Gani Can Öz (13th Week Unanswered Terms)

Silicon Steel
This steel was developed by the English metallurgist Robert Hadfield in 1900 and soon became the preferred core material for large transformers, motors and generators. The addition silicon to iron profoundly modifies the phase diagram as shown by figure.This means that such an ally may be recrystallized at any temperature without concern for phase change and single crystals of such an ally can be made by slow solidification from liquid or by recrystalization at ay desired temperature. (Introduction to magnetic materials, Bernard Dennis Cullity,Chad D. Graham)

Hydrohoning
A special form of grit blasting is hydrohoning in which the abrasive medium is sespended in a liquid which is then directed onto the surface in the form of a high-pressure jet. (Handbook of ceramic grinding and polishing, Ioan D. Marinescu, Hans Kurt Tönshoff, Ichiro Inasaki)

Rheocasting
Rheocasting is the casting semisolid slurries, which is conducted within the liquidus-solidus range of metallic alloy. This process uses molten ally as the starting material thus eliminating the demand of specially feedstock materilas. In comparison with conventiobnally cast parts, rheocast components the following advantages: Homogeneous distribution of microporsity, Less tendency of shrinkage pipe and crack formation, Less tendency of micro and macrosegragation, A fine and nondendritic grain structure.

Reverse Redrawing
When high drawing ratios are required, the process is decomposed into two or several steps, in order to increase the formability by preventing localisation of the deformation in the cup wall. Re-drawing processes are usually sorted out in two categories: direct and reverse re-drawing.The first one corresponds to a process in which the different punches are always in contact with the same blank side whereas during reverse re-drawing, the punch travel occurs in two opposite directions and the outside of the part during the first stage becomes the inside of the part in the second stage. The advantages of the reverse process are a more compact tooling, without new positioning of the part in-between the two stages, a better surface aspect than in the case of a direct process because the outside is in contact only once with the die radius and finally a smaller number of bending–unbending operations. (Experimental and numerical study of reverse re-drawing of anisotropic sheet metals S. Thuilliera,*, P.Y. Manacha, L.F. Menezesb, M.C. Oliveira)

Nibbling
Sheet metal cutting process in which a rapidly reciprocating punch slots sheets along desired path. (Academic Press dictionary of science and technology, Christopher G. Morris,Academic Press)

Microfabrication
As the name implies, microfabrication involves, all processes that make products on the submilimeter scale. Many traditional and nontradiotional processes are capable of doing so: Wires are drawn to a few micrometers in diameter; metal foils are rolled to a few microns in thickness. ( Introduction to manufacturing processes, John a. Schey)

Chemical Voper Depositon - CVD
Chemical vapor deposition (CVD) is a versatile process in which gas-phase molecules are decomposed to reactive species, leading to film or particle growth. CVD processes can be used to deposit a wide range of conducting, semiconducting, and insulating materials. (Chemical Vapor Deposition Based Synthesis of Carbon Nanotubes and Nanofibers Using a Template Method G. Che, B. B. Lakshmi, C. R. Martin, and E. R. Fisher, Rodney S. Ruoff)

Fluidity Index
Although none is accepted universally, several tests have been developed to quantify fluidity. One such test is shown in Fig.5, where the molten metal is made to flow along a channel at room temperature. Obviously this length is a function of the thermal properties of the metal and the mold, as well as the design of the channel. The fluidity index is the length of the solidified metal in the spiral passage. The greater the length of the solidified metal, the greater is its fluidity. (Umm Al-Qura University Lecture Notes of Casting, Chapter 2)

Osman Suzen 030060804 14th week

Beam Deposition Processes (BD): Beam deposition (BD) processes enable the creation of parts by melting and deposition of material from powder or wire feedstock. Although this basic approach can work for polymers, ceramics, and metal matrix composities, it is predominantly used for metal powders. Thus, this technology is often referred to as "metal deposition" technology. To avoid limiting the readers' understanding to just metal built materials, however, we will refer to this category of processes as beam deposition processes.
Most commercialized BD processes enable complete melting of powders using a focused high-power laser beam as the heat source. Research variants include using an electron beam or plasma source in place of laser beam or the use of a thin meatl wire instead of powder as the build material. In many ways, BD techniques can be in an identical manner to laser cladding and plasma welding machines. However, BD machines are considered as those which are designed to create depositions of complex 3D shapes directly from CAD files, rather than the traditional welding and cladding technologies, which where designed for repair, joining, or to apply coatings and do not typically use 3D CAD data as an input format. ( Additive Manufacturing Technologies - Ian Gibson, David W. Rosen, Brent Stucker - page 237 )

