Additive manufacturing of wet-spun polymeric scaffolds for bone tissue engineering
Dario Puppi &Carlos Mota &Matteo Gazzarri &Dinuccio Dinucci &Antonio Gloria &
Mairam Myrzabekova &Luigi Ambrosio &Federica Chiellini
Published online:6July 2012
#Springer Science+Business Media,LLC 2012
Abstract An Additive Manufacturing technique for the fabrication of three-dimensional polymeric scaffolds,based on wet-spinning of poly(ε-caprolactone)(PCL)or PCL/hydroxyapatite (HA)solutions,was developed.The pro-cessing conditions to fabricate scaffolds with a layer-by-layer approach were optimized by studying their influence on fibres morphology and alignment.Two different scaffold architectures were designed and fabricated by tuning inter-fibre distance and fibres staggering.The developed scaf-folds showed good reproducibility of the internal architec-ture characterized by highly porous,aligned fibres with an average diameter in the range 200–250μm.Mechanical characterization showed that the architecture and HA load-ing influenced the scaffold compressive modulus and strength.Cell culture experiments employing MC3T3-E1preosteoblast cell line showed good cell adhesion,prolifer-ation,alkaline phosphatase activity and bone mineralization on the developed scaffolds.
Keywords Tissue engineering .Scaffolds .Wet-spinning .Additive manufacturing .Polycaprolactone
1Introduction
Bone tissue engineering is one of the most promising approaches to be used as alternative to the conventional autogenic or allogenic surgical techniques for bone tissue repair (Marolt et al.2010).Scaffold-based tissue engineer-ing strategies involve the use of a biodegradable,porous scaffold that serves as structural template to fill the tissue lesion and to support cell-cell interactions and extracellular matrix (ECM)formation (Puppi et al.2010).Under optimal conditions,cells harvested from donor tissues,including adult or stem cells,are expanded in culture and associated with a scaffold of synthetic and/or natural origin.The scaf-fold/cells construct is then implanted in the targeted site where the defect can be regenerated as consequence of a good interaction with the host tissue.
Macro and micro-structural properties of the scaffold affect not only cells survival,signalling,growth,propaga-tion and reorganization,but play also a major role in mod-elling cell shape and gene expressions,both related to cell growth and preservation of native phenotypes (Leong et al.2003;Karageorgiou and Kaplan 2005).Since the first pio-neering experiments carried out by Langer and Vacanti more than 20years ago (Vacanti et al.1988;Langer and Vacanti 1993),several studies have reported different materials pro-cessing techniques for the fabrication of polymeric scaffolds with a macro-and micro-architecture suitable for tissue engineering applications.These include,among others,sol-vent casting combined with particulate leaching,freeze dry-ing,gas foaming,melt moulding,fibre bonding,phase separation,electrospinning and rapid prototyping techni-ques (Puppi et al.2010).
D.Puppi :C.Mota :M.Gazzarri :D.Dinucci :M.Myrzabekova :F.Chiellini
Laboratory of Bioactive Polymeric Materials for Biomedical and Environmental Applications (BIOlab),
Department of Chemistry and Industrial Chemistry,University of Pisa,
via Vecchia Livornese 1291,San Piero a Grado (Pi),56010Pisa,Italy
A.Gloria :L.Ambrosio
Institute of Composite and Biomedical Materials,National Research Council,Naples,Italy
F.Chiellini (*)
via Vecchia Livornese 1291,56010San Piero a Grado (Pi),Pisa,Italy
e-mail:federica@dcci.unipi.it
Biomed Microdevices (2012)14:1115–1127DOI 10.1007/s10544-012-9677-0
Wet-spinning is a non solvent-induced phase inversion technique allowing for the production of a continuous micrometric polymer fibre through an immersion precip-itation process:a polymeric solution is injected directly into a coagulation bath containing a poor solvent for the polymer,and the solution filament solidifies because of polymer desolvation caused by solvent–non-solvent exchange(Puppi et al.2011b).Among other techniques for manufacturing polymeric fibres employed in biomedical applications,wet-spinning has been mostly used to process natural polymers,such as chitin and chitosan(Tuzlakoglu et al.2008),which cannot be formed by other spinning techni-ques.A growing body of literature has recently proposed wet-spun microfibres for TE applications,including chitosan fibres(Tuzlakoglu et al.2004),braided poly(L-lactic acid) (PLLA)/chitosan fibres(Zhang et al.2007),starch-based non-woven fibrous meshes(Pashkuleva et al.2010; Tuzlakoglu et al.2010;Leonor et al.2011),poly(ε-caprolac-tone)(PCL)fibres(Williamson and Coombes2004),star poly (ε-caprolactone)(*PCL)non-woven fibrous meshes(Puppi et al.2011a;Puppi et al.2011b).In particular,assemblies of wet-spun fibres,obtained by either physical bonding of prefabricated fibres or by a single-step method involving the continuous,randomly-oriented deposition of the solid-ifying fibre in the coagulation bath,have been shown to possess a three-dimensional(3D)structure with high and interconnected porosity suitable for tissue engineering pur-poses(Tuzlakoglu et al.2004;Pashkuleva et al.2010; Tuzlakoglu et al.2010;Leonor et al.2011;Puppi et al. 2011a;Puppi et al.2011b).However,these fabrication methods don’t allow an accurate control over scaffold exter-nal shape and internal morphology(Puppi et al.2011a; Puppi et al.2011b).
Additive manufacturing(AM),which can be defined as “the process of joining materials to make objects from3D model data,usually layer upon layer”(ASTM2010),has been extensively applied for the fabrication of3D scaffolds by employing different techniques,such as stereolitography, selective laser sintering,3D printing and fused deposition modelling(FDM)(Woodruff and Hutmacher2010).Thanks to their ability to produce porous polymeric matrices with reproducible and customized microstructure and macro-shape,such techniques represent a significant breakthrough in scaffolds manufacturing.In particular,over the past dec-ade and since the first work reported by Hutmacher on scaffolds fabricated by FDM(Hutmacher2000),a number of studies have been published on melt extrusion-based AM techniques for application in tissue engineering(Wang et al. 2004;Woodfield et al.2004;Domingos et al.2009;Mota et al.2011).These techniques involve the fabrication of layers of parallel strands with different orientation one on top of the other,by depositing with a predefined pattern an extruded filament of a polymer melt.
PCL is a semicristalline polymer that has been widely investigated in bone tissue regeneration applications because of its biocompatibility and slow degradation (Williams et al.2005;Koh et al.2006;Rai et al.2007; Woodruff and Hutmacher2010).However,the implantation of PCL substitutes into bone defects typically can present various drawbacks,such as lack of integration with the surrounding tissue because of an inflammatory reaction, encapsulation into fibrous tissue and mechanical strength reduction associated with material degradation(Taylor et al. 1994;Kokubo et al.2003;Schiller and Epple2003).The incorporation of hydroxyapatite(HA),a synthetic calcium phosphate ceramic that mimics the natural apatite composi-tion of bones and teeth,into biodegradable polyesters has been investigated as an effective means of improving the osteoconductivity and mechanical properties of bone implants and creating a pH buffer against the acidic degra-dation products of the polymeric matrices(Ural et al.2000; Kikuchi et al.2004;Kim et al.2004;Koh et al.2006; Wutticharoenmongkol et al.2007).
