My project is a welding positioner which is basically a machine that can lift, t

Question

My project is a welding positioner which is basically a machine that can lift, tilt, and rotate a plate. The rotation of the plate is going to be moved by a motor. Now, I am having trouble calculating the load inertia of the plate plus items that could be placed on top. Our sponsor asked us to calculate the load inertia so that we can find the right motor to be able to combat the load inertia. However, I am confused on what load inertia is. It seems to be an old term for moment of inertia, but I am not entirely sure. Load inertia is the term my sponsor gave us. So, I was wondering if you could help me.

I also have to calculate the load inertia and be able to use that value to determine which motor would work. Imagine a 36" diameter rotary plate carrying a 36" by 36" 1000 lb box. The plate is made of steel.

Explanation / Answer

Inertia is an objects resistance to a change in speed.

In an electromechanical system, both motor and load have inertia. The ratio of load inertia to motor inertia is an important aspect.

Inertia ratio = Jl/Jm ; where Jl is inertia of the load reflected to the motor, Jm is the inertia of motor.

Some motor sizing guidelines stipulate that the the inertia ratio should be 10:1 or lower.

To calculate the load inertia we need to add all the inertia of rotating parts.

Jl = Jd+Je+Jc ;Jd is Inertia of actuator, Je is inertia of external load, Jc is inertia of coupling.

If the inertia ratio is high then, we need to add a gearbox or increase the size of the motor.

For the example you need to multiply the radius square with the weight i.e 18*18*1000 = 324,000

Then divide it with gravitational constant which is 386 in/sec²

324000/386 = 839.378 lb-in-sec² is the resultant load inertia .

Related Questions

Navigate

• Browse (All)
• Browse M
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.