DENTAL MILLING MACHINE AND DENTAL MILLING METHOD FOR PRODUCING A DENTAL OBJECT

Description

[0001] The present invention relates to a dental milling machine for producing a dental object and dental milling methods for producing a dental object.

[0002] The longer a milling tool is in use, the duller it becomes, as coated diamonds, for example, wear out. This causes the milling tool to be pushed sideways during machining, and less material is removed. When manufacturing dental objects, it can happen that a finished crown does not fit the intended stump or has a poor fit because too little material was removed.

[0003] Therefore, the milling tool of the dental milling machine is changed from time to time. The workpiece or milling tool is measured by the dental milling machine, and the milling paths are then corrected accordingly. However, this task requires a complex and space-consuming measuring probe. The milling tool is often changed too early, resulting in high material costs for the user. It can also happen that insufficient quality of the milling tool goes undetected, or that a worn-out milling tool is clamped in and not recognized by the dental milling machine. This can even lead to a cutter breakage.

[0004] In addition, milling templates, which define the milling paths and the associated process parameters, such as feed rate or spindle speed, are designed for each indication based on the worst-case scenario. However, this rarely occurs in practice (less than 20%). Therefore, this milling template is slow and inflexible. Conversely, this is not optimal for over 80% of milled parts. Furthermore, developing the milling template is time-consuming.

[0005] It is therefore the technical object of the present invention to reliably detect the condition of a machining tool in a dental milling machine in a simple manner.

[0006] US2009129882 discloses methods, systems, and devices for monitoring tool breakage and wear in a dental milling machine, wherein a first accelerometer is located adjacent to the spindle and can detect vibrations associated with the rotation of the milling tool. A processor in communication with the first accelerometer receives data and processes it to detect changes indicative of a breakage of the milling tool.

[0007] This technical problem is solved by the subject matter according to the independent claims. Technically advantageous embodiments are the subject matter of the dependent claims, the description, and the drawings.

[0008] According to a first aspect, the technical problem is solved by a dental milling machine for producing a dental object, comprising a sensor unit for detecting signals generated by a machining tool; and an electronic control unit for controlling the machining tool based on the detected signals. The dental milling machine achieves, for example, the technical advantage that the condition or wear of the machining tool can be detected during machining of the workpiece. If the condition of the machining tool is known, the milling program can be adjusted or corrected so that the fit of the manufactured dental object always remains within the specifications. The detected signals allow the dental milling machine to "feel" what is happening between the workpiece and the machining tool during machining. An appropriate correction can then be made.

[0009] In a technically advantageous embodiment of the dental milling machine, the signal is a sound signal generated by the machining tool in the workpiece, a vibration signal generated by the machining tool in the workpiece, and / or a force signal exerted by the machining tool on the workpiece.

[0010] The sound signal can be a sound in the air or a sound in the workpiece. This provides the technical advantage, for example, of being able to easily and quickly detect the condition of the machining tool with high precision.

[0011] In a further technically advantageous embodiment of the dental milling machine, the dental milling machine is configured to perform a simulation based on the detected signals in order to calculate a milling process. This achieves the technical advantage, for example, that different milling processes can be simulated in advance using suitable parameters and based on the detected state of the machining tool. From the set of simulated milling processes, the one that enables the fastest machining of the dental object or the one that enables the most gentle milling process with the least wear on the milling tool can then be selected.

[0012] According to the invention, the electronic control unit is configured to control a feed rate, a path distance, and / or a rotational speed of the machining tool based on the detected signals. The electronic control unit can be configured to control the machining tool in real time based on the detected signals. This achieves, for example, the technical advantage that the workpiece can be machined efficiently and precisely.

[0013] In a further technically advantageous embodiment of the dental milling machine, the control unit is configured to determine wear of the machining tool based on the detected signals. This provides the technical advantage, for example, that the machining tool can be replaced as it becomes worn.

[0014] In a further technically advantageous embodiment of the dental milling machine, the control unit is configured to control the machining tool based on the determined wear. A dimensional correction can be controlled depending on the condition of the machining tool. This achieves the technical advantage, for example, of further increasing machining accuracy over the entire service life of a milling tool.

