NEW METAL SPRAYING SYSTEM FOR CAPACITORS ENDS

The MEC High Velocity Arc Spraying System permits consistently fine deposits of zinc spraying to the capacitor end to enable soldering of leads and provide a surface for attaching the terminals.

The Arc Spraying Zinc and Tin-Zinc coatings give cooler deposits, there is less damage to capacitors and the product is more consistent. Arc spraying also offers higher productivity. The Advantages of Arc Spraying :

• Parallel spraying plume and higher particle velocities give better penetration of the foil windings.

• The lower heat input to the capacitors gives more consistent products.

• Arc Spraying is inherently more consistent in operation.

• Arc Spray coatings are denser and contain less oxide.

• The lower heat input to the capacitors gives reduced scrap rates.

• Arc Spraying equipment is easily automated.

• Electric energy costs are cheaper than fuel gas / oxygen.

• No energy is consumed when not spraying.

• Stop - Start operation is easier.

• Electric supplies are generally more readily available.

• Potentially flammable and explosive gases are not required.

Electromagnetic interference can affect many types of sensitive electronic equipment. Since plastics are transparent to high frequency electromagnetic radiation, interference can pass through unprotected housings to cause transit errors in computers, corruption of process control signals, instability in medical apparatus (e.g. pace makers) and jamming of security systems. 

For effective screening of plastic housing, it is necessary to provide a conductive surface which will attenuate the radiation. The screen contains (or excludes) electromagnetic energy by reflection and/or absorption to prevent outside signals effecting the apparatus or prevent the screened equipment from interfering with other electronic divides.

The Metallizing Arc Spray Process achieves electromagnetic screening by applying a thin (125 microns or less) coating of zinc without over heating the plastics substrate at lower cost than other techniques and is more effective.

Our Arc Spray Process offers considerable advantages over other interference screening methods such as foils or taps, electroplating, vacuum metallizing and conductive paints. It gives dense, metallic coatings at high production rate. The coating are instantly usable, well bonded and sufficiently durable to withstand service flexing and handling abrasion.

PLASMA COATING ON BLAST FURNACE TUYERES

In iron and steel making process each composed of a vast number of production facilities, equipment maintenance is an important issue from the stand point of equipment functions that directly govern the production capacity, product quality and or reduction in enormous maintenance costs. Most of the problems with iron and steel making furnace are erosion, wear resistance and oxidation at high temperatures.

Thermal spraying has created revolution in the steel industries and brought about many benefits, which includes lower maintenance cost, better, product quality, and higher production capacity.

The burning of copper tuyeres due to molten slag and metal splash in the blast furnaces is a serious problem for the steel industry. The productivity of the blast furnace reduces due to the burning of the tuyer (increase of cooling water into the furnace). The burnt tuyer has to be replaced leading to a further drop in productivity of the furnace as replacement of the burnt tuyer requires the shutting down of the blast furnace for long period which hamper the production.

To overcome the burning of copper tuyers MEC has carried out the coating of blast furnace tuyer nose portion by two layers of ceramics by Plasma Spray System. Apart from giving thermal insulation to the copper tuyer, the ceramic coating also resists wear and particle erosion due to the high hardness ( 700 to 800 VHN micro hardness ) of the ceramic coating. The coating development work was carried out for a leading manufacturer of Iron & Steel in India.

COPPER SPRAY REDUCES CONTACT RESISTANCE IN CLAMPS

Copper and Aluminium alloys are the most widely used electro-conductive materials. To distribute electricity in high tension and very high tension switching station, there is often the need to conduct electrical power from copper connecting points of power sources to the copper connection points of electric appliances, for examples, by aluminium or aluminium-steel cables. Many types of power armatures and clamps are manufactured for joining aluminium and copper conductors by casting of dissimilar metals, pressing or embedding the copper parts into aluminium alloy, resistance welding etc.

