WO2023087571A1

WO2023087571A1 - Pipe winding device and winding method thereof

Info

Publication number: WO2023087571A1
Application number: PCT/CN2022/078668
Authority: WO
Inventors: 职承涛; 施刚成
Original assignee: 金龙精密铜管集团股份有限公司; 中科金龙金属材料开发有限公司
Priority date: 2021-11-16
Filing date: 2022-03-01
Publication date: 2023-05-25
Also published as: CN114160606A

Abstract

A pipe winding device, comprising a conveying mechanism (1), a bending mechanism (2) and a tray unit (3), and further comprising: a horizontal moving unit (4), the horizontal moving unit comprising a moving base (41) and a first driving device (42), the moving base being fixedly connected to an output end of the first driving device, the moving base comprising a moving frame (411), a connecting member (412) and a bearing plate (413), and the bearing plate being fixedly connected to the moving frame by means of the connecting member; a vertical moving unit (5), the lower part of the vertical moving unit being fixed on the bearing plate, and the upper part passing through the moving frame and being fixedly connected to the tray unit; and a servo control unit (8), the servo control unit being electrically connected to the horizontal moving unit and the vertical moving unit. Also disclosed is a pipe winding method which drives a tray to move according to an Archimedes spiral trajectory, and shapes of pipelines in an axis coil are regular, and scratches caused by friction between adjacent pipes in transportation are reduced. The device facilitates processing and production, and is convenient to assemble and disassemble and high in practicability.

Description

A pipe winding device and winding method thereof

technical field

The invention relates to the technical field of pipe materials, in particular to a pipe rewinding device and a rewinding method thereof.

Background technique

In the production and processing of metal pipes, in order to facilitate the transportation of metal pipes, a rewinding machine is generally used to wind the metal pipes into an axis disk. At present, the rewinding machine is suitable for crimping and winding hard metal pipes, but not suitable for crimping and winding soft metal pipes and semi-hard metal pipes. It is crimped and wound into an axis disk, and then annealing is performed on the hard metal tube of the whole disk to finally form the required soft metal tube. However, in the process of annealing, the hard metal tube needs to be treated at high temperature. At high temperature, the hard metal tubes in contact with each other are likely to interact with each other and cause adhesion, which affects the quality of the metal tube.

In order to effectively avoid the problem that the metal tubes in contact with each other are prone to sticking during the annealing process of the entire hard metal tube, the existing technology has improved the traditional rewinding machine, such as the invention patent with the patent number CN102688910B A rewinding device is proposed, which includes a conveying mechanism for conveying metal pipes; a wire take-up mechanism, which includes a pipe reel, a slewing support arranged under the pipe reel, and a first device for driving the pipe reel to rotate. The driving device also includes a lifting support that is fixedly connected to the slewing support through an intermediate piece, a second driving device that drives the lifting support up and down, and a base that supports the wire take-up mechanism. Annealing the hard metal tubes before using the above-mentioned winding device can effectively solve the problem that the metal tubes in contact with each other are prone to sticking during the annealing process of the entire disk of hard metal tubes.

Although this patent can solve the problem that the metal tubes in contact with each other are prone to sticking during the annealing process of the entire disk of hard metal tubes, the distribution of the inner wire tubes in the wound axis roll is disordered, and the entire axis roll Several irregular and loose shapes are likely to cause scratches due to friction between adjacent metal pipes during transportation.

Contents of the invention

The object of the present invention is to propose a pipe winding device, which has a simple structure, is easy to process and produce, is easy to assemble and disassemble, and has strong practicability.

The technical scheme that realizes the object of the present invention is:

A pipe rewinding device, including a conveying mechanism, a bending mechanism and a pallet unit, the conveying mechanism conveys the soft metal pipe to the bending mechanism for bending, and then rolls on the pallet unit;

It also includes a horizontal moving unit, the horizontal moving unit includes a moving base and a first driving device, the moving base is fixedly connected to the output end of the first driving device, wherein the moving base includes a moving frame slidingly connected to the base, and a connection through the upper part of the base parts and the bearing plate, the bearing plate and the moving frame are fixedly connected through the connecting piece;

It also includes a vertical mobile unit, the lower part of the vertical mobile unit is fixed on the bearing plate, and the upper part passes through the mobile frame and is fixedly connected with the pallet unit as an integral structure;

It also includes a servo control unit, the servo control unit is electrically connected with the horizontal moving unit and the vertical moving unit.

