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5-Regular Member

## Impact Force Generated By Machine

Anbody Can Help Me ?

I want to calculate the impact force generated by a press machine having following specs

Torque output by gearbox = 1606 Nm , Shaft Eccentricity = 22.5 mm , Pin Joint at Shaft , Ball Joint at Connecting Rod.

I have applied force motor to pin joint of shaft. How can i calculate the maximum impact force generated  by the press for Time t = 300 milli sec contact with  the part. the weight of Slider and upper part of tool is 20 Kg approx. I want to calculate the force generated by press using MDO.

Thanks ,

Pritam

1 ACCEPTED SOLUTION

Accepted Solutions
17-Peridot
(To:preetamnegi7)

If you are still working on this I have a suggestion that will show how very high the force will be that the fixture and shafts will need to withstand.

Model the impact shaft as a stiff spring with the impacting end held.

Increase the stiffness/force of the spring until the motor reaches very close to stall torque very close to bottom dead center on the eccentric joint.

In order to do this you will need a realistic model of friction because otherwise the force is infinite to stop the motor since at bottom dead center there is no component of force about it axis other than friction.

Use a measure for the spring force generated.  This is the maximum force possible which is now also seen to be dependent on friction and the stiffness of the impact shaft.  Since it is dependent on stiffness, that is one of the reasons FEA would be desired, but this method should produce the maximum possible quasi-static force whereas the real flex of the whole setup would reduce this from the maximum.  The inertial effects would increase this from the maximum but for really slow movement inertia can be neglected.  I assume it is acting as a press, not hammer, however your title mentioned impact which sounds more like a hammer action.

Also, you want two pin joints at the top, the gearbox and the eccentric joint.  You also want maybe a slider to limit the head to up down motion and the ball joint could be a cylinder to remove over-constrained degrees of freedom.  (otherwise one of the pin joints could be changed from pin to cylinder)

My guess is you will see 100s of kN for force, which likely produces a lot of flex in your setup.

5 REPLIES 5
21-Topaz I
(To:preetamnegi7)

Impact force requires an FEA solution. It depends significantly on the elasticity and plasticity of all the parts involved.

5-Regular Member
(To:dschenken)

Hi there, Thanks for reply . May be the term i am using was wrong, I want to caculate the Max force generated by my machine.

Do not want to do FEA Analysis.

21-Topaz I
(To:preetamnegi7)

That's too bad. You need to perform a transient FEA impact analysis to determine the impact loads.

To determine force you need to solve  F = k x, so you need to find k, which requires FEA and you need to determine x, which means figuring out which parts of the structure will be subject to dymanic accleration and how far they will move because of it, which also requires FEA.

Do you think the impact force would change if the machine was made of rubber or ice or glass?

17-Peridot
(To:preetamnegi7)

If you are still working on this I have a suggestion that will show how very high the force will be that the fixture and shafts will need to withstand.

Model the impact shaft as a stiff spring with the impacting end held.

Increase the stiffness/force of the spring until the motor reaches very close to stall torque very close to bottom dead center on the eccentric joint.

In order to do this you will need a realistic model of friction because otherwise the force is infinite to stop the motor since at bottom dead center there is no component of force about it axis other than friction.

Use a measure for the spring force generated.  This is the maximum force possible which is now also seen to be dependent on friction and the stiffness of the impact shaft.  Since it is dependent on stiffness, that is one of the reasons FEA would be desired, but this method should produce the maximum possible quasi-static force whereas the real flex of the whole setup would reduce this from the maximum.  The inertial effects would increase this from the maximum but for really slow movement inertia can be neglected.  I assume it is acting as a press, not hammer, however your title mentioned impact which sounds more like a hammer action.

Also, you want two pin joints at the top, the gearbox and the eccentric joint.  You also want maybe a slider to limit the head to up down motion and the ball joint could be a cylinder to remove over-constrained degrees of freedom.  (otherwise one of the pin joints could be changed from pin to cylinder)

My guess is you will see 100s of kN for force, which likely produces a lot of flex in your setup.

5-Regular Member
(To:SweetPeasHub)

I think your reply is relevant, But still i am not 100 % clear.

Sorry for impact term, I used impact due to the reason the force is being transferred to work-piece within 300 milli second. Currently  using force sensor to validate the real assy.