Hole Position Errors Research Articles

How Is a Cutting Guide With Additional Anatomical References Better in Fibular-Free Flap Mandibular Reconstruction? A Technical Strategy.

Computer-assisted surgery is used to design and manufacture cutting guides in mandibular reconstructions with fibula-free flaps. To improve the outcomes of the procedure, the aim of this research was to investigate and compare the accuracy of mandibular reconstruction following the use of 2 versus 3 anatomical reference cutting guides. Eighteen sets of prototype bone models retrieved from an ameloblastoma patient were used for mock operations. The mandibular segmental osteotomies and fibular reconstructions were performed using 2 and 3 anatomical reference cutting guides in vivo surgeries. After reconstruction, the accuracy of the placed reference points was measured by superimposition of computed tomography images. The error in cutting guides when using 2 or 3 anatomical references showed no significant difference. The fibular and condylar errors of the cutting guide between 2 and 3 anatomical references showed no significant difference in every plate type. The difference in screw hole position errors between 2 and 3 anatomical reference cutting guides was not statistically significant. Two anatomical reference cutting guides are sufficient and reasonable enough for mandible resection. However, there were some limitations and errors in our study.

Improvement in hole-pose error for aerospace drilling applications based on Hermite surface reconstruction and manifold error similarity

Hole position accuracy and perpendicularity are significant factors in aerospace drilling. This study presents a novel compensation method with reference holes to reduce the hole position error and initial normal deviation for automated drilling systems. The hole-pose error and related generalized addition and subtraction methods are first defined using quaternions. Subsequently, approaches for accurately measuring the pose of the reference hole and calibrating the coordinate system are proposed. On this basis, the position error and initial normal error are estimated by bilinear interpolation based on the error similarity on the two-dimensional manifold, where the manifold coordinates are obtained by Hermite surface reconstruction. Subsequently, the hole-pose error is compensated for by generalized addition. For the initial normal modification, a compensation strategy utilizing the data of processed adjacent holes for interpolation was adopted. In addition, for situations in which it is inconvenient to arrange real reference holes on the product, a compensation approach employing virtual reference holes was designed. Finally, simulations and experiments are conducted, and the results demonstrate that the position error and initial normal deviation are effectively reduced by at least 42.25% and 74.68% with the proposed method, which further ensures that the indicators meet the requirements of aerospace drilling.

A combined hole position error correction method for automated drilling of large-span aerospace assembly structures

PurposeAerospace assembly demands high drilling position accuracy for fastener holes. Hole position error correction is a key issue to meet the required hole position accuracy. This paper aims to propose a combined hole position error correction method to achieve high positioning accuracy.Design/methodology/approachThe bilinear interpolation surface function based on the shape of the aerospace structure is capable of dealing with position error of non-gravity deformation. A gravity deformation model is developed based on mechanics theory to efficiently correct deformation error caused by gravity. Moreover, three solution strategies of the average, least-squares and genetic optimization algorithms are used to solve the coefficients in the gravity deformation model to further improve position accuracy and efficiency.FindingsExperimental validation shows that the combined position error correction method proposed in this paper significantly reduces the position errors of fastener holes from 1.106 to 0.123 mm. The total position error is reduced by 43.49% compared with the traditional mechanics theory method.Research limitations/implicationsThe position error correlation method could reach an accuracy of millimeter or submillimeter scale, which may not satisfy higher precision.Practical implicationsThe proposed position error correction method has been integrated into the automatic drilling machine to ensure the drilling position accuracy.Social implicationsThe proposed position error method could promote the wide application of automatic drilling and riveting machining system in aerospace industry.Originality/valueA combined position error correction method and the complete roadmap for error compensation are proposed. The position accuracy of fastener holes is reduced stably below 0.2 mm, which can fulfill the requirements of aero-structural assembly.

Punched belt hole position deviation analysis of float type water level gauge

The key parts of the float type water level gauge instrument is perforated belt, The size and tolerance requirements of its aperture is: (1) alternation of 100+0.2 and 100-0.2, (2) 200±0.1, (3) 1000±0.15, (4) 10000±0.2. The single hole position: alternation of 100+0.2 and 100-0.2; double: 200±0.1, and ensure the best hole position error avoidance tends to be one-way, that is to say: when the punched belt combined with a water wheel rotating line moving, The hole position error to single direction increase or decrease, caused the water level nail gradually and close to the edge of the hole, and then edge and final punched belt was lifted. This paper uses the laser drilling process of steel strip for data collection and analysis. It is found that this method cannot meet the tolerance requirements and the double stamping processing method with adjustable cylindrical pin is feasible.

