Which one of the following CANNOT impart linear motion in a CNC machine?
Show Hint
- Linear motor
- Ball screw
- Lead screw
- Chain and sprocket
The Correct Option is D
Solution and Explanation
In a CNC machine, the tool or table must move in a precise, controllable and repeatable linear path. The mechanism must either: (a) directly generate linear motion, or (b) convert rotary motion to linear displacement with very low backlash.
Step 2: Evaluate each option.
Linear motor: Produces direct linear motion using electromagnetic force → suitable for CNC.
Ball screw: Converts rotary to linear motion with rolling ball contact → very high precision.
Lead screw: Also converts rotary to linear motion (sliding contact) → acceptable precision.
Chain and sprocket: Designed for transmitting rotary motion between shafts. It suffers from backlash, uneven motion, elongation due to wear, and poor repeatability. Therefore, it cannot deliver precise linear motion required in CNC machines.
Step 3: Conclusion.
Only the chain–sprocket mechanism cannot provide accurate linear motion.
Final Answer: Chain and sprocket
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