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Question #: 3547

Question: I am asking what to set my steps per using your kit stepper motors and a 1/2"x13 lead screw with Mach3

Current Solution

Here is the formula for steps/inch (steps per inch)

Steps = how many steps for a full ration of the motor = standard motor steps x number of microsteps for each step
Standard motor steps for our stepping motors is 200 steps per revolution.
Microsteps are selected on the driver and are shown as full, 1/2, 1/4, 1/8, 1/16, 1/32 etc... Use the denominator for the number of microsteps per step.

Inches = how far the travel is for one full rotation of the motor. For the 1/2" - 13 TPI (threads per inch), the travel length will be 1"/13 or .076923". So, for one revolution of the motor, the travel distance will be .076923 inches.

So, the steps = 200 * microsteps, let's make this 1/4 just for the formula.
The inches will be .076923. Plug those into the formula:
Steps / inch = (200 * 4) / .076923 This can also be written as:
200 * 4 / (1 / 13) = 10,400

Respond:

Other Possible Solutions to this Question

  • With a 1/2 lead screw what is the optimal steps for the stepper motor driver 1/16, 1/8, 1/4 etc

    We typically use a 1/4 microstepping for lead screws, but you want to determine the microstepping only after you determine what resolution you want on that axis of the machine.

    The formula:
    Resolution is steps per inch or steps per milimeter

    I will go over this using steps/inch:
    steps = motor steps x driver microstepping
    inch = the amount of travel with one full stepper motor rotation

    In the case of our 1/2" 5 start 10 TPI lead screw, the axis will travel .5 inches with one stepper motor rotation.

    Let's use 1/4 microstepping (4 microsteps for each stepper motor step)

    Therefore:
    (200 steps x 4) / .5 inches =
    800 steps / .5 inches =
    1600 steps/inch

    Now let's use 1/2 microstepping (2 mistrosteps)

    (200 steps x 2) / .5 inches =
    400 steps / .5 inches =
    800 steps/inch

    Remember that increasing microsteps, the torque is also reduced, but the smoothness from the motor is increased.

    Click the link to respond:
    With a 1/2 lead screw what is the optimal steps for the stepper motor driver 1/16, 1/8, 1/4 etc

  • How can I decrease the rapid acceleration of the cutter from a completed cutting operation to a new location so that the stepper motor will not lose its steps and mess up the machine zero settings? I am using CamBam and Mach3 on my machine with a chain drive. what is the best way to reduce accleration

    Decreasing the speed of acceleration in the cutter? Meaning of your router/spindle?, To modify the speed of a router will be going to the router itself and modifying the speed, but if a spindle is being used modifying it will be done either manually in the VFD (VFD Setup:
    Change PD001 to '0' (source of run commands)
    Change PD003 to 300 (main frequency - Hz)
    Change PD004 to 300 (base frequency - Hz)
    Change PD005 to 400 (max operating frequency - Hz)
    Change PD006 to 2.5 (intermediate frequency - Hz)
    Change PD008 to 220 (max voltage - V)
    Change PD009 to 15 (intermediate voltage - V)
    Change PD010 to 8 (minimum voltage - V)
    Change PD011 to 100 (frequency lower limit - Hz)
    Change PD142 to 7 (rated motor current - Amps)
    Change PD143 to 2 (motor pole number)
    Change PD144 to 3000 (rated motor revolution))<- make sure these are your settings in the VFD. If the spindle is wired to the breakout board and is working through Mach 3 then the modification will be done in your CamBam/Feed rate settings.

    Click the link to respond:
    How can I decrease the rapid acceleration of the cutter from a completed cutting operation to a new location so that the stepper motor will not lose its steps and mess up the machine zero settings? I am using CamBam and Mach3 on my machine with a chain drive. what is the best way to reduce accleration

  • I need the calculation to determine the stepper motor torque to find the load that it can withstand in horizontal position using a lead screw at 1/2" diameter with 13 TPI.

    There are two main questions that we can answer with respect to motor torque and the mechanical advantage of lead screws, 1) What torque motor do you need to lift a particular weight, or 2) What maximum weight will my motor torque be able to lift.

    This formula uses Newtons (N) as it's final unit. Use this with the included radius (R) to determine the torque. Newtons can easily be converted to lbs or ounces using online conversions.

