Dental Restoration Machining Path Compensation for Tool Deflection
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Solution Overview
Problem
Dental restoration machining with rotationally symmetric tools often results in contour falsification and increased processing time due to tool deflection, particularly during machining of inlays and partial crowns with fluctuating tool/workpiece overlap, leading to quality issues like uneven support and edge breakouts.
Innovation Solution
A computer-implemented method predicts tool deflection using machining parameters like overlap length and force, modifying the machining path by adding material oversize at primary damage locations during pre-machining and selectively removing excess material in post-machining steps, allowing for reduced contour distortion and shorter processing times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If two-step machining (pre-machining with fast grinding followed by post-machining with fine grinding) is used to compensate for contour falsification, then manufacturing precision is improved, but processing time increases significantly
Solution Approach 1:
The patent applies preliminary action by predicting tool deflection and contour falsification before machining occurs. A computational model calculates the expected contour distortion based on tool parameters, workpiece properties, and machining conditions. This prediction allows the system to pre-compensate for deflection effects, eliminating the need for extensive post-machining correction and reducing processing time while maintaining precision
Solution Approach 2:
The patent changes parameters by dynamically adjusting machining parameters (such as depth of cut, feed rate, and tool path) based on predicted contour falsification. The system modifies these parameters in real-time to compensate for expected tool deflection, thereby achieving accurate contours without requiring a second machining step, thus resolving the contradiction between precision and time
2Productivity
If fast grinding with large infeed is used for pre-machining to remove excess material, then productivity is improved, but contour falsification increases due to tool deflection
Solution Approach 1:
The patent implements feedback by using a computational model that continuously predicts contour falsification based on machining parameters. This prediction feedback allows the system to adjust machining parameters dynamically during pre-machining operations, enabling high material removal rates while compensating for tool deflection effects to maintain contour accuracy
Solution Approach 2:
The system performs preliminary calculation of contour falsification before machining begins. By knowing the expected deflection in advance, the system can plan the machining strategy to remove material efficiently while avoiding excessive tool load that would cause dangerous deflection, thus achieving both high productivity and precision
3Manufacturing precision
If thinner tools are used to machine details and thin walls, then manufacturing precision is improved, but tool strength decreases making them more susceptible to deflection
Solution Approach 1:
The patent changes parameters by optimizing tool path parameters (such as feed rate, depth of cut, and engagement angle) specifically for thin tools. The computational model predicts deflection for the specific thin tool being used and adjusts machining parameters to minimize tool load while maintaining machining precision, enabling successful use of thin tools without excessive deflection
Data Source
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AI summary
The present invention relates to a method of machining at least one dental restoration (1) from a workpiece (2) using one or more dental tools (3), comprising: a step of defining a target contour (4) of the dental restoration (1); characterized by further comprising: a step of predicting the deflection of the dental tool (3) during pre-machining through a model based on one or more machining parameters; a step of determining based on the prediction step one or more primary locations (5) at which the target contour (4) would have been damaged during pre-machining; a step of modifying the target contour (4) or the corresponding machining path by adding an oversize of material (6) substantially only at the primary locations (5) for preventing damage; and a step of pre-machining the workpiece (2) based on the modified target contour (7) or the corresponding modified machining path.