CA1103317A - Plasma-arc cutting method - Google Patents
Plasma-arc cutting methodInfo
- Publication number
- CA1103317A CA1103317A CA298,157A CA298157A CA1103317A CA 1103317 A CA1103317 A CA 1103317A CA 298157 A CA298157 A CA 298157A CA 1103317 A CA1103317 A CA 1103317A
- Authority
- CA
- Canada
- Prior art keywords
- base metal
- arc
- nozzle
- plasma
- distance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K10/00—Welding or cutting by means of a plasma
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- Mechanical Engineering (AREA)
- Arc Welding In General (AREA)
- Plasma Technology (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method for cutting by a plasma arc in which the nozzle is directly contacted with the base metal to be cut and is at the same electrical potential, and wherein the electrode is first approached near to the base metal to strike the arc and then withdrawn from it to an appropriate cutting distance, and which permits a thinner cutting line to be made and thinner materials to be cut.
A method for cutting by a plasma arc in which the nozzle is directly contacted with the base metal to be cut and is at the same electrical potential, and wherein the electrode is first approached near to the base metal to strike the arc and then withdrawn from it to an appropriate cutting distance, and which permits a thinner cutting line to be made and thinner materials to be cut.
Description
11~);~317 This invention relates to a plasma-arc cutting method which is casily practiced and more effective than a conventional method.
In tne operation of a conventional plasma-arc cutting machine, the ~nd of a nozzle is separated by a certain gap from the surface of the base metal to be cut.
Since tne electrode of a conventional plasma-arc cutting machine is arranged at a fixed position with respect to the nozzle, the distance between the electrode and the base metal depends directly on the distance between the end of the nozzle and the base metal. The aistance between the electrode and the base metal should be maintained within a certain range so as to obtain a stable plasma-arc. Consequently, it requires a great deai of skill to operate a conventional plasma-arc cutting machine. When an operator uses such a cutting machine, he watcll~es the end of the nozzle in order to maintain its proper distance away from tne ~ase mctal. ~ence, because the intense light generated by the arc inevitabiy comes into his e~es, he requires an eye shield.
Furthermore, it is known that the diameter of the opening cut in the ~ase metal is about '~wice as large .~ ~
1~ 3317 as the diameter of the r.ozzle when the optimum distance between the nozzle and the base metal is maintained. However, if the diameter of the nozzle is made smaller so as to reduce the diameter of the opening cut in the base metal, at a certain point there results a series arc which is generated via the nozzle. Accordingly, it is impossible to make the diameter of the cut opening as small as one wishes by reducing the diameter of the nozzle.
It is an object of the present invention to provide a plasma-arc cutting method free from the abovementioned defects, in which no skill is required io maintain the distance between the electrode and the base metal, and in which the diameter of the opening cut in the base metal is almost the same as that of the nozzle of the cutting machine, and in-which there is no need for the operator to observe the intense light generated by the arc.
This object is accomplished accor~ing to the present invention by a plasma-arc cutting method comprising contacting the end of a nozzle with a base metal, an electrode being away from the base metal, during the operation of cutting the base metal;
passing an arc from the electrode to tne base metal through the nozzle end; and changing the distance between an electrode and the _~, 1~03~17 base metal from a first distance employed while striking an arc between them to a second distance employed while cutting the base metal with the arc.
The present invention will now be described in detail with reference to the accompanying drawings, in which:
Fig. 1 is a sectional view of the nozzle of a conventional plasma-arc cutting machine;
Fig. 2 is a sectional view of the nozzle of a plasma-arc cutting machine according to the present invention;
Fig. 3 is a schematic view of a plasr.la-arc and a wall rr.ember of the present invention; and Fig. 4 is a schematic view of the electric circuit
In tne operation of a conventional plasma-arc cutting machine, the ~nd of a nozzle is separated by a certain gap from the surface of the base metal to be cut.
Since tne electrode of a conventional plasma-arc cutting machine is arranged at a fixed position with respect to the nozzle, the distance between the electrode and the base metal depends directly on the distance between the end of the nozzle and the base metal. The aistance between the electrode and the base metal should be maintained within a certain range so as to obtain a stable plasma-arc. Consequently, it requires a great deai of skill to operate a conventional plasma-arc cutting machine. When an operator uses such a cutting machine, he watcll~es the end of the nozzle in order to maintain its proper distance away from tne ~ase mctal. ~ence, because the intense light generated by the arc inevitabiy comes into his e~es, he requires an eye shield.