Powder Bed Fusion Processes (PBF) : Powder bed fusion (PBF) processes were among the first commercialized AM processes. Developed at the University of Texas at Austin, USA, Selective Laser Sintering (SLS) was the first commercialized powder bed fusion process. Its basic method of operation is schematically shown in Fig 5.1, and all other PBF processes modify this basic approach in one or more ways to enhance machine productivity, enable different materials to be processed, and/or to avoid specific patented features.
All PBF processes share a basic set of characteristics. These include one or more thermal sources for inducing fusion between powder particles, a method for controlling powder fusion to a prescribed region of each layer, and mechanisms for adding and smoothing powder layers.
The SLS process was orginally developed for produsing plastic prototypes using a point-wise laser scanning technique. This approach has been extended to metal and ceramic powders; additional thermal sources have been utilized; and variants for layer-wise fusion of powdered materials now exist. As a result, PBF processes are widely used world-wide, have a broad range of materials (including polymers, metals, ceramics and composites) which can be utilized, and are increasingly being used for direct digital manufacturing of end-used products, as the material properties are comparable to many engineering-grade polymers, metals and ceramics. ( Additive Manufacturing Technologies - Ian Gibson, David W. Rosen, Brent Stucker - page 103)

Photoiniator System: The role of the photoinitiator is to convert the physical energy of the incident light into chemical energy in the form of reactive intermediates. The photoinitiator must exhibit a strong absorption at the laser emission wavelenght, and undergo a fast photolysis to generate the initiating species with a great quantum yield. The reactive intermediates are either radicals capable of adding to vinylic or acrylic double bonds, thereby initiating radical polymerization, or reactive cationic species which can initiate polymerization reactions among epoxy molecules. The free-radical polymerization process was outline in Fig4.4, with the formation of free radicals as the firs step. In typical case in SL, radical photoinitiator systems include compounds that undergo unimoleculer bond cleavage upon irradiation. This class includes aromatic carbonly compounds that are known to undergo a homolytic C-C bond scission upon UV exposure. The benzoyl radical is the major initiating species, while the other fragment may, in some cases, also contribute to the initiation. The most efficient photoinitiators include benzoin ether derivatives, benzyl ketals, hydroxyalkylphenones, (alfa)- amino ketones, and acylphosphine oxides. The Irgacure family or radical photoinitiators from Ciba Specialty Chemicals is commonly used in SL. ( Additive Manufacturing Technologies - Ian Gibson, David W. Rosen, Brent Stucker - page 68)

Automated Fabrication (Autofab): This term was popularized by Marshall Burns in his book of the same name, which was one of the first texts to cover this technology in the early 1990s. The emphasis here is on the use of automation to manufacture products, thus implying the simplification or removal of manual tasks from the process. Computers and microcontrollers are used to control the actuators and to monitor the system variables. This term can also be describe other forms of Computer Numerical Controlled (CNC) machinig centers since there is no direct reference as to how parts are built or the number of stages it would take to built them, although Burns does primarily focus on the technologies also covered by this book. ( Additive Manufacturing Technologies - Ian Gibson, David W. Rosen, Brent Stucker - page 6)

Özgür METİN, 030040004, 14th Week

Liquid Polymer Systems for Additive Manufacturing

The first commercial system was the 3D Systems Stereolithography process based on liquid photopolymers. A large portion of systems in use today are, in fact, not just liquid polymer systems but more specifically liquid photopolymer systems. However, this classification should not be restricted to just photopolymers, since a number of experimental systems are using hydrogels that would also fit into this category. Furthermore, the Fab@home system developed at Cornell University in the USA and the Reprap systems originating from Bath University in the UK also use liquid polymers with curing techniques other than UV or other wavelength optical curing methods.

Using this material and a 1D channel or 2 1D channel scanning method the best option is to use a laser like in the Stereolithography process. Droplet deposition of polymers using an array of 1D channels can simplify the curing process to a floodlight (for photopolymers) or similar method. This approach is used with machines made by the Israeli company Objet who use printer technology to print fine droplets of photopolymer “ink”. One unique feature of the Objet system is the ability to vary the material properties within a single part. Parts can have softfeel, rubber-like features combined with more solid resins to achieve an overmolding effect.

