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Robot manipulators can be applied to material removal processes, presenting advantages as compared with CNC machine tools, such as: more flexibility, lower initial cost, lesser waste of material, and better surface finishing on the parts. The objective of this work is present a study about robots used to material removal applications.
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The paper presents the optimisation method, with the use of the apparatus of mass service theory, of the number of CNC machine tools in a robotized manufacturing system that can be served by a single robot-manipulator. Calculations were performed for the technology of casing components machining for electric micromachines. The selected optimisation...
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... Subtractive technologies-such as computer numerical control machining, laser cutting, water jet cutting, electron beam cutting or electrical discharge machining-use computer-driven machines to cut away material when fabricating the predetermined computer-aided-designed (CAD) object. 9,10 In contrast, additive technologiessuch as SLA, selective laser sintering, fused deposition modeling or 3D printing-are used to fabricate the objects by gradually adding materials. 11 Although most IOS manufacturers offer fabrication of dental casts based on intraoral scan data, there is a lack of studies in which investigators evaluated the dimensional accuracy of these casts. ...
Objective: To evaluate the accuracy of full-arch stereolithographic (SLA) models obtained from scans of different intraoral scanners (IOS).
Method: A full-arch acrylic resin model with 14 prepared abutments was digitized using an industrial laser scanner (reference scanner) as well as three IOSs (CEREC AC Bluecam, Sirona, Bensheim, Germany; Lava™ C.O.S, 3M ESPE, St. Paul, USA; iTero™, Cadent Inc., Carlstadt, USA). The scans (N=5) obtained from several IOS systems were sent to the manufacturer to produce five physical SLA models. These models were scanned with the reference scanner resulting in fifteen datasets per scanner (five physical models, three scans/physical model). Using 3D-evaluation software, the datasets were superimposed (best-fit algorithm) and compared for accuracy between different groups and the reference scan. The reliability of the computer-aided analysis was expressed in terms of trueness and precision. A one-way ANOVA was implemented to compute differences within groups (precision) as well as with the reference scan (trueness). A level of statistical significance of p<0.05 was set.
Result: The mean trueness values of the SLA model scans performed with CEREC AC Bluecam, Lava C.O.S., and iTero were, respectively, 75.80 ± 14.31 µm, 67.50 ± 21.65 µm and 98.23 ± 30.24 µm. Data analysis yielded statistically significant differences between all scanners (p<0.05). The mean precision values for scans performed with the aforementioned scanners were, respectively, 21.62 ± 12.23 µm, 13.77 ± 6.75 µm and 48.83 ± 43.06 µm. Statistically significant differences were found between CEREC AC Bluecam and iTero as well as Lava C.O.S and iTero (p<0.05).
Conclusion: All tested stereolithographic models showed an acceptable level of accuracy and can therefore be considered applicable for full-arch restorative procedures.
Increasing productivity by higher cutting speed and achieving high precision of machined products at the same time is an important trend in the development of manufacturing technologies and metalworking machine tools. If the traditional method of exchangeable components in assemblies will lead to inefficient precise processes, the product costs will increase. The proposed energy-informational model considers a procedural system establishing the ratio of the cutting speed and the speed of physical processes in the machine tools. The energetic limit for the attainability of associated processes describes the allowable speed of materials processing by the machine tools. Stiffness of machine tool structures for highest precision manufacturing becomes comparable to work piece geometrical accuracy and manufacturing process tolerances. This paper gives several examples for admissible limits of increased productivity by increased process speeds in various manufacturing technologies for both traditional cutting and innovative methods.
This chapter describes the history and development of photolithographic systems, explaining the origins of modern stereolithography and photomask system. It also highlight the importance of a modern prototype and summarizes the techniques currently available to produce prototypes.
Background:
Little is known about the accuracy of physical dental casts that are based on three-dimensional (3D) data from an intraoral scanner (IOS). Thus, the authors conducted a study to evaluate the accuracy of full-arch stereolithographic (SLA) and milled casts obtained from scans of three IOSs.
Methods:
The authors digitized a polyurethane model using a laboratory reference scanner and three IOSs. They sent the scans (n = five scans per IOS) to the manufacturers to produce five physical dental casts and scanned the casts with the reference scanner. Using 3D evaluation software, the authors superimposed the data sets and compared them.
Results:
The mean trueness values of Lava Chairside Oral Scanner C.O.S. (3M ESPE, St. Paul, Minn.), CEREC AC with Bluecam (Sirona, Bensheim, Germany) and iTero (Align Technology, San Jose, Calif.) casts were 67.50 micrometers (95 percent confidence interval [CI], 63.43-71.56), 75.80 μm (95 percent CI, 71.74-79.87) and 98.23 μm (95 percent CI, 94.17-102.30), respectively, with a statistically significant difference among all of the scanners (P < .05). The mean precision values were 13.77 μm (95 percent CI, 2.76-24.79), 21.62 μm (95 percent CI, 10.60-32.63) and 48.83 μm (95 percent CI, 37.82-59.85), respectively, with statistically significant differences between CEREC AC with Bluecam and iTero casts, as well as between Lava Chairside Oral Scanner C.O.S. and iTero casts (P < .05).
Conclusion:
All of the casts showed an acceptable level of accuracy; however, the SLA-based casts (CEREC AC with Bluecam and Lava Chairside Oral Scanner C.O.S.) seemed to be more accurate than milled casts (iTero).
Practical implications:
On the basis of the results of this investigation, the authors suggested that SLA technology was superior for the fabrication of dental casts. Nevertheless, all of the investigated casts showed clinically acceptable accuracy. Clinicians should keep in mind that the highest deviations might occur in the distal areas of the casts.
In machining, the main wear mechanism on the flank surface of a tool is commonly believed to be abrasive wear [1,9]. Accordingly, work materials with a higher concentration of hard inclusions are expected to develop higher flank wear rates. However the previous turning experiment [9] with plain carbon steels containing varying amounts of cementite inclusions did not exhibit the expected flank wear behavior Other imperative phenomenon must be occurring at the tool-work material interface during machining, which diminishes the abrasive action of the cementite inclusions. To investigate this behavior a series of turning tests with AISI 1045, 1070, and 4340 steels have been conducted; and the newly generated surface layers are examined for phase identification using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and Transmission Electron Microscopy (TEM). At high cutting speeds (>200 m/min), flank wear is diminished as the cementite phase at the newly formed surface dissociates and diffuses into the matrix of the austenitic phase. Because the heated austenite phase is cooled extremely rapidly, martensitic and in some case even retained austenitic phases are formed. This is the evidence of phase transformation, which explains the flank wear data observed in [9]. In addition, phase transformation explains the scatter in flank wear data in the literature because the onset of phase transformation depends on the exact composition of the work materials as well as interfacial conditions such as temperature and pressure. This paper reports the experimental evidence of phase transformation and its consequence oil flank wear in machining annealed steels.
