MXPA06008416A - Thermal spray device and methods using a preheatedwire - Google Patents

Abstract

The present invention provides a thermal spray gun apparatus and methods that improves the operating efficiency of the thermal spray process by preheating the wire feedstock prior to the wire reaching the combustion chamber of the thermal spray gun. Methods and arrangements for preheating the feed wire prior to or after the point the wire is engaged by the spray gun's wire feeding mechanism are disclosed.

Description

- - THERMAL SPRAY APPARATUS AND METHODS USING A WIRE PREHEATED BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates generally to the field of methods and apparatus for flame spray. Specifically, the invention provides an improvement of the combustion operation with the thermal wire spraying process by preheating the wire to allow increased wire feed speeds and improved thermal efficiency.

DESCRIPTION OF THE RELATED ART The process of thermal spraying of combustion wire is used in a variety of applications including, for example, corrosion protection of both structures and components and obtaining worn bars and other parts. The procedure involves feeding wire raw material through a combustion chamber. In conventional wire gun constructions, the wire is generally axially fed through the gun at a speed controlled by a pair of feed rollers which hold the wire and rotate it to push the wire through the wire chamber. combustion, which may include a gas head nozzle distribution and an air cap. The nozzle distribution generally includes a ring of burner jets or other heating mechanism surrounding the wire conduit through which a fuel gas mixture is passed and burned. The heat of the flame heats and softens the front tip of the wire as the tip passes into the air cap and a stream of high velocity discharge gas is directed against and impinges on the softened tip by atomizing the metal (or other material that can be melted by heat) in the form of particles. These molten particles are then propelled from the gun onto the substrate to form a coating. The combustion process must provide sufficient heat to raise the wire material to the melting point and also to then provide the energy necessary to melt the wire. The speed at which these physical changes occur is a limiting factor in the efficiency of application of the coating. The wire feed speed and flame settings must be balanced to produce continuous casting of the wire to provide fine particulate spray. A flow of annular compressed air in the air cap atomizes and accelerates the particles towards the substrate. Variables such as the diameter and the composition of the wire material are some factors that determine the amount of energy that is required to carry out both the heating and the casting of the wire. These variables are usually predetermined by the wire material and the coating requirements. However, other process variables, such as the ambient or wire temperature before entering the combustion chamber, can also alter the amount of energy (and speed) required to transform the wire into molten particles. If the wire can be heated before reaching the combustion chamber then more energy will be available to melt the wire versus increase the temperature of the wire. The benefits of preheating the powder prior to injection into a plasma gun have been previously recognized. Preheating the powder supplied to the gun has improved efficiency by reducing the amount of energy needed in the plasma boom to melt the powder raw material or, alternatively, to increase the amount of powder feed raw material that can be fused with a given plasma pen.

The application of the preheating principles of the powders prior to injection into a plasma gun is not directly transferable to thermal firing processes of combustion wire. Unlike particles, the heated wire must remain sufficiently hard to allow the wire feed mechanisms (eg feeder rolls) to pull the wire through the combustion gun. Another concern is the loss of heat from the wire that occurs if the wire is preheated at some point away from the combustion chamber of the spray gun. Typical wires such as copper or aluminum are ideal for loss of heat to the environment. This loss of heat limits the efficiency of the preheating process and the efficiency of the combustion process. Therefore, there remains a need in the art for a combustion wire thermal spraying apparatus and method that can provide improved efficiency and at the same time solve the above limitations.