Further, the vertical moving unit includes a tray rotation drive device, a lifting device and an outer stop bar device, wherein the tray rotation drive device is fixed at the bottom of the tray unit; the upper end of the lift device is fixedly connected with the tray unit, and the lower end is fixed on the bearing plate; the outer stop The upper end of the rod device is arranged outside the edge of the tray unit, and the lower end is fixed on the bearing plate.

Further, the tray rotation driving device includes a rotating tray, a first slewing bearing and a second driving device; one side of the rotating tray is fixedly connected to the tray unit, and the other side is fixedly connected to the first slewing bearing; the output end of the second driving device is connected to the second A slewing bearing is fixedly connected.

Further, the lifting device includes a lifting guide rail width, a support base, a connecting piece, a screw lifter and a third driving device; the lifting guide rail width is vertically fixed on the moving seat; the supporting base is slidingly connected with the lifting guide rail width; one end of the connecting piece is connected to the supporting base Fixedly connected, the other end is fixedly connected to the pallet unit; one end of the screw lift is fixedly connected to the support base, and the other end is fixedly connected to the output end of the third driving device.

Further, the outer bar device includes an outer bar, a fixed plate, a second slewing bearing, a lifting plate, an outer bar lifting guide rail and a fourth drive device; the upper part of the outer bar is in contact with the edge of the pallet, and the lower part is in contact with one side of the fixed plate. Fixed connection; one end of the second slewing support is fixedly connected to the other side of the fixed plate, the other end is fixedly connected to one side of the lifting plate, and the other side of the lifting plate is fixedly connected to the output end of the fourth driving device.

Another object of the present invention is to propose a winding method for a pipe winding device, which drives the tray to move according to the Archimedes spiral trajectory, the shape of the inner pipelines of the axis roll is regular, the overall appearance is beautiful, and the adjacent metal pipes during transportation can be reduced. Scratches caused by rubbing between tubes.

The technical scheme that realizes another object of the present invention is:

A winding method of a pipe winding device, the specific winding method is:

The conveying mechanism conveys the soft metal tube to the bending mechanism for bending and then rolls it on the pallet unit;

During the winding process, the servo control unit controls the horizontal movement unit and the vertical movement unit to control the tray unit to move horizontally, vertically and rotate;

The horizontal movement unit controls the tray unit to move horizontally; the lifting device in the vertical movement unit controls the tray unit to move vertically; the tray rotation drive device controls the tray unit to rotate;

The servo control unit controls the horizontal moving unit and the vertical moving unit so that the tray unit makes the axis rolls of each layer distributed in an Archimedes spiral.

In the servo control unit control program of the present invention, the specific program control principle is:

First, according to the polar coordinate equation of the Archimedes spiral, the formula for calculating the polar radius r of the copper pipe helical motion polar coordinates is:

r=a+bθ

Formula 1)

In the above formula (1),

a is the initial position of the helix; t is the pitch of the helix; θ is the polar angle variable in the coordinate equation.

The formula for calculating the curvature radius R is derived as follows:

The calculation formula for deriving the length L of the copper pipe helix is:

The calculation formula of W for the bending tooling roller servo control system is derived as follows:

In formula (4), A, B, C, and D are constants determined by the bending mechanical structure.

The calculation formula of the servo control coefficient E for the movement of the winding center position is derived as follows:

E=R+E ₀

Equation (5)

E ₀ in formula (5) is the initial position of the winding center.

Using the principle of the above formula, according to the length L of the tube, the bending roller servo control W, the winding center movement servo control E, and the winding speed G can be controlled at the same line speed, and the tray winding curvature R and winding speed G The product of is the linear velocity of the copper pipe, which forms a complete Archimedes spiral servo control. The vertical moving device moves up and down to move down 0.94 pipe diameters per layer, and 0.94 is an empirical value. In actual control, the bending The position of the roller, the control of the speed of the winding table and the control of the lifting of the winding table are set with fine-tuning switches, so as to correct the error between theory and practice, so as to ensure the geometric shape and make the whole more neat and beautiful.