[0015] In a further technically advantageous embodiment of the dental milling machine, the sensor unit is designed to detect a spindle current signal. This provides the technical advantage, for example, of allowing the condition of the machining tool to be easily determined.

[0016] In another technically advantageous embodiment of the dental milling machine, the sensor unit is designed to detect the signals without contact with the workpiece. This can be achieved, for example, by a sensor unit that detects a sound signal, a vibration, or a spindle current. The sensor unit is not in direct contact with the workpiece. This achieves the technical advantage, for example, of easily determining the condition of the machining tool.

[0017] In another technically advantageous embodiment of the dental milling machine, the sensor unit is mechanically coupled to the workpiece. The sensor unit is in direct contact with the workpiece. The sensor unit can be connected directly to the workpiece or the workpiece holder. This provides the technical advantage, for example, of allowing the signals generated during machining of the workpiece to be accurately recorded.

[0018] According to a second aspect, the technical problem is solved by a dental milling method for producing a dental object, comprising the steps of detecting signals generated by a machining tool using a sensor unit; and controlling the machining tool based on the detected signals using an electronic control unit. The dental milling method achieves the same technical advantages as the dental milling machine according to the first aspect.

[0019] In a technically advantageous embodiment of the dental milling method, a simulation is performed based on the signals to calculate a milling process. The simulation can use a digital twin of the dental milling machine. This makes it possible to simulate the dynamics of the dental milling machine. This also achieves the technical advantage, for example, of being able to easily and quickly detect the condition of the machining tool with high precision.

[0020] In another technically advantageous embodiment of the dental milling process, the path distance and / or rotational speed of the machining tool are controlled based on the detected signals. This also achieves the technical advantage of allowing the workpiece to be machined quickly and precisely with as little wear as possible.

[0021] In another technically advantageous embodiment of the dental milling method, wear of the machining tool is determined based on the signals. This also provides the technical advantage, for example, that the machining tool can be replaced as it wears.

[0022] In another technically advantageous embodiment of the dental milling process, the machining tool is controlled based on the measured wear. This also achieves the technical advantage of further increasing machining accuracy.

[0023] In another technically advantageous embodiment of the dental milling method, a spindle current signal is recorded. This provides the technical advantage, for example, of easily determining the condition of the machining tool.

[0024] The invention is as defined in the claims.

[0025] Embodiments of the invention are illustrated in the drawings and are described in more detail below.

[0026] They show: Fig. 1 is a schematic view of a dental milling machine; Fig. 2 is an error during machining of a workpiece; Fig. 3 is a diagram illustrating the feed and load of a machining tool; and Fig. 4 is a block diagram of a dental milling method for producing a dental object.

[0027] Fig. 1 shows a schematic view of a dental milling machine 100. The dental milling machine 100 is used to produce a dental object 101, such as a crown, a bridge, a veneer, an abutment, an inlay, or an onlay. The dental object 101 is produced by the dental milling machine 100 using a machining process from a blank as a workpiece 105. For this purpose, a machining tool 109 is rotated by means of an electrically driven rotary spindle 111. The material of the workpiece is removed by the movable machining tool 109 until the desired spatial shape of the dental object 101 is achieved. The machining tool 109 can be a milling tool or a polishing tool for the workpiece 105.

[0028] The dental milling machine 100 includes a sensor unit 103 for detecting a signal caused or generated by the machining tool 109 during machining of the workpiece 105. The signal corresponds to a physical quantity during the machining of the workpiece 105. This can be, for example, a vibration, structure-borne sound, acoustics, or a force that occurs during the machining of the workpiece 105. The sensor unit 103 is capable of detecting signals generated by the machining tool 109 during the machining of the workpiece 105. The signals can be detected individually or simultaneously. By detecting the signals during the machining of the workpiece, the dental milling machine 100 receives feedback during the machining.

[0029] The detected signals are forwarded to an electronic control unit 107, where they are evaluated. The electronic control unit 107 controls the machining tool 109 based on the detected signals. The signals are evaluated and the control system of the dental milling machine 100 is adjusted in real time. According to the invention, the electronic control unit 107 controls a rotational speed, a feed rate, and / or a spatial movement of the machining tool 109.

