Stereolithography is one of the most important Additive Manufacturing Technologies currently available. This technology involves the curring or solidification of a liquid photosensitive polymer through the use of an irradiation light source , whicih supplies the energy that is needed to induce a chemical reaction bonding large numbers of small molecules , and forming a highly cross –linked polymer.
Stereolithograpihc processes transform a multifunctional prepolymer into a cross linked polymer through a chain reaction initiated by reactive species generated by light exposure.
(Stereolithography: Materials, Processes and Applications ; Paulo Bártolo , pg:7 , 2011)
Stereolithography( New and better)
In theory liquid resin stereolithography machines consist of a umtainer that is at the same time build chamber and storage space. filled with a liquid monomer It is equipped with a build platfomi moveable at the 4-direction and a laser scanner unit, which -writes" or projects the current layer information on to the surface of the resin bath thereby eunng one layer The platform carries the model (on supports that hold projections and unconnected model parts in place and facilitates the defined lowering of the model ea to the build platform and its removal from the platform) and lowers it by one layer thickness after a layer is solidi-fied. A new layer is then prepared (recoating), again exposed and thereby solidified, and no forth In this way the model "grows.' layer by layer from bottom to top (Fig 3-4)
All laser-supported stereolithography processes aim to solidify one layer resulting from single solidificabons so-called vends Voxels. which ideally have the shape of a paraboloid of revolution. result from the energy distribution m the laser been and the penetration characteristics of the resin. To achieve the necessary.) compound stability, the voxels of one layer and those of two neighboring layers penetrate one another (overcure) The actual penetration depth (called cure depth) of the laser is thereby deep, than the layer thickness and the generation of onc layer and its interlockmg wtth the lower preccdms layer takes place simultaneously .
Fig 3-4
(Gebhardt A. Rapid Prototyping, page:83
Plastic calendering (Manufacturing technique)
The plastic is heated and rolled between two or more rollers until it forms a continuous sheet.In terms of production, calendering is viable from 1000000-m upwards.
calendering has a number of variations, according to the materials used and the desired result.The technique will eventually include the effects gained by die-stamping(artificial leather effect, for example), printing, coating of metallic films and etc.
(materiology by Daniel kula and elodie ternaux p.283)
Plastic calendering (new and better)
Calendering can achieve surprising accuracy on the Nickness of a sheet. Typically Ne tolerance is +-0.005 mm but to achieve.. it is essential to have very close control over roll temperatures, speeds and proximity. In addition, Ne Nmensions of the rolls must be very precise. The production of the rolls is akin to Ne manufacture of . injection moulding tool in the sense that very high machining skills are required. The parocular features of a calender roll are a on if 0f171 specified surface finish, minimal eccentricity and a special bar. profile (crown') to compen.te for roll deflection under Ne very high presofifi. developed between the rolls.
Since calendefing is a method of producing shwtffilm it must be consid-ered to be in dire. competition with extrusion hwed processes. In gene., film blowing afid die extrusion methods are preferred for materials such as polyeNylene, polypropylene and polystyrene but calendcring has Ne major advantage of causing very little thennal degradation a. so it is widely used for heat sensitive materials such as PVC.
(Crawford R.J. Plastic Engineering. Page: 315)
(My definition is the better than the older one. Because give much more specific detail about plastic calendering and giving example what kinf of plastic can be calendering)
Electroplanting ( Manufacturing technique) (better)
1)Theory
The article to be electroplated is first cleaned thoroughly. A suitable electrolyte is taken in a tank made up of insulating material( cement, rubber, glass etc.). Suppose anode is made up of coating metal (M). During electrolysis the concentration of electrolytic solution remains unaltered since the metal ion deposited from the solution are replenished continuolusly by the reaction of free anions with anode metal. IfCuSO solution is used as ana electrloyte, then it ionizes as;
CuSO → Cu(+) + SO (-) Ionization
On passing current Cu ions move to cathoed and get deposited there
Cu(+) + 2e(-) → Cu ( At Cathode)
The free SO(-) thus formed is dissolved in the electrolyte. So there is complete replenishment of electrolytic salt during electrolysis.