Controlling the area to be exposed using digital micro-mirror devices (DMD) or other high-resolution display technology obviates the need for any scanning at all, thus increasing throughput and reducing the number of moving parts. DMDs are generally applied to micron-scale additive approaches, like those used by Microtec in Germany. For normal-scale systems Envisiontec uses high-resolution DMD displays to cure photopolymer resin in their low-cost AM machines. The 3D Systems V-Flash process is also a variation on this approach, exposing thin sheets of polymer spread onto a build surface.

(Gibson I., Rosen D. W., Stucker B., Additive manufacturing technologies: Rapid prototyping to direct digital manufacturing, p. 29)

Discrete Particle Systems for Additive Manufacturing

Discrete particles are normally powders that are generally graded into a relatively uniform size and shape and narrow distribution. The finer the particles the better, but there will be problems if the dimensions get too small in terms of controlling the distribution and dispersion. Again, the conventional 1D channel approach is to use a laser, this time to produce thermal energy in a controlled manner and, therefore, raise the temperature sufficiently to melt the powder. Polymer powders must therefore exhibit thermoplastic behavior so that they can be melted and re-melted to permit bonding of one layer to another. There are a wide variety of such systems that generally differ in terms of the material that can be processed. The two main polymer-based systems commercially available are the Selective Laser Sintering (SLS) technology marketed by 3D Systems and the EOSint processes developed by the German company EOS.

Application of printer technology to powder beds resulted in the 3D Printing (3DP) process. This technique was originally developed by researchers at MIT in the USA. Printing technology is used to print a binder, or glue, onto a powder bed. The glue sticks the powder particles together to form a 3D structure. This basic technique has been developed for different applications dependent on the type of powder and binder combination. The most successful approaches use low-cost, starch- and plaster-based powders with inexpensive glues, as commercialized by ZCorp, USA. Ceramic powders and appropriate binders as similarly used in the Direct Shell Production Casting (DSPC) process used by Soligen to create shells for casting of metal parts. Alternatively, if the binder were to contain an amount of drug, 3DP can be used to create controlled delivery-rate drugs like in the process developed by the US company Therics. Neither of these last two processes has proven to be as successful as that licensed by ZCorp. One particular advantage of the ZCorp technology is that the binders can be jetted from multinozzle printheads. Binders coming from different nozzles can be different and, therefore, subtle variations can be incorporated into the resulting part. The most obvious of these is the color that can be incorporated into ZCorp parts.

(Gibson I., Rosen D. W., Stucker B., Additive manufacturing technologies: Rapid prototyping to direct digital manufacturing, p. 30)

Molten Material Systems for Additive Manufacturing

Molten material systems are characterized by a pre-heating chamber that raises the material temperature to melting point so that it can flow through a delivery system. The most well- nown method for doing this is the Fused Deposition Modeling system developed by the US company Stratasys. This approach uses an extrusion technique to deliver the material through a nozzle in a controlled manner. Two extrusion heads are often used so that support structures can be fabricated from a different material to facilitate part cleanup and removal.

Printer technology has also been adapted to suit this material delivery approach. One technique, developed initially as the Sanders prototyping machine, that later became Solidscape, USA, is a 1D channel system. A single jet piezoelectric deposition head lays down wax material. Another head lays down a second wax material with a lower melting temperature that is used for support structures. The droplets from these print heads are very small so the resulting parts are fine in detail. To further maintain the part precision, a planar cutting process is used to level each layer once the printing has been completed. Supports are removed by inserting the complete part into a temperature-controlled bath that melts the support material away, leaving the part material intact. The precision of Solidscape machines makes this approach ideal for precision casting applications like jewelry, medical devices, and dental castings. Few machines are sold outside of these niche areas.

The 1D channel approach, however, is very slow in comparison with other methods and applying a parallel element does significantly improve throughput. The Thermojet from 3D Systems also deposits a wax material through dropletbased printing heads. The use of parallel printheads as an array of 1D channels effectively multiplies the deposition rate. The Thermojet approach, however, is not widely used because wax materials are difficult and fragile when handled. Thermojet machines are no longer being made, although existing machines are commonly used for investment casting patterns.

(Gibson I., Rosen D. W., Stucker B., Additive manufacturing technologies: Rapid prototyping to direct digital manufacturing, p. 30)

Solid Sheet Systems for Additive Manufacturing

One of the earliest AM technologies was the Laminated Object Manufacturing (LOM) system from Helisys, USA. This technology used a laser to cut out profiles from sheet paper, supplied from a continuous roll, which formed the layers of the final part. Layers were bonded together using a heat-activated resin that was coated on one surface of the paper. Once all the layers were bonded together the result was very like a wooden block. A hatch pattern cut into the excess material allowed the user to separate away waste material and reveal the part.

