Designing a Mechanism to Cut Aluminum Bar: Help Needed!

[hdp12]

Hi there

So we have a group design project in my mechanical systems 2 class and it basically goes as follows:
design a mechanism to cut a half inch aluminum bar in half using a standard hacksaw blade and 4 AA batteries. You have to use a motor w/ input > 5000 rpm for the 'main' component

we conceptualized a system which implements a chuck to hold the bar while the motor rotates it at a certain ratio and it linear translates back and forth across the saw blade which has increasing depth against the bar...

I got a lot of work done, so far. such as deriving the approximate number of linear translations necessary such that the cut debris does not completely clog the blade (2.5 times)...

I'm stuck on force though. I'm trying to figure out the proper amount of normal force (or any kind, I guess) to apply to either the blade or the rod against the blade ...

I found some equations / theories (in multiple places) that relate the force to the volume of debris generated, the 'sliding distance' and the hardness of the softer material... but nowhere can I find any elaboration on this hardness. Does anyone know? is it a hardness ratio between the two materials?

the equations are
V = K*F*l/H
and
d (depth of wear) = K*F*l/(H*A)I basically just want to mathematically calculate and optimize the theoretical requirements but I feel like I haven't yet learned exactly what I need to do.

If someone would help me, that would be so awesome :)

thankss

 

[KataKoniK]

Hello there,

It's great to hear that you've made progress on your design project so far. It sounds like you have a good conceptualization for your mechanism and have already started thinking about important factors such as debris management.

Regarding the force needed for the cutting process, it's important to consider the properties of the materials involved. In this case, the hardness of the aluminum bar and the saw blade are key factors in determining the force required for cutting. Hardness is a measure of a material's resistance to indentation or scratching, and it is usually measured on a scale such as the Rockwell scale.

When it comes to cutting, the hardness of the material being cut should be lower than the hardness of the cutting tool in order for the tool to effectively remove material. In your case, the aluminum bar is the softer material and the saw blade is the harder material. This means that the force applied to the blade should be enough to overcome the resistance of the aluminum and cause it to be cut.

The equations you have found are likely based on experimental data and may not take into account the specific properties of your materials. It would be best to use these equations as a starting point, but also consider conducting your own experiments or simulations to determine the optimal force needed for your specific design.

I hope this helps and good luck with your project!