Method To Exert a Downwards Force (Force created by screw threads?)

In summary: It would definitely be easier to just use a machine than to try and build one yourself.In summary, the Force testing machine uses an electric motor to turn a screw and generate the force. The force depends on the spring constant and the compression distance.
  • #1
Kalus
37
0
I am trying to come up with an automated method to exert a force of around 250N downwards onto a plate.

The possibilites that i have looked at so far are Weight (although this has been discounted due to the size of the weight that would be needed), Hydraulic and Pneumatic systems. However, it has just occurred to me that the sort of Force testing machines that are avaliable in in Mech/Mat labratories (such as http://www.forcegauge.net/catalog/products/specification/mx500n-e.pdf) are electrically powered and use none of the above methods.

My thoughts are that they use some screw mechanism... although, i would like more information as to how the screw works? Is it a case of an electric motor with enough torque to turn a long thread that has the force implement on?
Also, how is Force created by screw threads (like in workshop vices?) In the case of these where they hold the force is it a case of friction between the metals that hold them tight?

If anyone has a diagram of how the above force testing machine works, that would be brilliant.

Many thanks,

Kalus
 
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  • #2
how about using a big spring that you can compress with screws to generated the force required depending on the amount of compression you produce?

F=-kx
F-Force
k-spring constant
x-compression distance (negative as you force direction is opposite to your direction of motion, compression)
 
  • #3
How much displacement do you require? Would a 3-bar roller type mechanism work?
 
  • #4
What are the rest of the requirements? It is easy to hook up a pneumatic cylinder and relay with a known pressure and area to put that small of a load on a plate.
 
  • #5
FredGarvin said:
What are the rest of the requirements? It is easy to hook up a pneumatic cylinder and relay with a known pressure and area to put that small of a load on a plate.

I agree this would probably be easier than designing a power screw because the force depends on coefficient of friction which may not be easy to predict.
 
  • #6

1. What is the definition of "Method To Exert a Downwards Force"?

The method to exert a downwards force refers to the use of screw threads to create a force in a downward direction. This force is created by the rotation of the screw, which causes it to move along its threads and push or pull on an object.

2. How do screw threads create a downwards force?

Screw threads create a downwards force through a process called mechanical advantage. The threads of a screw are designed to increase the distance over which a force is applied, making it easier to exert a larger force with less effort. This allows the screw to push or pull an object downwards with greater force than would be possible with a direct application of force.

3. What are some common uses for the "Method To Exert a Downwards Force"?

The method to exert a downwards force is used in many applications, including construction, manufacturing, and mechanics. Some common examples include using screws to hold objects together, to lift or lower heavy objects, or to adjust the tension of a surface or material.

4. Are there different types of screw threads that can be used to create a downwards force?

Yes, there are several types of screw threads that can be used to create a downwards force, including coarse threads, fine threads, and square threads. Each type has its own advantages and is suited for different applications.

5. How does the pitch of a screw thread affect the downwards force it can create?

The pitch of a screw thread refers to the distance between each thread. A smaller pitch means there are more threads per inch, which creates a smaller mechanical advantage and therefore requires more effort to exert a downwards force. A larger pitch, on the other hand, has fewer threads per inch and creates a larger mechanical advantage, making it easier to exert a larger downwards force with less effort.

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