Aim of the present work was the development of an AM technique allowing enhanced controlled over internal and external architecture of microfibrous polymeric scaffolds fabricated by wet-spinning.By exploiting a computer-assisted wet-spinning system,the processing conditions for the fabrication of3D scaffolds,with different architectures and made of either PCL or PCL/HA composite,were opti-mized.The developed scaffolds were characterized for their morphology and elemental composition by means of scan-ning electron microscopy(SEM),under backscattered elec-tron imaging and microanalysis,and micro-computed tomography(Micro-CT),as well as for their mechanical compression properties using a uniaxial testing machine. In vitro cell culture experiments employing MC3T3murine preosteoblast cells were carried out in order to evaluate the scaffolds cytocompatibility.Cell response,in terms of via-bility,proliferation,morphology,differentiation and bone mineralization,was investigated by tetrazolium salts (WST-1cell proliferation reagent),confocal laser scanning microscopy(CLSM),alkaline phosphates activity(ALP) and alizarin red staining(ARS)respectively.
2Materials and methods
2.1Additive manufacturing of wet-spun scaffolds
2.1.1Materials
Poly(ε-caprolactone)(PCL,CAPA6800,Mw080000g·mol?1) was kindly supplied by Solvay(Italy),hydroxyapatite (HA)nanoparticles(size<200nm)were purchased from Sigma-Aldrich(Italy).All the solvents and chemical
reagents were purchased from Sigma-Aldrich (Italy)and used as received.
2.1.2Preparation of polymeric solutions
PCL was dissolved in acetone at 35°C,under gentle mag-netic stirring for 3h to obtain homogeneous solutions of various concentrations.For the production of composite scaffolds,the desired amount of HA was added to the polymer solution and left under vigorous stirring for 2h to achieve a homogeneous dispersion.On the base of some preliminary investigations,the weight ratio between HA and PCL was chosen to be 25%.
2.1.3Fabrication of 3D polymeric scaffolds
The polymeric solution was placed in a glass syringe con-nected to a blunt tip stainless steel needle (Gauge 23)through a plastic tube.By using a programmable syringe pump (KDS100,KD Scientific,MA)the solution was injected at a controlled feeding rate directly into a bath of ethanol.The X-Y movement of the needle and the Z move-ment of the build platform were controlled by an in-house made computer-controlled system allowing for the produc-tion of 3D structures layer-by-layer (Fig.1).
Various processing parameters,such as polymer concen-tration (C PCL ),solution flow rate (F),initial distance between the needle tip and the collection plate (Z 0),inter-fibre needle translation distance (d xy ),X-Y translation velocity (V dep )and Z inter-layer needle translation distance (d z ),were investigated in order to optimize the process for the fabrication of scaffolds with different internal architec-tures.Rectangular prism-shaped PCL scaffolds with the base measuring 15×15mm and the height measuring around 5mm were produced for morphological and com-pressive mechanical characterization.Wet-spun scaffolds were removed from the coagulation bath after production,then placed in a vacuum chamber for 48h and finally stored in a desiccator.
2.2Morphological characterization 2.2.1Scanning electron microscopy (SEM)
Samples were cut from the produced scaffolds and charac-terized by scanning electron microscopy (SEM,model JEOL LSM5600LV,Japan)under backscattered electron imaging and elemental microanalysis.The average fibre diameter and inter-fibre distance were determined by means of ImageJ 1.43u software on micrographs with a 50X mag-nification;morphological parameters were calculated over 30measurements per specimen,taken from randomly selected fields.Scaffold elemental composition was ana-lyzed on five random areas (80×50μm)of each sample.2.2.2Micro computer tomography (Micro-CT)
Micro-computed tomography (Micro-CT)was carried out on scaffolds using a SkyScan 1072system (Aartselaar,Belgium).A rotational step of 0.9°over an angle of 180°was imposed.Cross-sections and 3D models of PCL and PCL/HA structures were reconstructed using SkyScan ’s software package,Image J software,Rapidform and Materi-alise Mimics.
2.3Mechanical characterization
Compression tests were carried on scaffolds in order to assess their mechanical behaviour.Block-shaped specimens were characterized by a length (l)of 15.0mm,a width (w)of 15.0mm and a height (h 0)of about 5.0mm.Six samples for each kind of scaffold were characterized at a rate of 1mm/min and up to a strain value of 0.5mm/mm,using an INSTRON 5566testing machine.The stress σwas defined as the measured force (F)divided by the total area of the apparent cross section of the scaffold (A 00l ?w):σ?
F A 0
e1
T
Fig.1(a )Scheme of
computer-aided wet-spinning apparatus;(b )layer-by-layer process
whilst the strainεwas evaluated as the ratio between the structure height variationΔh and its initial height h0:
"?Δh
h0
e2T
2.4Biological characterization
2.4.1Cell seeding
Scaffold samples were placed in a24wells plate,sterilized under UV light for half an hour each side and then washed with70%ethanol:water solution for3h.After ethanol removal,scaffolds were extensively washed with phosphate buffer saline(PBS1X,pH7.4),containing a penicillin/ streptomycin solution(1%),and then left overnight at 37°C in a5%CO2.The solution was then substituted with complete culture medium and samples were incubated for 24h before cell seeding.Mouse calvaria-derived preosteo-blastic cells MC3T3-E1(subclone4ATCC CRL-2593) were obtained from the American Type Culture Collection (ATCC CRL-2593)and cultured as monolayers in Alpha Minimum Essential Medium(α-MEM-Sigma),containing ribonucleosides,deoxyribonucleosides and sodium bicar-bonate,supplemented with L-glutamine[2mM],fetal bovine serum(10%),penicillin:streptomycin solution[100 U/mL:100μg/mL](1%)and antimycotic.The cultures were maintained at37°C and5%CO2.Confluent cells at passage25were trypsinized(0.25%trypsin containing 1mM EDTA),centrifuged and resuspended in complete medium.Subsequently0.5x104cells per scaffold were seeded onto scaffolds in a24well plate and,after one hour of incubation at37°C and5%CO2,600μl of complete medium were added to each well,followed by incubation in a humidified atmosphere at37°C.In order to induce and promote cells osteoblastic phenotype expression,some scaf-folds were cultured in osteogenic medium obtained by sup-plementing theα-MEM with ascorbic acid(0.3mM) (Quarles et al.1992).The medium was replaced every48h.
2.4.2Cell viability and proliferation
Cell viability and proliferation were measured by using the cell proliferation reagent WST-1(Roche)after7,14,21,28, 35and43d of cell culturing.The test is based on the mitochondrial enzymatic conversion of the tetrazolium salt WST-1into formazan,the soluble product.The assay was performed by incubating cell-seeded scaffolds for4h with the WST-1reagent,diluted1:10,at37°C and5%CO2. Measurements of formazan dye absorbance were carried out with a microplate reader(Biorad)at450nm,with the reference wavelength at655nm.2.4.3Alkaline Phosphatase(ALP)activity
ALP activity was determined in cultured MC3T3-E1-scaffold constructs after7,14,21and28d of cell culturing. The measurement was assessed with a colorimetric method based on the conversion of p-nitrophenyl phosphate into p-nitrophenol by the ALP enzymatic activity.Scaffolds were washed three times with PBS and then placed into1ml of a lysis buffer,containing Triton X-100(0.2%),magnesium chloride[5mM]and trizma base[10mM]at pH10.Samples underwent freezing-thawing cycles by keeping at–20°C and subsequently at room temperature(RT)(Wutticharoenmongkol et al.2007).This process was repeated three times in order to extract the intracellular ALP(Wang and Y u2010).Afterwards, a volume of20μl of supernatant was taken from the samples and added into100μl of p-nitrophenyl phosphate substrate (Sigma).A standard calibration,prepared dissolving ALP from bovine kidney(Sigma)in the same lysis buffer,was added to the substrate and the reaction was left to take place at37°C for 30min.The reaction was stopped by adding50μl of2M NaOH solution and after5min absorbance was measured at 405nm in a microplate reader.The molar concentration of ALP was normalized with the total protein content of each sample, which was measured using Bradford protein assay(Pierce).The amount of the proteins was calculated against a standard curve. The results for ALP activity assay were reported as nano-moles (nmol)of substrate converted into product per minute and mg of total proteins.
2.4.4Mineralized matrix deposition analysis by Alizarin Red Staining(ARS)
The mineralized matrix deposition was analyzed by using the ARS method(Stanford et al.1995;Ozkan et al.2009) after7,14,21,28,35and43d of cell culturing.Scaffolds fixed with3.8%p-formaldehyde at RT for30min,were stained with2%Alizarin Red solution pH4for10min. After the dye incubation,samples were extensively rinsed with sterile de-mineralized,in order to remove the dye excess.To quantify the amount of calcium deposited on the scaffolds,the red matrix precipitate was dissolved in 10%cetylpyridinium chloride(CPC)solution pH7,and the optical density of the solution was read with a micro-plate reader at565nm.A standard calibration of ARS was carried out in CPC buffer.Unseeded scaffolds were treated with the same procedure,as blank.
2.4.5Cell morphology investigation by Confocal Laser Scanning Microscopy(CLSM)
Morphology of MC3T3-E1cells grown on the prepared scaffolds and3D culture organization were investigated by means of CLSM.Cells were fixed with3.8%p-formaldehyde
for30min in PBS1X,permeabilized with a PBS1X/Triton X-100solution(0.2%)for15min and incubated with a solution of4′-6-diamidino-2-phenylindole(DAPI)(Invitro-gen)and phalloidin-AlexaFluor488(Invitrogen)in PBS for 45min at room temperature in the dark.After dye incuba-tion,samples were extensively washed with PBS and observed by including specimen in-between two glass cover slips.All steps of the above procedure were performed under gently shaking on an orbital shaker in order to enhance solution penetration into scaffold structure.A Nikon Eclipse TE2000inverted microscope equipped with an EZ-C1confocal laser and Differential Interference Con-trast(DIC)apparatus was used to analyze the samples (Nikon).A405nm laser diode and an Argon Ion Laser (488nm emission)were used to excite respectively DAPI and FITC fluorophores.Images were captured with Nikon EZ-C1software with identical instrumental settings for each sample.Images were further processed with The GIMP (GNU Free Software Foundation)image manipulation soft-ware and merged with Nikon ACT-2U software.
2.5Statistical analysis
All the in vitro biological tests were performed on triplicate samples for each material.
Quantitative data were presented as mean±standard devi-ation(SD).Data sets were screened by one-way ANOV A and a Tukey test was used for post hoc analysis;significance was defined at p<0.05.
3Results and discussion
Techniques based on a layered manufacturing strategy rep-resent an effective approach for the control at the microscale over the internal architecture,external shape and size of tissue engineering scaffolds.In this study,an innovative AM technique for the fabrication of wet-spun polymeric scaffolds was developed.The processing conditions for the manufacturing of3D wet-spun PCL and PCL/HA composite scaffolds with different internal architectures were investi-gated,and the developed scaffolds were characterized for their morphology,compressive mechanical properties and cytocompatibility using the MC3T3-E1murine preosteo-blast cell line.
3.1Additive manufacturing of3D wet-spun structures The scaffold fabrication process involved the extrusion of a polymeric solution through a X-Y translating needle that was immersed into a coagulation bath(Fig.1).A layer composed of parallel fibres was fabricated by depositing the solidifying solution filament with a predefined pattern,and3D architectures were built up with a layer-by-layer process by fabricating layers with different fibre orientation (0–90°lay-down pattern)one on top of the other.
By optimizing the processing parameters,two different scaffold architectures were developed(Fig.2):one (PCL1mm)was obtained with an X-Y inter-fibre needle translation distance(d xy)of1mm and0.5mm staggered fibre spacing between successive layers with the same fibre orientation;the other one(PCL0.5mm)was obtained with a d xy of0.5mm.
Besides d xy,the most influent processing parameters on fibres alignment and morphology were polymer concentra-tion(C PCL),solution flow rate(F),starting needle tip-collection plane distance(Z0)and deposition velocity(V dep
) Fig.2(a)PCL1mm(left)and PCL0.5mm(right)scaffold architectures;
(b)3D PCL scaffolds fabricated by AM(64layers)
(Table1).PCL/HA composite scaffolds with the above described two architectures were successfully fabricated by processing a suspension of HA nanoparticles in PCL solu-tion and applying the processing conditions optimized for plain PCL scaffolds.
Due to its superior rheological and viscoelastic proper-ties with respect to various resorbable-polymer counter-parts,PCL has been widely investigated during the past two decades for the manufacturing of a large range of scaffold structures,including nanofibre meshes,foams, knitted textiles and rapid prototyped constructs.As recently reviewed by Woodruff and Hutmacher(Woodruff and Hutmacher2010),a vast array of AM techniques with a layered manufacturing strategy has been proposed for the fabrication of PCL scaffolds,such as those based on laser and UV light sources(i.e.stereolithography,selective laser sintering,solid ground curing),3D printing,melt extrusion-based techniques(i.e.FDM and precision extruding deposition)and direct writing techniques.In addition,wet-spinning of PCL solutions was recently pro-posed for the fabrication of3D non-woven microfibrous scaffolds through a single-step process(Puppi et al. 2011a;Puppi et al.2011b).However,this technique, besides requiring a continuous handiwork,suffers from poor control over scaffold microstructure and shape.The AM technique developed during the present activity allows for overcoming these disadvantages by exploiting a computer-assisted wet-spinning system that enables to design and manufacture by a layer-by-layer approach, PCL-based3D constructs with improved control over scaffold microarchitecture and shape.The employment of a computer as an integral part of the developed manufac-turing system enables the enhancement of the process automation,thus increasing the production rate and mini-mizing the human intervention,and the design of custom-ized scaffolds that can meet specific requirements for different applications in terms of accurate anatomical geometry,tunable inner pore size and controllable inter-pore connectivity.In addition,the developed technique does not require high temperatures and involves the use of solvents classified with low toxic level,thus allowing for the loading of bioactive agents without compromising their bioactivity.3.2Morphological analysis
SEM analysis using backscattering electron imaging showed good reproducibility of internal architecture and good degree of fibres alignment for the two kinds of PCL architecture developed.The fibres presented a highly porous morphology both in the outer surface and in the cross section,with a pore size of few micrometers(Fig.3).More-over,PCL/HA composite scaffolds revealed a morphology close to that of plain PCL scaffolds.
As reported in Table1,PCL1mm scaffolds showed signifi-cantly smaller fibre diameter(202.1±11.7μm)in compari-son with PCL0.5mm scaffolds(238.4±13.4μm);HA loading resulted in larger diameter in the case of PCL/HA1mm (240.7±13.4μm)while it did not affect significantly dimen-sion in the case of PCL/HA0.5mm(241.7±21.5μm).The inter-fibre distance(defined as the minimum distance between two adjacent fibres within the same layer)was in the range700–950μm for PCL1mm and in the range200–350μm for PCL0.5mm.
Figure4shows representative images obtained from Micro-CT analysis of PCL/HA scaffolds with the two devel-oped architectures.This analysis highlighted the well defined morphology and the architectural features of the structures.In particular,it showed the good degree of fibre alignment in the inner part of the scaffolds(Fig.4(a)and(b) and confirmed that the developed AM technique is a power-ful tool to manufacture scaffolds characterized by a repeat-able structure.
Figure5shows representative electron back scattering microanalysis spectra of PCL/HA composite scaffolds. Chemical composition analysis of fibre surface revealed the presence and quite homogeneous distribution of phos-phorus(P)and calcium(Ca)elements,unequivocally asso-ciated with the presence of HA.However,some white spots (Fig.5(b))were observed in high magnification micro-graphs of fibre surface.The marked differences in intensity of analogue energy peaks between the spectra of wide fibre surface areas(Fig.5(a))and those of white spots(Fig.5(b)) revealed that they were mainly composed of HA elements.
Upon immersion of a homogeneous polymeric solution into a coagulation bath,typically a dense,non-porous layer (skin)is formed at the interface with the non solvent because
Table1Processing conditions, fibre diameter and inter-fibre distance of the different kinds of scaffold.Morphological param-eters are expressed as average±standard deviation Scaffold C PCL(w/v)F(mL/h)Z0(mm)V dep(mm/min)Fibre diameter
(μm)
Inter-fibre
distance(μm) PCL1mm10% 1.45300202.1±11.7872.5±65.4 PCL0.5mm8%11170238.4±13.4256.3±36.4 PCL/HA1mm10% 1.45300240.7±13.4807.5±41.8 PCL/HA0.5mm8%11170241.7±21.5262.3±59.5
of instantaneous non-solvent diffusion into the polymer solution (Tsay and McHugh 1992;Wienk et al.1996).The spongy morphology of the outer surface and cross section of the fibres constituting the scaffolds developed during the present work is likely due,as suggested by previous studies on phase inversion mechanism (Wienk et al.1996;Barton et al.1997),to a delayed liquid –liquid demixing.In compar-ison with dense strands fabricated by melt-based AM tech-niques (e.g.FDM),such highly porous fibre morphology can present some advantages in influencing,in addition to the biodegradation rate and the mass transfer associated to drug release phenomena,the mechanisms regulating
cell
Fig.3Representative
backscatter SEM micrographs of the two scaffold
architectures:top view and cross-section of PCL 1mm (top )and PCL 0.5mm (bottom )scaf-folds.Insert high magnification micrographs show porosity of the outer surface and cross sec-tion of the fibres
adhesion and proliferation (Karageorgiou and Kaplan 2005).The HA microaggregates detected on the fibres surface are likely due to the not perfectly homogenous suspension of HA nanoparticles in the PCL solution.Future research will investigate whether such aggregates were leached out dur-ing the pre-treatment stages before in vitro studies or in vivo implantation (e.g.sterilization,scaffold preconditioning).
3.3Mechanical characterization
The effect of HA loading and scaffold architecture on com-pressive mechanical properties of the developed scaffolds was assessed using a uniaxial testing machine (strain rate 01mm/min,maximum strain 00.5mm/mm).As shown in Fig.6,the stress-strain curves of the manufactured
PCL
Fig.4Representative images obtained from Micro-CT analysis:cross section of (a )PCL/HA 1mm and (b )PCL/
HA 0.5mm ;3D reconstructions of (c )PCL/HA 1mm and (d )PCL/HA
0.5mm
Fig.5Representative EBS micrograph and elemental analysis of PCL/HA scaffold:(a )spectra of the wide fibre surface area;(b )spectra of a white spot onto fibre surface
and PCL/HA scaffolds were characterized by an initial linear region at low values of strain,followed by two further regions with different stiffness.
Data reported in Table 2showed that PCL 0.5mm displayed significantly higher compressive modulus and higher max-imum stress in comparison with PCL 1mm structure,as well as PCL/HA composite scaffolds in comparison with plain PCL scaffolds.
The compressive mechanical properties of the developed scaffolds are quite different from those of load-bearing bone tissues which experience high stresses and low strains dur-ing in vivo physiological loading.The stiffness of this kind of scaffolds would need thus to be significantly improved in order to broaden their applications in bone regeneration.Their mechanical behaviour is consistent with that reported in previous works on melt extrusion-based AM of PCL scaffolds (Hutmacher et al.2001;Kyriakidou et al.2008;Gloria et al.2009,M.Domingos et al.2009;Bartolo et al.2011),showing stress-strain curves characterized by three regions with different slope,although they differ in the absence of a central plateau region with roughly constant stress as well as in the much lower values of compressive modulus and mechanical strength.These differences might be related to the highly porous fibre morphology that can
cause a different mechanical response of the single fibre.The enhanced mechanical properties as consequence of HA loading corroborate the results of a number of studies on polymer/inorganic composite scaffolds (Rezwan et al.2006).The higher compressive modulus and strength of PCL 0.5mm scaffolds in comparison with those of PCL 1mm can be explained with their higher fibre packing density.Future studies will be dedicated to tuning the internal archi-tecture parameters (e.g.inter-fibre distance,fibre staggering,lay-down pattern),and assessing the effect of phase inver-sion conditions (e.g.polymer concentration,solvent/non solvent system,temperature)and deposition parameters (e.g.deposition velocity,flow rate,needle inner diameter)on fibre morphology and consequently on the overall scaf-fold mechanical performance.A possible strategy to enhance the mechanical properties envisages the increase of fibre packing density together with the decrease of fibre diameter by acting on parameters such as inter-fibre dis-tance,polymer concentration and deposition velocity.More-over,the tuning of phase inversion conditions may help reducing single fibre porosity in order to develop scaffold architectures with a good compromise between morphology and mechanical requirements.3.4Biological characterization
As shown in Fig.7(a)and (b),the developed scaffolds were able to support the proliferation of MC3T3-E1cells in the two investigated typologies of scaffolds (plain PCL and PCL/HA)and growing conditions (non-osteogenic and osteogenic).Despite the low values of cell proliferation at day 7,an increasing trend was evident for all the tested samples,with an average peak of proliferation between 28and 35d of culture.Cells grown onto plain PCL 1mm scaf-folds reached slight higher values of proliferation if com-pared with the ones grown onto plain PCL 0.5mm ,while PCL/HA scaffolds showed slight lower cell proliferation
in
Fig.6(a )Typical stress-strain curves obtained for scaffolds compressed at a rate of 1mm/min up to a strain value of 0.5mm/mm:(a )PCL 1mm and PCL/HA 1mm structures;(b )PCL 0.5mm and PCL/HA 0.5mm structures
Table 2Compressive modulus and maximum stress,reported as mean value ±standard deviation,for the different kinds of scaffold devel-oped.The samples were compressed at a rate of 1mm/min up to a strain value of 0.5mm/mm Scaffold Compressive Modulus (MPa)
Maximum stress (50%strain)(MPa)
PCL 1mm
0.12±0.050.26±0.05PCL/HA 1mm 0.21±0.050.39±0.03PCL 0.5mm
0.60±0.200.34±0.10PCL/HA 0.5mm
0.90±0.24
0.47±0.11
comparison with unloaded scaffolds.The two different cul-ture conditions instead did not show a marked difference in cell proliferation.
