Mask welding:
A laser beam diverged out in the shape of a line is translated across the parts to be joined through a mask or shield.The laser beam heat is joint wherever a weld seam is not masked (shadowed).Mask welding can result in very high resolutions between welded and non-welded areas.Today it is possible to produce a weld width of less than 100 μm.
(Plastics pocket power welding, Hanser,p.66) 00.26
Vicat Softening Temperature:
The vicat softening temperature is the temperature at which a flat needle will penetrate a sample a total of 1mm under a given load or heating rate (50 or 120 C per minute).This test is similar to HDT but its applicability is limited.It is primarily used for specific design or quality purposes.
The sample is placed flat in an oil bath:the specimen has a minimum thickness and width of 12.7 mm and 3.05mm ,respectively.Acceptable loads are 10 and 50N,depending on sapmle type.Samples may be heated to 50 C or 120 C.The needle should have a blunt end with a surface area of 1mm^2.The temperature at which the needle penetrates the sample 1mm is recorded.
(Understanding plastics testing,Donald C.Hylton,p.39) 11.05 14/04/2011
Anodizing
Although the previous processes are normally performed without electrolysis ,anodizing is an electrolytic treatment that produces a stable oxide layer on a metallic surface.Its most common applications are with aluminum and magnesium, but it is also applied to zinc, titanium and other less common metals.Anodized coatings are used primarily for decorative purposes;they also provide corrosion protection.
It is instructive to compare anodizing to electroplating since they are both electrolytic processes.Two differences stand out.1)In electrochemical plating,the workpart to be coated is the cathode in the reaction.By contrast, in anodizing the work is the anode ,whereas the processing tank is cathode.2)In electroplating the coating is grown by adhesion of ions of a second metal to the base metal surface.In anodizing the surface coating is formed through chemical reaction of the substrate metal into an oxide layer.
Anodized coatings usually range in thickness between 0.0025 and 0.075 mm.Dyes can be incorporated into the anodizing process to create a wide variety of colors;this is especially common in aluminium anodizing.Very thick coatings up to 0.25 mm can also be formed on aluminium by a special process called hard anodizing these coatings are noted for high resistance to wear and corrosion
(Fundamentals of modern manufacturing; materials,processes and systems,3rd edition, MikellP.Groover, p.674-675)20.21
Hot Drawing
Hot drawing is a process of making cup shaped or cylindrical components from a sheet metal blank,which is first heated to hot working temperature and later place on a die and a punch is hammered on it from the top,resulting into a cup shaped form.Hot drawing of the sheet metal blank into a cylindirical form is accomplished by repeating the operation of drawing at several stages,for example,the cup shaped product is heated again and drawn into a longer cylindirical pieced with reduced diameter.Further drawing is carried out on horizontal drawn-bench and the final finished cylinder with longer length and much reduced diameter.
This way,by drawing through a number of dies arranged in descending order of their diameter,reduction in wall thickness is gradual in various stages.The farther end of the drawn product being blind ,can be cut off the produce a long pipe with through the hole.Hot drawing is a useful process in the sense that the mechanical and chemical properties of the metal (under drawing )remain unimpaired.
The process is commonly used for the production of thick walled seamless tubes and cylinders.
(Manufacturing Processes,J.P.Kaushish, p.411)01.38 17/04/2011
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