A stepper motor drive having step angle 7.2°/step is used for dri...
Stepper Motor Drive and Axis in NC Machine
The given problem involves a stepper motor drive and an axis in an NC (Numerical Control) machine. We need to determine the positional accuracy of the axis.
Step Angle of the Stepper Motor
The stepper motor used in the NC machine has a step angle of 7.2° per step. This means that for each step the motor takes, it rotates by an angle of 7.2°.
Gear Ratio
The motor is connected to the lead screw through a gear with a gear ratio of 1/3. The gear ratio is defined as the ratio of the output speed to the input speed. In this case, for every 3 revolutions of the motor, the lead screw makes 1 revolution.
Lead Screw Parameters
The lead screw has a pitch of 3 mm, which means that for every complete revolution of the screw, it moves forward by a distance of 3 mm. Additionally, the lead screw has 2 starts. This means that there are two separate threads wrapped around the screw, which allows for a higher linear speed.
Calculating the Linear Travel per Motor Step
To calculate the linear travel per motor step, we need to consider the combined effect of the motor step angle, gear ratio, and lead screw parameters.
1. The lead screw moves forward by a distance of 3 mm for every revolution.
2. The gear ratio of 1/3 means that the lead screw completes one revolution for every 3 motor revolutions.
3. The motor has a step angle of 7.2° per step, which means that it takes 50 steps to complete one revolution (360° / 7.2° = 50).
4. Combining these factors, the linear travel per motor step can be calculated as follows:
Linear travel per motor step = (3 mm / 1 revolution) * (1 revolution / 3 motor revolutions) * (1 motor revolution / 50 motor steps)
Linear travel per motor step = 0.02 mm
Positional Accuracy
The positional accuracy of the axis is determined by the smallest increment of movement that can be achieved. In this case, the linear travel per motor step is 0.02 mm.
To determine the positional accuracy, we need to find the number of motor steps required to achieve a movement of 1 mm. This can be calculated as follows:
Number of motor steps for 1 mm = 1 mm / 0.02 mm = 50 steps
Therefore, the positional accuracy of the axis of the machine is 50 steps, which is equivalent to 40 mm.
Summary
- The stepper motor drive has a step angle of 7.2° per step.
- The gear ratio between the motor and lead screw is 1/3.
- The lead screw has a pitch of 3 mm and 2 starts.
- The linear travel per motor step is calculated as 0.02 mm.
- The positional accuracy of the axis is determined to be 40 mm.
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