A practical method of improving hole position accuracy in the robotic drilling process

The industrial robots have the remarkable advantage of flexibility over CNC machine tools in material removal of the large or complex parts, especially in hole drilling. However, the lower stiffness and thus the lower machining accuracy of the robotic drilling hinder its widespread use. Aiming at the enhancement of hole position accuracy, the optimization for stiffness of the robotic drilling system before processing and the compensation for hole position error in processing are proposed. Firstly, the maximum operating stiffness of the robotic drilling system in a certain machining task is obtained by optimizing installation angle of the motorized spindle to the end flange of the robot, which lays the foundation of a high machining accuracy of hole position. And then based on the position of the hole to be drilled, the calculation method of its corresponding compensation value is introduced, which takes both the deformation of the robot’s end under the force on it and the robot absolute positioning error into account. As for a certain robotic drilling system, it is much easier to implement to predict, and then pre-compensate the machining error of hole position for the various parts. The results reveal that the hole position errors reduce sharply at the average rate of 84.45% with compensation in all robotic drilling tests, which proves the proposed method as a practical and effective way to improve the robotic drilling accuracy of hole position.

Deployment and evaluation of a dual-sensor autofocusing method for on-machine measurement of patterns of small holes on freeform surfaces.

This paper presents and evaluates an active dual-sensor autofocusing system that combines an optical vision sensor and a tactile probe for autofocusing on arrays of small holes on freeform surfaces. The system has been tested on a two-axis test rig and then integrated onto a three-axis computer numerical control (CNC) milling machine, where the aim is to rapidly and controllably measure the hole position errors while the part is still on the machine. The principle of operation is for the tactile probe to locate the nominal positions of holes, and the optical vision sensor follows to focus and capture the images of the holes. The images are then processed to provide hole position measurement. In this paper, the autofocusing deviations are analyzed. First, the deviations caused by the geometric errors of the axes on which the dual-sensor unit is deployed are estimated to be 11 μm when deployed on a test rig and 7 μm on the CNC machine tool. Subsequently, the autofocusing deviations caused by the interaction of the tactile probe, surface, and small hole are mathematically analyzed and evaluated. The deviations are a result of the tactile probe radius, the curvatures at the positions where small holes are drilled on the freeform surface, and the effect of the position error of the hole on focusing. An example case study is provided for the measurement of a pattern of small holes on an elliptical cylinder on the two machines. The absolute sum of the autofocusing deviations is 118 μm on the test rig and 144 μm on the machine tool. This is much less than the 500 μm depth of field of the optical microscope. Therefore, the method is capable of capturing a group of clear images of the small holes on this workpiece for either implementation.

Planet position errors in planetary transmission: Effect on load sharing and transmission error

In this paper an advanced model of spur gear transmissions developed by the authors is used to study the influence of carrier planet pin hole position errors on the behaviour of the transmission. The model, initially conceived for external gear modeling, has been extended with internal meshing features, and thus increasing its capabilities to include planetary transmission modeling. The new features are presented, along with the summary of the model general approach. The parameters and characteristics of the planetary transmission used in the paper are introduced. The influence of carrier planet pin hole position errors on the planet load sharing is studied, and several static cases are given as examples in order to show the ability of the model. Tangential and radial planet pin hole position errors are considered independently, and the effect of the load level is also taken into account. It is also given attention to the effect on the transmission error of the transmission. Two different configurations for the planetary transmission are used, attending to the fixed or floating condition of the sun, and the differences in terms of load sharing ratio are shown.

GD&T-Based Characterization of Short-Range Non-contact 3D Imaging Systems

We present a series of test metrics, artifacts, and procedures for characterizing and verifying the operating limits of a short-range non-contact three-dimensional imaging system. These metrics have been designed to correspond to dimensioning and tolerancing metrics that are widely used in industry (e.g. automotive, aerospace, etc.). We introduce operating limit metrics that correspond with the geometric dimensioning and tolerancing (GD&T) metrics of Form (Flatness and Circularity), Orientation (Angularity), Location (Sphere, Corner, and Hole Position Errors), and Size (Diameter, Sphere-spacing, Plane-spacing and Angle Errors). An example is presented to illustrate how these metrics, artifacts, and associated test procedures can be used in practice.

