Zhengying Wei, Yiping Tang, Wanhua Zhao and Bingheng Lu
This paper describes the rapid development process for emitter which is the key part in water‐saving irrigation device. The design of labyrinth‐channel in emitters, the generation…
Abstract
This paper describes the rapid development process for emitter which is the key part in water‐saving irrigation device. The design of labyrinth‐channel in emitters, the generation of process‐oriented structural CAD model, the building of emitter prototype and its integrative experimental model based on RP are introduced in detail. The emitter prototypes can be directly applied to irrigation experiments and production practice, and hence the rapid development of drip irrigation emitters can be realized.
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Maoliang Wu, Wanhua Zhao, Yiping Tang, Dichen Li and Bingheng Lu
Stereolithography (SL) is a kind of rapid prototyping technology which uses the laminate manufacturing to fabricate parts. With the development of RP, some new RP processes have…
Abstract
Stereolithography (SL) is a kind of rapid prototyping technology which uses the laminate manufacturing to fabricate parts. With the development of RP, some new RP processes have boomed rapidly. Compact prototyping system (CPS) is a kind of novel stereolithography method which utilizes conventional UV light as the light source. After transmitting by optic fiber and focusing through lens set, the light is intensified and can be used to cure the photopolymer. Compared with the laser SL prototyping apparatus, this apparatus has unique characteristics on its driving system and light path system. Discusses the characteristics and corresponding consequences of the driving system and light path system, and analyzes the light energy distribution and the corresponding line shapes. Since each layer is constructed from a serial of lines, the scanning parameters, especially scanning speed and hatch gap, will influence the overall light intensity which determines the layer thickness, section shape and ultimately the prototyping accuracy. The driving system, due to the non‐uniform moving speeds, could cause the shape error of the lines. A light shutter, keeping the light only illuminating on resin surface within given curing areas, is employed to solve this deficiency.
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Guangshen Xu, Wanhua Zhao, Yiping Tang and Bingheng Lu
To satisfy the demands for rapid prototyped small‐size objects with intricate microstructures, a high‐resolution stereolithography (SL) system is developed.
Abstract
Purpose
To satisfy the demands for rapid prototyped small‐size objects with intricate microstructures, a high‐resolution stereolithography (SL) system is developed.
Design/methodology/approach
This novel SL system consists of a single mode He‐Cd laser, an improved optical scanning system, a novel recoating system and a control system. The improved optical system consists of a beam expander, an acoustic‐optic modulator, a galvanometric scanner and an F‐θ lens; the recoating system consists of roller pump, resins vat with an integrated high‐resolution translation stage and part building platform and a scraper. Experimental studies were performed to investigate the influences of building parameters on the cured line width and depth.
Findings
With the SL system, a laser light spot with a diameter of 12.89 μm on the focal plane and resin layers with a thickness of 20 μm have been obtained. The experimental results indicate that cured depth and width increase with the ratio of laser power to scanning speed, and cured line with a width of 12 μm and a depth of 28 μm was built, which showed the capability building microstructures with this new SL system.
Research limitations/implications
The building area limited to 65 × 65 mm, is smaller than that of current SL system.
Practical implications
Small objects with intricate microstructures can be fabricated with the SL system.
Originality/value
The high‐resolution SL system provides a solution to the problem that has hampered the progress of SL process into a high resolution ranges below 75 μm.
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Duan Yugang, Zhou Yuan, Tang Yiping and Li Dichen
The purpose of this paper is to improve the mechanical and thermal properties of photosensitive resin for rapid prototyping (RP) by modifying with nano‐TiO2.
Abstract
Purpose
The purpose of this paper is to improve the mechanical and thermal properties of photosensitive resin for rapid prototyping (RP) by modifying with nano‐TiO2.
Design/methodology/approach
The silane coupling agent was selected to treat the surface of anatase nano‐TiO2 particles. The IR spectrum showed that the hydroxyl (−OH) group on the surface of nano‐TiO2 reacted with the coupling agent effectively. The effects of TiO2 content on the curing depth and viscosity of the photosensitive resin were studied by experiments. The mechanical properties including tensile strength, tensile modulus, flexural strength and hardness were tested according to ASTM standards. The thermal stability of modified photosensitive resin was tested by differential scanning calorimetry.
Findings
The comprehensive performance of the modified photosensitive resin was good when TiO2 content was at 0.25 per cent, the tensile strength was increased by 89 per cent from 25.26 to 47.82 MPa, the tensile modulus increased by 18 per cent from 2,001 to 2,362 MPa, the flexural strength and the hardness increased by 6 and 5 per cent, respectively. In addition, the plasticity and heat stability of modified photosensitive resin were also improved obviously.
