[alfonsonog]

increasing the torque of the stepper motors can they run faster without missing steps? i need speed up my cnc router, i have 1200 oz on the Y, 640 on the X and 264 oz on Z, i am planing to change the 1200 oz motor to the X axis and the 640 oz to the Z axis then get two newones of 2550oz-in for the Y axis, will this help to increase speed and keep on track without missing steps?

[ger21]

Typically, the larger the stepper, the slower they'll turn. So you may actually go slower with larger motors. At what rpm are they losing steps? How large is the machine? Is it screw driven? What type of screws? You may be able to go faster by gearing up with a belt.

[LeeWay]

They may turn slower, but faster without missing steps. They are stronger so depending on how much stronger, yes they could turn faster, but you may want to do some calculations.

Will the drives and PS handle them? If so, then what you propose may give you faster travels without lost steps.

[alfonsonog]

My machine is 48 x 96 cutting area, it is rack and pinion driven with belt and pulley geared on the Y and X axes, Z axis is screw driven, it runs ok at 130 inches per minute in cutting and about 250 on rapid moves,
the power supply is only 36 volts, somebody told me that using a 72 v power supply instead will speed up the motors but im not sure they may blow up?, the drivers are gecko 201, they can handle 80v. missing steps occurs when lot of repetitive moves, and or if i try to increase the rapid position speed the motors stalls, i need a least 180 in per min of cutting and faster rapid moves to go from point to piont without missing steps, what can i do?
thanks for the suggestions.

[ger21]

What are the motors ratings? V, A, and mH? doubling the voltage should double your speed, if you don't exceed the motors capabilities. What reduction are you using, and what is the pinion diameter?

[alfonsonog]

i don't know exactly how to read the v.a of the steppers for example, the one 640 oz-in
is V 4.05, A 4.5 , MH 6.8, how to calculate the max power supply voltage?
the pinion is 1-5/32" overall diameter and has twelve teeth, the motor pulley is 1" dia. and the big pulley is 3-13/16" dia. the Z motor is attached directly to the screw, on the Y axis the machine has only one 1200oz-in motor, maybe using two one on each side of the gantry will help?

[ger21]

32 x sq rt of 6.8 = 83 Volts optimal power supply, so yes, you can use a 72V supply and it should roiughly double your top speed.

[alfonsonog]

can you explain me how did you do the calculation for the max voltage rating of the motor?

[ger21]

32 times the square root of the motors inductance. It's a formula that Gecko has tested and found that it gives the best performance with the least amount of motor heating.

[alfonsonog]

ok i understand, thank you very much for your help, maybe later i will have lot of more questions about the machine since i want to upgrade it to make it better. have a great day.

[alfonsonog]

one more question, what the wires configuraton would be better? serial, parallel, unipolar,
wich one can give more torque or speed, because impedance is different betwen each configuration, power supply voltage depend on this also. what you recommend for this.

[LeeWay]

You really need the motor chart to figure it out or at least I do.
It tells you how many amps and voltage each type wiring uses or needs.
Do you have a link to the place where you got your motors?

[alfonsonog]

yes they are in www.novakon.net i want to get two motors to drive the Y axis one on each end of the gantry the steppers are model RS34-2500S it is 2550oz-in,now i need to figure it out what configuration would be better for higher torque and speed, then what type of power supply is needed for this aplication, the X axis would be driven by 1200oz-in and Z axis by 640 0z-in, this two motors are existing on the machine.

[ger21]

Parallel will give much higher speeds than series.

[alfonsonog]

since stepper motors have higher torque at low speed and they lose torque at higher speed, reducing the pulleys diameter can give higher speed at the pininon gear with low speed at the motot shaft, may this work?