Furthermore, it is known that the diameter of the opening cut in the ~ase metal is about '~wice as large .~ ~
1~ 3317 as the diameter of the r.ozzle when the optimum distance between the nozzle and the base metal is maintained. However, if the diameter of the nozzle is made smaller so as to reduce the diameter of the opening cut in the base metal, at a certain point there results a series arc which is generated via the nozzle. Accordingly, it is impossible to make the diameter of the cut opening as small as one wishes by reducing the diameter of the nozzle.
It is an object of the present invention to provide a plasma-arc cutting method free from the abovementioned defects, in which no skill is required io maintain the distance between the electrode and the base metal, and in which the diameter of the opening cut in the base metal is almost the same as that of the nozzle of the cutting machine, and in-which there is no need for the operator to observe the intense light generated by the arc.
This object is accomplished accor~ing to the present invention by a plasma-arc cutting method comprising contacting the end of a nozzle with a base metal, an electrode being away from the base metal, during the operation of cutting the base metal;
passing an arc from the electrode to tne base metal through the nozzle end; and changing the distance between an electrode and the _~, 1~03~17 base metal from a first distance employed while striking an arc between them to a second distance employed while cutting the base metal with the arc.
The present invention will now be described in detail with reference to the accompanying drawings, in which:
Fig. 1 is a sectional view of the nozzle of a conventional plasma-arc cutting machine;
Fig. 2 is a sectional view of the nozzle of a plasma-arc cutting machine according to the present invention;
Fig. 3 is a schematic view of a plasr.la-arc and a wall rr.ember of the present invention; and Fig. 4 is a schematic view of the electric circuit
2~ of a control means used in a plasma-arc cutting machine according to the present invention.
Referring to the drawings, in Fig. 1 there is shown an essential part of a conventional plasma-arc cutting ntachine. As the cutting machine 1 is operated, ~103317 the nozzle end 2 is separated by a certain gap L from the surface 4 of a base metal 3 which ls to be cut.
The distance L' between the electrode and the S base metal 3 depends on the distance L between the nozzle end 2 and the base metal 3. This distance L' between the electrode and the ~ase metal 3 should be .aintained within a certain range so as to obtain a stable plasma-arc 5. Accordingly, it requires a great deal of skill to operate such a plasma-arc cutting machine.
~hen an operator uses this cutting machine, he watches the nozzle end 2 in order to r.laintain the proper distance L between the nozzle end 2 and the surface 4 of the base r,letal 3. Tnus, because the intense light generated by the arc 5 inevitably shines into his eyes, he requires an eye shield.
Furthermore, it is ~no~Jn that the dian~eter D of the opening 6 cut in the base metal 3 is about twice as large as the diameter D' of the nozzle when the optimur.l distance between the nozzle 2 and the base metal 3 is maintained.: ~owever, as explained above, the size of the openins 6 cannot arbitrarily be reduced :` 1103;~ 7 by reducing the size of the nozzle D', since at a certain point a series arcing problem occurs.
In Fig. 2 there is shown the essential part of a plasma-arc cutting machine 11 of the present invention, corresponding to the part illustrated in Fig. 1 of a prior-art machine.
The nozzle end 14 of a nozzle 13 is contacted with a surface 16 of a base metal 15. A cathode electrode 17 is then broua,ht towards the base metal 15 in a flow of argon gas, resulting in striking an arc 12. The arc 12 is generated between the electrode 17 and a first anode point 18. Then nitrogen gas is added to the flow of argon gas, the gas flow speed itself may be changed, and the electrode 17 is moved away from the surface 16 to establish the proper electrode distance 1 for cutting. The nozzle 18 is then moved along the base metal surface 16, keeping its contact therewith, and thereby the base metal is cut.
There are provided radially disposed escape grooves 19 of an inverted U-shape for venting the gas flow at the nozzle end 14.
During the cutting of the base metal lS, the range of motion of the anode point 18 formed on the base metal 15 does not expand beyond the nozzle diameter d and no anode point 18 transfer to the nozzle 13 occurs.
,~
-1~3317 rl~his is an engineering fact, and is not fully understood, but is believed to be a consequence of the thermal pinch cffect due to the nozzle 13. It can be illustrated in another way.
Fig. 3 shows a part of the side wall 33 of the conductive nozzle 13 and the cathode electrode 37.