    Effort = Sf + (Load/(2 x pi x (R/p) x Se))

    where:
    p = pitch of the screw
    Se = screw efficiency = Standard lead screw will be between 20% (.2) and 40% (.4)
    Sf = static force. This is the force that is needed to start the movement. The number may be eliminated, but it is good to use a number in the 5 N to 20 N range.
    Load = the expected load that the effort will need to carry (i.e., the router and the included axis assembly that the motor will need to lift)
    R = radius of the lead screw


    This formula is based on the "law of the machine"

    The final effort amount with its unit of newtons and R will be the torque. For example, if the effort comes to 100 N (newtons) and the R is .5 inches, then you can assume that the effort is 50 N-in since it would take twice the effort to turn form the one inch mark from the center of the shaft.

    Example:

    Load = 90 N (20.2 lbs)
    R = 1 inch since that is the length from the center of the shaft that the motor is rated
    p = 1 inch / 13 = .08 inches

    Effort = 5 N + (90 N / (2 x 3.14 x (1 / .08) x .2))
    Effort = 5 N + (90 N / (6.28 x 12.5 x .2))
    Effort = 5 N + (90 N / (15.7))
    Effort = 5 N + (5.73 N)
    Effort = 10.7 N = 2.4 lbs = 38.4 oz-in

    I am putting the oz-in on the end because the formula considers the distance from the center of the shaft to be one inch.

    Therefore, a 425 oz-in motor would be able to lift a 20.2 lb Router with its accompanying assembly. If the assembly and router is heavier, plug in the numbers and determine the effort required.

    With a bit of algebra, the formula can be rewritten to find the load:

    Load = (Effort - Sf) x (2 x pi x (R/p) x Se)

    Another formula that does not consider friction at all:

    Effort = (Load x p) / (2 x pi x R)

    Lets see if we get similar results:

    Effort = (20 lb x .08 inches) / (2 x 3.14 x 1)
    Effort = 1.6 / 6.28 = .255 lbs = 4.08 oz-in

    The results from both formulas appear to be very small because a 13 TPI screw will have enormous mechanical advantage.

    It is evident that the first formula that does consider friction that we are loosely estimating is far more conservative than the second formula. Either way, even the most conservative formula shows that the 425 oz-in motor will handle very large weights. If you are using a lead screw with only two turns per inch, .5 inch pitch, you can determine the requirements with the first formula.

    Example for a 10 TPI 5 start (2 turns per inch) lead screw:

    Load = 90 N (20.2 lbs)
    R = 1 inch since that is the length from the center of the shaft that the motor is rated
    p = 1 inch / 2 = .5 inches

    Effort = 5 N + (90 N / (2 x 3.14 x (1 / .5) x .2))
    Effort = 5 N + (90 N / (6.28 x 2 x .2))
    Effort = 5 N + (90 N / (2.512))
    Effort = 5 N + (35.83 N)
    Effort = 40.828 N = 9.18 lbs = 146.88 oz-in

    Customer Response:
    thank you so much

    Additional Information:


    Additional Information:


    Additional Information:
    how do i calculate torque of stepper motor if lead screw coupled to motor shaft and load applied by lead screw on plate is 100 kg by vertically

    Additional Information:
    Pls


    Additional Information:
    1m 16mmdiameter ball screws calculations

    Click the link to respond:
    I need the calculation to determine the stepper motor torque to find the load that it can withstand in horizontal position using a lead screw at 1/2" diameter with 13 TPI.

  • My stepper motors are randomly and frequently stalling while using the Pokeys57CNC controller board, any idea what could be the issue?

    I would suspect that the velocity and/or acceleration is too high for the amp setting on the driver. Consider increasing the current amp setting on the driver is the motor can handle the current, or decrease the velocity and/or acceleration.

    You might also want to check to see if you have any mechanical binding on the machine. To check, remove the mechanical drive mechanism so the axis slides freely and slide it from end to end to feel if you have any tight areas or binding.

    Click the link to respond:
    My stepper motors are randomly and frequently stalling while using the Pokeys57CNC controller board, any idea what could be the issue?

  • I need the calculation to determine the stepper motor torque to find the load that it can lift using a lead screw at 1/2" diameter with 13 TPI.

    There are two main questions that we can answer with respect to motor torque and the mechanical advantage of lead screws, 1) What torque motor do you need to lift a particular weight, or 2) What maximum weight will my motor torque be able to lift.

    This formula uses Newtons (N) as it's final unit. Use this with the included radius (R) to determine the torque. Newtons can easily be converted to lbs or ounces using online conversions.

    Effort = Sf + (Load/(2 x pi x (R/p) x Se))

    where:
    p = pitch of the screw
    Se = screw efficiency = Standard lead screw will be between 20% (.2) and 40% (.4)
    Sf = static force. This is the force that is needed to start the movement. The number may be eliminated, but it is good to use a number in the 5 N to 20 N range.
    Load = the expected load that the effort will need to carry (i.e., the router and the included axis assembly that the motor will need to lift)
    R = radius of the lead screw


    This formula is based on the "law of the machine"

    The final effort amount with its unit of newtons and R will be the torque. For example, if the effort comes to 100 N (newtons) and the R is .5 inches, then you can assume that the effort is 50 N-in since it would take twice the effort to turn form the one inch mark from the center of the shaft.

    Example:

    Load = 90 N (20.2 lbs)
    R = 1 inch since that is the length from the center of the shaft that the motor is rated
    p = 1 inch / 13 = .08 inches

    Effort = 5 N + (90 N / (2 x 3.14 x (1 / .08) x .2))
    Effort = 5 N + (90 N / (6.28 x 12.5 x .2))
    Effort = 5 N + (90 N / (15.7))
    Effort = 5 N + (5.73 N)
    Effort = 10.7 N = 2.4 lbs = 38.4 oz-in

    I am putting the oz-in on the end because the formula considers the distance from the center of the shaft to be one inch.

    Therefore, a 425 oz-in motor would be able to lift a 20.2 lb Router with its accompanying assembly. If the assembly and router is heavier, plug in the numbers and determine the effort required.

    With a bit of algebra, the formula can be rewritten to find the load:

    Load = (Effort - Sf) x (2 x pi x (R/p) x Se)

    Another formula that does not consider friction at all:

    Effort = (Load x p) / (2 x pi x R)

    Lets see if we get similar results:

    Effort = (20 lb x .08 inches) / (2 x 3.14 x 1)
    Effort = 1.6 / 6.28 = .255 lbs = 4.08 oz-in

    The results from both formulas appear to be very small because a 13 TPI screw will have enormous mechanical advantage.

    It is evident that the first formula that does consider friction that we are loosely estimating is far more conservative than the second formula. Either way, even the most conservative formula shows that the 425 oz-in motor will handle very large weights. If you are using a lead screw with only two turns per inch, .5 inch pitch, you can determine the requirements with the first formula.

    Example for a 10 TPI 5 start (2 turns per inch) lead screw:

    Load = 90 N (20.2 lbs)
    R = 1 inch since that is the length from the center of the shaft that the motor is rated
    p = 1 inch / 2 = .5 inches

    Effort = 5 N + (90 N / (2 x 3.14 x (1 / .5) x .2))
    Effort = 5 N + (90 N / (6.28 x 2 x .2))
    Effort = 5 N + (90 N / (2.512))
    Effort = 5 N + (35.83 N)
    Effort = 40.828 N = 9.18 lbs = 146.88 oz-in

    Customer Response:
    thank you so much

    Additional Information:


    Additional Information:


    Additional Information:
    how do i calculate torque of stepper motor if lead screw coupled to motor shaft and load applied by lead screw on plate is 100 kg by vertically

    Additional Information:
    Pls


    Additional Information:
    1m 16mmdiameter ball screws calculations

    Click the link to respond:
    I need the calculation to determine the stepper motor torque to find the load that it can lift using a lead screw at 1/2" diameter with 13 TPI.

  • how to calibrate stepper motors with ballscrews In mach3

    The easy way is to use Mach3's calibration process to calibrate the axis with the ballscrew coupled to the stepper motor. This is done in the settings tab of Mach3 and clicking the button just above the "Reset" button called "Set Steps Per Unit". A dialog box will appear asking how far you want Mach3 to move that axis. Mach3 will move that axis at a distance that is determined by the existing steps per unit value set in the motor tuning dialog box (config menu -> motor tuning). Not knowing the distance that this axis will travel, it's best to use a very small value.

    The more difficult way and the technique that should be used to create the initial value for the step per unit in the motor tuning dialog box. Use the steps/unit formula. This example will use inches.

    Steps/Inch
    = ((motor natural steps) x microsteps) / (the travel for one complete revolution)

    The travel for one revolution would be the distance a ball nut will travel with one complete turn of the ball screw. This is generally the number of starts / threads per inch. Say the ball screw has 5 starts (5 threads starting from the beginning of the screw) and 10 threads per inch (TPI), then the travel for one complete turn of the screw would be 5/10, or 1/2".

    Say you set the microstepping to be 1/4 on the stepper motor driver and your stepper motor has 200 natural steps per revolution (1.8 degrees per step), then the total steps would be 200 x 4 = 800.

    So, the steps/inch is 800 / 1/2" = 1600 steps per inch

    Hope that helps

    Click the link to respond:
    how to calibrate stepper motors with ballscrews In mach3

  • Lost Comm with steppers: I have been running Mach3 with my Black Toe for years. This morning, I booted up, motors locked up. Started Mach, hit reset, and nothing. Can't move. Checked plugs. Diag screen says OK. What to look for? I have the BYOCNC Computer/contoller box.

    New clues. I loaded a different profile I have used for another machine and my Black Toe moves. Of course all the settings are different. I load my normal profile and no ports, pins, or outputs light up.

    Click the link to respond:
    Lost Comm with steppers: I have been running Mach3 with my Black Toe for years. This morning, I booted up, motors locked up. Started Mach, hit reset, and nothing. Can't move. Checked plugs. Diag screen says OK. What to look for? I have the BYOCNC Computer/contoller box.

  • got my stepper motors wired to the information on your website using USB Bob and the motors don't step they keep turning like an old drill until they stop

    So, if I understand correctly, the stepping motor will turn on command, but the motor will only turn in one direction. Check the output of your direction signal wire. Check the wire voltage when you command the motor to turn on one direction in the planet-cnc software. Then check the voltage when you command the motor to turn in the other direction. The voltage should be different in each case.

    Click the link to respond:
    got my stepper motors wired to the information on your website using USB Bob and the motors don't step they keep turning like an old drill until they stop

  • I'm building my own machine using your motors and drivers. What is the best dip switch settings for the 3.0 amp drivers powering the 425 oz motors

    The settings that you will use for your 3.0 amp driver to properly power and turn your 425 oz-in stepper motor will cheifly depend on your application and the mechanical parts you are using on your machine. In all circumstances, the amp setting for the stepper motor (according to the datasheet) should be 2.8 amps. Use the closest setting on the driver without going over.

    Here is a good rule of thumb for the microstepping which will correspond to the resolution, but wil also affect torque. You always want to try to achieve the best torque and resolution for the axis you are moving but go with the lowest microstepping possible. In cases where there is mechanical advantage, like a lead screw scenario, where for each motor revolution, the axis move a very small amount, you will want a very low microstep value. This is because the mechanical configuration will provide most of the finer resolution and you will not need the microstepping to assist in this. Increase the microstepping only in conditions where the axis is not moving smooth enough, or where there is a mechanical disadvantage. A mechanical disadvantage would be where the stepper motor is causing a great amount of movement in the axis and the resolutions suffers from this condition. Increase the microstep value up to your desired resolution, but don't go over since the torque of the motor will decrease.

    Click the link to respond:
    I'm building my own machine using your motors and drivers. What is the best dip switch settings for the 3.0 amp drivers powering the 425 oz motors

  • I have theNema 24, 425 Oz stepper motors kit what are my Ports and Pins?

    The ports and pins are designated by the breakout board that you have, Now here are the schematics for both(https://www.buildyourcnc.com/item/electronicsAndMotors-parallel-breakout-relay#prettyPhoto/2/ and https://www.buildyourcnc.com/item/electronicsAndMotors-electronic-component-USB-Controller-Breakout#prettyPhoto/2/) Which for the Parallel the pins will be 1,14,2,3,4,5,6,7,8,9. For 1,14 you will need to use them together for a additional axis. Setup will be (ex.mach3) step in (2) / direction pin (3). continued for other pins, 4,5 6,7 etc.
    Now for the USB it has the label on the board right next to the terminal blocks, x-axis/etc.

    Click the link to respond:
    I have theNema 24, 425 Oz stepper motors kit what are my Ports and Pins?