BRIEF DESCRIPTION OF THE INVENTION Accordingly, the present invention solves the deficiencies mentioned above in conventional thermal spray gun apparatuses by providing an apparatus and methods that improve the thermal spray process by preheating the raw material wire before entering the combustion chamber of the thermal spray gun. The preheating of the feed wire for a thermal spray or combustion wire process improves the operating capacity of the combustion wire gun through higher feed rates and high operating efficiencies. In one embodiment, the invention provides a method for producing a coating with a thermal spray gun that includes a wire feeder and a combustion chamber. The method includes the steps of providing a wire raw material with wire of heat-meltable material, heating the wire from the wire raw material to a temperature higher than the ambient conditions, and using the wire feeder to feed the wire to the wire. inside of the thermal spray gun. The method also includes the steps of feeding the heated wire into the combustion chamber at a point where the front tip of the wire is melted and atomized in such a way that the spray stream containing the material capable of being melted by heat it is driven from the tip of the wire and, finally, direct the spray stream towards a substrate to produce a coating thereon. In another embodiment, the invention provides a thermal spray gun for wire combustion. The gun includes a nozzle means for generating an annular heating flame, a heating means for preheating a wire of heat-meltable material at a temperature higher than ambient conditions, a feed means for feeding the wire axially from the nozzle inside the heating flame so that the wire is melted to a tip of the wire by heating flame and atomizing means to atomize the molten material from the wire tip and to drive the atomized material in a spray stream. Another embodiment of the invention provides a method for supplying heated wire raw material to a combustion chamber of a thermal spray gun. The method includes the steps of providing a wire raw material with wire of material capable of being melted by heat, heating the wire of the wire raw material to a temperature above ambient conditions and using the wire feeder to feed the wire. wire inside the thermal spray gun. The method finally includes the step of feeding the heated wire into the combustion chamber. In still another embodiment, a thermal spray gun wire combustion system is provided. The system includes a gun body, a buckle mounted on the gun body, an angular gas cap extending from the nozzle with a passage therethrough defining a combustion chamber, one or more feed rolls for receiving a front end of a wire and feed the forward end axially through the nozzle conduit and into the combustion chamber, and a heater to raise the temperature of a portion of the wire above ambient conditions before the portion to enter to the nozzle passage.

BRIEF DESCRIPTION OF THE DRAWINGS The attached drawings are included to provide a further understanding of the invention and are incorporated and constitute a part of this specification. The attached drawings illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the figures: Figure 1 illustrates a wire combustion gun with a preheating device, according to an embodiment of the invention; Figure 2 illustrates a wire combustion gun with a preheating device, according to another embodiment of the invention; Figure 3 illustrates a wire combustion gun with two preheating devices, according to another embodiment of the invention; Figure 4 provides a process flow diagram of a method for applying a coating with a wire combustion gun using a preheated wire, according to one embodiment of the invention; and Figure 5 provides a process flow diagram of a method for applying a coating with a wire combustion gun using a preheated wire, according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. With reference to Figure 1, a schematic of a wire combustion gun system is shown, according to one embodiment of the present invention.

