Quick Casting Research Articles

Study of Shell Cracking Behavior and its Remedies in Investment Casting Process Using Quick Cast Rapid Prototype Polymer Patterns

Investment casting has emerged as the foremost casting process for manufacturing of intricate parts where better dimensional accuracy is required. Use of rapid prototyping polymer patterns is one of the major advancements in investment casting process. Elimination of die making step as required in the traditional wax process makes it quicker and a cost effective process. The direct conversion of 3D CAD data into rapid prototyping pattern decreases development time, chances of costly mistakes, minimizes sustaining engineering changes and extend product lifetime by adding necessary features and eliminating redundant features early in the design.

Design and research of a new kind of minimally invasive fixation device in orthopaedics

A new kind of external fixation for orthopaedics was designed in order to overcome the shortcomings of high weight, difficult operation and high degree of injury for the conventional external fixation. This device uses the so called quick casting method, which can be quickly concreted, to efficiently reduce the injury to patients. It is mainly composed of the macromolecule casting material and the steel stainless nails which fasten the device to the bone. In order to verify the feasibility of the designed structure, FEM (finite element method) was used to simulate the real condition of the load when the device was used after an operation. At the same time, optimum design was also carried out for the number and dimension of the nails in order to obtain the best operation effect. It was concluded from the simulated result that when the real load was applied on the fastened broken bone, the relative displacement of the broken border was just 0.33 mm, which was much lesser than the permitted limit (1 mm). This was in line with the request to cure the patients whose bones are broken and it showed the correctness of the design. Finally, in order to prove the feasibility of the design, ten sheep were used as specimen. It was concluded from X-ray sketches of 2, 4 and 8 weeks that there is no relative displacement between the borders of the broken bone and the bone that was well healed. This indicated that this scheme can be feasibly used to cure the broken bones. However, this design scheme can be used as an effective treatment means. Key words : External fixation for orthopaedics, quick casting, x-ray image, cure.

Design and research of a new kind of minimally invasive fixation device in orthopaedics

A new kind of external fixation for orthopaedics was designed in order to overcome the shortcomings of high weight, difficult operation and high degree of injury for the conventional external fixation. This device uses the so called quick casting method, which can be quickly concreted, to efficiently reduce the injury to patients. It is mainly composed of the macromolecule casting material and the steel stainless nails which fasten the device to the bone. In order to verify the feasibility of the designed structure, FEM (finite element method) was used to simulate the real condition of the load when the device was used after an operation. At the same time, optimum design was also carried out for the number and dimension of the nails in order to obtain the best operation effect. It was concluded from the simulated result that when the real load was applied on the fastened broken bone, the relative displacement of the broken border was just 0.33 mm, which was much lesser than the permitted limit (1 mm). This was in line with the request to cure the patients whose bones are broken and it showed the correctness of the design. Finally, in order to prove the feasibility of the design, ten sheep were used as specimen. It was concluded from X-ray sketches of 2, 4 and 8 weeks that there is no relative displacement between the borders of the broken bone and the bone that was well healed. This indicated that this scheme can be feasibly used to cure the broken bones. However, this design scheme can be used as an effective treatment means. Key words : External fixation for orthopaedics, quick casting, x-ray image, cure.

Fabrication of Maxillofacial Implant Using CAD CAM System

We present an approach that combines Computer Tomography (CT), reverse engineering (RE) and rapid prototyping (RP) for individual implant production in maxillofacial surgery. 3D acquisition of the patient’s skull is performed, after acquisition of data; an individual computer-based 3D model of the bony defect is generated. These data are transferred into RE software to create the implant using a computer-aided design (CAD) model, which is directed into the RP machine for the production of the physical model. The implant is then directly used in investment casting such as “Quick Cast” pattern to produce the titanium model. In the clinical reports presented here, reconstructions of one patient with mandible bone defects were performed using this method. The custom prostheses perfectly fit the defects during the operations, and surgery time was reduced.

