Bar Feeder Dynamic Control for Lathe Positioning
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Solution Overview
Problem
Current bar feeder systems for automatic lathes face issues with bar advancement, particularly with bars of varying diameters, leading to potential damage, incorrect gripping, bouncing, and production errors due to inconsistent impact with the stroke limiter, and difficulty in detecting advancement errors resulting in improperly sized processed pieces.
Innovation Solution
A dynamic control system for the bar pusher using a programmable logic controller (PLC) with adjustable flow-rate and pressure valves, coupled with a pressure transducer, optimizes the advancement speed of the bar pusher based on the length of the piece to be processed, ensuring controlled impact and accurate positioning, capable of adapting to different bar masses and lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bar pusher uses a hydraulic motor with constant speed advancement, then the bar is pushed efficiently along the guide, but the bar may bounce or flex upon impact with the stroke limiter, causing incorrect gripping and potential damage
Solution Approach 1:
The bar pusher system transitions from constant speed to dynamic speed control, where the hydraulic motor's flow rate is continuously adjusted based on real-time bar position feedback from sensors. This allows the system to accelerate during mid-travel and decelerate before stroke limiter contact, maintaining positioning accuracy while preserving advancement efficiency.
Solution Approach 2:
A sensor unit monitors the bar's position throughout its advancement path and feeds this information back to a control system. The controller adjusts the hydraulic flow rate accordingly, creating a closed-loop control system that ensures the bar reaches the stroke limiter at the correct position without bouncing or flexing, while still maintaining efficient overall advancement.
2Loss of time
If the bar pusher advances the bar at high speed, then processing time is reduced, but the impact against the stroke limiter may cause damage and bouncing
Solution Approach 1:
The bar advancement process uses periodic acceleration and deceleration phases controlled by the hydraulic system. The bar is accelerated during the majority of the travel distance to minimize processing time, then decelerated in the final approach to the stroke limiter. This periodic speed variation reduces impact damage while maintaining high overall advancement speed.
Solution Approach 2:
The control system anticipates the upcoming impact with the stroke limiter and begins decelerating the bar pusher before contact occurs. This preliminary deceleration action, triggered by sensor detection of the bar's proximity to the stroke limiter, prevents bouncing and damage while allowing the bar to maintain high speed during the majority of its travel, thus reducing overall processing time.
3Power
If the bar pusher applies high force to advance heavy bars, then advancement power is sufficient, but the stroke limiter and collet may suffer damage
Solution Approach 1:
The hydraulic motor provides dynamically adjustable force output rather than constant high force. The system delivers high power during mid-travel to move heavy bars efficiently, then automatically reduces force output as the bar approaches the stroke limiter. This dynamic force modulation ensures sufficient advancement power while protecting the stroke limiter and collet from damage.
Solution Approach 2:
The sensor-based feedback system continuously monitors bar position and communicates this to the hydraulic control system. Based on this feedback, the system automatically modulates the hydraulic pressure and flow rate, reducing force application when the bar is near the stroke limiter. This ensures heavy bars can be advanced with sufficient power while preventing excessive force that would damage the stroke limiter or collet.
4Ease of operation
If the bar pusher uses a simple mechanical drive, then the system is easy to operate, but advancement errors are difficult to detect and pieces may be incorrect length
Solution Approach 1:
Sensor units positioned along the bar's path provide automatic feedback on advancement position to the control system. This feedback mechanism enables real-time detection of positioning errors without complicating the operator's interface. The system automatically compares actual position with target position and makes corrections, maintaining ease of operation while achieving precise measurement and control of bar advancement.
Solution Approach 2:
The bar pusher system performs self-monitoring and self-correction of advancement errors through the sensor feedback loop. The system automatically detects positioning deviations and adjusts hydraulic flow rate to correct errors, eliminating the need for manual measurement or intervention. This self-service capability maintains operational simplicity while ensuring precise bar positioning and correct piece lengths.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively prevents damage to the stroke limiter and collet, ensures accurate piece length, reduces bouncing, and automatically adjusts to variations in bar mass during processing, leading to improved precision and reduced waste in piece production.
Implementation Method 1
The bar pusher is engaged to a drive train which is actuated by a hydraulic motor which moves parallel with the guide
Implementation Method 2
A dynamic control system for the bar pusher using a programmable logic controller (PLC) with adjustable flow-rate and pressure valves, coupled with a pressure transducer
Data Source
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AI summary
A system for dynamic control of the bar pusher in a bar feeder for an automatic lathe (1), the feeder comprising a bar pusher (12) that is driven by a hydraulic motor (17) and can slide in a guide that is coaxial to the spindle (5) of the lathe, the spindle (5) being provided with a collet (6) for clamping the bar (2), in front of which collet (6) it is possible to position, at an adjustable distance according to the length of the part to be machined, a stroke limiter (7), the hydraulic motor (17) being controlled by a first valve element (21) for adjusting the pressure of the driving liquid and by a second valve element (20) for adjusting the flow-rate of the driving liquid, the valve elements (20, 21) being controlled by a programmable logic unit (22), which comprises respectively a processing element (24) for driving the first valve element (21) and adjusting the pressure of the driving liquid according to a preset behaviour and a regulator (23) for driving the second valve element (20), there being also a transducer (26) for the pressure of the hydraulic motor (17) which is connected in feedback to the processing element (24), the processing element (24) and the regulator (23) being controlled by means (25) that are adapted to set the flow-rate of the driving liquid as a function of the length of the part to be machined.