The side wall 33 is in electrical contact with the base metal 35, and is at a fairly large radial distance rl from the cathode 37. It is found that the anode point 38 formed on the base metal 35 by the arc 32 wanders, and the arc 32 spreads out like a shower, as shown by the dotted lines in Fig. 3.
Now, if the nozzle 13 is changed for a smaller one ~ that is, one which has a smaller internal radius r2 ~ as indicated by the two-dotted lines in Fig. 3, and the electrical contact of the nozzle 13 with the ~ase metal 35 is maintained, it ~0 is found that the anode point 38 does not transfer to the wall member 33. Instead, the arc shower 32 is contracted, as shown by the two-dotted lin~s in Fig. 3.
However, if the electrical contact of the nozzle 13 ar.d the base metal 35 is broken, so that they are electrica~ly isolated from one another, a series arc is yenerated via the wall member 33 between the cathode 37 and the base metal 3~5.
1~()3317 In the machine shown in Fig. 2, the reason for mixing nitrogen gas into the stream of argon gas while the base metal 15 is being cut is that then the anode point 13 easily migrates through the thickness of the base metal 15 around the cavity being cut. Accordingly thick base metal may be cut readily.
Since the nozzle end 14 contracts the base metal 15 and surrounds the anode point 18, the anode point 18 cannot wander outwards on the base metal beyone the nozzle. ~Ience an opening of diameter d' which is almost the same as the nozzle diameter d is obtained. The cutting width is thus reduced by half, compared with that of a conventional process.
In other words, the cutting efficiency increases, and therefore the temperature rise of the base metal decreases. TnereLore the distortion of the base metal caused by heat when cutting also is much reduced, and consequently a thin piece of base metal may be readily cut, even though heretofore it has been difficult to cut such thin base metal by using a plasma arc.
In Fig. 4 there is shown a contro~ means for the plasma-arc cutting machine or the present invention which utilizes the contact of the no~.71e 13 with the base metal 15. The control means includes a relay 11~3317 contacts 21. Then the electric current is supplied from an electric source 22 to the cathode electrode 17, with the result that the arc 18 is struck, and the plasina-arc cutting machine is started.
The relay device 20 may be further adapted ~o actuate a control device which automatically adjusts appropriately the time for genera~ing the arc and varies the distance between the electrode 17 and the base metal 15.
From the above description it is readily understood that according to the present invention is provided a plasma-arc cuttiny machine which is easily operated without emission of intense light, which requires little skill, which makes a cut of reduced width and accordingly is of greater practical efficiency, and which minimises the temperature rise of the base metal so as more readily to process thin base ~etal. In view of the abovement oned facts, a small size pencil-type plasma-arc cutting machine can readily bc provided. Further, since it is easy to maintain the distance between the electrode and the base metal, this method may be conveniently applied to an automatic plasma-arc cutting machine which is nur.erically controlled by a computer, .'' ~
Referring to the drawings, in Fig. 1 there is shown an essential part of a conventional plasma-arc cutting ntachine. As the cutting machine 1 is operated, ~103317 the nozzle end 2 is separated by a certain gap L from the surface 4 of a base metal 3 which ls to be cut.
The distance L' between the electrode and the S base metal 3 depends on the distance L between the nozzle end 2 and the base metal 3. This distance L' between the electrode and the ~ase metal 3 should be .aintained within a certain range so as to obtain a stable plasma-arc 5. Accordingly, it requires a great deal of skill to operate such a plasma-arc cutting machine.
~hen an operator uses this cutting machine, he watches the nozzle end 2 in order to r.laintain the proper distance L between the nozzle end 2 and the surface 4 of the base r,letal 3. Tnus, because the intense light generated by the arc 5 inevitably shines into his eyes, he requires an eye shield.
Furthermore, it is ~no~Jn that the dian~eter D of the opening 6 cut in the base metal 3 is about twice as large as the diameter D' of the nozzle when the optimur.l distance between the nozzle 2 and the base metal 3 is maintained.: ~owever, as explained above, the size of the openins 6 cannot arbitrarily be reduced :` 1103;~ 7 by reducing the size of the nozzle D', since at a certain point a series arcing problem occurs.
In Fig. 2 there is shown the essential part of a plasma-arc cutting machine 11 of the present invention, corresponding to the part illustrated in Fig. 1 of a prior-art machine.
