Stepper Motor Technique: A Reflection Based On Torque

STEPPER MOTOR SELECTION BASED ON TORQUE http://www.linengineering.com/stepper-motors/4118.aspx

Every manufacturer provides datasheet for the value of holding torque, torque vs rotational speed graph for a stepper motor. A stepper motor can supply only a specific amount of torque at a particular speed. The y-axis of the graph represents torque in N/m and the x-axis represents speed of the motor in rotations per second (rps) .The rps second of the stepper motor will depend on the printing speed. The printing speed is measured in mm/s, and as the printing speed increases the stepper motor has to revolve its shaft faster to move the parts in the same amount of time. Printing speed varies from anywhere between 50 to 100 mm/s and for the faster

The first step involves marking a point on the filament at the entry point of the extruder and another one at 100 mm from the first point. The motor is then given command to extrude 100 mm. If the amount of material extruded is of right quantity then the second marked point will be at the entrance of the extruder. If not, either the material extruded can be greater or less than the required value. When the amount of material extruded is less, the distance between the second point and the entrance to the extruder is measured and this is used for calculating the new step value for the motor. When the amount of material extruded is more the second point marked enters the extruder and the distance between the second point and the entrance can be measured by reversing the extruder motor to remove the

If calibration of the axis motors is not performed, the movements of each axis will not be accurate resulting in inaccurate dimensions of the 3D printed product. The calibration process involves marking the initial position of the part mounted on each axis. This can be print bed mounted on the x-axis , the printed head assembly mounted on y-axis and the extruder mounted on the z-axis. The motor is then given the command to move 100 mm. After the motor has completed its movement the final position of the part mounted on the axis is marked. The difference between the initial and final position is measured and if it is found to be 100 mm, then there is no necessity of calibration. However a difference in this value with the input value will require the motor to be calibrated. The new steps can be calculated using formula given