2) Aim of Electroplanting
1. To increase the resistance to corrosion of plated metal.
2. To improve the surface properties.
3. To improve physical appearance and hardness
4. To improve the resistance to chemical attack and wear resistance
5. To increase the decorative and commercial value of the metal
3)Characteristics of Electroplating
1. Thickness
2. Hardness
3. Protective Values
5. Temperature
6. Current Density
7. Agitation of Bath
8. Throwing Power
9. Cleaning of Article to be plated
10. Choke of solvent
11. Concentration of metal ions in the bath
(D Singh, Balraj Deshwal, Satish Kumar Vats, Comprehensive Engineering Chemistry, p. 151-152)
Electroplanting (new)
The component (cathode) abd the metalizing source material (anode) are submerged in the aqueos electrolyte where a direct electirical current drives metal ions from source to the component, creating thin metal coating.
Functions: Color texture, reflectivity; corrosion resistance, wear resistance, providing electrical conductivity, and good electrical contact.
(Ashby M. Jonhnson K. Materials and Desing. page:308)
( Honestly said that, older one iste better one it was explained totally and giving every detail about this technique. )
( Honestly said that, older one iste better one it was explained totally and giving every detail about this technique. )
Copolymers (Material type)
Nowadays there is a general tendency towards having 'alloys'.The main objective is to unify the positive properties without combining the bad ones.The mixture is not intimate, it is more of a co-existence.
Polymers are no exception to the rule, which is why we are witnessing an increase in the number of copolymers.A current famous example is ABS, Acrylonitrile-Butadiene-styrene, used for interior automotive components such as dashboards or door handles and mobile phone and vaccum cleaner bodies.The copolymer
polypropylene-polymide(pp-pa) is also widely used in the field of automotive manufacturing for rear-view mirrors and bodywork parts.
(materiology by Daniel kula and elodie ternaux p.68)
Copolymers (new and better)
where n and m range between 10 and 20, and the proportiow of the two constituents are around 50% each.
( Groover M. P. Fundumentals of Modern Manufacturing.3rd Edt Page:152)
(My definition is the best one because explain properly and gives example. And my definition has a formula to easy the understand this unknown type of material)
(My definition is the best one because explain properly and gives example. And my definition has a picture to easy the understand this unknown type of manufacturing technique)
(My definition is the best one because explain properly and gives example. And my definition has a formula to easy the understand this unknown type of material)
3D Printing (Manufacturing Technique)
One of the most advanced printing technologies involves 3D printing. There are several types of 3D printers, including nano printers for printing on the nano scale. There are 3D printers that print various types of materials. You will find printers that use plastic, powder, and paper even cholate and sugar. The possibilities are endless when you think about the types of materials you can use for 3D printing. 3D printers are available in all shapes and sizes. Some take up an entire room, and some can be easily placed on your desktop.
(Singh S., Begining Google Sketchup for 3D Printing, 2010, p.XVI)
3D Printing (new and better)
Three,Dirnensional Printing this Rapid Protyping technology was developed at MIT. Three dimensional printing (3DP) builds the part in the usual layer-by-layer fashion using an ink-jet printer to eject an adhesive bonding material onto sucmssive layers of powder. The binder is deposited in areas corresponding to the cross sections of the solid part, as determined by slicing the CAD geometric model into layers. The binder holds the powdels together to form the solid part, while the unonded powders remain loose to be removed later. While the loose powders are in place during the build process, they provide support for overhangang and fragile features of the part. When the build process is completed, the part is heat treated to strengthen the bonding, followed by removal of the loose powders. To further strengthen the part, a sintering step cam be applied to bond the individual powders. ,
( Groover M. P. Fundumentals of Modern Manufacturing. 3rd Edt. Page:793)
(My definition is the best one because explain properly and gives example. And my definition has a picture to easy the understand this unknown type of manufacturing technique)
No comments:
Post a Comment