Cell-material interactions and cell seeding density play a crucial role on cell attachment,thus influencing cell prolif-eration in the first week of culture (Kommareddy et al.2010).The observed low cell proliferation at day 7of culture was probably due to the large pore size of the prepared scaffolds that was not effective in retaining a sig-nificant number of cells during the seeding procedure.However,despite the low initial number of attached cells,the investigated scaffolds were able to support the prolifer-ation of the MC3T3-E1cell line during the following weeks.The decrease in cell viability at day 43was likely due to the limited available surface left on the construct for the expan-sion of the culture,as corroborated by CLSM analysis.The slower cell proliferation observed on HA-loaded constructs correlates with the detected amount of ALP suggesting a more pronounced differentiation process on HA-loaded scaffolds (Quarles et al.1992
).
Fig.7MC3T3-E1cell line cultured on PCL and PCL/HA scaffolds.Cell proliferation:(a )plain PCL,(b )PCL/HA;ALP activity:(c )plain PCL,(d )PCL/HA;calcium deposits by means of ARS method:(e )plain PCL,(f )PCL/HA.non ost:non osteogenic medium;ost:osteogenic medium
Results showed comparable levels of ALP activity for both structures(plain PCL and PCL/HA)and geometries (PCL1mm and PCL0.5mm),with a time-dependent increasing trend(Fig.7(c)and(d)).As expected the investigated con-structs cultured in osteogenic medium showed higher levels of ALP(Alcaín and Burón1994;Wang and Yu2010).The presence of HA in the PCL scaffolds could have helped MC3T3-E1to trigger expression of the enzyme.This phe-nomenon was markedly evident at day28in the scaffolds with the0.5mm geometry,demonstrating the efficacy of the synergy between the HA and the osteogenic medium. (Calvert et al.2005;Wutticharoenmongkol et al.2007).
The ALP values detected from the MC3T3-E1cells cultured on both plain and HA loaded PCL structures sug-gested that the marked starting point of the differentiation process took place between14and21d of culture.These time-dependent changes in ALP production indicated the division of osteoblast development into two distinct stages (Quarles et al.1992).The initial phase was characterized by active replication of undifferentiated cells.In this regard, during the first two-three weeks,cultures displayed a rapid increase in cell number(Fig.7(a)and(b)),but these immature cells expressed low levels of ALP(Fig.7(c)and(d))and failed to mineralize(Hoemann et al.2009).The second phase was characterized by a diminished cell proliferation,and expres-sion of bone cell phenotype.The down-regulation of the replication,quite evident for all the samples and the culture conditions in the period between21and28d of culture, was coupled to the expression of high levels of ALP,a marker of mature osteoblast function.Indeed,ALP activity, low during active replication,increased significantly with the onset of growth arrest(Quarles et al.1992).The obtained results supported the analysis of the formation of the mineralized ECM that increased at day21,in coinci-dence with the increasing values of ALP.In fact,ALP is believed to be involved in the hydrolysis of pyrophosphate (inhibitor of the mineralization process)towards inorganic phosphate,that induces the mineralization occurring by means of apatite formation(Beck et al.1998;Calvert et al. 2005;Wutticharoenmongkol et al.2007).
Moreover,the delay in the maximum expression of ALP can be explained on the basis of the cellular three dimen-sional organization.In fact,it is likely that the up-regulation for the production of ALP was triggered by cellular contacts and/or expression of ample amounts of early matrix proteins as type I collagen,fibronectin and TGF-β1.In these3D structures cells need in the“initial phase”to form multilayered clusters reaching the adequate confluence that acts on the decrease of the rate of proliferation and on the expression of the bone isoform of ALP(Wutticharoenmongkol et al.2007; Park2010).
During the first three weeks of cell culturing appreciable values of matrix mineralization were not observed,confirming data reported by the literature that consider the ECM mineralization a late stage indicator of osteoblastic phenotype(Whited et al.2011).Since day21,cells cultured on scaffolds showed to be involved in the production of high levels of mineralized ECM,with an increasing trend during the culture time(Fig.7(e)and(f)).The values of ARS detected from plain PCL0.5mm constructs treated with ascorbic acid were particularly remarkable.Moreover,cells grown on PCL/HA scaffolds displayed levels of ARS roughly10 times higher in respect to the amount detected in cultured plain PCL samples.
These findings were consistent with other studies in which polymer-HA composite scaffolds increased bone ECM formation and mineralization of preosteoblasts when compared to scaffolds without a biomimetic apatite compo-nent(Whited et al.2011
).
Fig.8CLSM microphotographs resuming MC3T3-E1cell cultured on PCL and PCL-HA based scaffolds,at different end-points. PCL0.5mm scaffold samples cultured for7days(a),21days(b),and 28days(c)show increasing cellular population.PCL0.5mm(d)and PCL-HA0.5mm(f)comparison indicates no difference at day35in cellular presence.PCL1mm at35days(e)exhibits a lower inter-fibre cell bridging.Scale in(a)applicable to all picture sets
Fluorescent staining of cytoskeleton and nuclei showed morphology of cells grown on cultured scaffolds.After7d of cell culture,microscopic observation showed diffused presence of preosteoblast cells adherent on fibres surface with a variable shape and spreading.F-actin organization was consistent with early stages of cell adaptation to the material(Hutmacher et al.2001),exhibiting great stress fibres stretched along the cytoplasm,and a low cell number coherent with the quantitative proliferation data(Fig.8(a)). Yet cellular presence was higher on lower layers fibres likely due to cells slid down after the seeding procedure. No apparent difference was detectable for number and mor-phology of cells by comparing the two structures(PCL1mm and PCL0.5mm)and the two different materials(PCL and PCL-HA)at early stages.The analysis of samples cultured for longer times showed a progressive increase in cells colonizing the polymeric structure in all the experimental conditions.By the third week,cells started to exhibit a polygonal morphology and to form discrete groups to yield, at the fourth week,large cell clusters extensively covering fibres surface and spanning through the layers with complex inter-cellular connections(Fig.8(b)and(c)).
These observations were in accordance with the differ-entiation pathway proposed for the preosteoblasts in vitro, after an early growing latency,morpho-functional cellular aggregates are developed and single cell morphology is not distinguishable(Quarles et al.1992).At the fifth week, cultured samples exhibited a nearly full cellular colonization of available fibre surface by a wide continuous cell culture net.In many cases single cells,or multiple cell structures, were observed to bridge adjacent fibres layers(Fig.8(d)and (f)).The formation of a complex multicellular coverage did not allow the observation of peculiar morphological differ-ences in cell morphology in cultured scaffolds in any of the experimental conditions.In PCL0.5mm scaffold samples (Fig.8(d)),due to the shorter inter-fibre distance,cellular covering of the gap between fibres was achieved earlier than in PCL1mm scaffolds(Fig.8(e)).Moreover,no further differ-ences were observed in35d cultured PCL-HA scaffolds compared to the analogous of plain PCL(Fig.8(f)).