CAD-CAM Prosthesis in Maxillo-Facial Surgery

To improve the maxillofacial surgery outcome, modern manufacturing methods such as rapid prototyping (RP), reverse engineering (RE) and medical imaging data have been utilised to manufacture custom-made prostheses after previous failed reconstructive surgery. After acquisition of data, an individual computer-based 3D model of the bony defect was generated and transferred into RE software to create the prosthesis CAD model. Then the physical model of the prosthesis was fabricated by RP technique. The precise fit of the prosthesis was evaluated using the prosthesis and skull models. The prosthesis was then directly used in investment casting such as “Quick Cast” pattern to produce the titanium model. In the clinical reports presented here, reconstructions of one patient with large mandible bone defects were performed using this method. The custom prostheses perfectly fit the defects during the operations, and surgery time was reduced. These cases showed that the prefabrication of a prosthesis using modern manufacturing technology is an effective method for maxillofacial defect reconstruction.

Comments on the Paper “Production of Zr<SUB>55</SUB>Cu<SUB>30</SUB>Ni<SUB>5</SUB>Al<SUB>10</SUB> Glassy Alloy Rod of 30 mm in Diameter by a Cap-Cast Technique” (Yoshihiko Yokoyama, Enrico Mund, Akihisa Inoue and Ludwig Schultz, Mater. Trans. 48 (2007) 3190–3192.)

1. Summary of the Title Paper This paper describes a new casting technique and the required oxygen level for successful production of Zr55Cu30Ni5Al10 glassy alloy rod up to 30 mm in diameter. The casting technique named ‘‘cap-cast method’’ consisted of arc-melting the alloy followed by quick casting into water cooled copper mold; a copper ‘‘cap’’ is used to compress the alloy melt at 1 kN from the top surface immediately after casting. This cap is needed to prevent shrinkage cavity and to enhance the cooling speed of the alloy melt. Low oxygen level, less than 45 mass ppm in the starting zirconium metal, was required to obtain homogeneous Zr55Cu30Ni5Al10 glassy alloy rod. Otherwise, crystalline inclusions were observed in the glass matrix. It is also stated that ‘‘the formation of a single glassy phase in the half topside of master alloy’’ was confirmed for the as-arc melted button ingots, cooled naturally on the copper hearth. It is concluded that (1) the purity level of alloy component is an important factor to produce glassy alloy rods with large size and (2) the Zr55Cu30Ni5Al10 glassy alloy rods of up to 30 mm in diameter could be produced by means of the cap-cast technique; the critical size of glassy alloy rods is 20 mm by the conventional cast technique using copper molds.

Individually Prefabricated Prosthesis for Maxilla Reconstruction.

The reconstruction of maxillofacial bone defects by the intraoperative modeling of implants may reduce the predictability of the esthetic result, leading to more invasive surgery and increased surgical time. To improve the maxillofacial surgery outcome, modern manufacturing methods such as rapid prototyping (RP) technology and methods based on reverse engineering (RE) and medical imaging data are applicable to the manufacture of custom-made maxillary prostheses. After acquisition of data, an individual computer-based 3D model of the bony defect is generated. These data are transferred into RE software to create the prosthesis using a computer-aided design (CAD) model, which is directed into the RP machine for the production of the physical model. The precise fit of the prosthesis is evaluated using the prosthesis and skull models. The prosthesis is then directly used in investment casting such as "Quick Cast" pattern to produce the titanium model. In the clinical reports presented here, reconstructions of two patients with large maxillary bone defects were performed using this new method. The custom prostheses perfectly fit the defects during the operations, and surgery time was reduced. These cases show that the prefabrication of a prosthesis using modern manufacturing technology is an effective method for maxillofacial defect reconstruction.

