Thiết kế máy cắt biên dạng ống tự động điều khiển CNC

Commerciahzed pipe cutting machines are many different types such as large pipe cutter CNC controls, small cutter on the surface of the pipe follow fixed rails, equipment or tube bevelin

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BY CNC CONTROL

THIET KE MAY CAT BifiN DANG 6 N G T U D O N G DIEU KHIEN CNC

Msc Phan Huy Le, AssocProf.PhD Bui Van Hanh

Department of Welding Engineering and Metal's Technology- School of Mechanical Engineering

Hanoi University of Science and Technology

ABSTRACT

The manufacture of auto-lifred oilrig and the oil pipeline system in the petroleum refinery are important projects, occupying a large volume in Vietnam's industry In such works, the process of making structural system from steel tube is mostly works The tube cutting especially at the intersection

of multiple tubes, is required to have accurate edges It is important to have precision gap welding

in progress of assembly welding after that Manual cutting has the disadvantages such as low productivity, wide, inexactly gap welding, wasting welding metal, leading to increase stress, strain

in the intersections of the tubes The solution automatically CNC controlled cutting causes the increasing performance, beautiful cutting edge, steady gap welding This report introduces the result

of research, design automotive cutting system It includes four sections; design calculation mechanical system, building equation of machine's orbital, design controller and control algorithms

Keywords: CNC, Automatic pipe profile cutting, oilpipe, nut

TOM TAT

Viec che tao chdn gidn khoan ddu khi vd cdc he thdng dudng ong ddn ddu, khi cda cdc nhd mdy Igc ddu dang la cdc cong trinh quan trgng, chiem khdi lugng ldn trong cong nghiep Viet Nam Trong cdc cong trinh do, viec che tao ket cdu he dng ddn td phoi thep dng chiem chu yeu Viec cat cdc ong dd yeu cdu diit do chinh xdc cao nhdm ddm bdo khe hd hdp ly cho qud trinh hdn lap ghep

he thong ong ve sau, ddc biet Id tai cdc nut giao nhau cda nhieu dng PhUdng phdp cat thu cdng cd nhuac diem la cho ndng sudt thdp vd ddc biet Id khe hd hdn ldn ldm tang lUdng kim loai dip din den ldm tdng dng sudt vd bien dang tcii nut giao nhau cua cdc ong Gidi phdp cat tU dgng dieu khien CNC cho ndng sudt cao vd mep cat dep, khe hd hdn dong deu Bieu dd cho phep nhdn dudc mdi hdn

cd chdt lUdng cao, it cong venh, hien dang Bdi bdo gidi thieu cdc ket qud nghien cdu tinh todn thiet

kl mdy cat hien dang ong tU dgng dieu khien CNC ldm viec tqi hiin trudng Ndi dung bao gom cdc phdn; Tinh todn thiet kehe thong ddn dgng vd truyen dgng xdy diing phudng trinh quy diio cat cho mdy, thiet kehe thong dieu khien vd xdy dung thudt todn dieu khien

Tii khoa: CNC, cat dng tU dgng ong ddn ddu, nut

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1 INTRODUCTION

In fact, to cut pipes follow the intersection

of two pipes before welding, there are many

different ways classified two main types: cut

manually or by machine Commerciahzed

pipe cutting machines are many different types

such as large pipe cutter CNC controls, small

cutter on the surface of the pipe follow fixed

rails, equipment or tube beveling cutting

ma-chining On the large mower, the cutter head

has 3-axis motion and tubes rotate However,

the actual production requites to cut the tube

to achieve high accuracy right on the site To

solve this demand, it is forced to use CNC

cutting machines Nevertheless, in Vietnam,

the available CNC cutting machines are large,

operate on the principle of rotating pipe

dur-ing cuttdur-ing and cuttdur-ing machines are fixed in

the workshop The inconvenience of this kind

of cutter is hard to induct and dismount tubes

on the site On the other hand, rotating the

tubes, which have large site and volume (12 m

length, diameter from 400 mm to 1000 mm,

av-erage thickness 40 mm) requires a lot of energy

From above analysis, the authors have proposed

design solutions orbital cutter CNC pipe work

at the site according to the principle of spinning

tube cutter, tube fixes in the cutting process

2 BUILDING SOLUTIONS

Through analyzing the existing design

of the cutter, the authors have chosen the

fol-lowing solutions:

• This machine is portable cutting machine,

using plasma or acetylene-oxygen flame to be

able to cut various metals, including nonferrous

metals

size, small volume (<20 kg), can be easily in-stalled on different diameter tubes, are fixed by the cable system

• The machine is controlled automati-cally follow the orbital from intersection of two cylinders Its model has two degrees of freedom: the first degree is spinning around the tube axis (the whole machine), the second -degree transfer along the straight-line parallels

to axis of the tube (the cutting head) Head tilt angle is adjusted by hand before cutting

This cutting machine has compact

Figure 1: System of cutting machine

2.1 Calculate and design mechanical transmission and body of machine

Mechanical structure of this machine include some main parts: (fig 2)

1- Main body;

2- Clusters of driver wheels; 3- Cable system;

4- Servo motor 1;

5- Cutting head;

6- Ball screw assemblies;

7- Servo motor 2

TAP CHI CO KHi VIET NAM, S6 8 nam 2014

Figure 2: Mechanical structure of cutter

Cluster of drive wheels performs the

task of creating rotational motion around the

tube This cluster includes tooth belt driven,

wave gear reducer and proactive textured

wheel The rotation around the tube axis is created

by roll motion of proactive wheel on surface of

tube

Cable assembly is kept on the main

body by the ringbolt This cluster is responsible

for keeping the machine on the surface of tube,

creating pressure and friction force between

wheel and tube

Ball screw assembly performs linear

motion along the axis of tube This cluster

includes the second servomotor, screw and

cutting clamping The cutting clamping is

re-sponsible for fix cutting head on machine and

adjusts the distance between the head and

surface of tube

2.2 Building equation of intersection of two

cylinder

Figure 3: Coordinate system

General problem of two intersection cylinders is:

Considering two cylinders with axis is two overlap lines;

The angle between 2 center fine is (p; The distance between 2 center line is 1^; The first cylinder radius is R 1;

The second cylinder radius is R,;

In the decade coordinate Oxyz, cylinder equation is:

x^ + y-=R^

To facilitate the calculations, we switch

to the cylindrical coordinate system By trans-forming the coordinate system, it can be cho-sen equations of Tl cylinder in simple form;

The cylindrical coordinate system of T^

is Oxyz, so equation of T, in Oxyz is:

{x = a

y-R,.sin(^,)

z = R|.cos(^i)

The cylindrical coordinate system of T

is OX|y|Z|, so equation of T^ in Ox^y^Zj is:

ix = Rj.cos(^,)

y-R sin(6'.)

z = ^

Equation of T^ in Oxyz coordinate system can be obtained from equation of T^ in

Ox y|Z| by moving coordinate system:

- Translating Ox^y^z^ along Oy: 1^^

- Rotatmg OxjjZj an angle (p around Oy axis

Meanwhile, the transfer matrix is' '^

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c o s ^ 0 s i n ^ 0

0 1 0 0

- s i n ^ 0 c o s ^ 0

0 0 0 1

1 0 0 0

0 1 0 /„

0 0 1 0

0 0 0 1

costp 0 s'mtp 0

0 1 0 7,

- s i n ^ 0 cos^ 0

0 0 0 1

cos^ 0 sin ip 0

0 1 0 / ,

- s i n ^ 0 costp 0

0 0 0 1

''R,cos(.e,f

^OxI^lzl

c o s ^ 0 sin Cf) 0

0 1 0 ;„

- s i n ^ 0 c o s ^ 0

0 0 0 1

R^sin{e,)

Equation of T, in Oxyz is

X = R, cos (6j) Cos (<p)+ p Sin ((p)

y=R,.'Sin (6,) +10

z=-R^ sin (cp).cos (e2)+p.cos (9)

Intersection of two cylinders is root of

equations;

R2 cos(e,) cos((p)-if sm((p)=a

R,sm(e2) + lj=Ri.sm(ei)

-R .sm((p).cos(9j>t^.cos(cp)=R,.cos(ei)

Root of above equations is:

1 |R:.co<ej I

a>i(ip) I =^/R'-R,=.air(9,>2J<,.ai<9JJ„4.V3il(ip) J

1 ;R-aa:(i)).co<6,) -j ccs:?) I = / R ; - R ; - S ! I I = ( 9 J - 2 J ? ai<9,)Vlo" J

|'R sm(e.)H^ ]