The problem encountered in manufacturing there clamps is a suitable mechanical and electrical connection of both parts. The higher the contact resistance, then the higher the heat of production, which leads to temperature increases in the clamp and subsequent power losses. Significant power losses, when such types of instrument clamps and armatures are used and also the high demands placed on their production, led to further development of the clamps. The new method of production is based on fabrication of the body (armature, clamp etc.) with an aluminium alloy, whereas the contact area for attachment of the copper member is covered by a plasma sprayed coating of copper alloy.

This method allows uniform and reproducible properties of current transition between the connecting member and the body of an armature or clamp, and at the same time suppress corrosion at the aluminium copper boundary. Test measurements of the contact resistance between the copper and aluminium parts shows that the lowest contact resistance was obtained by using a copper coating deposited by plasma spraying.

Molds made of gray cast iron for casting pig iron ingots are subjected to severe temperature fluctuations in a manner similar to those in the die casting process except that the principal damage mechanism is high pressure erosion caused by the molten metal. The main life limiting factor for mold damage is the formation of surface cracks arising from thermal fatigue.

The life of the pig iron ingot molds can be increased to nearly 3000 cycles, without any damage to the mold, by giving a thermal spray coating of Aluminium oxide. Thermal sprayed aluminium oxide coatings improve the thermal fatigue properties of gray cast iron for molds by modifying the surface to improve the detachability of solidified pig iron from the molds and thus the life of the mold. The coating thickness is usually upto 200 microns and a bond coat of NiCrAl is usually applied.

The high production rate demands of the LPG Cylinders and Paper Capacitor manufacturers has lead to higher rates of Arc Sprayed Zinc Coatings. The Wire Feed Tube made of plastic moves on the guide fitted on the automatic zinc spray plant. Due to higher production rates the movement of the wire feed tube on the guide, which is made of M. S. has more than doubled, this causes the wire feed tube to wear out very fast and consequently cause misalignment of the wire feeding.

An LLDPE Coating was given by the powder flame spray apparatus on the wire feed tube guide. This soft LLDPE coating eliminated the problem of wear of the wire feed tube and the movement of the wire feed tube also became smoother due to low coefficient of friction of the LLDPE Coating.

SPECIAL PURPOSE THERMAL SPRAY SYSTEM FOR RECLAMATION & MANUFACTURING OF GLASS MOULDS PLUNGERS

"MEC" has developed a new machine for spray and fusing of Nickel based alloy powders on Glass Mould Plungers. The machine consists of two spray booths, one for spraying and other for fusing. System includes automatic vertical movement arm, which holds the flame spray gun, MEC Powderjet-85. The vertical transverse of the spray gun is closed monitored and speed can be controlled through the control panel.

The spray angle can be adjusted preset for the process. The spraying parameters can be set on the flame spray gun depending upon the dimensions of the glass mould plunger. The combination of motor speed (rotation of mould) and vertical traverse speed of the arm, are controlled to ensure uniform and homogeneous deposition of the powder on the plungers.

Recently similar machine has been sold to M/s Ballarpur Industries Ltd., Pondicherry (India) for their new glass bottle manufacturing plant. This Nickel based powder spraying and fusing has enhanced the mould life of ordinary MS and CI glass mould plungers by 13 - 17 times.

HARD SURFACING OF WIRE DRAWING DRUMS

Wear of wire drawing drums is a very common problem in the wire handling industries, as, even a minor wear affects the quality of wire. Whether this wire is used for fine steel rope or for bearing rollers, wire surface quality is a must, which, is directly affected by Drawing Drum's surface.

"MEC" has come up with a revolutionary set up of hard surfacing, which has given excellent results. The working life of drum has increased by many times which has reduced their maintenance cost drastically.

This is a field proven technology, tested at India's leading wire manufacturers. The system is combination of surface preparation and hard surface coating.

"MEC" has comes to the assistance of steel mill rolls to create traction between the hot ingot and roll surface. Traction coating can be given on roll surface by thermal spraying method.