The nozzle end 14 of a nozzle 13 is contacted with a surface 16 of a base metal 15. A cathode electrode 17 is then broua,ht towards the base metal 15 in a flow of argon gas, resulting in striking an arc 12. The arc 12 is generated between the electrode 17 and a first anode point 18. Then nitrogen gas is added to the flow of argon gas, the gas flow speed itself may be changed, and the electrode 17 is moved away from the surface 16 to establish the proper electrode distance 1 for cutting. The nozzle 18 is then moved along the base metal surface 16, keeping its contact therewith, and thereby the base metal is cut.
There are provided radially disposed escape grooves 19 of an inverted U-shape for venting the gas flow at the nozzle end 14.
During the cutting of the base metal lS, the range of motion of the anode point 18 formed on the base metal 15 does not expand beyond the nozzle diameter d and no anode point 18 transfer to the nozzle 13 occurs.
,~
-1~3317 rl~his is an engineering fact, and is not fully understood, but is believed to be a consequence of the thermal pinch cffect due to the nozzle 13. It can be illustrated in another way.
Fig. 3 shows a part of the side wall 33 of the conductive nozzle 13 and the cathode electrode 37.
The side wall 33 is in electrical contact with the base metal 35, and is at a fairly large radial distance rl from the cathode 37. It is found that the anode point 38 formed on the base metal 35 by the arc 32 wanders, and the arc 32 spreads out like a shower, as shown by the dotted lines in Fig. 3.
Now, if the nozzle 13 is changed for a smaller one ~ that is, one which has a smaller internal radius r2 ~ as indicated by the two-dotted lines in Fig. 3, and the electrical contact of the nozzle 13 with the ~ase metal 35 is maintained, it ~0 is found that the anode point 38 does not transfer to the wall member 33. Instead, the arc shower 32 is contracted, as shown by the two-dotted lin~s in Fig. 3.
However, if the electrical contact of the nozzle 13 ar.d the base metal 35 is broken, so that they are electrica~ly isolated from one another, a series arc is yenerated via the wall member 33 between the cathode 37 and the base metal 3~5.
1~()3317 In the machine shown in Fig. 2, the reason for mixing nitrogen gas into the stream of argon gas while the base metal 15 is being cut is that then the anode point 13 easily migrates through the thickness of the base metal 15 around the cavity being cut. Accordingly thick base metal may be cut readily.
Since the nozzle end 14 contracts the base metal 15 and surrounds the anode point 18, the anode point 18 cannot wander outwards on the base metal beyone the nozzle. ~Ience an opening of diameter d' which is almost the same as the nozzle diameter d is obtained. The cutting width is thus reduced by half, compared with that of a conventional process.
In other words, the cutting efficiency increases, and therefore the temperature rise of the base metal decreases. TnereLore the distortion of the base metal caused by heat when cutting also is much reduced, and consequently a thin piece of base metal may be readily cut, even though heretofore it has been difficult to cut such thin base metal by using a plasma arc.
In Fig. 4 there is shown a contro~ means for the plasma-arc cutting machine or the present invention which utilizes the contact of the no~.71e 13 with the base metal 15. The control means includes a relay 11~3317 contacts 21. Then the electric current is supplied from an electric source 22 to the cathode electrode 17, with the result that the arc 18 is struck, and the plasina-arc cutting machine is started.
The relay device 20 may be further adapted ~o actuate a control device which automatically adjusts appropriately the time for genera~ing the arc and varies the distance between the electrode 17 and the base metal 15.
From the above description it is readily understood that according to the present invention is provided a plasma-arc cuttiny machine which is easily operated without emission of intense light, which requires little skill, which makes a cut of reduced width and accordingly is of greater practical efficiency, and which minimises the temperature rise of the base metal so as more readily to process thin base ~etal. In view of the abovement oned facts, a small size pencil-type plasma-arc cutting machine can readily bc provided. Further, since it is easy to maintain the distance between the electrode and the base metal, this method may be conveniently applied to an automatic plasma-arc cutting machine which is nur.erically controlled by a computer, .'' ~
Claims (5)
1. A plasma-arc cutting method comprising:
contacting the end of a nozzle with a base metal, an electrode being away from base metal, during the operation of cutting the base metal;
emitting an arc from the electrode to the base metal;
and changing the distance between the electrode and the base metal from a first distance employed while striking an are between them to a second distance employed while cutting the base metal with the arc.
contacting the end of a nozzle with a base metal, an electrode being away from base metal, during the operation of cutting the base metal;
emitting an arc from the electrode to the base metal;
and changing the distance between the electrode and the base metal from a first distance employed while striking an are between them to a second distance employed while cutting the base metal with the arc.