New laser rapid prototyping method and its applications

To against the demerits of currently main RP technology, a novel method of laser rapid prototyping is presented, which is based on solid boundary surface separating. This method naturally combines the advantages of both. LOM which builds a part by 2D contour scanning and SLS which can process multi-kind of powdery materials. Furthermore, it can overcome some of the limitations of SLS such as low efficiency, low density and hardness, bad precision and surface smoothness, etc. Using the self-developed RP system, optimal processing parameters are obtained by a method that combines the results of temperature measured by the infrared thermal imaging system and laser energy distributed model simulated with ANSYS. The apply investigation is carried on and three dimensions rapidly manufacturing of foundry mold and quick casting of metal part are achieved by this novel method, and a metal bevel gear is successfully produced by pattern-less quick casting.

Custom fabrication of a composite hemi‐knee joint based on rapid prototyping

PurposeTo present a custom design and fabrication method for a novel hemi‐knee joint substitute composed of titanium alloy and porous bioceramics based on rapid prototyping (RP) and rapid tooling (RT) techniques.Design/methodology/approachThe three‐dimensional (3D) freeform model of a femur bone was reconstructed based on computerized tomography images via reverse engineering and the 3D reconstruction accuracy was evaluated. The negative image of artificial bone was designed with interconnected microstructures (250‐300 μm). The epoxy resin mould of a hemi‐knee joint and the negative pattern of an artificial bone were fabricated on Stereolithography apparatus. Based on these moulds, a titanium‐alloy hemi‐knee joint and a porous‐bioceramic artificial bone were created by quick casting and powder sintering (known as RT) techniques, respectively. After assembling, a composite hemi‐knee joint substitute was obtained.FindingsThe 3D reconstructed freeform model of the femur bone conformed to the original anatomy within a maximum deviation 0.206 mm. The sintered artificial bone had interconnected micropores (250 μm) and microchannels (300 μm). After implanting in vivo, the composite hemi‐knee joint substitute matched well with the surrounding tissues and bones with sufficient mechanical strength.Research limitations/implicationsFurther in‐vivo research is needed to provide the evidence for tissue growth into the ceramic structures and long‐term viability and stability of the implant.Originality/valueThis method enhances the versatility of using RP in the fabrication of tissue‐engineered substitutes, especially when individual matching is considered. Although this paper took a customized hemi‐knee joint substitute as an example, it is capable of fabricating other artificial substitutes with a variety of biomaterials.

Custom fabrication of composite tibial hemi-knee joint combining CAD/CAE/CAM techniques

A custom fabrication approach combining computer-aided design (CAD), computer-aided engineering (CAE), and computer-aided manufacturing (CAM) techniques for constructing a novel composite tibial hemi-knee joint is presented. Anatomical modelling was used to provide the computer model with specific geometry for individuals and the finite element method (FEM) was adopted to understand the loading distribution on each component of the composite substitute. Rapid prototyping (RP) was employed to build the negative patterns, based on which the titanium alloy tibial tray and the porous artificial bone were custom fabricated through quick casting and powder sintering techniques. The results show that the titanium alloy component bears most of the loading while the artificial bone shares little, which could prevent it from fracturing in vivo. The final porous artificial bone has controllable microchannels (600 microm) and random micropores (100-200 microm), which ensures full interconnectivity and is expected to address the biological consideration. Clinical application demonstrates that the composite tibial hemi-knee joint has enough mechanical strength and can fit with the upper hemi-knee joint. This novel approach provides a new way to repair large bone defects in the loading sites.

Gypsum-bonded investment and dental precision casting (III) Composition of investment for the quick casting technique.

A simultaneous differential thermal analysis and thermogravimetry method previously established was used to estimate the composition of gypsum-bonded investment marketed for the quick casting technique. Three commercial investments of this type were heated to 700 degrees C at 10 degrees C/min and the hemihydrate content was estimated by the mass decrease reached at 300 degrees C after subtracting the mass decrease at 100 degrees C as moisture content. The hemihydrate contents were between 25% and 30%, which appears to be the range also chosen for the conventional gypsum-bonded investment of cristobalite type over 70 years by the industry. However, the new type of investment contained both cristobalite and quartz. The small sample size is a disadvantage of the present method but this can be overcome by more frequent use of the method by investigators.