0247 NEUROCOGNITIVE REHABILITATION –A FOUR-CASE PILOT STUDY

With the advent of probing systems and their integration with machining centers, coordinate metrology-based datum establishment is eliminating the need for precision hard-contact locators in many machining applications. Unfortunately, the coordinate data collected by these systems are often subject to noise in the form of random and biased errors of the workpiece datum features and measurement system. Consequently it is important to use datum-establishment algorithms that are insensitive to noise and that lead to the least measurable machined-feature error.This paper describes a simulation analysis that was carried out to evaluate the performance of three datum-establishment methods: 3–2–1, sequential least-squares (SQLS) and simultaneous least-squares (SMLS). The analysis involved the simulated drilling of three holes in a two set-up process. Simulated coordinate data were obtained from three planar, nominally orthogonal surfaces subject to perpendicularity errors and random roughness errors. Workpiece datum reference frames were fitted to this data using the three methods, the holes were drilled relative to these reference frames, and their position errors were computed relative to an ANSI-Y14.5M-defined reference frame.This analysis demonstrated that the SMLS method results in significantly less hole-position error [0.0173 mm average, 0.0146 mm standard deviation (SD)] than either the 3–2–1 method (0.0943 mm average, 0.0143 mm SD) or the SQLS method (0.0904 mm average, 0.0245 mm SD). This is despite the fact that the datum reference planes (ANSI Y14.5M) used to define these errors are defined sequentially relative to the extrema of the datum features, whereas the SMLS method defines the datum reference planes simultaneously with the purpose of minimizing fitting error.

An examination of the effect of variation in datum targets on part acceptance

The use of datum targets within Geometric Dimensioning and Tolerancing (GD&T) is commonplace in industry today. Datum targets are used primarily for manufacturing and inspection setups where it is not practical to have tooling that contacts the entire surface of the datum. Establishing a simulated datum from datum targets may be done physically or mathematically. In the process of establishing a simulated datum, there are several possible sources of variation. Any variation or error in establishing the datum will manifest itself as variation or error in the measurement of the distance between the feature and the datum. This paper examines the effect of variation in datum targets on part acceptance using both mathematical analysis and simulation. The focus of this examination is diametric positional tolerance of holes that reference the datum established by datum targets. A three-dimensional mathematical model of the hole position error with respect to the datum target variation is developed. Then, simulation is adopted to identify the major sources of hole position error due to errors in datum targets. It is found that the datum target variation has a profound effect on the measured location of holes referencing those datums. Explanation and validation for accepted practice are offered and some additional basic guidelines are developed for the placement of datum targets relative to hole patterns.

An analysis of the effect of datum-establishment methods on the geometric errors of machined features

With the advent of probing systems and their integration with machining centers, coordinate metrology-based datum establishment is eliminating the need for precision hard-contact locators in many machining applications. Unfortunately, the coordinate data collected by these systems are often subject to noise in the form of random and biased errors of the workpiece datum features and measurement system. Consequently it is important to use datum-establishment algorithms that are insensitive to noise and that lead to the least measurable machined-feature error. This paper describes a simulation analysis that was carried out to evaluate the performance of three datum-establishment methods: 3–2–1, sequential least-squares (SQLS) and simultaneous least-squares (SMLS). The analysis involved the simulated drilling of three holes in a two set-up process. Simulated coordinate data were obtained from three planar, nominally orthogonal surfaces subject to perpendicularity errors and random roughness errors. Workpiece datum reference frames were fitted to this data using the three methods, the holes were drilled relative to these reference frames, and their position errors were computed relative to an ANSI-Y14.5M-defined reference frame. This analysis demonstrated that the SMLS method results in significantly less hole-position error [0.0173 mm average, 0.0146 mm standard deviation (SD)] than either the 3–2–1 method (0.0943 mm average, 0.0143 mm SD) or the SQLS method (0.0904 mm average, 0.0245 mm SD). This is despite the fact that the datum reference planes (ANSI Y14.5M) used to define these errors are defined sequentially relative to the extrema of the datum features, whereas the SMLS method defines the datum reference planes simultaneously with the purpose of minimizing fitting error.