  • how do you calibrate steps per inch using Mach3 and a 1/2x13 lead screw

    You will first need to derive the number of turns per inch that your lead screw produces. If there is only a single start (typical all thread screws), then the turns per inch is the same as TPI (threads per inch). If there is multiple starts, then the number of starts is divided by the TPI to determine the turns per inch. For example, 10 TPI with 5 starts is 10 / 5 = 2 turns per inch. Now that we know this, we can get the number of steps per inch as described in the previous question: take the number of steps per revolution that the motor will output. This will be the number of full steps that you motor produces (typically 200, or 1.8 degrees per step) multiplied by the microstepping per step to which the driver is configured. Simply multiple the number of turns per inch and the number of steps per revolution and you will get the steps per inch. Ok, lets see the formula:

    200 steps * 16 microsteps * 2 turns per inch = 6400 steps per inch


    Additional Information:
    14798


    Additional Information:
    hallo i have cnc with ball screw 2.5mm of pith..n driver stepping 1/16 how to setup step value

    Additional Information:
    i have ball screw with 2.5 mm of pith n 1 start motor 200 step 1/16 driver stepping

    Click the link to respond:
    how do you calibrate steps per inch using Mach3 and a 1/2x13 lead screw

  • Have checked stepper motor wires dozens of times and they are wired like diagram says. Stepper motors will not turn under power. I am using laser control option. What should I do?

    This sounds like a problem with the step (pulse) signal. The driver motors receive two signals from the computer via the board -- one is high or low and tells the motors which direction to turn, one is a square wave pulsed signal(quick that tells the motor to turn or a constant high signal that tells the motor to maintain its position. With an oscilliscope you can check for proper signal at the board. If you bought the board from us, please contact us to arrange a return authorization.

    Click the link to respond:
    Have checked stepper motor wires dozens of times and they are wired like diagram says. Stepper motors will not turn under power. I am using laser control option. What should I do?

  • With the Mach3 USB board, my stepper motors are moving or spinning slowly.

    If your motors turn very slowly using your Mach3 USB board, then either the pulse from the board is being output at a slow rate or the motor drivers are set to a higher than expected microstepping:

    The Mach3 USB board outputs the pulse rather than the computer, but Mach3 controls this pulse frequency within the motor tuning section. First, determine if the travel distance is correct with the computer and the physical travel of the machine.

    If the travel is different, then your stepper motor driver's microstepping is incorrect, or the steps per inch/mm in the motor tuning within Mach3 is incorrect.

    If the travel is correct, then simply change the velocity and acceleration parameters to your desired level. If Mach3 will not achieve the velocity you desire, then decrease your stepper motor driver's microstepping setting, readjust the step per inch/mm in mach3 and readjust the acceleration and velocity to your desired levels.

    Click the link to respond:
    With the Mach3 USB board, my stepper motors are moving or spinning slowly.

  • I HAVE ONE OF YOUR SMALLER STEPPER MOTORS RUNNING MY X AXIS BRIDGE CRANE AND IF IT IS MOVED TO FAST THE MOTOR SOUNDS LIKE SKIPPING STEPS WILL 651OZ REQUIRE A DIFFERENT POWER SUPPLY CONTROLER?

    Yes, the 651 oz/in motor requires a driver that is compatible to the motors (the motor will draw 6 amps max and the driver paired with this motor will be able to allow for a 6 amp draw). I would also recommend a 36 volt power supply for better high velocity performance.

    Click the link to respond:
    I HAVE ONE OF YOUR SMALLER STEPPER MOTORS RUNNING MY X AXIS BRIDGE CRANE AND IF IT IS MOVED TO FAST THE MOTOR SOUNDS LIKE SKIPPING STEPS WILL 651OZ REQUIRE A DIFFERENT POWER SUPPLY CONTROLER?

  • What are the toggle switch settings on the stepper motor drivers for the .5 in. lead screw 10 tpi 2 turns per inch? Thankyou!

    On the top of the stepper motor drivers is a grid with the appropriate toggle switch positions for the lead screw being used. If it is 2 turns per inch, the proper toggle switch positions would be 01101110. Try this and see if it works.

    Click the link to respond:
    What are the toggle switch settings on the stepper motor drivers for the .5 in. lead screw 10 tpi 2 turns per inch? Thankyou!

  • Do you sell leadscrews and ballnuts that are 5 TPI? I'd like 0.001" per step, using a 200 steps/rev (1.8 degree) motor.