As used herein, the term "wire" is used generically to designate both wires and bars. In general, a source 1 of wire raw material is provided from which a wire 2 that passes a heating section 9 into a thermal spray device 3 is supplied as feed. The wire 2 can be copper, bronze, aluminum, tin, zinc, steel or any other material suitable for processing through a thermal wire spray device for combustion. The heating section 9 is shown as a resistive heating device with a power supply 5 and electrical contacts 6 and 7 which touch the wire 2 at two points before the wire is fed into the thermal spray device 3. The heating section 9 can be a separate device between the source 1 of wire raw material and the thermal spray device 3, or the heating section 9 can be integrated into the thermal spray device 3. The power source 5 can be a source of DC power (direct current) or any other power source for heating the wire, known to those skilled in the art. Although resistive heating can provide the most efficient heating, induction heating, conductive heating, radiation heating or a combination of heating methods can also be used within the heating section 9. The thermal spray device 3 contains a wire feeder 4 for receiving the wire 2 and feeding the wire to the combustion chamber 10 of the thermal spray device 3. (The combustion chamber 10 is generally contained within the nozzle of the thermal spray device). The wire feeder 4 may include one or more rollers for holding and advancing the wire 2. However, other conventional wire feeders known in the art may be used with the proviso that the wire feeder 4 can withstand the temperatures of the wire. wire above the environment, which can be approximated to the melting point of the wire material. The different types of wire feeders and the different wire materials will influence the determination of the operational temperatures to prevent the wire from softening to the point where mechanical feeding is not feasible. As an example of improved efficiency resulting from the invention, the amount of heat energy that is required to increase the temperature of one gram of copper wire to the point of melting from a typical room temperature is 0.39 BTU. The amount of energy to melt one gram of copper wire at the melting temperature is about 0.22 BTU. Therefore, if the wire raw material is brought to the wire casting point an additional 198% of wire can be melted with a given combustion parameter for the raw material of copper wire. Similar results are obtained for other wire raw materials including aluminum (145%), molybdenum (227%), tin (75%) and zinc (152%). Increasing the temperature of the raw material to any appreciable amount increases the amount of wire that can be processed. In this way, beneficial improvements can be obtained by increasing the temperature of the raw material at points lower than the melting temperature. Additional efficiencies of preheating also they can be observed because the means of energy used to heat the wire provide a more efficient energy transfer mechanism compared to heating the wire in the combustion flame prior to casting. The transfer of heat from a stream of hot gas to a solid or liquid material in a typical thermal spray operation usually has an efficiency of less than 30% while direct heating by a resistive or inductor means, for example, approaches 100%, assuming that heat loss to the external environment is minimized. In the configuration shown in the figure 1, a key operational efficiency factor is to ensure that the heated wire 2 remains hard enough to facilitate the wire feeder 4 to pull the wire through the thermal spray device 3. Wire raw materials such as bronze or copper, which soften before reaching casting temperatures, are limited in how close to the melting temperature it can be preheated and still be mechanically fed through the thermal spray device. In some cases, these types of wires can only be preheated to about half the melting temperature before they become too soft to be mechanically fed reliably. Another factor of operational efficiency is the loss of heat from the wire 2 that occurs if the wire 2 is preheated at some point away from the thermal spray device 3 as in the configuration of Figure 1. For materials such as copper, these losses They can be significant and can limit the thermal efficiency and can also alter the temperature that the wire can effectively reach. In addition, most combustion guns use cooling air at the point of entry of the wire into the combustion chamber. This air will result in additional cooling of the wire and a subsequent decrease in wire temperature. These losses can be reduced by elaborating the integral heating section 9 to the housing of the thermal spray device 3. This configuration provides greater proximity to the heating section 9 with the combustion chamber 10 and can further reduce heat loss because the enclosure of the housing will retain heat. Even greater efficiencies can be obtained by heating the wire after the drive rolls pass-as will be described in relation to the embodiment shown in Figure 2. The configuration of Figure 1 can be easily fed back onto conventional thermal spray guns. Figure 2 shows another embodiment of a wire combustion gun system, according to the present invention. In general, a source 11 of wire raw material is provided from which a wire 12 is fed through the heating section 19 into a thermal spray device 13. As in the case of the embodiment of Figure 1, the wire 12 can be any material suitable for processing through a thermal wire spray device for combustion. In Figure 2, the thermal spray device 3 includes a wire feeding mechanism 14 for receiving the wire 12 and feeding the wire past the heating section 19 and into the combustion chamber 20 of the thermal spray device 13. The heat of the incineration gas in the combustion chamber 20 softens the forward tip of the wire 12. A high velocity stream of discharge gas is directed from the air cap of the combustion chamber 20 against the smoothed front tip, atomizing the 12 wire as it melts to form the particles 18. The atomized particles 18 are driven from the gun by the discharge gas stream, onto a substrate to form a coating. The heating section 19 is shown as a resistive heating device with a power supply 15 and electrical contacts 16 and 17 that touch the wire 12 at two points after the wire is fed past the wire feeder 14 of the device 13 of the device. thermal sprinkler. Other heating means, alone or in combination, can also be used within the heating section 19. The wire feeder 14 may include one or more rollers or other conventional means for holding and advancing the wire 12. The configuration in Figure 2 allows the wire 12 to be heated to the melting temperature of the wire material. In this modality, the heat loss in the preheated wire 12 is minimized due to several factors. First, the close proximity of the heat source 19 to the combustion chamber 20 reduces the time that the wire 12 must be cooled. Second, the heat radiated from the combustion chamber helps limit the cooling. Third, the housing of the thermal spray device 3 retains the heat in the preheating area, including the portion of the wire 12 that moves immediately after the heating section 19. Figure 3 shows another embodiment of the invention. In this embodiment, a source 21 of wire raw material is provided from which a wire 22 is fed by passing two separate heating sections into the interior of the thermal spray device 13. A first heating section 9 is located upstream of the thermal spray device and in particular before the wire has contact with the wire feeder 14. A second heating section 19 is located downstream of the wire feeder 14 and before the combustion chamber 20 of the thermal spray device 13. A high velocity stream of discharge gas is directed from the air cap of the combustion chamber 20 against the smoothed forward tip of the wire 22, atomizing the wire 22 in the form of particles 28. The atomized particles 28 are driven from the gun on a substrate to form a coating. As in the case of the embodiment of Figure 1, the wire 22 can