2. A plasma-are cutting method according to claim 1, wherein the nozzle is conductive and is at the same electric potential as the base metal while the base metal is being cut.
3. A plasma-arc cutting method according to claim 1 or claim 2, wherein said first distance is less than said second distance.
4. A plasma-arc cutting method according to claim 1 or 2, wherein said first distance is less than said second distance and argon gas flows through the nozzle when the arc is being struck, and a mixture of argon and nitrogen gas flows through the nozzle while the base metal is being cut.
5. A plasma-arc cutting method according to claim 1 or 2, wherein the arc is struck by applying an electric voltage from an electric source by means of a relay device which is actuated by the contacting of the nozzle with the base metal.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3473277A JPS53119766A (en) | 1977-03-30 | 1977-03-30 | Plasma melt cutting method |
| JP52-34732 | 1977-03-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1103317A true CA1103317A (en) | 1981-06-16 |
Family
ID=12422477
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA298,157A Expired CA1103317A (en) | 1977-03-30 | 1978-03-03 | Plasma-arc cutting method |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS53119766A (en) |
| CA (1) | CA1103317A (en) |
| DE (1) | DE2812329C2 (en) |
| FR (1) | FR2385482A1 (en) |
| GB (1) | GB1594058A (en) |
| HK (1) | HK39384A (en) |
| MY (1) | MY8500510A (en) |
| SG (1) | SG17284G (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE444902B (en) * | 1983-09-29 | 1986-05-20 | Adolf Gunnar Gustafson | SKERBRENNARE |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE566144A (en) * | 1957-03-27 | |||
| NL300801A (en) * | 1962-12-05 | |||
| US3366773A (en) * | 1963-09-06 | 1968-01-30 | Mc Donnell Douglas Corp | Portable spot welder and method |
| FR1483454A (en) * | 1966-06-15 | 1967-06-02 | Kjellberg Elektroden & Maschin | Electrical coupling and device for automatically lifting electric arc plasma torches |
| JPS4869490A (en) * | 1971-12-21 | 1973-09-20 | ||
| JPS5248106B2 (en) * | 1972-06-12 | 1977-12-07 | ||
| JPS4929249A (en) * | 1972-07-14 | 1974-03-15 | ||
| JPS519700B2 (en) * | 1973-01-30 | 1976-03-29 | ||
| DE2308276A1 (en) * | 1973-02-20 | 1974-08-22 | Messer Griesheim Gmbh | Plasma welder with choke in auxiliary arc A.C. supply - prevents over-heating of limiter |
| US3851864A (en) * | 1973-06-26 | 1974-12-03 | Lukens Steel Co | Apparatus and process for suppression of noise and fumes generated by plasma-arc cutting operation |
| DE2346961A1 (en) * | 1973-09-18 | 1975-04-03 | Union Carbide Gmbh | Hand-held plasma arc burner - esp. for metal cutting, and needing no water-cooling |
| DE2416732C2 (en) * | 1974-05-02 | 1982-05-06 | Vsesojuznyj naučno-issledovatel'skij proektno-konstruktorskij i technologičeskij institut elektrosvaročnogo oborudovanija, Leningrad | Device for plasma processing of electrically conductive materials |
-
1977
- 1977-03-30 JP JP3473277A patent/JPS53119766A/en active Granted
-
1978
- 1978-03-03 CA CA298,157A patent/CA1103317A/en not_active Expired
- 1978-03-21 DE DE19782812329 patent/DE2812329C2/en not_active Expired
- 1978-03-22 GB GB1128178A patent/GB1594058A/en not_active Expired
- 1978-03-28 FR FR7808857A patent/FR2385482A1/en active Granted
-
1984
- 1984-02-25 SG SG17284A patent/SG17284G/en unknown
- 1984-05-03 HK HK39384A patent/HK39384A/en unknown
-
1985
- 1985-12-30 MY MY8500510A patent/MY8500510A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPS53119766A (en) | 1978-10-19 |
| FR2385482A1 (en) | 1978-10-27 |
| DE2812329A1 (en) | 1978-10-12 |
| HK39384A (en) | 1984-05-11 |
| DE2812329C2 (en) | 1983-02-24 |
| GB1594058A (en) | 1981-07-30 |
| SG17284G (en) | 1985-03-08 |
| FR2385482B1 (en) | 1981-03-06 |
| JPS5617990B2 (en) | 1981-04-25 |
| MY8500510A (en) | 1985-12-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |