Vacuum Casting Machine Research Articles

Investigation on mechanical and tribological characterization of Gr filled AA7075 alloy composite using Taguchi method

Current research work emphasis on the mechanical and tribological characteristics of the graphite reinforced AA7075 alloy composite. The samples were developed with various proportions (0, 1, 3, 5, and 7 wt%) of Gr particulate in Al alloy matrix using the high vacuum casting machine. The physical and mechanical characterization like density, void content, hardness, impact strength, flexural strength, and compressive strength were experimentally estimated. The dry sliding wear performance of the composite specimens was also estimated. The various samples were ranked based on the wear rate performance using the Taguchi method. The experimental results reveal that the estimated tribological and mechanical performance enhances with the addition of Gr weight percentage. Hence, the performance of 7 wt% Gr particulate in AA7075 shows better wear resistance.

Assessment of mechanical and sliding wear performance of Ni particulate filled 7075 aluminium alloy composite

Abstract The current research work aims to examine mechanical as well as the wear characteristics of the Ni reinforced with 7075 aluminium alloy. The specimens were developed with different weight percentage (0, 2, 4, 6 and 8 wt%) of Ni particulate in Al alloy matrix using the high vacuum casting machine. The physical properties such as density, followed by void content and hardness, and mechanical characteristics like impact, flexural and compressive strength were experimentally evaluated. The sliding wear performance of the developed samples was studied. The different samples were ranked based on the wear rate performance using the Taguchi method. Scanning electron microscopy was used to analyse the sliding wear behavior of the worn surfaces. The experimental outcome revels that the evaluated tribological and mechanical performance has increased with the addition of Ni. Hence, the performance of 8 wt% Ni particulate in Al 7075 shows better wear resistance.

Dry Sliding Wear Behavior of Titanium Metal Powder Filled Aluminum Alloy Composites for Gear Application

In the current research work, the influence of titanium metal powder on wear beheviour of Al 7075 composites is investigated. These composites were fabricated by using the high vacuum casting machine. The Tribological beheviour of titanium metal powder aluminum alloy composites was investigated by performing dry sliding experiments as a function of wear with a E-31 harden steel disk( 62 HRC) as the counterpart on pin on disk machine . Wear experiments were performed for normal load of 20, 35, 50 , 65 and 80 N at sliding velocities of 0.25, 0.5, 0.75, 1, 1.25 m/s and sliding distance (250 ,500, 750, 1000 and 1250 m at room temperature. The tests were performed on Taguchi’s L25 orthogonal array and the effect of working parameters on wear rate was studied using ANOVA. To investigate the dominant sliding wear mechanism for different steady state experiment conditions, the SEM micrograph of worn surfaces were analyzed using scanning electron microscopy. The wear rate was found to minimum as compared to unfilled alloy and the wear resistance improves the aluminum alloy composites. Finally, it was investigated that the analysis of microstructure and wear properties of titanium metal powder filled alloy composite.

Digital Manufacturing Process Chain for One-Off Replacement Parts: A Precision Casting Case Study

The need to manufacture a copy of a mechanical part typically arises when a single replacement part is necessary and is out of stock or out of production altogether. For parts with intricate details and associated accuracy requirements, investment casting may be preferred to machining, for size and detail reasons, or 3D printing, for material reasons. This work applies the digital manufacturing paradigm to one-off vacuum-aided rapid investment casting focusing on the process chain rather than on engineering issues. 3D laser scanning, digital model construction by surface fitting, casting model making by exploiting additive manufacturing, material investigation using scanning electron microscopy, casting simulation exploring process parameter scenarios, as well as the corresponding implementation on a vacuum casting machine are the pertinent interlinked steps and techniques. The added value of this work is that for each process link the important steps and the potential pitfalls are analyzed in detail using as an example a cylinder liner from a model car engine. Quality of the result was quite acceptable, the main benefit of the streamlined approach being that “right-first-time” parts can be achieved.