be any material suitable for processing through a thermal wire spray device for combustion. The use of a heating source both upstream and downstream of the wire feeder 14 allows the wire to be preheated to a point below the melting temperature at which the wire is strong enough to pass through the wire feeder 14. wire, and then preheat more, to a higher temperature (at or near the point of melting the wire) before entering the combustion chamber. The heating sections 9 and 19 may be of the same type or of different types. As stated in the above, the speed at which the combustion process occurs is a factor limiting the speed of application of a thermal coating. Similarly, the rate of increase in wire temperature can also become a limiting factor. In the embodiment of Figure 2, the preheating exposure area (which can be governed, for example, by the size of the thermal spray device) and the feed rate will impact the manner in which the preheating of the wire It can be carried out by means of a given energy source. The embodiment of Figure 3 shows for a reduction in the energy demand of the downstream heating section. In operation, the device according to the configuration of Figure 1 of the present invention is used as follows: A wire feed source 1 suitable for use in the thermal spray device is provided. The wire 2 is fed from the wire feed source 1 through the heating section 9, which may or may not be operational at that time, and is then connected to the wire feeder 4 of the thermal spray device 3 . If the heating section 9 of the device is not operational before the connection of the wire 2 to the wire feeder 4, the initial feed rates of the thermal spray device will be the same as those of conventional combustion spray guns until the First section of preheated wire 2 reach the combustion chamber. Once the reheated wire 2 reaches the combustion chamber 10, the wire 2 is atomized and driven from the gun 3 onto a substrate to form a coating. Because this first section 2 of preheated wire is closer to the melting point of the wire compared to the previous sections, the atomization process will require less energy to be carried out and allow a faster wire feed speed subsequently. The operational efficiency will continue to improve as the improved feed rates reduce the amount of heat loss in the following sections of the wire 2 before the wire 2 reaches the chamber 10 is burned. These improvements will continue through the operation until equilibrium is achieved in the wire feed procedure. The combustion wire gun and the heater, as shown in Figure 1, are tested under laboratory conditions. The raw material of wire is copper, with the following procedural properties: Diameter of copper wire: 0.318 cm (1/8 inch) Density of copper wire: 8.96 g / cc Copper wire cast point: 1083 ° C Specific heat of copper wire: 0.000365 BTU / g * C Latent heat of cast iron wire: 0.195 BTU / g Heat of combustion, acetylene: 1470 BTU / cubic foot First, a typical combustion wire procedure parameter for acetylene copper spraying is used to spray the wire raw material without preheating the wire. The maximum wire feed speed that is obtained with the fully fused wire as it comes out at the front of the gun is determined to be 151 g / min. The determination of the maximum wire feed is made by observing the length of the non-molten wire tip extending out from the front of the gun. An unmelted 9.5 mm (0.375 inch) tip is considered the maximum wire speed. The gun produces - 0 - 66,150 BTU / h using a standard acetylene spray parameter for copper. The same conditions as in the previous test are then repeated with the heated wire at a calculated temperature of 566 ° C (approximately half the copper melting point) measured at the point before the wire enters the spray gun. combustion wire. The maximum wire feed speed obtained with the non-cast wire tip extending the same 9.5 mm (0.375 inch) as it exits at the front of the gun is determined to be 190 g / min. The result is a 26% increase in wire feed speed without any increase in gas flow or change in gun parameters. The amount of energy used to heat the wire is 12.768 BTU / h. From the first test, 66,150 BTU / h are required to spray 151 g / min, from the second test 78,918 BTU / h is required to spray 190 g / min -an increase in operating efficiency for a total procedure of 5%. Figure 4 provides a flow chart of method 100 for producing a coating with a thermal spray gun including a wire feeder and a combustion chamber. The method begins with step 101 where a wire raw material of the material capable of being melted by heat is provided, such as copper, bronze, aluminum, tin, zinc or any other material suitable for processing through a thermal spray device of combustion wire. Then, advancing to step 102, the wire raw material is heated to a temperature higher than ambient conditions. For example, in step 102, the wire can be heated to a temperature closer to the melting temperature of the wire material to which the wire can still pass through the wire feeder of the thermal spray device (i.e. optimal pre-feeding temperature). However, heating the wire at any temperature above ambient conditions will improve the operating efficiency of the thermal spray process. In step 103, the preheated wire is coupled by the wire feeder of the thermal spray device. Depending on the time between step 102 and step 103, the temperature at which the wire is heated in step 102 may actually exceed the optimum pre-feed temperature so that the cooling of the wire can approach the optimum feed-in temperature in the moment of step 103. In step 104, the wire feeder of the thermal spray device is used to feed the wire raw material into the combustion chamber at a point where a wire tip is formed where the material it is melted and atomized so that a spray stream containing material susceptible to being melted by heat is driven from the wire tip. A final stage 105 may include directing the spray stream to a substrate 'to produce a coating thereon. Figure 5 provides a flow diagram illustrating another embodiment of a method 200 for producing a coating with a thermal device including a wire feeder and a combustion chamber. As with the previous method, this method begins in step 201, whereby a wire raw material of material susceptible to melting by heat is provided. Then, advancing to step 202, the wire is coupled by the wire feeder of the thermal spray gun. In step 203 the wire can be heated as close as possible to the melting temperature of the wire material. However, heating the wire at any temperature above ambient conditions will improve the operating efficiency of the thermal spray process. In step 204, the wire feeder of the thermal spray gun drives the preheated wire raw material into the combustion chamber to a point where a wire tip is formed where the material melts and atomizes. such that a spray stream containing the material capable of being melted by heat is driven from the tip of the wire. A final stage 205 may include directing the spray stream to a substrate to produce a coating thereon. In one embodiment of the invention, the methods described in Figures 4 and 5 can be combined in a single method to obtain the efficiencies of both of the previous methods. In this combined method, a source of wire raw material is provided from which a wire is fed past two separate heating sections within a thermal spray device. Before reaching the thermal spray gun wire feeder, the wire is heated to a temperature above ambient conditions, preferably the optimum pre-feeding temperature. After passing through the wire feeder the wire raw material is again heated, preferably to the thermal melting of the wire material. Although exemplary embodiments of the invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Now, numerous variations, changes, and substitution will be apparent to those skilled in the art, not substantive, without departing from the scope of the invention described herein by the applicants. Accordingly, it is intended that the invention be limited only by the spirit and scope of the claims, as will be granted.