The beneficial effects of the present invention are:

(1) The present invention has simple structure, is easy to process and produce, and is convenient to assemble and disassemble, and has strong practicability;

(2) The winding method of the present invention can drive the tray to move according to the Archimedes spiral track, the shape of the internal pipelines of the axis roll is regular, the overall appearance is beautiful, and the scratches caused by friction between adjacent metal pipes during transportation can be reduced .

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without paying creative labor.

Fig. 1 is a kind of overall structure schematic diagram of the present invention.

Fig. 2 is a structural schematic view of direction A in Fig. 1 .

Fig. 3 is a partially enlarged schematic view of the outer bar device of the present invention.

Fig. 4 is a structural schematic diagram of the unwinding mechanism of the present invention.

Fig. 5 is a schematic diagram of a simple connection relationship of the invention.

In the figure: 1. Conveying mechanism; 2. Bending mechanism; 21. Tooling roller; 22. Bending roller; 23. Bending roller drive electric cylinder; 24. Servo motor; 3. Pallet unit; 31. Wooden pallet; 32. Fixed block ; 33. support piece; 4. horizontal moving unit; 41. moving seat; 411. moving frame; 412. connector; 413. bearing plate; 42. first driving device; Unit; 51. Pallet rotation driving device; 511. Rotating pallet; 512. First slewing bearing; 513. Second driving device; 52. Lifting device; 521. Lifting rail width; 522. Support base; .Screw lifter; 525. The third driving device; 53. Outer stop rod device; 531. Outer stop rod; 532. Fixed plate; 533. Second slewing bearing; 534. Lifting plate; ; 536. The fourth driving device; 6. Base; 7. Unloading mechanism; 701. Rotary shaft; 702. Unloading driving cylinder;

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The embodiments and drawings are merely reference embodiments for describing the present invention, and the present invention is not limited thereto but only by the claims. The drawings described are merely schematic and not limiting. For the purpose of further illustrating the present invention, in the drawings, the size of some of the elements may be exaggerated and not drawn on scale. The dimensions and relative dimensions do not correspond to actual reductions in the practice of the invention. Furthermore, the terms first, second and third etc. in the description and claims are used to distinguish similar elements and not necessarily to describe a sequence in time, space, in order or in any other way. It is to be understood that the terms used above are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

As shown in Figure 1, Figure 2, Figure 4 and Figure 5, a pipe winding device includes a conveying mechanism 1, a bending mechanism 2 and a tray unit 3, and the conveying mechanism 1 conveys the soft metal pipe to the bending mechanism 2 for bending Finally, roll up on the tray unit 3;

It also includes a horizontal moving unit 4, the horizontal moving unit 4 includes a moving base 41 and a first driving device 42, the moving base 41 is fixedly connected to the output end of the first driving device 42, wherein the moving base 41 includes a moving base 6 that is slidably connected to the base 6 The frame 411 , the connecting piece 412 penetrating through the upper part of the base, and the carrying plate 413 , the carrying plate 413 is fixedly connected to the moving frame 411 through the connecting piece 412 .

The pedestal in the present invention can be the pedestal in the prior art, such as the pedestal in the invention patent with the patent number CN102688910B, or it can also be a bearing seat of other forms to ensure that it can carry other equipment and that there are internal openings for movement. Seat 41 has space for horizontal and vertical movement.

The output end of the first driving device 42 is fixedly connected with the moving base 41 to drive the vertical moving device connected with the moving base 41 to move horizontally, and the first driving device 42 is a linear driving device, which can drive the moving base 41 according to the R curvature center move. In the existing linear drive device, the electric cylinder integrates the servo motor 24 and the lead screw, adopts closed-loop servo control, and has high movement precision. A pressure sensor is also added, and the thrust control precision is high; the electric cylinder also has low noise. , high rigidity, impact resistance and simple operation and maintenance. Therefore, the first driving device 42 of the present invention is preferably an electric cylinder.

