Dental Milling Tool Length Referencing via Workpiece Arm Contact
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Solution Overview
Problem
Conventional tool length measuring systems are not cost-effective for small CNC machines, and existing dental milling machines lack an efficient method for automatic calibration and incorporation of tool manufacturing tolerances, leading to inaccuracies due to tool wear and variable clamping positions.
Innovation Solution
A dental milling machine with a rotatably mounted chuck and a movable abutment element on a workpiece arm, coupled with a control device that detects contact between the abutment element and the milling tool using an encoder, allowing for precise measurement and storage of the tool length without external measuring devices, enabling automatic calibration and reference positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional tool length measuring systems are used, then measurement capability is provided, but cost-effectiveness deteriorates for small CNC machines
Solution Approach 1:
The system uses the workpiece arm's own movement capability to perform tool length measurement, eliminating the need for external measuring devices. The control device automatically calculates tool length based on position data from the encoder during the arm's movement, making the measurement system self-sufficient and cost-effective.
Solution Approach 2:
The patent replaces complex mechanical measuring systems with an electronic sensing approach using an encoder to detect the position of the workpiece arm. The measurement is performed through electronic data processing rather than mechanical contact or optical external devices, reducing system complexity and cost.
2Measurement precision
If manual calibration is performed to account for tool wear and clamping position variations, then measurement accuracy is maintained, but time consumption and operational complexity increase
Solution Approach 1:
The system automatically performs calibration by utilizing the workpiece arm's movement and the encoder's position detection. The control device autonomously calculates the reference position based on measured data, eliminating the need for manual intervention and significantly reducing calibration time while maintaining high accuracy.
Solution Approach 2:
The encoder provides continuous feedback on the workpiece arm's position during movement. The control device uses this feedback data to automatically calculate and update the reference position, creating a closed-loop system that adapts to tool wear and clamping variations without manual input.
3Measurement precision
If external measuring devices are used for tool length measurement, then measurement capability is provided, but device complexity and cost increase
Solution Approach 1:
The patent extracts the measurement function from external devices and integrates it into the existing workpiece arm system. By using the arm's movement and the encoder already present in the machine, the measurement capability is obtained without adding external measuring equipment, thereby reducing overall system complexity.
Solution Approach 2:
The workpiece arm serves multiple functions: it performs the machining operation and simultaneously performs tool length measurement. The encoder serves dual purposes by monitoring both the arm's positioning for machining and providing data for measurement calculations, eliminating the need for dedicated measuring devices.
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 solution provides precise and automatic reference positioning during tool replacement, accounting for tool wear and manufacturing tolerances, ensuring accurate machining by eliminating the need for external measuring devices and allowing for continuous monitoring of tool length and shape.
Implementation Method 1
The motor is an encoder-coupled drive motor, wherein a loss of step of the stepping motor detected by the encoder is signaled or detected as abutment of the abutment element on the tool
Data Source
AI summary
A dental milling machine is provided with a tool which is guided in a chuck. A workpiece arm is mounted opposite the tool to be able to be moved at least in the direction of the spindle axis. With a control device it can be moved in relation to the workpiece, especially by means of a drive motor of the workpiece arm. The workpiece arm has an abutment element, whereby the control device moves the tool and the abutment element towards each other until they abut each other. The control device can be used to detect abutment of the abutment element with respect to the tool, in particular with respect to its tip, in particular by decelerating the (relative) movement of the tool and the abutment element towards each another, upon contact of the tool and the abutment element. This position may be signaled as a reference position and, especially may be stored.