4Conclusions
The main result attained during the present activity was the development of a layer-by-layer AM technique allowing for the production by computer assisted wet-spinning of custom-ized tissue engineered PCL or PCL/HA composite scaffolds. In particular,it was shown that it is possible to manufacture 3D structures with controlled and reproducible internal micro-architecture and external shape by collecting with a predefined pattern a solidifying filament of PCL solution into a coagu-lation bath.Tuning of manufacturing parameters enabled to customize the internal architecture features,such as inter-fibre distance and fibres staggering.Differently to what commonly observed in scaffold produced by melt extrusion-based AM, the fibres constituting the scaffolds showed a highly porous morphology,due to the phase inversion process,that wors-ened the scaffold mechanical performance.However it is reasonable to hypothesize that spongy fibre morphology could positively affect mass transfer related to the exchange of nutrients and bioactive agents.The developed PCL and PCL/HA scaffolds with the two investigated structures were able to support the adhesion and proliferation of MC3T3-E1 preosteoblast cells that colonized the inner parts of structures during43d cell culturing experiments.The tested scaffolds were able to support the mechanism of differentiation of preosteoblast cells stimulating the production of high levels of mineralized ECM.In addition,HA loading into the scaf-folds and ascorbic acid addition to culture medium signifi-cantly enhanced bone mineralization and ALP activity.
The present study opens new possibilities for the fabrica-tion of3D structures with a layered manufacturing approach by employing other biodegradable polyesters that are well suited for wet-spinning processing(e.g.*PCL(Puppi et al. 2011a;Puppi et al.2011b),PLLA(Gao et al.2007)and poly (lactic-co-glycolic acid)(Mack et al.2009)).In addition,an ongoing work that will be published in a forthcoming paper is also addressed to the development by computer-assisted wet-spinning of anatomically-shaped,clinically-sized scaffolds for the in vivo treatment of bone tissue defects. Acknowledgments This work was done within the framework of the European Network of Excellence“EXPERTISSUES”(Project NMP3-CT-2004-500283).Mr.Piero Narducci of University of Pisa,Italy,is acknowledged for recording SEM images.
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丰田精益生产(TPS/Lean Manufacturing)的精髓及案例 很多人把自働化和自动化混淆，经常认为花大价钱钱买好设备就万事大吉，这正是很多国内企业陷入的误区。导致高价买的设备有些不但没有省人，反而增加了编程调试维护保养的技术人员，有些转线周期长更换夹具复杂导致稼动率低甚至束之高阁，这种现象在国内企业非常普遍。自働化—是一种基于精益理念具有人的智慧的设备，是在IE技术和标准作业的基础上，结合自动化元器件而设计的特殊设备。保证品质为目标，同时兼顾节省人力提高效率的柔性设备。 丰田精益生产(TPS/Lean Manufacturing)的精髓是:即时制(JIT)和自动化(Jidoka) JIT：JustIntime,及时制 JIT用一句话描述就是消耗最少的必要资源,以正确的数量，生产和运送正确的零件。 在这种模式下工作，可以最大程度上降低库存，防止过早或者过度生产。大多数公司更倾向用库存来避免潜在的停线风险，而丰田却反其道而行之。通过减少库存“逼迫”对生产中产生的问题做及时且有效的反应。当然JIT这一模式对解决问题的能力是相当大的考验，在能力不足的情况下，会有相当大的断线风险。Jidoka :Buildinquality,自动化，日语表标为“自働化" 字面含义是自动化，日语里表示为“自動化”而在丰田TPS系统里，特意给“動”字加上了“人”字旁变成了“慟”换句话说，TPS/精益生产渴望生产的过程控制能像“人”一样智能，在第一时间就异常情况下自动关闭。这种自动停机功能可以防止坏件流入下游，防止机器在错
误的生产状态下造成损坏，也可以让人更好的在当前错误状态下进行故障分析。当设备能够做到自动分析故障时，就可以将监管机器的“人”真正解放出来，做到对人力成本的节省。 在这边只介绍了精益生产的精骨直，但要能真正做至JIT和Jidoka,需要相当深厚的“基础”和牢固的“地基”。 截图来自与丰田TPS (Toyota Production System,丰田精益生产系统)手册，这张图形象描写了TPS/Lean Manufacturing/精益生产的逻辑。 地基是设备可靠性(Stability=可靠性)基础是平稳生产(Hejunka= 平准化+ Standardized Work=标准化作业+ Kaizen=持续改善) 顶梁柱是JIT和Jidoka房顶，即最终目的，是做到产具有最高品质，最低价格，最快交付时间。但需要指出的是，精益生产并非是丰田独有，许多企业都或多或少的参考丰田的精益生产总结出自己的一套精益生产流程。而且精益生产的惠及面已经远超出汽车制造的范畴，Nike (耐克)，Uniqlo (优衣库)，Intel (英特尔),Kimberley-Clark (金佰利)等等也都是采用精益生产。 5个案例，秒懂精益生产精髓 1、自动化与防呆防错一个小改善的大效果 有一家生产复印机的工厂，他们的复印机里面有一个小风扇，这个小风扇非常重要，一旦装反了，就会导致机械损坏。但由于是流水线作业，操作工在装配时，由于疲劳、遗忘等
制造技术基础复习基本概念、基本原理英语表达参考 Review the Basic Concepts and Principles of Fundamentals of Manufacturing Technology in English CHAPTER ONE DESIGN FOR MECHANICAL PROCESS PLANNING Section 1 Basic concepts ? Production procedure of mechanical products ? Process procedure of machining Elements of Process procedure of machining 1 sequence 工序； 2 installation 安装； 3 station 工位； 4 step 工步； 5 pass 走刀 ? Sequence : process procedure that consists of several sequences during which workers operate on the works continuously in the same place;(操作者、加工地、工作对象—— 人为划分，相对可变) ? Installation: in a sequence if the work is required to put into position and clamp several times ,the part of sequence done in one positioning and clamping is called an installation;(确定） ? Station : In an installation, by using the indexing or moving device the work is changed its position relatively to the cutting tool. All the tasks done for the work in one machining position in an installation is termed as the station;(确定） ? Step ：In one station if the surface cut, cutting tool, velocity, and feed remain unchanged, these working contents are thought of as the step.(加工表面、刀具、切削 速度、进给量任一改变均为另一工步） ? Pass: When the surface of the work is cut for any one time ,such task carried out is named as the pass ? (刀具在加工表面的每一次切削） ? Processing system : ? a system that contains the work to be machined, fixture that holds the work in the proper position, cutting tool that machines the work directly, and machine tool that gives the power and provide the movements to accomplish the processing. In recent years the gauging and measuring is added to the system. Relationship between the batch and the pattern of production N-program of production, Q-annual turnout of the product n-number of the components a year, -share rate, -waste rate , F -annual working days , A- number of days for inventory, -number of components in a lot A Program of production In a period of planning, the turnout of product and schedule to be fulfilled is called program. (计划期的产量加进度=生产纲领） The turnout in one year planning is named the annual program . B Batch of production At a time, the number of identical products to be put into production or to be produced is termed as batch of production. (一次投入生产的同一产品的数量=生产批量） Process planning for machining operations : stipulated document for technological process (机械加工工艺规程：以工艺文件形式规定的机(1%%)N =Qn αβ++b N F n =A
Manufacturing Engineering and Technology—Machining Serope kalpakjian；Steven R.Schmid 机械工业出版社2004年3月第1版 20.9 MACHINABILITY The machinability of a material usually defined in terms of four factors: 1、Surface finish and integrity of the machined part; 2、Tool life obtained; 3、Force and power requirements; 4、Chip control. Thus, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin (stringy) cured chips, if not broken up, can severely interfere with the cutting operation by becoming entangled in the cutting zone. Because of the complex nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more, approximate machinability ratings are available in the example below. 20.9.1 Machinability Of Steels Because steels are among the most important engineering materials (as noted in Chapter 5), their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead and sulfur to obtain so-called free-machining steels. Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (second-phase particles), which act as stress raisers in the primary shear zone. As a result, the chips produced break up easily and are small; this improves machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers in