It also includes a vertical moving unit 5 , the lower part of the vertical moving unit 5 is fixed on the bearing plate 413 , and the upper part passes through the moving frame 411 and is fixedly connected with the tray unit 3 as an integral structure. The moving frame 411 of the present invention is a frame structure, and its interior is penetrated for the vertical movement unit 5 to pass through.

It also includes a servo control unit 8 which is electrically connected to the horizontal movement unit 4 and the vertical movement unit 5 . The servo control unit 8 is a servo control system in the prior art, and it is mainly used to precisely control the displacement or rotational speed of the relevant driving devices in the horizontal movement unit 4 and the vertical movement unit 5, so that each layer of wire coils has a Mead spiral distribution. The concrete connection relation of servo control unit 8 and horizontal movement unit 4 and vertical movement unit 5 is as follows: the first driver 42 in servo control unit 8 and horizontal movement unit 4, the second driver 513 in the vertical movement unit 5, the first The three driving devices 525 and the fourth driving device 536 are electrically connected to control the rotation, horizontal movement and vertical movement of the tray unit 3 .

The bending mechanism 2 is an existing structure, specifically: the bending mechanism 2 includes a tooling roller 21, a bending roller 22, a bending roller driving electric cylinder 23 and a servo motor 24; wherein, the tooling roller 21 is used to determine the running axis of the pipe; the bending roller 22 is used to bend the pipe to form a curvature, the bending roller driving electric cylinder 23 is used to drive the bending roller 22 to move, and the servo motor 24 is used as a power source to drive the bending structure to work.

Pallet unit 3 comprises wooden support 31, fixed block 32 and support member 33; Wherein, wooden support 31 is used for carrying coil material; Fixed block 32 is used for wooden support 31 accurate positioning; Support member 33 is used for supporting wooden support 31 and determining The position of the outer stop rod 531 makes the outer stop rod 531 rotate with the pallet;

The horizontal moving unit 4 includes a laterally moving guide rail 43 laterally fixed on the base 6 , which can ensure the moving track of the moving seat 41 .

Further, the vertical moving unit 5 includes a tray rotation drive device 51, a lifting device 52 and an outer bar device 53, wherein the tray rotation drive device 51 is fixed on the bottom of the tray unit 3; the upper end of the lifting device 52 is fixedly connected with the tray unit 3, and the lower end It is fixed on the bearing plate 413 ; the upper end of the outer bar device 53 is set outside the edge of the tray unit 3 , and the lower end is fixed on the bearing plate 413 .

In the present invention, the delivery mechanism 1 continuously transports the pipe to the bending mechanism 2 for bending; the bending mechanism 2 bends the semi-hard or soft pipe according to the curvature R of the Archimedes spiral; the tray unit 3 is used for Place the bottom support carrying the coil material; the tray rotation drive device 51 drives the tray to move according to the Archimedes spiral track, and the tube is harvested into a multi-layer Archimedes spiral coil; the lifting device 52 is used to control the position of the coil layer and The height of the roll; the outer stop bar device 53 is used to limit the outer diameter of the roll and unload the roll; the mobile seat 41 is the base of the carrying tray unit 3, the tray rotation drive device 51, the lifting unit and the outer stop bar device 53, and can be The curvature R of the Archimedes spiral changes to move the winding center up and down to fit the Archimedes spiral; the fixed base 6 carries the movable seat 41 to move horizontally.

Further, as shown in Fig. 1 and Fig. 5, the tray rotation driving device 51 includes a rotating tray 511, a first slewing bearing 512 and a second driving device 513; one side of the rotating tray 511 is fixedly connected with the tray unit 3, and the other side is connected with the second A slewing support 512 is fixedly connected; the output end of the second driving device 513 is fixedly connected to the first slewing support 512 .

Rotating tray 511 is used to drive wooden tray 31 to rotate; Slewing bearing is used to support rotating tray 511; A geared motor is also arranged between the slewing bearings 512 . The tray unit 3 is driven to rotate by the tray rotation driving device 51 .

Further, as shown in Fig. 1 and Fig. 5, the lifting device 52 includes a lifting guide rail width 521, a support base 522, a connector 523, a screw lifter 524 and a third driving device 525; the lifting guide rail width 521 is vertically fixed on the moving base 41 Above; the support seat 522 is slidingly connected with the lifting guide rail width 521; one end of the connecting piece 523 is fixedly connected with the support seat 522, and the other end is fixedly connected with the tray unit 3; one end of the screw lifter 524 is fixedly connected with the support seat 522, and the other end is connected with the third The output end of the driving device 525 is fixedly connected.

The lifting guide rail width 521 is arranged on the moving seat 41 on both sides of the lifting screw mandrel, which can ensure that the device is more stable in the lifting process, and the lifting track of the vertical moving unit 5, the supporting seat 522 is the main body of lifting; the screw lifter 524, driven Lifting seat lifts; the third driving device 525 drives the screw lifter 524 to lift.

Further, as shown in Fig. 1, Fig. 3 and Fig. 5, the outer stop rod device 53 includes an outer stop rod 531, a fixed plate 532, a second slewing bearing 533, a lifting plate 534, an outer stop rod lifting guide rail 535 and a fourth Driving device 536; the upper part of the outer stop rod 531 is in contact with the edge of the tray, and the lower part is fixedly connected with one side of the fixed plate 532; one end of the second slewing support 533 is fixedly connected with the other side of the fixed plate 532, and the other end is fixed with one side of the lifting plate 534 The other side of the lifting disc 534 is fixedly connected to the output end of the fourth driving device 536 .

The outer stop rod 531 is used to limit the outer diameter of winding; the fixed disc 532 is used to fix the outer stop rod 531, and the second slewing support 533 enables the outer stop rod 531 to rotate with the tray unit 3; the lifting disc 534 is used to connect the slewing support and lift Drive, the outer stop rod lifting guide rail width 535 ensures the outer stop rod 531 lifting track; the fourth driving device 536 is an electric cylinder, which is used to drive the outer stop rod 531 to lift along the guide column.

Further, as shown in Figure 4, the pipe rewinding device of the present invention also includes an unwinding mechanism 7, and the unwinding mechanism 7 includes a rotary shaft 701 and an unloading drive cylinder 702, and the rotary shaft 701 and the unwinding drive cylinder The output terminal of 702 is fixedly connected. When the coil is unloaded, the cylinder is pushed out, and it is 70-90 degrees with the running center line, so as to leave the winding workbench, which is convenient for unloading the coil.

A winding method of a pipe winding device, the specific winding method is:

The conveying mechanism 1 conveys the soft metal tube to the bending mechanism 2 for bending and then rolls it on the tray unit 3;

During the winding process, the servo control unit 8 controls the tray unit 3 to move horizontally, vertically and rotate by controlling the horizontal movement unit 4 and the vertical movement unit 5;

The horizontal movement unit 4 controls the tray unit 3 to move horizontally; the lifting device 52 in the vertical movement unit 5 controls the tray unit 3 to move vertically; the tray rotation drive device 51 controls the tray unit 3 to rotate;

The servo control unit 8 controls the horizontal movement unit 4 and the vertical movement unit 5 so that the tray unit 3 makes the axial rolls of each layer be distributed in an Archimedes spiral.

The servo control unit 8 is electrically connected to the first driving device 42 , the second driving device 513 , the third driving device 525 and the fourth driving device 536 respectively. In this way, each driving device can be controlled, so that each driving device cooperates to control the movement of the tray unit 3, so that each layer of axis rolls forms a perfect Archimedes spiral, further reducing friction between tubes, and ensuring the quality of axis rolls.

The specific implementation manners described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific implementation methods of the present invention and are not intended to limit the present invention. Inventions, any modifications, equivalent replacements and improvements made within the gist of the present invention shall be included within the protection scope of the present invention.