Originality/value
The paper provides a low‐cost method to greatly improve the performance of photosensitive resin for RP. The modified photosensitive resin prepared according to the formulas in this paper has been successfully employed in RP equipment of Xi'an Jiaotong University, China.
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Zhengying Wei, Yiping Tang, Wanhua Zhao and Bingheng Lu
The paper aims to summarize the design theory for labyrinth channels of water saving emitters.
Abstract
Purpose
The paper aims to summarize the design theory for labyrinth channels of water saving emitters.
Design/methodology/approach
On the basis of extracting the structural parameters of labyrinth channels in water saving emitters, the hydraulic performance experiments on the integral emitters fabricated with higher resolution rapid prototyping technology are performed. Then, using multivariable linear regression, formulas of pressure versus flow rate and regression plots for different emitters are induced.
Findings
The formulas of flow rate versus structural parameters are summarized based on the trapezoid‐type channel unit, and verified through experiments. The relationships between flow rate, pressure and structural parameters of channels are established.
Research limitations/implications
The effect of emitter fabrication error on the flow rate is analyzed, which provides a basis for parameterized structural design and accuracy control in the fabrication of future emitters.
Practical implications
The Q‐H‐n relationship equations are used to design emitters which have flow‐rate errors under both high‐ and low‐water pressure of less than 4 percent. So the Q‐H‐n relationship equation of the emitter is well proven and accurate which can guide the design for the structure of emitters with trapezoid labyrinth channels.
Originality/value
In this paper, a new stereolithography system has been used to fabricate accurately a drip irrigation emitter with a complex microstructure, which cannot be obtained with conventional RP or other manufacturing processes. Compared to other manufacturing process, this new technique has higher manufacturing accuracy and can reduce the manufacturing cost and time. Furthermore, a design theory for labyrinth channels of water saving emitters is established.
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Gangxian Zhu, Dichen Li, Anfeng Zhang, Gang Pi and Yiping Tang
The purpose of this paper is to investigate the influencing rule of the standoff distance variations between the nozzle outlet and the powder deposition point on forming…
Abstract
Purpose
The purpose of this paper is to investigate the influencing rule of the standoff distance variations between the nozzle outlet and the powder deposition point on forming dimensional accuracy.
Design/methodology/approach
The thin‐wall parts were built with three different standoff distances: 1 mm more than the powder focus length, equal to the powder focus length and 1 mm less than the powder focus length. Based on the experimental results, the steady standoff distance can be acquired and the difference between the building height and the ideal height of thin‐wall parts can be compensated automatically in several layers by theoretical calculation.
Findings
The experimental results show that the top surface unevenness of thin‐wall parts can be compensated automatically on the consequent successive layers when the standoff distance is less than the powder focal length from the nozzle outlet to the powder focal point, and the poorer results are obtained when the standoff distance is equal to or more than the powder focal length in the deposition of stainless steel 316L under open‐loop control.
Practical implications
The shape of parts affects the self‐regulation effect in practical applications, so the self‐regulation effect is useful when the single contour of parts is continuous straight faces and the surface of parts is perpendicular to the build platform, and will be useless for parts with holes.
Originality/value
According to the requirements under different process conditions in practical applications, one should first find out the relationship between the standoff distance and the building height of single‐trace cladding layer, and then use regression algorithm to obtain the stable standoff distance by simple theoretical calculation. The uniform building height, layer thickness and smooth surface can be obtained at the stable standoff distance under open‐loop control.
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Zhongzhong Chen, Dichen Li, Bingheng Lu, Yiping Tang, Minglin Sun and Zhen Wang
A new technique based on rapid prototyping (RP) is proposed to fabricate the mould of artificial bone composed of a nontoxic soluble material. The mould has both an external…
Abstract
A new technique based on rapid prototyping (RP) is proposed to fabricate the mould of artificial bone composed of a nontoxic soluble material. The mould has both an external structure that exactly coincides with the replaced natural bone and an internal 3D scaffolds simulating the bone microtubule structure. By injecting self‐setting calcium phosphate cement (CPC) with bone morphogenetic protein (BMP, a kind of bone growth factors) into the cavities of the mould, the CPC solidified and the micropores can be formed after the internal 3D scaffolds is dissolved, finally the artificial bioactive bone can be produced. This approach is better than the traditional fabrication process, which the latter method cannot fabricate an artificial bone with inter‐connective micropores so as to realize the osteo‐induction for lack of bioactivity. Through animal experiments, it shows that the simulated inter‐structure could provide artificial bone with proper voids for the growth of the bone tissue and the quick activation, and hence effectively speed up the bone growth by means of activating osteo‐conduction and osteo‐induction. So, the new method of fabricating artificial bone with biological behaviors is justified.