[0030] In addition, the electronic control unit 107 can calculate wear on the machining tool 109 from the detected signals and take this into account when controlling the machining tool 109. For example, if the detected signals indicate that the diameter of the machining tool 109 has decreased, the tool can be adjusted to compensate for the detected wear or bending of the tool. This process can then be repeated to continuously compensate for the wear on the machining tool 109.

[0031] The control unit 109 includes, for example, a microprocessor and an electronic data memory, such as a RAM memory. Processing programs and digital data for the acquired signals are stored in the data memory. The microprocessor can further process the digital data.

[0032] Based on signals from sensor unit 103, the condition of machining tool 109 can be determined, and the milling process can be adjusted and corrected with respect to the milled dimensions. There can be a defined, for example, linear, relationship between the condition of machining tool 109 and the detected signals. The larger the vibration signals, the greater the wear on machining tool 109, for example. However, a neural network can also be trained to determine the condition of machining tool 109, for example, based on the detected signals.

[0033] The signal detected by the sensor unit 107 can, for example, be a sound signal generated by the machining tool 109 in the workpiece 105. The sound signal can be recorded by a microphone as the sensor unit 103. The electronic control unit 107 then evaluates the detected sound signal.

[0034] The signal detected by the sensor unit 107 can, for example, be a vibration signal generated by the machining tool 109 in the workpiece 105. The vibration signal can be recorded by a vibration sensor as the sensor unit 103. The electronic control unit 107 then evaluates the detected vibration signal.

[0035] The signal detected by sensor unit 103 can, for example, be a force signal exerted by machining tool 109 on workpiece 105. The force signal can be recorded by a force sensor as sensor unit 103. The electronic control unit 107 then evaluates the detected force signal. This achieves the technical advantage, for example, of avoiding force peaks exceeding the load limit of the machining spindle or machining tool.

[0036] The signal detected by sensor unit 107 can, for example, be a spindle current signal from a spindle current flowing through an electric motor of a rotary spindle 111 during machining of the workpiece 105. The spindle current signal can be recorded by an ammeter as sensor unit 103. The electronic control unit 107 evaluates the detected spindle current signal. The dental milling machine 100 thus measures the spindle current and slows down the process if the milling cutter is old or worn. Under optimal conditions, the milling process can be accelerated.

[0037] The sensor unit 103 can detect the signals without contacting the workpiece 105. In this case, the sensor unit 103 does not directly touch the workpiece 105. For example, a microphone can record the sound signals transmitted through the air over a certain distance during the machining of the workpiece 105.

[0038] However, the sensor unit 103 can also be directly mechanically coupled to the workpiece 105. For example, a microphone can record the sound signals during the machining of the workpiece 105, which are transmitted directly through the workpiece 105 and measured thereon.

[0039] The control unit 107 can use a learning curve from adaptive methods. For example, a trained artificial neural network 113 can be used to detect a state of the machining tool 109. The artificial neural network 113 is a system of hardware and / or software that mimics the functioning of neurons in the human brain.

[0040] To this end, the neural network 113 recognizes trained patterns in the signals, such as the recorded sound signals, vibration signals, force signals, or spindle current signals. If the neural network recognizes a trained pattern in the signals, a specific condition or degree of wear of the machining tool 109 can be assigned to this pattern. If, for example, a specific vibration pattern occurs, the neural network recognizes that the machining tool has a wear of 10%. This correction can also be used during polishing, since the diameter of the polishing tool changes due to wear. However, this can also be solved by applying a constant force to the polishing tool.

[0041] The dental milling machine 100 allows the machining process to always be run within an optimal range, such as as fast as possible with minimal wear. Adjustment of the machining process can be ensured by the sensor unit 103. Since the dental milling machine 100 detects during the machining process whether it can be moved faster or more material can be removed, it is possible to accelerate the machining process. Tool breakage and chipping (small fractures in the workpiece) can be effectively prevented by the dental milling machine 100.

[0042] Fig. 2 shows an error during machining of a workpiece 105 and a predictability of a milling tool condition on the top (top) and bottom (bottom) of the workpiece 105. The mean absolute error of a prediction based solely on vibration data is approximately 12 µm. Therefore, it is possible to predict the tool life to within ± 6 crowns based solely on measured vibrations during the milling process. For this combination of dental milling machine 100 and machining tool 109, for example, an increase in deviation of 2 µm per milled crown is determined.