Gypsum-bonded Investment and Dental Precision Casting (IV) Transformation of III-CaS04 to II-CaS04

The degree of III-CaSO4 to II-CaSO4 transition was estimated on wet specimens, 25 mm in diameter and 50 mm high, prepared from a gypsum-bonded investment for quick casting. After 30 min from mixing the specimens were heated in a 700 degrees C furnace until a specimen temperature of 200 degrees C to 700 degrees C was reached. The estimation was made by measuring mass changes of the specimens before and after heating. The transition reached 39% at 350 degrees C. The same estimation method, when applied to a previous study, showed no transition to this temperature in dry specimens heated slowly (5 degrees C/min). The large difference in transition found between the wet and dry specimens was attributed to the formation of alpha- and beta-hemihydrate, respectively. At 350-450 degrees C, the transition was 3% and 48%, respectively. The pronounced latter transition, generally identified by differential thermal analysis of gypsum, appears as the major investment shrinkage demonstrating its dry dehydration process.

Gypsum-bonded investment and dental precision casting (II) investment for the quick casting technique.

Part I of this study presented a hypothesis that the thermal expansion of gypsum-bonded investment should become higher under heating conditions favorable for the formation of ahemihydrate. The present study aimed at proving this hypothesis by simulating the rapid heating condition employed in the quick casting technique. The expansion values obtained were 1.72-1.93% after 30 min in three investments, two rapid heating and one conventional types. Under a comparable measuring pressure a common laboratory measurement (5 degrees C/min) gave significantly lower expansions of 1.32-1.36% at 700 degrees C for the same investments (p<0.01). The shrinkage observed at 350-400 degrees C in this measurement was not observed in the rapid heating. Realistically large molds prepared from the conventional gypsum-bonded investment need to be investigated for their potentially high thermal expansion.

Evaluation of inserts for modular thermoplastic injection moulds produced by spin casting

Concurrent engineering enables a company to speed up its time to market: rapid prototyping forms a part of this approach. The term rapid tooling (RT) refers to the rapid creation of tools in much the same way as RP means the rapid creation of models. It is a method that offers both designers and manufacturers attractive advantages in the form of time compression and cost reduction. In an era of automated manufacturing the prototype can be produced layer by layer directly from a 3D CAD model using rapid prototyping (RP) techniques [Rapid prototyping and manufacturing, fundamental of stereolithography, SME, Dearborn, MI, 1992; Layer Manufacturing a Challenge of the Future, Tapir Publisher, Trondheim, Norway, 1992]. The drawback is that only a limited number of RP technologies cater for metal parts and taking the top three positions of vendors into account (Stratasys, 3D Systems, Sanders), their systems have no access to metal prototypes [Rapid prototyping, state of the industry report 1998, SME, Dearborn, MI, 1999]. Several RT techniques can be employed to save time in the manufacturing of plastic injection moulds: thermal spraying; quick casting, electroplating, direct metal sintering. These techniques have been subject to intensive study for a number of years and their extensive commercial potential makes them attractive propositions. Major advances in technology makes spin casting a fully proven tool for manufacturing and prototyping functional components. This paper describes the employment of spin casting for the construction of mould inserts in standard, commercial-grade pressure die casting zinc.

Shaping a thermoplastic object in the desired form without costly mechanical processing

In the field of RPT (rapid prototyping technologies), one of most limiting constraints is the restricted choice of possible materials. The state of the art is such that material choice is heavily dependent on process type, so that, except in a very few cases, the realized prototypes can only give, to the end-user, information about shape and design, or represent no more than a single step in a rapid prototyping process (as in the case of models in polycarbonate, produced with SLS techniques for quick casting). The problem is more acute for injection of plastic materials, because of the large number of available raw materials. In such cases, the only way to obtain a functional prototype, i.e. one produced both with the chosen material and injection method, consists of the realization of a test mold. Note that even though techniques such as high speed milling do indeed reduce the time-to-market, they however, weigh heavily on the budget. This project demonstrates that it is possible, for the case of thermoplastic products, to eliminate the intrinsic limitations that derive from the restricted choice of available materials for rapid prototyping. A process has been implemented which allows injection of different thermoplastic materials into a mold, realized with ceramic powder not yet sinterized. Practical results show that it is possible to shape a thermoplastic object in the desired form without costly mechanical processing.

Investigation of the effect of various build methods on the performance of rapid prototyping (stereolithography)

Stereolithography, which was the first commercially available Rapid Prototyping (RP) technique, currently represents a major portion of the worldwide RP market share. Parts manufactured with the stereolithography apparatus (SLA) are presently used for design verification, medical modeling and rapid tooling applications. Dimensional accuracy of the prototype is very important for design and form/fit applications. Tooling applications, such as patterns for investment casting, also require good surface finish. Stereolithography provides three different build styles and many part and recoat parameters which can be optimized for these various applications. This paper presents the results of an investigation into the effects of build styles (ACES, WEAVE and Quick CAST) and build parameters (Z level wait, pre-dip delay, dip velocity and acceleration, sweep period and workpiece geometry angle) on the performance measures of dimensional accuracy, surface roughness and build time. All of the prototypes were built on an SLA-250 which used the SL-5170 photopolymer resin. Statistical analysis of the results of the fractional factorial design showed that ACES produced the highest degree of dimensional accuracy while QuickCast was the least accurate build style. On a horizontal surface, ACES produced the best surface roughness and WEAVE produced the least desirable surface roughness. However, on an inclined surface, QuickCast produced the best surface roughness and ACES produced the least desirable surface roughness. The QuickCast workpieces were produced in the shortest time and ACES workpieces took the longest time. In addition to the statistical analysis, surface profiles of the prototypes were studied with Data Dependent Systems (DDS), a stochastic modeling and analysis methodology. DDS analysis of the surface profiles found that layer thickness was the major component of the profile on inclined planes and hatch and fill spacing were the major components on horizontal planes.

Development of dental quick casting with zircon-phosphoric acid investments

The application of zircon (ZrSiO4) that has high refractoriness, high thermal conductivity and a low coefficient of thermal expansion, to quick casting investment was studied. Various zircon powders and phosphoric acid solutions were tested with respect to the higher thermal shock resistance. The formulation and properties of zircon-phosphoric acid investment materials such as water/powder ratio, fluidity of slurry, setting time, setting expansion, thermal expansion, thermal analysis, green and fired compressive strength were measured. Formulation of zircon slurry for coating was zircon flower #600 30%, zircon flower #350 10%, and zircon sand CP 60%, and that for sanding was zircon flower #200. The mixing liquid was 15% phosphoric acid and liquid/powder ratio was 0.1. The slurry using phosphoric acid had good fluidity and good workability. The 24-hour green strength was 1 MPa, fired strength was 10 MPa, 24-hour setting expansion was -0.04% and the thermal expansion at 1000 degrees C was 0.31%. Immediately after coating with zircon slurry, the coating layer was dried, sintered and dewaxed by thermal shock. The thermal shock consisted of the following four-step manipulations. The first is hot air drying (50 degrees C, 5 minutes), the second is heat shock (900 degrees C, 3 seconds), the third is redrying (220 degrees C, 3 minutes) and the fourth is dewaxing (550 degrees C, 3 minutes). Small casting of pure titanium and K-metal could be done successfully by the quick casting method using the zircon-phosphoric acid investments. It was found that the total expansion of the secondary investments influenced the casting adapatability.