Claims (40)

- CLAIMS

1. Method for producing a coating with a thermal spray device having a wire feeder and a combustion chamber, the method is characterized in that it comprises the following steps: providing a wire raw material with wire of material capable of being melted by heat; heating the wire of the wire raw material to a temperature higher than the environmental conditions; use the wire feeder to feed the wire into the thermal spray device; feeding the heated wire into the combustion chamber to a point where the front tip of the wire is melted and atomized so that a spray stream containing the material capable of being melted by heat is propelled from the wire tip; and directing the spray stream to a substrate to produce a coating thereon.

2. Method as described in the claim 1, characterized in that the temperature above ambient conditions is a temperature up to and including the melting point of the material capable of being melted by heat.

Method as described in claim 1, characterized in that the wire is heated before entering the combustion chamber by one or more of induction heating, resistive heating, conduction heating and radiation heating.

4. Method as described in the claim 1, characterized in that the heating step is a first heating step that is carried out before the step of using the wire feeder.

Method as described in claim 4, characterized in that the first heating step increases the temperature of the wire so that an optimum feed-in temperature is obtained at the moment when the step of using the wire feeder occurs.

6. Method as described in the claim 4, characterized in that it further comprises a second heating step for heating the wire after the step of using the wire feeder.

Method as described in claim 6, characterized in that the second heating step increases the temperature of the wire at a temperature above ambient conditions to include the melting point of the material capable of being melted by heat.

Method as described in claim 1, characterized in that the step of heating the wire is carried out after the step of using the wire feeder.

Method as described in claim 8, characterized in that the temperature above ambient conditions is a temperature up to and including the melting point of the material capable of being melted by heat.

Method as described in claim 1, characterized in that the material capable of being melted by heat is predominantly copper, aluminum, tin or zinc.

11. Wire combustion thermal spraying device, characterized in that it comprises: a nozzle means for generating an annular heating flame; a heating means for preheating a wire of material capable of being melted by heat at a temperature higher than ambient conditions; a feeding means for feeding the wire axially from the nozzle into the heating flame such that the wire is melted at the tip of the wire by the heating flame; and an atomizing means for atomizing the molten material from the wire tip and driving the atomized material in a spray stream. - -

12. Spray gun, as described in claim 11, characterized in that the temperature above ambient conditions is a high temperature and includes the melting point of the material capable of being melted by heat.