^ ' R ' I

^.arosi ;

~l ViVjR;'m'(6,>2J! aa;e,)tc4j' i ' R Conditions for root exist: R, + 1 < R,

' V =R siii(6,)=

• cotg(e,)

[z =R,.oos(6,)= -R,.siii(i(i),cos(6,)+p.oos(i(i)

Transfer above equations to Decade co-ordinate system:

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1 rRjxxKce,) \

"^9) [±7R-, R,=jiin-(ej>.2Jl,.sin(e.)J,-l„'ai)(ip) J

y=Rj.siii(e,)tl,

z = ±^R,'-Rj^sin^(0, >.2Jlj.sin(ej).l,-lj=

With 6^ is a variable parameter in range 0 < 0^ <27t

Suppose the tube need be cut is T j, 9^ could be control parameter for the first servo motor:

So moving equation of the first degree of freedom:

e^=^-^Mag

'R,.sin(e,H

R;

^'-R,'A'(e,>2R.sm(9.).l„"V

With u is transmission ratio from first servomotor to proactive wheel

So moving equation of the second degree of freedom:

1 j^Rj 006(6,) -j

co6(9)[±^R, R,-.s!n-(e;>2A,.siii(e,)J„4j-.sil(<p) J

Design control system

Requirements:

The control system has function that drives movement of cutting machine during cutting

process through servomotor Movement of machine includes two following motions:

- First motion: Motion of the whole machine around tube

- Second motion: Motion of cutting head along axis of tube

Both two motions are created and combined together to make relative motion between

cutting head and tube follow orbit was calculated ' '

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paiameta

CoaaptAet

4 molioiis (kive]

card

pand

Control process as following algorithm diagram:

ConHmnncatioii droiit

z

l-Sovomotor

Odver — nitatia]

[notion

H

Z-Savonwtor Driv^ — t^m^tionmotioi

X

2- SovomotDi

Tooth bdt

dnv'ea, wave

gear

Rotabon of

machine

TraosUtion of cutting head

Figure 4: Control system

The control system must perform two

modes: automatic and manual In automatic

mode, cutting machine is automatically

controlled by software on computer The

mo-tion parameter: rotamo-tion angle of machine and

distance of cutting head, are calculated from

input geometry parameters of two tubes Input

parameters include diameters D l , D2 of two

tubes, angle and distance between two axes

Through motion driver card, control signal

pulse will be send to two ser\'omotors to control

the cutting head sticking exactly orbit This

cutting process is done simultaneously in real

and computer interface

(^ Start ^

/

Infvt pararoetet^

Sohiog oibital equation

X

Choose staxtmg point of oibit

to cut mm on cuttina pon-er

Display oibit on the screen, export conool sipuJ, starting

Figure 5: Control algorithm diagram

In manual control mode, cutting machine will rotate and cutting head will translate along axis of tube when pressing and holding the moving button by hand This mode is used when installing and adjusting the cutting head into right position In this mode, each motion

is independently controlled via buttons on software interface or manual control box

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Figure 6: Control interface

3.CONCLUSIONS:

The main content of this paper presents in the following contents:

- Provide design solution of potable tube cutting machine, bases on the theoretical basis about cutting profile of tube has been smdied: two cylinders with respective radius is R^, R^, overlap

in space with angle (p and axis distance 1 Since then, calculate to find the intersection between the tubes Equation will be build orbital motion of cutting head

- Selection of structural mechanics and conduct body design, driver system ensures most compact structure Total mass of this machine is less than 20 Kg it uses precision actuators, compact as: ball screw system, wave gear reducer to ensure accuracy edge

- Choose the design solution and control system based on the center console is com puter, driver system using servomotors and motion driver card This is optimal design solution for high accuracy motions

- Develop algorithms and control software written in C language and combine with OpenGL library •

Ngay nhan bai: 16/7/2014

Ngay phan bien: 17/8/2014

References:

[1] Pham Cong Ngo (2005), Automatic control theory Science and Technology Publishing House

[2] Trinh Chat, Le Van Uyen (2001), Mechanical transmission design guidlines Science and Technology

Publishing House

[3].http://www.hiwin.com/html/!inear%20stages/index.htmLRetrievedfromhttp://www.hiwin.com [4] http://www.koike.com/MachLnes/Machine.aspx?MachineID-44I(2010), Retrieved from http://www, koike.com/

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