Effects of pattern coating and vacuum assistance on porosity of aluminium lost foam castings

Lost foam casting (LFC) process has several advantages when compared to conventional sand casting techniques however formation of large amount of gaseous products during foam pattern removal increases porosity fraction of castings, especially for low melting point A1 and Mg alloys. In this study pattern coating and vacuum assistance at the time of filling were investigated and their characterizations in constant casting conditions have been determined. Green sand moulding technique was carried out for all moulds because it is necessary to obtain sound castings by using expandable polystyrene (EPS) foam patterns without refractory coating. Simple prismatic shaped patterns were prepared from cutting pieces from an EPS isolation board. A well-known A380 Al-Si-Cu casting alloy was cast at 730°C. As expected, pattern coating reduce the gas permeability and increase porosity however metal penetration into sand grains and surface roughening occurs without coating. Slight vacuum were applied to moulds with vacuum casting machine until solidification. Vacuum assistance enhanced gas removal and it has clear effect on decreasing porosity.

Vacuum Casting Bubble Automatic Elimination System Based on on-Line Machine Vision Detection

Bubbles in vacuum casting process are dense, tiny and overlapped. The difference between bubbles and the background is so indistinct that makes bubble detection a great difficulty. Bubble elimination has become the main obstacle in the way of vacuum casting machine’s automation development. Bubble automatic detection is the base of bubble elimination. A machine vision bubble on-line detecting and eliminating platform is constructed, using industrial high-speed CCD camera and professional LED illumination. According to the features of vacuum casting bubbles, the edge pixel ratio algorithm is designed especially for vacuum casting bubble detection. The algorithm is realized using VC++ and Open CV. The integrated system proposed can detect and eliminate vacuum casting bubbles on-line automatically. As it’s confirmed, there is an obviously positive correlation between the edge pixel ratio and the bubble denseness. This detection system makes sense in vacuum casting bubble elimination.

Hybrid Intelligence Process Parameters Setting and Optimization on Differential Pressure Vacuum Casting

Considering that the problem of traditional process parameters setting in vacuum casting machine is of long period, high cost and inferior quality stability, a kind of hybrid intelligent decision model which combined with case-based reasoning, neural network and fuzzy reasoning were established. First, use the case-based reasoning technology to extract the similar case from the case database. Then, use the initial parameters to run the mould trial. Finally, use the fuzzy reasoning technology to optimize the initial parameters according to the product defects. Based on the above-mentioned intelligence model, the related hardware and software system was established. The actual practice proved that the system is effective and can be used in practical production.

Research on the Method of Client Customization Design

A modular design idea oriented to client customization is proposed to achieve product diversification and personalization. The Key technology of customized design is studied to meet the market's requirement of short cycle, high quality and low cost in product design and manufacturing. In the detailed design stage, the method of Top Basic Skeleton (TBS) is applied, which improves the rapid response ability of product design and shortens the product development cycle. On this base, a rapid design method of customized vacuum casting machine is illuminated. In the dynamic and changing market environment, the rapid design method plays an important role in improving the competitive power of enterprise.

Dimensional accuracy analysis of implant framework castings from 2 casting systems

<h3>Purpose</h3> To compare the dimensional accuracy of implant framework castings from an argon vacuum casting machine with those from a centrifugal casting machine. <h3>Materials and Methods</h3> Three 4 × 10-mm external hex-type implants (3i/Implant Innovations) were embedded in an acrylic resin block 7 mm apart, with a 2 mm offset of the middle implant. Eight reference points were marked on the implant collars. Twenty implant bar frameworks were waxed with UCLA abutments, invested with a ringless system, and subjected to the same thermal cycle. Ten wax patterns were cast in gold alloy using an oxygen-propane torch and centrifugal casting system; 10 were cast using an argon vacuum casting machine (KDF; Denken). The White 1-screw technique was applied after sequentially tightening the mesial and distal abutment screws to 10 Ncm. Fit of the implant framework castings was evaluated by measuring the marginal opening between the casting and implant at the reference points. These measurements were averaged and statistically compared for differences. <h3>Results</h3> The mean marginal openings at the most distant measuring locations from the tightened retaining screw at location 1 was between 44 and 48 μm for the centrifugal system compared to between 28 and 32 mm for KDF (<i>P</i><.01). For screws tightened at location 3, the mean marginal openings at the most distant measuring locations were between 40 and 51 mm for the centrifugal system compared to between 27 and 29 μm for KDF (<i>P</i><.01). <h3>Discussion</h3> In comparison with the centrifugal casting and oxygen-propane system, the argon vacuum system was more accurate and user friendly and less technique-sensitive. <h3>Conclusion</h3> The argon vacuum casting machine tested produced more accurate, better-fitting implant-supported prosthesis frameworks than a conventional centrifugal casting system. The "1-screw" method of evaluating casting fit was most effective when either of the prostheses' end screws were tightened.—<i>Reprinted with permission of Quintessence Publishing.</i>