A similar approach was used by the Japanese company Kira, in their Solid Center machine, and by the Israeli company Solidimension with their Solido machine. The major difference is that both these machines cut out the part profile using a blade similar to those found in vinyl sign- aking machines, driven using a 2D plotter drive. The Kira machine used a heat-activated adhesive applied using laser printing technology to bond the paper layers together. The

Solido machine uses the plotter drive to draw adhesive to bond the layers and separate materials to ensure key features and boundaries are not bonded. Solido parts are made from polymeric sheet material that results in much stronger final parts.

(Gibson I., Rosen D. W., Stucker B., Additive manufacturing technologies: Rapid prototyping to direct digital manufacturing, p. 31)

Nonplanar Systems

There have been a few attempts at developing AM technology that doesn’t use stratified, planar layers. The most notable projects are Shaped Deposition Manufacture (SDM), Ballistic Particle Manufacture (BPM), and Curved Laminated Object Manufacture (Curved LOM). The Curved LOM process in particular aims at using fiber-reinforced composite materials, sandwiched together for the purposes of making tough shelled components like nose cones for aircraft using carbon fiber and armored clothing using Kevlar. To work properly, the layers of material must conform to the shape of the part being designed. If edges of laminates are exposed then they can easily come loose by applying shear forces. The Curved LOM process demonstrated feasibility but also quickly became a very complex system that required conformable robotic handling equipment and high powered laser cutting for the laminates.

It is possible to use short fibers mixed with polymer resins in FDM. Fibers can be extruded so long as the diameter and length of the fibers are small enough to prevent clogging of the nozzles. Like Curved LOM, it is somewhat pointless to use such a material in FDM if the layers are aligned with the build plane. However, if the layers were aligned according to the outer layer of the part, then it may be useful. Parts cannot be built using a flat layer approaching, in this case, and thus process planning for complex geometries becomes problematic. However, certain parts that require surface toughness can benefit from this non-planar approach.

(Gibson I., Rosen D. W., Stucker B., Additive manufacturing technologies: Rapid prototyping to direct digital manufacturing, p. 165)

Onur OZAYDIN_13th_Week_UNANSWERED_TERMS

1. Phase (About Composite Materials)

THE TERM PHASE INDICATES A HOMOGENEOUS MATERIAL, SUCH AS A METAL OR CERAMIC IN WHICH ALL OF THE GRAINS HAVE THE SAME CRYSTAL STRUCTURE, OR A POLYMER WITH NO FILLERS. BY COMBINING THE PHASES, USING METHODS YET TO BE DESCRIBED, A NEW MATERIAL IS CREATED WITH AGGREGATE PERFORMANCE EXCEEDING THAT OF ITS PARTS. THE EFFECT IS SYNERGISTIC.

(REF: FUNDAMENTALS OF MODERN MANUFACTURING, GROOVER M. P., JOHN WILEY & SONS 2007, PAGE 177)

3. Synthetic Composites

SYNTHETIC COMPOSITES ARE MODERN MATERIAL SYSTEMS NORMALLY ASSOCIATED WITH THE MANUFACTURING INDUSTRIES, IN WHICH THE COMPONENTS ARE FIRST PRODUCED SEPARATELY AND THAN COMBINED IN A CONTROLLED WAY TO ACHIEVE THE DESIRED STRUCTURE, PROPERTIES, AND PART GEOMETRY. THESE SYNTHETIC MATERIALS ARE THE COMPOSITES NORMALLY THOUGHT OF IN THE CONTEXT OF ENGINEERED PRODUCTS.

(REF: FUNDAMENTALS OF MODERN MANUFACTURING, GROOVER M. P., JOHN WILEY & SONS 2007, PAGE 177)

5. Discontinuous Fibers (Whisker)

DISCONTINUOUS FIBERS (CHOPPED SECTION OF CONTINUOUS FIBERS) ARE SHORT LENGHTS (L/D = ROUGHLY 100). AN IMPORTANT TYPE OF DISCONTINUOUS FIBERS ARE WHISKER – HAIR- LIKE SINGLE CRYSTAL WITH DIAMETERS DOWN TO ABOUT 0,001 mm (0,00004 in) AND VERY HIGH STRENGHT.

(REF: FUNDAMENTALS OF MODERN MANUFACTURING, GROOVER M. P., JOHN WILEY & SONS 2007, PAGE 179)

Ozlem Salman (13.week unanswered terms)

1 B spline surface

The same tensor product method used with Bezier curves can extend B-splines to describe B-spline surfaces. A rectangular set of data (control) points creates the surface. this set forms the vertices of the characteristic polyhedron that approximates and controls the shape of the resulting surface. (CAD/CAM Theory and Practice, İbrahim Zeid, McGraw Hill. 1991, p300.)
2 Coons patch

All the surface methods introduced thus far share one common philosophy; that is, they all require a finite number of data points to generate the respective surfaces. In contrast, a coons surface patch is a form of "transfinite interpolation" which indicates that the coons scheme interpolates to an infinite number of data points, that is, to all points of a cureve segment, to generate the surface. coons patch paticularly useful in blending four prescribed intersecting curves which form a closed boundary . (CAD/CAM Theory and Practice, İbrahim Zeid, McGrawHill, 1991. p304)

3Bilinear surface

A bilinear surface is a linear interpolation of the four corner points in the u and v direction. Only four corner points need to be supplied, but the boundaries of the bilinear surfaces are straight and surface generally tends to be flat. (CAD/CAM Theory and Practice, İbrahim Zeid, McGrawHill,1991. p294)

4Blending surface

This is a surface that connects two nonadjacent surfaces or patches. The blending surface is usually created to manifest C0 and C1 contuniuty with the two given patches. for patches or other orders, a B-spline blending surface may be generated in the following scenario. A set of points and their related v- tangent vectorsbeginning with P1 and ending with P2 can be geneareted along the v=1 edge of patch 1. smilarly a corresponding set can be generated along the v=0 edge of patch 2. cubic spline curve can now be created between the two sets. These curves can be used to generate an ordered rectangular set of points that can be connected with the B- spline surface which becomes the belending surface. (CAD/CAM theory an Practice, İbrahim Zeid, McGrawHill,1991, p309-310)

Ertan Toparlak 13th Week Unanswered Terms

13th Week Unanswered Terms

1-Effects of Welding Speed at Welding: The effect of increasing the welding speed for the same current and voltage is to reduce the heat input. The welding speed does not influence the electromagnetic force and the arc pressure because they are dependent on the current. The weld speed increase produces a decrease in the weld cross section area, and consequently penetration depth (D) and weld width (W) also decrease, but the D/W ratio has a weak dependence on travel speed . These results suggest that the travel speed does not influence the mechanisms involved in the weld pool formation, it only influences the volume of melted material. Normal welding speeds are from 100 to 500 mm/min depending on current, material type and plate thickness.

(Welding Robots Technology, System Issues and Applications, J. Norberto Pires, Altino Loureiro and Gunnar Bölmsjo,1st edition,P.33)

2- Filler Metals for Welding: Filler metals are generally used for plate thickness above 2 mm, having chemical composition similar to that of the parent material. Filler metal diameter is between 1.6 and 3.2 mm and in automatic systems is normally added cold from a roll or a coil.

(Welding Robots Technology, System Issues and Applications, J. Norberto Pires, Altino Loureiro and Gunnar Bölmsjo,1st edition,P.34)

3-Electrode Diameter for Welding: Chemical composition of the electrodes is similar to that of the materials being welded. Most usual electrode diameters are 0.8, 1, 1.2 and 1.6 mm. Electrodes of lower diameter are used for thin materials. Electrodes of 1.2 and 1.6 mm diameters are utilized in welding thicker materials and need higher currents, which produce larger weld pools. Electrodes of 1.6 mm diameter are not recommended for positional applications.

(Welding Robots Technology, System Issues and Applications, J. Norberto Pires, Altino Loureiro and Gunnar Bölmsjo,1st edition,P.43)

4-Welding Gases for Laser Welding: In laser welding two gases are commonly needed, the assisting gas to remove plasma, which is injected laterally, and a coaxial shielding gas to prevent atmospheric contamination. A root gas is also needed in keyhole welds where all the material thickness is melted. Helium and mixtures of argon and helium are used as welding gases. Argon shields the weld metal and helium is required to control the plasma formation in CO₂ laser welding. If Nd:YAGs are used for welding, the plasma formation is not an aspect of major concern and argon is the recommended welding gas. Small additions of oxygen, hydrogen or CO₂ can be used depending on material and process to increase productivity further. Helium, argon or mixtures of these gases are used for most materials, including reactive metals such as titanium or zirconium. For reactive materials the shielded area must be increased, because they are sensitive to air contamination down to low temperatures (400 ºC). Nitrogen can also be used for welding stainless steels in less demanding applications.

(Welding Robots Technology, System Issues and Applications, J. Norberto Pires, Altino Loureiro and Gunnar Bölmsjo,1st edition,P.52)

5-Welding Force for Resistance Spot Welding: The increase of the welding force reduces contact resistance because, in first analysis, it promotes the increase of contact area, due to deformation of surface asperities and eventually the rupture of surface oxide films. Electrode clamping forces must be high, particularly when welding low resistivity metals in order to reduce the proportion of heat generated in the interface electrode/workpiece.Electrode force must be increased with increasing current, unless part of the melted material of the nugget can be expelled. Other factors such as bad fit and lack of mechanical support contributes for the material expulsion. Distance of the weld to the edge of the sheets should be larger than 1.5 D, where D is the weld diameter. Excessively high forces are also undesirable because they can cause large surface indentation of the work-pieces and damage of the electrodes.Electrode clamping force increases with increasing thickness and strength of the work-pieces. Forces between 1000 and 15,000 N are usual for plate thicknesses up to 3 mm, though values of 20,000 N can be used in steel sheets 6 mm thick.
(Welding Robots Technology, System Issues and Applications, J. Norberto Pires, Altino Loureiro and Gunnar Bölmsjo,1st edition,P.60)

6-Non-consumable Electrodes: Non-consumable electrodes are composed of pure tungsten or of tungsten alloys.Pure tungsten electrodes can be used with DC but are more sensitive to contamination, have lower service life-cycle and exhibit higher tip deterioration than alloyed electrodes. These electrodes can be used in welding of aluminum and magnesium alloys on AC.

Thoriated tungsten (2% ThO2) electrodes are widely used in industrial applications due to its excellent resistance to contamination, easy arc starting and stable electric arc. Concerns about safety, because thorium oxide is radioactive, led to the development of other electrodes containing small proportions (around 2%) of simple earth rare elements such as lanthanum, yttrium and cerium or even mixtures of several elements.

(Welding Robots Technology, System Issues and Applications, J. Norberto Pires, Altino Loureiro and Gunnar Bölmsjo,1st edition,P.29)

7-Shielding Gas Regulator for Automatic Welding: The regulator is a device that reduces source gas pressure to a constant working pressure, independently of source pressure variations. Pressure reduction can be made in one or two stages. Regulators in two stages give in general more stable output flow.

(Welding Robots Technology, System Issues and Applications, J. Norberto Pires, Altino Loureiro and Gunnar Bölmsjo,1st edition,P.31)

8-Electrode Feed Unit for GMAW: The electrode feed unit and the welding control mechanism are generally furnished in one integrated package. The electrode feed unit pulls the electrode from the reel and pushes it through a conduit to the welding torch (gun). This unit is composed of a direct-current motor, that varies the motor speed over a large range, a gear box and two pairs of rolls with a pressure adjusting screw and wire guides, that transmit mechanical energy , straighten and guide the electrode. Knurled rolls are used for hard materials, such as steel electrodes, and V and U type rolls are used for softer materials, such as aluminum electrodes. For soft electrodes or long conduits pushpull systems can be used too. Theses systems are composed of two feed units, one that is close to the wire reel that pushes the electrode, and the other unit in the torch that pulls the electrode. In automatic and robotic welding systems the electrode is fed from a spool (15-18 kg) or large drum (200-475 kg) to minimize wire supply changing. Normally, the electrode feeder for robotic welding is mounted separate from the power supply.

(Welding Robots Technology, System Issues and Applications, J. Norberto Pires, Altino Loureiro and Gunnar Bölmsjo,1st edition,P.39)

9-Arc Striking Techniques for GTAW: Arc initiation by touch striking was used formerly in manual GTAW, but this technique is very sensitive to tungsten contamination, adversely affecting the service life of the electrode. High-frequency-high-voltage (e.g. 3 kV at 5 MHz) supplies are currently used in arc striking and AC arc stabilization in manual GTAW systems. This arc starting technique usually produces interference in electronic equipment in the vicinity of the power source.Programmed touch striking is an alternative technique developed for automatic systems. In this technique current and voltage are limited when electrode touches in the work-piece, in order to prevent electrode contamination. A pilot arc starting can also be used to initiate the main electric arc, though a more complex torch is needed.

(Welding Robots Technology, System Issues and Applications, J. Norberto Pires, Altino Loureiro and Gunnar Bölmsjo,1st edition,P.30)

Ertan Toparlak

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