Claims

A pipe rewinding device, comprising a conveying mechanism (1), a bending mechanism (2) and a pallet unit (3), the conveying mechanism (1) conveys a soft metal pipe to the bending mechanism (2) for bending, and then the pallet unit ( 3) wind up; it is characterized in that:

It also includes a horizontal moving unit (4), the horizontal moving unit (4) includes a moving seat (41) and a first driving device (42), and the moving seat (41) is fixedly connected to the output end of the first driving device (42), wherein, The mobile base (41) comprises a mobile frame (411) slidingly connected to the base (6), a connecting piece (412) and a carrying plate (413) running through the top of the base (6), the carrying plate (413) and the mobile frame ( 411) fixedly connected by a connector (412);

It also includes a vertical moving unit (5), the lower part of the vertical moving unit (5) is fixed on the bearing plate (413), the upper part passes through the moving frame (411) and is fixedly connected with the tray unit (3) as an integral structure;

It also includes a servo control unit (8), and the servo control unit (8) is electrically connected with the horizontal movement unit (4) and the vertical movement unit (5).
The pipe winding device according to claim 1, characterized in that:

The vertical moving unit (5) comprises a pallet rotating drive (51), a lifting device (52) and an outer bar device (53), wherein the pallet rotating driving device (51) is fixed on the bottom of the pallet unit (3); the lifting device ( 52) The upper end is fixedly connected with the tray unit (3), and the lower end is fixed on the bearing plate (413); the upper end of the outer bar device (53) is arranged outside the edge of the tray unit (3), and the lower end is fixed on the bearing plate (413).
The pipe winding device according to claim 2, characterized in that:

The pallet rotation driving device (51) includes a rotating pallet (511), a first slewing bearing (512) and a second driving device (513); one side of the rotating pallet (511) is fixedly connected to the pallet unit (3), and the other side is connected to the second A slewing support (512) is fixedly connected; the output end of the second driving device (513) is fixedly connected to the first slewing support (512).
The pipe winding device according to claim 2 or 3, characterized in that:

The lifting device (52) comprises a lifting guide rail width (521), a support seat (522), a connector (523), a screw lifter (524) and a third driving device (525); the lifting guide rail width (521) is vertically fixed on the moving on the seat (41); the support seat (522) is slidingly connected to the lifting guide rail (521); one end of the connector (523) is fixedly connected to the support seat (522), and the other end is fixedly connected to the pallet unit (3); the screw lift One end of (524) is fixedly connected to the support seat (522), and the other end is fixedly connected to the output end of the third driving device (525).
The pipe winding device according to claim 2 or 3, characterized in that:

Outer bar device (53) comprises outer bar bar (531), fixed plate (532), second slewing bearing (533), lifting disc (534), outer bar bar elevating rail width (535) and the fourth driving device ( 536); the upper part of the outer bar (531) is in contact with the edge of the pallet, and the lower part is fixedly connected with one side of the fixed plate (532); one end of the second slewing support (533) is fixedly connected with the other side of the fixed plate (532), and the other end It is fixedly connected with one side of the lifting disc (534), and the other side of the lifting disc (534) is fixedly connected with the output end of the fourth driving device (536).
The pipe winding device according to claim 4, characterized in that:

Outer bar device (53) comprises outer bar bar (531), fixed plate (532), second slewing bearing (533), lifting disc (534), outer bar bar elevating rail width (535) and the fourth driving device ( 536); the upper part of the outer bar (531) is in contact with the edge of the pallet, and the lower part is fixedly connected with one side of the fixed plate (532); one end of the second slewing support (533) is fixedly connected with the other side of the fixed plate (532), and the other end It is fixedly connected with one side of the lifting disc (534), and the other side of the lifting disc (534) is fixedly connected with the output end of the fourth driving device (536).
Based on the pipe rewinding device described in any one of claims 1-6, it also includes a rewinding method for the pipe rewinding device, characterized in that: the specific rewinding method is:

The conveying mechanism (1) conveys the soft metal tube to the bending mechanism (2) for bending and then rolls it on the pallet unit (3);

During the winding process, the servo control unit (8) controls the tray unit (3) to move horizontally, vertically and rotate by controlling the horizontal movement unit (4) and the vertical movement unit (5);

The horizontal movement unit (4) controls the tray unit (3) to move horizontally; the lifting device (52) in the vertical movement unit (5) controls the tray unit (3) to move vertically; the tray rotation drive device (51) controls the tray unit ( 3) to rotate;

The servo control unit (8) controls the horizontal movement unit (4) and the vertical movement unit (5) so that the tray unit (3) makes each layer of axis coils distributed in an Archimedes spiral.