 

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Welcome to the PF.
The diameter of the lead screw is not the important parameter, you need to specify the pitch of the screw thread.
That will tell you how far the load will move for each turn of the crank handle, (your lever).
The speed you turn the crank will decide the speed the load moves.
 
Hi

Thanks for the reply. I took a TPI of 4 and etermined the torque required to move the load. I was basically looking for a way to related the RPM and the linear velocity, which I have figured out now.
Also, I'm trying to determine the fail conditions for the L-shaped support holding the lead screw and the lever, but I have no clue where to start. I've been trying to run simulations in Creo to determine this but to no avail. What stresses and strains should I take into consideration? And how will a force or torque on the lever lead to failure of the support?

Thanks!
 
If you assume the base plate is firmly attached, then only the vertical part of the mount will deflect when an axial force is applied by the lead screw. That will bend the material that is between the base and the lead screw. When the material bends the screw will be misaligned in the thread which will have other implications.
 
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Thanks for the answer! I decided to perform the analysis in Workbench instead of in Creo and did manage to get some results from your answer.

Thanks again!
 

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