[0043] Fig. 3 shows a diagram of the feed rate and load of the machining tool 109 during adaptive real-time control. The load B of the machining tool 109 is calculated from the force on the machining tool in the X direction. F X and the power F y on the machining tool in the y-direction as B = F x 2 + F y 2

[0044] When the load B increases, the control unit 107 reduces the feed rate accordingly in real time.

[0045] Fig. 4 shows a block diagram of a dental milling method for producing a dental object. The dental milling method includes step S101 of detecting signals generated by the machining tool 109 by a sensor unit 103; and step S102 of controlling the machining tool 109 based on the detected signals by an electronic control unit 107.

[0046] The dental milling process offers the technical advantages of allowing dental objects to be manufactured more precisely and producing less waste. Furthermore, the dental milling process is more robust than conventional methods.

[0047] The dental milling machine 100 can be configured to perform a simulation based on the acquired signals in order to calculate a milling process. In this case, several simulations with different parameters can be performed. From these simulations, the parameters that enable the desired machining process are then selected.

[0048] For example, a gentle milling process results in less wear on the milling tool, allowing more workpieces to be machined overall. A high-speed milling process mills the dental object out of the workpiece as quickly as possible. A precision milling process produces the dental object with the highest possible surface quality and fit. The parameters for these processes are derived from simulations.

[0049] All features explained and shown in connection with individual embodiments of the invention can be provided in different combinations in the subject matter according to the invention in order to simultaneously realize their advantageous effects.

[0050] All method steps can be implemented by devices suitable for performing the respective method step. All functions performed by physical features can be a method step of a method.

[0051] The scope of the present invention is given by the claims and is not limited by the features explained in the description or shown in the figures. LIST OF REFERENCE SYMBOLS

[0052] 100Dental milling machine 101Dental object 103Sensor unit 105Workpiece 107Control unit 109Machining tool 111Rotating spindle 113Neural network

Claims

1. A dental milling machine (100) for producing a dental object (101), comprising: - a sensor unit (103) for detecting signals caused by a machining tool (109); and - an electronic control unit (107) for controlling a feed rate, a path distance and / or a rotational speed of the machining tool (109) on the basis of the detected signals.

2. The dental milling machine (100) according to claim 1, wherein the signal is a sound signal generated by the machining tool (109) in the workpiece (105), a vibration signal generated by the machining tool (109) in the workpiece (105), and / or a force signal applied by the machining tool (109) to the workpiece (105).

3. The dental milling machine (100) according to any of the preceding claims, wherein the dental milling machine (100) is configured to perform a simulation based on the detected signals to calculate a milling process.

4. The dental milling machine (100) according to any of the preceding claims, wherein the control unit (107) is configured to determine wear of the machining tool (109) based on the detected signals.

5. The dental milling machine (100) according to any of the preceding claims, wherein the control unit (107) is configured to control the machining tool (109) based on the determined wear.

6. The dental milling machine (100) according to any of the preceding claims, wherein the sensor unit (103) is configured to detect a spindle current signal.

7. The dental milling machine (100) according to any of the preceding claims, wherein the sensor unit (103) is configured to detect the signals without contact with the workpiece (105).

8. The dental milling machine (100) according to any of the preceding claims, wherein the sensor unit (103) is mechanically coupled to the workpiece (105).

9. A dental milling method for producing a dental object, comprising the steps of: - detecting (S101) signals caused by a machining tool (109) by a sensor unit (103); and - controlling (S102) a feed rate, a path distance and / or a rotational speed of the machining tool (109) on the basis of the detected signals by an electronic control unit (107).

10. The dental milling method according to claim 9, wherein a simulation is performed based on the detected signals to calculate a milling process.

11. The dental milling method according to claim 9 or 10, wherein wear of the machining tool (109) is determined based on the detected signals.

12. The dental milling method according to claim 11, wherein the machining tool (109) is controlled based on the determined wear.

13. The dental milling method according to any of claims 9 to 12, wherein a spindle current signal is detected.