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Wurikaixi Aiyiti, Wanhua Zhao, Bingheng Lu and Yiping Tang
To fabricate fully dense components with low costs, a rapid prototyping (RP) system based on micro‐plasma arc welding (MPAW) was developed. The appropriate process parameters were…
Abstract
Purpose
To fabricate fully dense components with low costs, a rapid prototyping (RP) system based on micro‐plasma arc welding (MPAW) was developed. The appropriate process parameters were investigated to build the parts with good mechanical properties and surface smoothness.
Design/methodology/approach
A simplified overlapping model between deposited tracks was established to investigate the relationships among the overlapping parameters, such as the ratio of width to height of the deposited track cross‐section (λ), scan spacing and overlapping ratio. Some ER308L stainless steel parts were built by different overlapping parameters, and the surface smoothness, tensile strength and elongation of the parts were tested.
Findings
The overlapped surface smoothness, tensile strength and elongation of the parts built with larger λ were better than those built with smaller λ. The longitudinal tensile strength and elongation of the parts were better than the transverse data.
Research limitations/implications
The scanning direction obviously affected the tensile strength and elongation of the parts, so the multi‐directional scanning mode should be used to get isotropic parts.
Originality/value
This MPAW‐based RP system provides a solution to build fully dense metal parts with relatively lower costs. The appropriate process parameters can be obtained with the developed overlapping model.
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Shanglong Xu, Dichen Li, Bingheng Lu, Yiping Tang, Chaofeng Wang and Zhen Wang
The purpose of this paper is to adopt rapid prototyping (RP) technology to fabricate self‐hardening calcium phosphate composite (CPC) scaffolds with a controlled internal channel…
Abstract
Purpose
The purpose of this paper is to adopt rapid prototyping (RP) technology to fabricate self‐hardening calcium phosphate composite (CPC) scaffolds with a controlled internal channel network to facilitate nutrient supplying and cell growth using RP technique and investigate their in vitro performance.
Design/methodology/approach
Porous scaffolds should possess branched channels to ensure uniform cell feeding and even flow of culture medium to promote uniform cell attachment and growth. A new three dimensional (3D) flow channel structure has been designed based on conversation of energy and flow. The CPC scaffold possessing such a channel network was made by indirect solid free form fabrication. Negative model of scaffold was designed by Pro/E software and its epoxy resin mold was fabricated on a sterolithography apparatus and the CPC slurry was filled in these molds. After CPC was self hardened, the mold was baked. The mold was removed by pyrolysis and then the designed scaffold was obtained.
Findings
The sizes of the fabricated scaffolds were consistent with the designed. The average compressive strength of the scaffold is approximately 6.0 MPa. Computational fluid dynamics and perfusion culture results showed that such a 3D flow channel arrangement would lead to a more uniform distribution of flow and cells and good transportation of nutrients.
Research limitations/implications
The size errors of fabricated scaffolds could not escape and perfusion methods were difficult to control.
Originality/value
The basic design concept presented showed great promise for use in bone tissue engineering and fabrication method enhanced the versatility of scaffold fabrication. The designed scaffold structure made it possible to keep integrality of the scaffold when direct observation cells inside the channel by scanning electron microscopy (SEM).
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Weijun Zhu, Dichen Li, Zhengyu Zhang, Ke Ren, Xinglei Zhao, Dangguo Yang, Wei Zhang, Yan Sun and Yiping Tang
The purpose of this paper is to present a novel method to design and fabricate aeroelastic wing models for wind tunnel tests based on stereolithography (SL). This method can…
Abstract
Purpose
The purpose of this paper is to present a novel method to design and fabricate aeroelastic wing models for wind tunnel tests based on stereolithography (SL). This method can ensure the structural similarity of both external and internal structures between models and prototypes.
Design/methodology/approach
An aluminum wing‐box was selected as the prototype, and its natural modes were studied by FEA and scaled down to obtain the desired dynamic behavior data. According to similarity laws, the structurally similar model was designed through a sequential design procedure of dimensional scaling, stiffness optimization and mass optimization. An SL model was then fabricated, and its actual natural modes was tested and compared with the desired data of the prototype.
Findings
The first two natural frequencies of the model presented strong correlation with the desired data of the prototype. Both the external and internal structures of the model matched the prototype closely. The SL‐based method can significantly reduce the total mass and simplify the locating operations of balance‐weights. The cost and time for the fabrication were reduced significantly.
Research limitations/implications
Further investigation into the material properties of SL resins including stiffness and damping behaviors due to layered process is recommended toward higher prediction accuracy. Wind tunnel tests are needed to study the in situ performance and durability of SL models.
Originality/value
Although the paper takes a wing‐box as the study object, structurally similar SL models of entire wings can be obtained conveniently, benefiting from the low‐stiffness material properties of SL resins and the fabrication capacity to build complex structures of SL process. This paper enhances the versatility of using SL and other rapid prototyping processes to fabricate models to predict aeroelastic characteristics of aircraft.