    We sell leadscews and anti-backlash nuts at the moment. Ballnuts will be available from us in the future.

    Specifically to your question, you want 0.001" resolution:

    The formula: (we are looking for a minimum of 1000 steps per inch
    steps = (motors steps)/(travel with one motor rotation)

    steps = (200 natural motor steps) x (microsteps ) / 0.5" travel (1/2" leadscrew 10 TPI 5 Starts)

    steps = 200 * microsteps / 0.5"

    multiply both sides by 0.5":

    steps * 0.5" = 200 * microsteps

    divide both sides by 200:

    (steps * 0.5") / 200 = microsteps

    replace steps with 1000:

    (1000 * 0.5") / 200 = microsteps

    500 / 200 = microsteps

    2.5 microsteps will provide .001"

    I would recommend 4 microsteps (1/4 microstepping), so your formula will be as follows:

    steps = steps/inch = (200 * 4) / 0.5" = 800 / 0.5" = 1600 steps/inch

    Click the link to respond:
    Do you sell leadscrews and ballnuts that are 5 TPI? I'd like 0.001" per step, using a 200 steps/rev (1.8 degree) motor.

  • How do I configure my control program (i.e. Mach3, EMC2, etc.) for lead screw steps per inch?

    You will first need to derive the number of turns per inch that your lead screw produces. If there is only a single start (typical all thread screws), then the turns per inch is the same as TPI (threads per inch). If there is multiple starts, then the number of starts is divided by the TPI to determine the turns per inch. For example, 10 TPI with 5 starts is 10 / 5 = 2 turns per inch. Now that we know this, we can get the number of steps per inch as described in the previous question: take the number of steps per revolution that the motor will output. This will be the number of full steps that you motor produces (typically 200, or 1.8 degrees per step) multiplied by the microstepping per step to which the driver is configured. Simply multiple the number of turns per inch and the number of steps per revolution and you will get the steps per inch. Ok, lets see the formula:

    200 steps * 16 microsteps * 2 turns per inch = 6400 steps per inch


    Additional Information:
    14798


    Additional Information:
    hallo i have cnc with ball screw 2.5mm of pith..n driver stepping 1/16 how to setup step value

    Additional Information:
    i have ball screw with 2.5 mm of pith n 1 start motor 200 step 1/16 driver stepping

    Click the link to respond:
    How do I configure my control program (i.e. Mach3, EMC2, etc.) for lead screw steps per inch?

  • I have your Nema 24 electronics kit and am having problems with the Z axis dropping over time. I am using a PC 8902 motor. Any ideas on what the problem is? What should be the motor tuning values in Mach3? Thanks

    Make sure all your bolts/screws are tighten correctly and if using a lead screw make sure your anti-backlash nut is not offset. Now a default setting will be 10101100 for your driver dip switch settings and in motor tuning (mach3) 1600 steps per, 400.02 velocity, 4 in acceleration. now the acceleration and velocity can be adjusted to move your machine faster, but if set to high they could stall. Make sure you have the correct wiring from your motor to your driver (https://www.buildyourcnc.com/Documents/PN.SM60HT86-2008BF-U%20(inhouse%20PN.60BYGH303-13)%20(1).pdf).

    Click the link to respond:
    I have your Nema 24 electronics kit and am having problems with the Z axis dropping over time. I am using a PC 8902 motor. Any ideas on what the problem is? What should be the motor tuning values in Mach3? Thanks

  • stepper motor runs smooth then rough for a moment then smooth, etc. Does this at all steps, and connected motors.

    This sounds like it could be a loose wire, or poor connection with the motor wires. Make sure all wires that are to be connected to each other are soldered and use a lineman's splice when putting the wires together. Also, make sure that the wires going into the driver is securely fastened.

    If this is an issue where the motors have run well for a long time then just started to show this performance issue, then make sure that there are no wire ties or other binding method that is chaffing the wires. This would make the motors run oddly at certain travel positions where the chafing has caused a short with the wires.

    If this is an issue where you don't have the motor plugged in at all and are just trying to turn it by hand and this phenomenon is occuring, then make sure all of the wires are not touching each other. When wires are touching each other and you are trying to spin the shaft by hand, the motor will feed current back into the motor making it difficult to turn.

    Click the link to respond:
    stepper motor runs smooth then rough for a moment then smooth, etc. Does this at all steps, and connected motors.