13. Spray gun, as described in claim 11, characterized in that the heating means is one or more of induction heating, resistive heating, conduction heating and radiation heating.

14. Spray gun, as described in claim 11, characterized in that the heating means is positioned so that the wire moves past the heating means before making contact with the feed means.

15. Spray gun, as described in claim 14, characterized in that the heating means increases the temperature of the wire so that an optimum pre-feeding temperature is obtained at the moment when the heated wire reaches the feeding medium.

16. Spray gun, as described in claim 14, characterized in that it further comprises a second heating means, wherein the second heating means is located downstream of the supply means.

17. Spray gun, as described in claim 16, characterized in that the second heating means increases the temperature of the wire at a temperature above ambient conditions up to and including the melting temperature of the material capable of being melted by heat .

18. Spray gun, as described in claim 11, characterized in that the heating means is located so that the wire moves past the heating means after making contact with the feed means.

19. Spray gun, as described in claim 18, characterized in that the heating means heats the wire to a temperature up to and including the melting point of the material capable of being melted by heat.

20. Spray gun, as described in claim 11, characterized in that the material capable of being melted by heat heated by the heating means is predominantly copper, aluminum, tin or zinc.

21. Method for supplying raw material of heated wire to a combustion chamber of a thermal spray gun, characterized in that it comprises the following steps: providing a wire raw material with wire of material capable of being melted by heat; heating the wire from the wire raw material to a temperature above ambient conditions; Feed the wire into the thermal spray gun; and feed the heated wire in the combustion chamber.

22. Method as described in claim 21, characterized in that the temperature above ambient conditions is a temperature up to and including the melting point of the material capable of being melted by heat.

Method as described in claim 21, characterized in that the wire is heated before entering the combustion chamber by one or more of induction heating, resistive heating, conduction heating and radiation heating.

Method as described in claim 21, characterized in that the heating step includes a first heating step which is carried out before the step of feeding the wire to the thermal spray gun.

Method as described in claim 24, characterized in that the first heating step increases the temperature of the wire so that an optimum feed-in temperature is obtained at the moment when the step of feeding the wire into the interior of the wire is produced. thermal spray gun.

26. Method as described in claim 24, characterized in that it further comprises a second heating step of heating the wire after the step of feeding the wire into the thermal spray gun.

Method as described in claim 26, characterized in that the second heating step increases the temperature of the wire at a temperature above ambient conditions up to and including the melting point of the material capable of being melted by heat.

Method as described in claim 21, characterized in that the step of heating the wire occurs after the step of feeding the wire into a thermal spray gun.

29. Method as described in claim 28, characterized in that the temperature above ambient conditions is a temperature up to and including the melting point of the material capable of being melted by heat.

30. Method as described in claim 21, characterized in that the material capable of being melted by heat is predominantly copper, aluminum, tin or zinc.

31. Wire combustion thermal spray system, characterized in that it comprises: a gun body; a nozzle mounted on the gun body; an angular gas cap extending from the nozzle with a conduit therethrough defining a combustion chamber; one or more feed rollers for receiving the forward end of a wire and feeding the leading end axially through the nozzle passage and into the combustion chamber; and a heater for increasing the temperature of a portion of the wire above ambient conditions before the portion entering the nozzle passage.

32. System as described in claim 31, characterized in that the temperature above ambient conditions is a temperature up to and including the melting point of the wire.

33. System as described in claim 31, characterized in that the heater is one or more of an induction heater, an electric current that produces resistive heat, a source of hot gas and a radiation heater.

34. System as described in claim 31, characterized in that the heater is located so that the wire moves past the heater before finding the feed rollers.

35. System as described in claim 34, characterized in that the heater increases the temperature of the wire so that the optimum pre-feeding temperature is obtained at the moment when the heated wire reaches the feed rollers.

36. System as described in claim 34, characterized in that it further comprises: a second heater, wherein the second heater is located downstream of the feed rollers.

37. System as described in claim 36, characterized in that the second heater increases the temperature of the wire at a temperature above ambient conditions up to and including the melting temperature of the wire.

38. System as described in claim 31, characterized in that the heater is located so that the wire moves past the heater after finding the feed rollers.

39. System as described in claim 38, characterized in that the heating means heats the wire to a temperature up to and including the melting point of the wire.

40. System as described in claim 31, characterized in that the wire heated by the heater is predominantly copper, aluminum, tin or zinc.