The State Council recently announced the establishment of a national leading group for the upgrading of the country's manufacturing sector1, with Vice-Premier Ma Kai appointed as head of the group. One of the group's main responsibilities will be planning and coordinating2 the overall work to raise the country's manufacturing power. 日前，国务院宣布成立国家制造强国建设领导小组，国务院副总理马凯任组长。该小 组具体职责包括统筹协调国家制造强国建设全局性工作。 “制造强国”可以用manufacturing power表示。成立国家制造强国建设领导小组包 括在《中国制造2025》规划（"Made in China 2025" plan）中。该小组的具体职责还 包括审议推动制造业发展的重大工程专项（reviewing and propelling major manufacturing projects），加强战略谋划，指导各地区、各部门开展工作（directing relevant works in various regions and sectors），协调跨地区、跨部门重要事项，加 强对重要事项落实情况的督促检查（supervising and inspecting the implementation3 of major tasks）。 领导小组将制定新产业发展规划（draw up plans for new industries），同时组织各部门、地方发挥和协调技术、资源优势，向中国智造（intelligent / smart manufacturing）转变，未来细分领域的产业规划和扶持政策（supportive policies and plans for various industries）预计出台会相对密集。 1 sector n.部门，部分；防御地段，防区；扇形 参考例句： The export sector will aid the economic recovery. 出口产业将促进经济复苏。 The enemy have attacked the British sector.敌人已进攻英国防区。 2 coordinating v.使协调，使调和( coordinate的现在分词 )；协调；协同；成为同等 参考例句：
Features API Manufacturing By George Karris | August 22, 2005 How will changes in India and China affect API outsourcing? Related Features The role of active pharmaceutical ingredient (API) manufacturers in the pharmaceutical industry supply chain is evolving in response to newfound demands from customers and growing pressures from global competitors. Increasingly, innovators (marketers of brand drugs, as opposed to generic drug companies) are looking beyond their usual group of closely-knit European suppliers. Meanwhile, traditional generic companies are looking to India and China for bulk actives, while specialty pharma companies have generated new demands for more specialized capabilities than those required by traditional
Brick Manufacturing The process by which bricks are manufactured for the building industry can be outlined in seven consecutive steps. First the raw material, clay, which was just below the surface of soil in certain clay-rich areas has to be dug up by a digger. Then the lumps(块状) of clay are placed on a metal grid in order to break up the big chunks（大块）of clay into much smaller areas, which fall through the metal grid onto a roller, whose motion further segregates the bits of clay. Sand and water are added to make a homogenous（同质的，同类的）mixture, which is then either formed in moulds or cut into brick-shaped pieces by means of a wire cutter. Those fresh bricks are then kept in a drying oven for at least 24 and a maximum of 48 hours, several dozens if not hundreds of bricks at a time. The dried bricks are then transferred to a so-called kiln（窑，炉）, another type of high temperature oven. First they are kept at a moderate temperature of 200 ℃-1300 ℃ . This process is followed by cooling down the finished bricks for 48 to 72 hours in a cooling chamber. Once the bricks have cooled down and have become hard, they get packaged and delivered to their final destination, be it a building site or storage.
Manufacturing Processes Contents: Introduction 2 Engine block 2-4 Crank Shaft 5-9 Connecting rod 10-14 Conclusion 15 Appendices 16
Introduction: There are thirteen parts in the engine as shown in above figure, I will discuss three parts of the engine. Engine block, Crankshaft and Connecting rod.In the following section, I will discuss the function, material used, mechanical properties of the part, the quality requirements and the process used of producing those parts. Engine block:
1-1 Description: The Engine Block is a single unit that contains all the pieces for the engine. The block serves as the structural framework of the engine and carries the mounting pad by which the engine is supported in the chassis . The block is made of cast iron and sometimes aluminum for higher performance vehicles. The engine block is manufactured to withstand large amounts of stress and high temperatures. 1-2. Production requirements: The Internal design of the engine block must be extremely precise, because all parts must fit and be able to function properly once the entire engine is assembled. The outside design of the engine only has to fit fewer requirements like attaching to the car properly. Engines are made in all different shapes and sizes to fit inside the frame of the car, therefore a company must be able to manufacture many different engine block designs yet keep up with product demand. There are 6000-8000 engine blocks made a day at a highly qualified company, this may be for many different models. 1-3. Process Requirements: The Engine block goes through two manufacturing processes before it is ready for assembly. The first process is die casting manufactured
The Economist Global manufacturing Made in China? Asia’s dominance in manufacturing will endure. That will make development harder for others Mar 14th 2015 BY MAKING things and selling them to foreigners, China has transformed itself—and the world economy with it. In 1990 it produced less than 3% of global manufacturing output by value; its share now is nearly a quarter. China produces about 80% of the world’s air-conditioners, 70% of its mobile phones and 60% of its shoes. The white heat of China’s ascent has forged supply chains that reach deep into South-East Asia. This “Factory Asia” now makes almost half the world’s goods. China has been following in the footsteps of Asian tigers such as South Korea and Taiwan. Many assumed that, in due course, the baton would pass to other parts of the world, enabling them in their turn to manufacture their way to prosperity. But far from being loosened by rising wages, China’s grip is tightening. Low-cost work that does leave China goes mainly to South-East Asia, only reinforcing Factory Asia’s dominance (see article). That raises questions for emerging markets outside China’s orbit. From India to Africa and South America, the tricky task of getting rich has become harder. Work to rule China’s economy is not as robust as it was. The property market is plagued by excess supply. Rising debt is a burden. Earlier this month the government said that it was aiming for growth of 7% this year, which would be its lowest for more than two decades—data this week suggest even this might be a struggle (see article). Despite this, China will continue to have three formidable advantages in manufacturing that will benefit the economy as a whole.
