Core Drill Motor Control for Low-Speed Tapping in Hard Materials
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Solution Overview
Problem
Core drill bits experience reduced drilling and cutting power at low rotational speeds when operating in hard materials, leading to inefficient hole cutting due to high contact pressure and potential motor stoppage.
Innovation Solution
A method for operating a core drill using an electric motor with open- and closed-loop control, involving a tapping mode at a low rotational speed, detection of motor current thresholds, reduction of motor current, and implementation of oscillating motion control to maintain sufficient power at low speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the core drill bit is operated at low rotational speed in tapping mode, then the contact pressure is reduced and slipping is prevented, but the drilling and cutting power becomes insufficient
Solution Approach 1:
The patent applies periodic action by switching between tapping mode (low speed with current limiting) and drilling mode (high speed with full power) based on detected material contact conditions. The controller periodically adjusts motor speed and current thresholds, detecting material contact through current analysis and transitioning between operational modes to maintain both reliability and power efficiency.
2Productivity
If the contact pressure on the core drill bit is increased to improve drilling progress, then the drilling speed increases, but the rotational speed drops sharply or the motor stops
Solution Approach 1:
The patent implements feedback control by continuously monitoring motor current and rotational speed, comparing actual values against threshold values, and automatically adjusting operational parameters. The controller detects material contact through current analysis and adjusts speed and power settings accordingly, preventing motor stoppage while maintaining drilling progress through closed-loop control.
3Reliability
If the core drill bit operates at low rotational speed to reduce contact pressure, then slipping is prevented, but the drilling efficiency decreases
Solution Approach 1:
The patent applies dynamics by making the operational parameters adaptive rather than static. The controller dynamically adjusts motor speed, current thresholds, and power settings based on real-time detection of material contact conditions. The system transitions from static low-speed tapping mode to dynamic high-speed drilling mode when material contact is detected, optimizing both reliability and productivity throughout the drilling process.
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
This method allows for increased drilling and cutting power at low rotational speeds, ensuring efficient and continuous operation by managing motor current and reducing interruptions, thus enhancing the core drilling process.
Implementation Method 1
comprising an electric motor for driving a drilling tool, in particular a core drill bit
Implementation Method 2
comprising an open- and closed-loop controller for open- and closed-loop control of the motor power by means of the motor current
Data Source
AI summary
A method for operating a machine tool that includes an electric motor for driving a drilling tool and an open- and closed-loop controller for open- and closed loop control of the motor power. The method includes: operating the machine tool in a tapping mode at a first rotational speed value, where the first rotational speed value is lower than a predetermined idling speed value of the electric motor; detecting a predetermined first threshold value for the motor current; reducing the motor current to a predetermined second threshold value when the first threshold value is exceeded; operating the machine tool at a second rotational speed value, where the second rotational speed value is lower than the first rotational speed value; operating the electric motor at a predetermined motor current value; and operating the controller for closed loop control of the motor power via the motor current with an oscillating action.