Over-refractory casting technique as an alternative to one-piece multi-unit fixed partial denture frameworks

Soldering has been suggested to achieve acceptable fit of multi-unit fixed partial denture (FPD) frameworks of 3 or more elements. However, distortion of the entire framework may occur. The purpose of this study was to evaluate marginal fit in 1-piece-casting FPD frameworks comparing 2 casting techniques: the conventional technique (CT) and the over-refractory technique (ORT). The techniques were evaluated on castings made from commercially pure titanium (CP Ti; Tritan), titanium-aluminum-vanadium (Ti-6Al-4V), and nickel-chromium (Ni-Cr; VeraBond II) alloys. A metal master cast including 3 preparations was created to simulate a 5-unit FPD. The metal cast was duplicated in vinyl polysiloxane for fabrication of 60 working casts. For the CT, 0.7-mm-thick patterns were waxed on the casts using an electrical wax-dipping unit. Patterns were removed from the preparations before investing. For the ORT, the silicone impressions were poured with an investment material (Rematitan for CP Ti and Ti-6Al-4V, and Talladium for Ni-Cr). The patterns were waxed on the refractory casts, and the assembly was invested. Both CT and ORT (n = 10), CP Ti, and Ti-6Al-4V frameworks were cast using an arc-melting titanium vacuum-casting machine. The Ni-Cr frameworks were cast using an automated centrifugal-casting machine. The mean marginal discrepancies of the frameworks were measured at the mesial, distal, buccal, and lingual interfaces. Marginal gap measurements were recorded 3 times for each surface to the nearest 0.5 microm using a traveling microscope (x50). The data were analyzed with 2-way analysis of variance, followed by the Tukey HSD test (alpha=.05). Marginal discrepancies for the ORT specimens (82.8 +/- 1.7 microm for CP Ti; 64.4 +/- 1.3 microm for Ti-6Al-4V; and 77.2 +/- 1.5 microm for Ni-Cr) were significantly lower than those obtained for the CT specimens (106.3 +/- 2.6 microm for CP Ti; 75.7 +/- 0.8 microm for Ti-6Al-4V; 101.9 +/- 1.7 microm for Ni-Cr) (P < .05). For both techniques, marginal discrepancies were significantly different among the alloys evaluated, presenting the following order from greatest to least marginal discrepancy: CP Ti, Ni-Cr alloy, and Ti-6Al-4V (P < .05). The ORT for multi-unit FPD frameworks demonstrated significantly lower marginal discrepancies than the CT.

Facial prosthetic model fabrication using rapid prototyping tools

While computerized tomography (CT) and magnetic resonance imaging (MRI) technologies are highly commendable for their applications and usage, sometimes cases involving facial anatomy restoration may not necessarily require these highly sophisticated technologies. A suitable replacement that is also non‐contact and allows fast image capture is the laser digitizer surface scanner. This scanner takes only seconds to capture an image of the patient’s sound or healthy facial anatomy. By using the captured image data, it is possible, with the help of a surface data modeller rapid prototyping (RP) machine and vacuum casting machine, to manufacture the prosthesis for implant. Presents a novel approach for facial prosthesis fabrication through a case study of a prosthetic ear model using an integrated manufacturing system comprising the laser surface digitizer, surface data modeller, rapid prototyping system and vacuum casting system.

Cervical Caps: Old and Yet Too New

This brief history of the cervical cap which has served well for over 1000 years is followed by a lament that supply and distribution of the caps are limited to some Western countries; the cap does not have FDA approval; hence it is imported to a small number of distribution centers in the U.S. located exclusively in large cities with none in the South. The last qualitiative study of safety and efficacy of cervical caps was published in 1953. Because of the dearth of information on this time-tested contraceptive device most health clinic practitioners have taught themselves how to use the cap and are conducting their own studies to test the results. In a New Hampshire clinic 500 women have been fitted since June 1978 and 6 cap-failure pregnancies were reported. A clinic in Iowa City is conducting a year-long study of 90 women. In Berkeley 2 pregnancies occurred after 150 fittings in 6 months. Today in the U.S. the cap is being used legally for artificial insemination therapy to hold the sperm near the cervix after injection. A custom-fitted cap resulting from a mold made by a vacuum casting machine is envisioned; if it is patentable it is hoped that the caps will soon be in production with full FDA approval.