Teamcenter 制造过程管理 将PLM的创新功能，扩展到产品生命周期的制造阶段 概述 Teamcenter制造过程管理功能可以让用户在与产品开发相同的PLM环境中，对制造数据、过程、资源以及工厂信息进行管理。Teamcenter通过将制造数据模型扩展到用户的PLM环境，让用户的工程团队和制造团队都可以利用单一来源的产品开发、制造规划以及生产知识开展工作，拓宽了他们对产品生命周期全过程的洞察力 收益 有助于尽可能早地开始生产 加快了产量提升的速度 能更好地响应产品变更 有助于促进整个制造过程实现卓越运营 使整个企业创新过程中的可视化功能得到了增强 通过减少浪费、以及实现制造需求和产品开发的同步，能更快将产品推向市场。 利用全球化制造运营中的机遇，可以让你抓住不断变化的市场需求。 通过对制造资源和资本投资的优化，可以提高利润回报。 降低成本和的潜在违规性风险。
业务挑战 产品结构日益复杂 制造能力的分散性 日益加剧的竞争 日益增多的法规性问题 Teamcenter制造过程管理，可以让用户将PLM的创新扩展到产品开发过程之外，从而改进下游的制造过程。通过使你的工程团队和制造团队共享单一来源的产品开发和制造知识，Teamcenter能推动用户的精益制造和“面向制造的设计”的业务举措。 制造过程管理的价值 创新的成功并非止步于产品设计，而是涵盖了产品生命周期的每一个阶段；当真正步入实际商业化的时候，止步于产品设计的创新成果必然遭受失败的风险。而由于缺乏一个包括制造环节在内的完整创新计划，如今的企业面临着以下风险： ?市场交付延迟 ?成本无法预料 ?盈利机会丧失 生产效率有助于推动创新取得成功，并通过消除制造过程中的浪费过程和非增值的迭代，加快产品交付的速度。 当创新型产品为成功构筑市场而提供一个切入点的时候，世界一流的公司都明白：他们的创新产品设计要取得经济方面的成功，决定于他们的制造系统能否有效运营。 速度的持续重要性 市场信号并非孤立发出。 世界各地的公司都希望在机遇之窗向稍微迟钝的企业很快关闭之前，能够通过推出创新产品而获得竞争优势。 随着速度已成为当今企业的口头禅，不断加快的生产节奏却影响着企业对不断涌现的创新机遇作出快速响应的能力。 Teamcenter制造过程管理功能建立在世界广为接受的PLM基础之上——这种基础由于在促进实现真正的并行工程方面具有无与伦比的能力，因而可以让制造企业更快将自己的产品推向市场。
课程名称：Advanced Manufacturing Technology(先 进制造技术) 专业班级：机制091 学号：3090101310 姓名：孙作强 任课老师：钟相强 成绩：
Computer-aided design 专业：机制093 姓名：孙作强 指导老师：钟相强 Abstract: Computer-aided design also known as computer-aided design and drafting (CADD), is the use of computer systems to assist in the creation, modification, analysis, or optimization of a design. Computer Aided Drafting describes the process of creating a technical drawing with the use of computer software. CADD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing. CADD output is often in the form of electronic files for print or machining operations. CADD software uses either vector based graphics to depict the objects of traditional drafting, or may also produce raster graphics showing the overall appearance of designed objects. Keywords: CAD computer technology Introduction:The design of geometric models for object shapes, in particular, is occasionally called computer-aided geometric design (CAGD). In CAD, many commands are available for drawing basic geometric shapes. Examples include CIRCLE, POLYGON, ARC, ELLIPSE, and more. 1.1 Uses
Student NO.:13029956 Subject: Manufacturing Strategy Abstract What is a manufacturing strategy focus on in next ten years? Is it world- class, lean production, JIT, cells or TQM? Is it none of them, some of them or all of them? Under the world trade condition which strategy is more important for manufacturing? During this essay follow the logically evidence will give a conclusion that most important future plant equipment and technology for my next generation manufacturing strategy for any medium manufacturing enterprise. This article divided into two parts. It will introduce the basic information about manufacturing strategy. Then this essay will analyse currently manufacturing strategy and looking to the future (in next ten years) manufacturing strategy across world-class manufacturing strategy, special production manufacturing strategy and Computer Integrated manufacturing systems strategy. Key word: manufacturing, strategy, future
Design for Manufacturing Basic Principles of Designing for Economical Production 1. Simplicity 2. Standard Materials and Components 3. Standardized Design of the Product 4. Liberal Tolerances 5. Use Materials that are Easy to Process 6. Teamwork with Manufacturing Personnel 7. Avoidance of Secondary Operations 8. Design to Expected Level of Production 9. Utilize Special Process Characteristics 10. Avoid Process Restrictiveness Think of these principles as design guidelines…not as hard and fast rules. Guidelines do not hold true for all situations. There will always exceptions where doing something different than the rule will give a result that is better or probably just as good. However, in most cases, if you stay consistent with the rules as design goals, you are likely to have a more efficient, more robust, and less costly production method. 产品开发流程的重要性 Rule 1: Simplicity Description: --minimize the number of parts --use the least intricate shape --require the bare minimum precision --reduce the number of manufacturing operations Motivation: generally provides -- reduced cost -- improved reliability -- ease of easier servicing -- improved robustness Example: Dip stick swipe Rule 2: Standard Materials and Components Description: --use standard off-the-shelf parts
UG-Manufacturing模块培训教材 第一章加工环境 1.1加工环境 在一个Part文件中第一次选择Manufacturing模块进入NC加工应用后，必须设置加工环境，便于创建某种类型的操作。如：车床加工、平面铣、曲面铣等。要在Maching Environment 对话框中CAM Session Configuration中定义，一般使用默认值CAM_ General。 1.2配置 配置决定了设置类型和操作类型，以决定哪些设置可供选择。一般选择Mill_ Contour（因为我们将模板定义所有加工形式集中于此）。 1.3加工设置 指定配置后，选择加工设置（CAM Setup）中的样板文件对当前Part文件进行初始化，即点选Initialize项，出现操作导航工具。 第二章定义刀具、方法、几何体 2.1刀具定义 刀具类型一般由最初加工环境中的设置决定，但我们自己也可将具体所常使用的刀具编辑成刀具库来提高效率，减少出错机率（刀具参数输错），其它刀具定义在此不再赘述。 2.2方法 当创建操作类型，选定加工类型后，在加工对话框顶端Method项亦可定义，它可分别定义如：粗加工Mill_Rough、半精加工Mill_Semi_Finish、精加工Mill_Finish 等类型的参数（预留量、公差、进给等），当我们需要时，则在Method中点选定义的相关加工类型名称即可，不必反复定义。
2.3创建几何体对话框 创建几何体能定义几种类型的几何体，如：Mill_Bnd、Mill_Geom、MCS、Workpiece 及Mill_Area。一般地我们定义几何体用MCS来定义，使加工座标与工作座标WCS重合，以便于定位取数。定义过程略。 第三章操作类型 3.1操作类型选择 在Manufacturing中有三种基本操作类型：平面铣Planar_Mill、型腔铣Cavity_Mill、固定轴曲面轮廓铣Fix_Contour。 3.1.1平面铣Planar_Mill 平面铣Planar_Mill，顾名思义即只用来加工垂直于刀轴的平面的一种加工方法，因刀具始终沿着相同的边界切削，所以加工出的侧壁与底平面始终垂直，所以此方法只适用于有外形或有槽的粗加工或精加工。 3.1.2型腔铣Cavity_Mill 型腔铣Cavity_Mill是以平面的切削层Cut Levels来切削材料，即刀具在每层沿着几何体的轮廓加工。一般用于粗加工。 3.1.3曲面轮廓铣Fix_ContourPlanar_Mill 固定轴曲面轮廓铣Fix_Contour是沿曲面轮廓的深度切削材料，在每一位置，刀具始终沿着几何体的外轮廓同时有X、Y、Z轴的运动，即刀具路径始终与外轮廓曲面保持同距离（预留量）运动，故只能用于半精加工或精加工。 第四章参数设置 4.1共同选项及参数 平面铣Planar_Mill、型腔铣Cavity_Mill、固定轴轮廓铣Fix_Contour虽然用于不同类型的加工，但其基本参数选项相同，如：几何体Geometry、切削方法Cut Method、
Teamcenter Manufacturing process management Rationalize and leverage engineering assets while synchronizing and optimizing manufacturing deliverables fact sheet product programs to be managed under a single source of manufacturing planning and production requirements. manufacturing teams to share a single source of knowledge, resource allocation decisions impacting both domains
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