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Ricardoco
22-06-2012, 06:48 PM
Hi all, Can anyone tell me how much force could be applied to the top of a material using a Nema 23 and a 1605 ballscrew, I realise this would be dependant on the weight of the Z assembly, so lets say that weighed 5lbs. im sure there will be other information required so ask away.

Rick

Jonathan
22-06-2012, 07:09 PM
Not quite sure what you're asking - do you want to know how much force the motor can apply if the Z-axis pushes straight down into the material?

If so, then the answer is dependent primarily on what speed the motor is running at and clearly what motor/driver you are using. For sake of argument lets say it's a 3Nm motor on 70V, operating below the corner speed (about 880rpm = 4400mm/min), which is realistic as the Z-axis rarely goes very fast. Under those conditions the torque is a 2Nm.

Formula for driving force, F=T*2*pi*e/L where T is torque, L is pitch (m/rev) and e is efficiency (around 90% for ballscrew).

So with 2Nm on a 5mm pitch ballscrew, remembering that lead is in meters, you have; F=2*2*pi*0.9/0.005=2262N

We should factor in the weight of the Z-axis, but as you can see ballscrews/leadscrews can apply a huge amount of force so this is negligible in comparison. So in short don't stick your fingers under it!

Does that answer your question?

Ricardoco
22-06-2012, 07:22 PM
Not quite sure what you're asking - do you want to know how much force the motor can apply if the Z-axis pushes straight down into the material?

If so, then the answer is dependent primarily on what speed the motor is running at and clearly what motor/driver you are using. For sake of argument lets say it's a 3Nm motor on 70V, operating below the corner speed (about 880rpm = 4400mm/min), which is realistic as the Z-axis rarely goes very fast. Under those conditions the torque is a 2Nm.

Formula for driving force, F=T*2*pi*e/L where T is torque, L is pitch (m/rev) and e is efficiency (around 90% for ballscrew).

So with 2Nm on a 5mm pitch ballscrew, remembering that lead is in meters, you have; F=2*2*pi*0.9/0.005=2262N

We should factor in the weight of the Z-axis, but as you can see ballscrews/leadscrews can apply a huge amount of force so this is negligible in comparison. So in short don't stick your fingers under it!

Does that answer your question?

Over the weekend i will be loading my gantry (in lbs) in the middle to measure the deflection and too see if it needs more work, so i needed a guide weight to go by. my 3nm nema23 on 70v (good guess there) may be replaced with a nema 34 but ive not decided which one yet.

Jonathan
22-06-2012, 07:46 PM
Over the weekend i will be loading my gantry (in lbs) in the middle to measure the deflection and too see if it needs more work, so i needed a guide weight to go by.

I'd be wary of using the Z-axis to do that as unless you have something to measure the force, such as putting bathroom scales underneath the Z-axis, you could seriously damage something - 2262N is 508lb.f.


my 3nm nema23 on 70v (good guess there) may be replaced with a nema 34 but ive not decided which one yet.

How much does your Z-axis weigh, just the bit that moves up and down so we can work out the motor and driver? It'll be quite a lot with the spindle and motor you're planning on, but generally such high speed isn't required on the Z-axis anyway.

Ricardoco
22-06-2012, 07:57 PM
I'd be wary of using the Z-axis to do that as unless you have something to measure the force, such as putting bathroom scales underneath the Z-axis, you could seriously damage something - 2262N is 508lb.f..

LOL thankyou for the warning but im not that heath... I have a motorcycle scissor lift with digital weight guage on it and that can go beyond 1.5 tone, so we should be ok there and i will be building my Z when i know what forces i will require it to achieve.




How much does your Z-axis weigh, just the bit that moves up and down so we can work out the motor and driver? It'll be quite a lot with the spindle and motor you're planning on, but generally such high speed isn't required on the Z-axis anyway. Ahhh now there is a question..lol, I will not be able to answer that until i have my Spindle and Motor. So for now i am working on reducing any twist or flex on the gantry itself.

Ricardoco
22-06-2012, 08:46 PM
LOL thankyou for the warning but im not that heath... I have a motorcycle scissor lift with digital weight guage on it and that can go beyond 1.5 tone, so we should be ok there and i will be building my Z when i know what forces i will require it to achieve.



Ahhh now there is a question..lol, I will not be able to answer that until i have my Spindle and Motor. So for now i am working on reducing any twist or flex on the gantry itself. I am also considering belt drive 2:1 gearing so it wont be fast anyhow, but i need to test the gantry Re-inforce if need be test again and work out what stepper and driver i require so neither the stepper or the gantry is stressed beyond its capability.