A very common practice is to throw a shovel full of sand on hot ingot creating some traction between the smooth roll surface and hot ingot. Our process consist of spraying 0.1 mm to 0.15 mm thick coating of nickel aluminium wire in the forming grooves for traction with MEC Sprayjet-88 combustion wire spray gun.

This interesting and simplified process does not require any preheating, surface preparation by grit blasting or rough threading. This coating consist of nickel aluminide which is not prone to oxidation like roll material. The traction coating can be performed again and again without any damage to the roll surface. Thus a single roll can be used for a considerably longer time period.

The extrusion operation normally begins with a solid round bar. This bar is cut into short pieces called billets. The billet is prepared according to the requirements of the end product. The billet is then heated to the extrusion temperature and the heated billet is next coated with powdered glass during transfer to the extrusion press. The billet is then moved into the container and put under high pressure which forces the metal through the die to produce the desired shape. The product, still hot, is now air-cooled or rapidly water quenched.

Additional operations may be performed based on the product being produced but this first stage of the process is vital to controlling the quality and integrity of the extrusion. Die performance at high temperature is a major problem.

The use of the Ceramic Rod Coating on the die surface provides several benefits :

• The Rokide EZ coating is inert at high temperature with the metals being extruded.

• The coating provides high temperature insulation preventing wash out at the corners and other critical surfaces allowing multiple uses of the original die blank. Dies can be recoated for further use.

• The coated die prevents the scoring of extruded billets as the coated die surface is not oxidized during extrusion.

• Users of Rokide EZ coatings have reported that the coated dies allow longer extrusions to be made without the problem of the seizure or failure.

• The Rokide system is a low investment process providing ease of operation and low maintenance which is critical for an in-house production operation.

The reclamation of crankshaft (and many other components) by Arc Spraying can generate considerable saving over the replacement cost. Savings of 50% are common and on large components as much as 90% may be saved.

The need for reclamation may be to correct manufacturing errors to repair an obsolete part or a part that has worn excessively in service. The function of coating is to provide a highly wear resistant bearing surface on the connecting rod and main bearing journals. Regardless of crankshaft or bearing material, the key to success in this application is scrupulous attention to all details of cleaning, surface preparation, spraying and finishing and most especially the quality of finish produced on sprayed coating.

MEC arc sprayed coating provides a smooth, wear resistant bearing surface with low coefficient of friction, this not only extends the service life of crankshaft but also lengthens the life of the connecting rod bearing particular the Babbitt bearing.

Crankshaft which require a hard surface on the crank pins and main journals, arc spraying is the best build-up method, since a minimum of stock removal is required after the build-up metal is applied. In addition, arc spraying is a cold process, so risk of distortion due to heat of welding and need for subsequent strengthening is eliminated.

The requirement for metal spray may be to repair obsolete parts, correct manufacturing error or apply hard facing on areas prone to excessive wear in use. The clutch assembly parts such as pressure plate faces, diaphragm spring and clutch release lever have been reclaimed by arc spray, flame spray or powder spray for well over 10 years on fully commercial basis by clutch re-manufacturing specialists.

In use, clutch pressure plates will wear and form heat cracking on its operative face reducing it below acceptable tolerance. The clutch diaphragm spring will wear on its tip ends at the point where its comes into constant contact with the thrust bearing. The clutch release leaver will wear on its operative face it below acceptable tolerance.

The reclamation of clutch assembly parts by thermal spraying process saving of upto 50% are common where on large components saving upto 90% may be achieved.

"MEC" has developed D-Bond compound suitable for liquid masking of surfaces / areas not to be sprayed. This compound will substitute adhesive and metallic tapes in some cases, where, liquid masking is more convenient.

"MEC" D-Bond is a water-soluble suspension, which can be brushed onto any integrated surface prior to spraying to prevent adhesion of sprayed metal. It will not spread or bleed at the edges during spraying. It does not require any special preparation to apply. There is no risk of warping or distortion to the part sprayed. 

"MEC" D-Bond is fully indigenous and meant for applications similar to Metco's Masking Compound.