CNC Router and it's stepper!

[watzmann]

Hi All ,

am building a 3 Axis router , this axis runs on a power screw which drived by three stepper motors , the machine bed is 3 meter long x 2.5 meter wide ,

BUT :

i have a problem that am not sure that my stepper motor that am using will be sufficient to move the X axis for examle, my load on X axis is about 50 Kg ,

can you tell plz how to calculate this problem ?

my stepper specification is on this link
http://www.astrosyn.co.uk/docs/l-series-stepper.pdf

am using motor model L707 , and am running it under 12 Volt and 2 amps maximum,

hope to hear soon from you

[DieGuy]

that is a 7 volt motor. with 280 N/cm

better get Gecko's with a 70 volt supply and drive them.

[watzmann]

sorry but what does geckos mean

[ger21]

Stepper motor drives. http://www.geckodrive.com

[watzmann]

but why to use this drivers , am going to build my own driver,
my problem now is to caclulate the required torque, and if my motor will move this load or not

[ger21]

but why to use this drivers , am going to build my own driver,
my problem now is to caclulate the required torque, and if my motor will move this load or not

You won't be able to build a better drive than the Gecko for the price.

Force = (2 x pi x motor torque)/screw lead

[fyffe555]

Whats the voltage limit of your drivers?
Are the drivers bipolar or unipolar?
What lead leadscrew are you using?
What linear bearing are you using?
How fast do you want to go?

To truely calculate the torque needed to move your axis you need to add together; your motors inertia, your leadscrews inertia, friction load due to leadscrew bearings, friction load due to linear bearings and the weight of gantry. Take your answer in Newtons or what ever and then factor in your leadscrews efficiency to determine the torque required from your motor.

280Ncm or ~400oz-in would move it but you haven't got a enough torque to move it very fast. The torque curve of these motors drops off rapidly after a few hundred RPM's so if axis speed is an issue you have a problem. Roughly speaking at 300rpm and a .2in lead screw its going to take you almost two minuites to rapid from one end of your table to the other - assuming the screw doesn't whip at 300rpm and being >3m long.

With a Stepper motor you need to provide 10-25 x the motor voltage depending on who you talk to. A gecko (70+volts) could only supply about 10x and most drivers 5-7 times so you're going to be slow.

You can't get more speed by increasing the lead as the effective force will reduce accordingly.

[watzmann]

Actually speed as for me is not a big problem , it doesn't matter really if the motors is slow ,
am using driver with limit of 30 Volts and 2 Amps but i'll run my motors with only 12 volts, my power screw is 2.50 meter long with 4 mm pitch,

it's so important as for me to kow whether this motors has the enough torque or not , speed is not required here .

p.s.s my motors is brand new so it's still powerful

waiting for your opinion

[ger21]

Torque drops off rapidly as speed increases. The higher the voltage used, the slower the torque falls off. Those motors are on the small side. And running them on 12V would give you only a small fraction of their rated torque, and probably less than 100 rpm.

[fyffe555]

try this another way ; to be practical It Will Not Work.

12v and 2a isn't enough to drive your motor to anything like its rated torque. 12v is too low. 2A more than motor rated and could damage the motor.

Even at full power the motor isn't strong enough for your table size and weight, at 12v it might have trouble turning the screw alone.

If your driver is a current resistor type rather than a chopper driver you're in even worse shape.

There are lots of calculations you need to do before you go spending the money on a table that size.

[watzmann]

what's ur opinion if i raised the voltage to 30 volts, i hope it would work this time ,

this motor can stand volts up to 70 Volt and 2 Amp , am sure the company told me that.

and they tell also in the specification that this motor has a high torque within this compact housing .